When I was studying Biomechanics there was a huge amount of terms I had to learn and understand for the test on the final exam, and at present with studying Applied Movement Neurology, I thought it would be a great idea to have a solid reference point. This will really help any student in these fields to better understand how the whole bodily system functions in relation to human movements. With any scientific domain, there can be complex terminology. For the novice who’s just beginning their journey towards the Mountain of understanding, the terms that get thrown around can be confusing, overwhelming and exhaustive.

To help the beginner, intermediate and advanced, alike, navigate this world, and its accompanying language, I thought it would be helpful to create a one-stop-shop of glossary of terms.  The list presented below should be enough for the average person to gain a better understanding of what’s being talked about amongst even the most advanced practitioners.

Programming Terms

These are words and phrases you’ll come across when folks are discussing how to program workouts for their training.

Rep: Abbreviation for “repetition.” The number of times you lift and lower a weight in one set of an exercise. So if you lift the barbell 5 times before you rack it, that’s “5 reps.”

Set: A group of reps. If a workout calls for 3 sets of 10 reps (3×10), you’ll perform 10 reps of the lift. That’s one set. Rest. Perform the second set of 10 reps. Rest. Perform the third set of 10.

Intensity: “How heavy.” How heavy a weight is in comparison to your one-rep max (the maximum amount of weight that you can lift for a given exercise). The heavier the weight, the more intense the lift. Intensity is NOT mental perception of exertion.

Volume: “How much.” There are a few ways to determine volume. The most common way is to look at how many total reps and sets are completed in a given workout. So 5 sets of 10 reps would be high volume compared to 3 sets of 3.

Another way to measure volume is to multiply the number of total reps performed for an exercise by the weight lifted to get your total “tonnage.” So if you squatted 250lbs for 3 sets of 5, your tonnage volume using this method would be 3,750lbs (15 total reps x 250lbs).

Frequency: “How often.” Frequency could refer to how often a movement is trained a week, how often a muscle group is trained a week, or how often a workout is performed a week. E.g., some programs call for you to work out just three times a week, while others call for you to work out every day.

Duration: How long a workout lasts. The time from the beginning of the workout to the end.

Density: “How much work in a set time.” Density is a combination of volume and duration. A one-hour workout with 3 different lifts consisting of 3 sets of 5, plus aerobic conditioning at the end is more dense than an hour-long workout with 2 different lifts consisting of 3 sets of 3, plenty of rest between sets, and no conditioning at the end.

PR: Personal Record — the most weight you’ve ever lifted on a particular lift.

1RM: Abbreviation for “one rep max.” The maximum amount of weight that you can lift for a given exercise. The easiest way to determine your 1RM is to put weight on the bar until you can’t lift it more than once. If you don’t want to do that, you can use different calculators out there that try to predict what your 1RM would be based on the weight you can lift for reps.

Doubles: Sets of two reps.

Triples: Sets of three reps.

Rating of Perceived Exertion (RPE): Also known as the Borg Scale. RPE is a subjective (determined by you the lifter) measurement of how hard an exercise feels. The Scale goes from 0-10. For most barbell training, your sets of an exercise should be somewhere between RPE 6 and 10.

Failure: The point in an exercise when your muscles are so fatigued that you can’t perform any more reps with strict form. Sometimes you’ll see workouts telling you “perform a set until failure.” This means you just crank out as many reps as you can (with strict form) on that set. Usually it’s the last set in a workout that you go until failure on.

Sometimes failure occurs even without you wanting it to. If a workout calls for a set of 5, but you can only perform 4, you’ve gone to failure.

AMRAP: Abbreviation for “As many reps as possible.” Similar to saying “go to failure.” In CrossFit, this term can also refer to “As many rounds as possible.”

Forced Reps: Reps that are performed past failure with the assistance of a spotter. For example, let’s say you have a set of 5 to perform on the bench press and you experience failure at rep 3. When your spotter sees that you’re struggling, he’ll grab the bar and lift up on it just enough so you can complete the next two reps before you rack. Those last two reps are forced reps. Some research shows that forced reps may help with short-term progress, but most research says you’re better off avoiding forced reps for long-term gains. In fact, most high-level Olympic and power lifters avoid forced reps all together.

Stress-Recovery-Adaptation Cycle: The stress-recovery-adaptation cycle is based on the principle outlined in Hans Selye’s “General Adaption Syndrome,” which was originally published in 1936. This principle states that when the body is exposed to stress (or “alarm” as Selye called it) it will begin a biological process to deal with that stress, recover from it, and then adapt and compensate so that it is better prepared to handle it if exposed to the same stressors again.

All programming, progressions, and periodizations are based on this highly valuable principle. Lifters must utilize the principle of “progressive overload,” where we stress the body a bit more each time in order to properly utilize the stress-recovery-adaptation cycle. In short, our training session is the stressor that causes a disruption in homeostasis and an increase in fatigue. We then spend the days following the stressful training session trying to recover through rest, proper nutrition, etc., and then our body adapts (bigger and stronger) and is ready to handle that stressor again, only to be given a heavier stressor the next time, starting the stress-recovery-adaptation cycle all over again.

Novice Lifter: This doesn’t refer to how long you’ve been lifting, but rather how long it takes for you to fully recover and adapt from workout to workout. A novice lifter is a lifter who can fully recover and adapt from workout to workout within 24-72 hours. What does it mean to fully recover and adapt? It means you can add more weight to your next workout without missing the number of prescribed reps. Basically, every workout is a PR day if you’re a novice lifter.

Being a novice lifter is therefore not about your number of years lifting; if you’re a guy who’s been haphazardly lifting weights for 10 years, but then decided to lift more deliberately and started progressively adding weight to your workouts each week, you’d still be considered a novice, despite your decade of lifting experience. It takes about six to nine months before a novice lifter stops seeing gains at each workout. When that happens he becomes an…

Intermediate Lifter: Instead of recovering and adapting from every workout, this lifter recovers and adapts weekly. In other words, new PRs are set once a week or maybe even once every three weeks. When you’re an intermediate lifter, your programming will change to factor for slower adaptation.

Here’s an interesting catch: Someone who may just be starting out with weight training could be considered an intermediate lifter rather than a novice lifter. These folks are considered “situational intermediate lifters.” They’re intermediate lifters because of their specific situation. Elderly beginning lifters likely won’t be able to fully recover and adapt from every single workout because as you get older, the body’s ability to adapt to physical stress gets slower. Individuals with high-stress jobs or jobs that don’t allow them to sleep enough (like police officers, firefighters, active duty military) will also be considered situational intermediate lifters. These folks, even though they may just be starting out with lifting, will see gains week to week instead of workout to workout.

Advanced Lifter: This lifter recovers and adapts monthly+ (new PRs are accomplished every 1-3 months usually).

Linear Progression: Only one variable (usually intensity or weight) is incrementally increased per workout to invoke the stress-recovery-adaptation response. Usually this is done by adding a little more weight to each lift in each workout. Linear progression is best suited for novice lifters. Starting Strength is a linear progression program for novice lifters.

Periodization: When you can no longer improve from workout to workout (you become an intermediate), you must begin planned programming, which is called periodization. Periodization includes a variation in volume, intensity, and/or frequency, and often involves “loading” and “deloading.”

Loading: A planned period of training time (usually 1-3 weeks) during a periodization program of increased intensity, volume, or frequency, where the body is not allowed to fully recover and fatigue slowly accumulates in the system. This is done so that the body can be stressed enough to elicit an adaptation response, and thus get stronger.

Deloading (or Unloading): A planned period of training time (usually 1-2 weeks) during a periodization program where intensity, volume, or frequency is reduced to allow for the dissipation of accumulated fatigue. This is done so that proper recovery can be accomplished to allow the stress-recovery-adaption cycle to occur.

Over-Reaching: Over-reaching occurs when the stressor is such that it cannot be fully recovered from before the next session, and thus some fatigue accumulates. For example, maybe you go for 225lbs for 3 sets of 5, when you should have done 215lbs. This, in itself, is not a bad thing if the body is given a period of deloading to allow the body to fully recovery and adapt.

Over-Training: Overtraining occurs when over-reaching stressors occur with too much frequency or with such intensity that the body cannot recover and adapt to better prepare itself for the same stressor. It causes a break in the stress-recovery-adaptation cycle.

Over-training can occur with marathon runners who don’t give themselves enough time to recover between training sessions and races. You also see it crop up with CrossFitters who exercise with such extreme exertion that they live in a constant state of soreness and injuries, or at worst get rhabdomyolysis, where muscle fibers actually die and their contents are released into the bloodstream and filtered by the kidneys. With time and rest, eventually the body can and will recover from these traumatic events, but it will not adapt to a better version of itself, as it should in the normal stress-recovery-adaptation cycle.

Western Periodization: Western periodization is the most popular form of programming for intermediate and early-advanced strength athletes, where the programming moves from higher volume and lower intensity (12-16 weeks out from a competition), to high intensity and lower volume as the competition approaches.

Concurrent Periodization: Multiple physical skills are trained and improved, or at least maintained at the same time. This is most appropriate for intermediate lifters, since strength training alone causes an increase in all physical abilities for a novice lifter.

CrossFit programming is done this way (jack-of-all-trades, master-of-none). Westside Powerlifting has traditionally used a version of this periodization to try and make their competitive powerlifters bigger, stronger, more explosive, and even more conditioned all at the same time. Louie Simmons (the father of modern powerlifting) mistakenly called this “conjugate” programming, but it is far closer to concurrent periodization, since his lifters tried to improve all aspects of lifting in a single training cycle.

Conjugate/Block Periodization: (Advanced Programming/Periodization) Specific blocks of training (usually 2-6 weeks long) are organized to focus on one specific physical skill or attribute while trying to maintain the others. This is most appropriate for advanced lifters and athletes (power lifters, Olympic weightlifters, collegiate throwers, etc.) Conjugate programming will also almost always use many variations of the lifts or athletic movements while far out from a competition so that general adaptations take place, and then as the competition nears, the exercise selection is dramatically reduced to only the competitive movements to allow specific adaptations to take place. This was the primary style of training for the Soviets in the 1960s-1980s (when they were killing the rest of the world in international sport).

Bulgarian Method/Specificity Training: (Extremely Advanced Programming/Periodization) Only the competition movements and one or two other exercises are used to adapt and get stronger. This style of periodization is named after the Bulgarians because it is the primary method of training that they have used for nearly fifty years to dominate the sport of Olympic weightlifting. The Bulgarians train extremely heavy (high intensity) all the time, with very high frequency (usually 2-4 training sessions per day), relatively low volume per session, and only train the snatch, the clean-and-jerk, the front squat, and the back squat in their training.

Circuit Training: Performing back-to-back-to-back exercises (usually 2-4 different exercises) without rest in between.

Full Body Training: Training the entire body in one session because you view the body as a system rather than a combination of individual parts. For example, in the Starting Strength program, a lifter will perform 3 workouts a week where they will squat, press (or bench press), and pull (deadlift or power clean and usually chin-ups) every single session. You hit both the upper and lower body every single workout. CrossFit also utilizes full body training.

Split Training: With split training, instead of doing lifts that train the entire body in a single workout, you’ll only focus on one major section or movement. The most common split for strength/performance athletes is two lower days per week concentrating on squats and deadlifts (and cleans), and two upper body days concentrating on presses (press, bench press, dips) and upper body pulling (pull-ups, chin-ups, curls, etc.)

Body Part Training: Bodybuilders, whose are focused on aesthetics over performance, will view the body as individual parts and will train one or two of those parts in isolation apart from the rest of the body in a body part split program. With these routines, you may be working out five days a week: Monday: Leg Day; Tuesday: Back Day; Wednesday: Shoulder Day; Thursday: Chest Day; Friday: Tricep and Bicep Day.

Physical Skills Terms

When you train, you can train for a wide variety of physical skills.

Fitness: Originally, fitness was defined as the ability to be fully prepared for the specific tasks you had to perform. Therefore the fitness needed for a baseball player would be different than the fitness needed for a distance runner. However, in today’s culture, CrossFit has really redefined fitness as a measure of one’s ability to perform the “10 general physical skills,” which they define as “cardiorespiratory endurance, stamina, strength, flexibility, power, speed, coordination, agility, balance, and accuracy.” Of course, not everyone agrees that these are the primary 10 physical skills, nor that all physical skills are created equal.

Strength: Force produced against an external resistance. When you’re lifting a barbell, the barbell acts as the external resistance. The more force you can produce, the stronger you are. Strength also makes all other physical attributes better.

Power: Power is strength displayed quickly. It’s the ability to contract a large amount of muscle units in a short amount of time. Examples of power in action: standing vertical jump, power clean, sprinting, punching.

Speed: The ability to minimize the time cycle of a repeated movement. This could mean running speed or how fast you can perform a repeated movement such as a barbell movement, jump rope, etc.

Agility: Ability to quickly change body position or direction of the body.

Muscular Endurance: Muscular endurance is the ability of a muscle or group of muscles to sustain repeated contractions against a resistance for an extended period of time. Long-distance and high-rep calisthenics (push-ups, pull-ups) are displays of muscular endurance.

Cardiovascular Endurance (better called Respiratory/Oxidative Efficiency): The ability for your body to gather, process, and deliver oxygen.

Glycolytic Efficiency: The ability of the body to convert glucose into the energy needed for muscle contraction during high intensity exercise, and the ability of your body to efficiently rid itself of lactate/hydrogen (the primary waste product of glycolosis).

Flexibility: Traditionally defined as having complete range of motion around a joint. A more useful definition according to Rippetoe is the “ability of the muscles that limit motion around a joint to extend beyond their resting length.”

Performance vs aesthetics: Two possible goals for training. Performance-based training is focused on improving a specific domain of fitness, be it strength, power, speed, or agility. Little or no attention is paid to how “shredded,” “ripped,” or “jacked” you look. Aesthetic-based training is focused on sculpting the body so that you look good, rather than on whether you’re stronger, faster, or more powerful.

Biomechanics and Kinesiology

When you read descriptions of exercises, writers will often use biomechanical and kinesiological terms to explain how the exercise is done. In this section you’ll find the most common words and phrases you’ll come across in the fitness literature.

Concentric Contraction: The contraction of a muscle, resulting in its shortening. When you curl a dumbbell up towards your body, that’s a concentric contraction. Concentric contractions generally cause less soreness and inflammation than eccentric contractions.

Eccentric (Negative) Contraction: The lengthening of a muscle under load. It’s the contraction that occurs in the “negative” or lowering part of a movement. For example, when you’re lowering the bar to your chest on the bench press, you experience an eccentric contraction in your chest muscles. Eccentric contractions generally cause more soreness and inflammation than concentric contraction, because more muscle damage occurs during this portion of the movement (which isn’t necessarily a bad thing).

Isometric Contraction: The contraction of a muscle without significant movement. For example, this is what your back, spinal erector muscles, and abdominals do during a squat or deadlift. They are in isometric contraction, but they aren’t the muscles doing the prime moving of the barbell. Really your entire “core” works this way. Its job is to stabilize, via isometric contraction, the entire trunk, so that no energy is lost between the base of support (the floor) and the load (the barbell). Another example, is when bodybuilders “flex” their muscles to force blood into the muscles without actually moving the joints that the muscles cross.

Compound Movement: Exercises or movements that involve more than one joint and muscle group. Squats, deadlift, bench press, shoulder press, power cleans, and pull-ups are examples of compound movements. The benefits of compound movements are many; they give the biggest bang for your buck for the time spent on them, they work the body as a complete system instead of piece-by-piece, they create a major hormonal response that causes your body to produce more testosterone and growth hormone (naturally), and they get you bigger and stronger faster than anything else.

Isolation Movement: Exercises or movements that involve only one joint and a limited number of muscle groups. Examples: bicep curls, leg curls, hamstring curls, tricep extensions. The benefits of isolation movements are almost entirely aesthetic — they cause more sarcoplasmic hypertrophy (muscle storage growth) than heavy compound movements, which can lead to larger-looking muscles, but not necessarily stronger muscles.

Supplemental Exercise: A supplemental exercise is usually a compound exercise performed immediately after the main exercise for the purpose of bolstering, supporting, and improving the main exercise. For example, if bench press is your main exercise for the day, you may then switch to heavy dumbbell bench presses as the supplemental exercise for the day.

Accessory/Auxiliary Exercise: Accessory exercises are performed after the main and supplemental exercises for the purposes of increased work capacity, antagonist muscle training (the opposite of the main muscle groups you just trained), hypertrophy, prehab, rehab, and support of the main lifts. Pull-ups, bicep curls, and ab work are good examples of auxiliary exercises to a barbell strength training program.

Plyometrics: A type of exercise that involves a rapid eccentric contraction followed quickly by explosive concentric contraction. Used to increase power and speed. The most common plyometric exercises involve jumping movements. Usually you jump down from a box and then immediately jump back on top of it over and over again. Care must be taken with plyometrics as they put a lot of stress on the joints and tendons. Other plyometric options are explosive push-ups, and various medicine ball throws.

Midline: A kinesiology term describing an imaginary line running down the middle of the body, and separating its right and left sides.

Flexion/Extension: Movements that affect the angle between two parts of the body. Flexion movements decrease the angle between a segment and its proximal segment. Bending the elbow towards you in a bicep curl is a flexion movement because the angle between your forearm and bicep decreases. Squatting down is a flexion movement because the angle between your thigh and calf decreases

Extension movements increase the angle between a segment and its proximal segment. Straightening your elbow in a tricep pushdown is extension. Rising up from a squat uses hip and knee extension. Straightening up in a deadlift also uses hip and knee extension.

Supination/Pronation: Rotation of the foot or forearm so that the sole or palm face anteriorly (supination) or posteriorly (pronation). When your palms face out from your body, they’re in a supine position; when they face in, they’re pronated. “Overhanded” grip on deadlifts or pull-ups is pronation. “Underhanded” grip is supination.

Adduction/Abduction: Abduction and adduction refer to motions that move a structure away from or towards the center of the body.

Abduction occurs when a body part moves away from the midline of the body. When you lift your arms so your hands are level with your shoulders (like you would in lateral raises), that’s abduction of the shoulder. When you shove your knees out in a squat, that’s abduction (the outside muscles of your butt are the primary abductors).

Adduction is when body parts move towards the midline of the body. When you lower your arms down to your side that’s adduction of the shoulder. When your knees come back in as you stand up in a squat, your adductors (the inside of your thigh) are at work.

Internal/External Rotation (Medial/ Lateral): Internal rotation is rotation of an appendage towards the midline of the body. External rotation is rotation away from the midline of the body.

Stretch Reflex: When a muscle is quickly lengthened under load (eccentric phase) a rebound effect takes place much like a quick stretching of a rubber band. This is why it is harder to pull a deadlift from the floor and reset each rep than to touch-and-go each rep after the first rep. It would also be much more difficult to start a bench press or squat from the bottom as opposed to the top.


If you want to understand what’s happening in your body when you get stronger, you need a basic understanding of physiology when it comes to how muscles increase in size and strength.

Motor Neuron: Nerve cell that sends signals to muscle fibers to contract. Motor neurons come in different sizes depending on the number and type of muscle fibers they are attached to. One motor neuron could signal just a few muscle fibers or up to thousands to contract.

Muscle Fiber: Long, cylindrical cells that muscles are made up of. Muscle fibers are what give skeletal muscle their striped or striated appearance.

Slow Twitch Fibers: Also known as Type I fibers. Type of muscle fiber that relies on oxygen and fatty acids to produce the energy/ATP (more on that in a bit) necessary to fuel muscle contraction. Slow twitch fibers get their name because the oxygen-dependent process they use to produce ATP takes much longer than the process fast twitch fibers use. Slow twitch fibers are smaller, generate less force, and have less potential for enlargement than fast twitch fibers. Slow twitch fibers, however, are very resistant to fatigue. They are what you use to stand, sit up straight, and walk. Exercise that requires muscular endurance — such as long-distance running — use more slow twitch fibers.

Fast Twitch Fibers: Also known as Type IIA or Type IIB; when it comes to strength training, the focus is on Type IIB. Type of muscle fiber that relies on glycolysis — or the breakdown of glycogen — to create the ATP necessary to fuel muscle contraction. Fast twitch fibers get their name because glycolysis produces ATP much more quickly than the oxygen-dependent process utilized by slow twitch fibers. Fast twitch fibers are much larger, can generate much more force, and have more potential for enlargement than slow twitch fibers. Fast twitch fibers, however, fatigue much more quickly than slow twitch fibers.

You use fast twitch fibers when you lift heavy weight or when you sprint. Strength training increases the size of fast twitch fibers as well as increases the number of fast twitch fibers in your body, which results in you becoming stronger.

All or None Muscle Principle: A muscle fiber contracts at 100% or it doesn’t contract at all. Therefore, if you lift a weight that is 50% of your max, then 50% of the potential muscle fibers that could be used to lift that weight contract at 100% and the rest of them don’t contract at all. It is not possible for 100% of your muscle fibers to contract at 50% of their power. Therefore, in order to utilize ALL the potential muscle fibers used in lifting a weight, then either 100% of your max must be lifted OR more repetitions must be performed, so that as muscle fibers fatigue, new fresh muscle fibers are called upon to “pick up the slack.”

ATP: Short for adenosine triphospate (3 phosphates). Essentially it’s the scientific word for the body’s energy. It’s an enzyme responsible for transporting energy in all cellular processes in the body. ATP is required for muscle contraction, thus it is an extremely important molecule when it comes to strength. More ATP and better ATP processing = more strength.

ATP can be produced in three ways:

The recycling of previously stored ATP by creatine phosphate (nerd alert: ATP breaks off one of its phosphates in the energy use process, and becomes adenosine diphosphate. Creatine phosphate then comes along and says, “Hey, ADP, you can have my phosphate,” turning it back into ATP to be utilized as energy again, which is another reason why creatine phosphate is awesome)
Through non-oxygen dependent glucose metabolism (glycolysis)
Through oxygen-dependent metabolism that utilizes fatty acids (oxidization).
Muscle cells are always using oxidation of fatty acids to produce ATP during aerobic respiration (we never stop breathing). However, when large amounts of energy are needed, such as in a heavy set of squats, your muscle cells deplete whatever stored ATP you have. To replenish stores, the body uses creatine phosphate to recycle used ATP. If the exercise lasts for more than 10-12 seconds (like when lifting for reps or sprinting), muscle cells begin to use glycolysis (or the burning of glycogen/carbs) to replenish ATP stores. Glycolysis produces large amounts of ATP, but the buildup of hydrogen ions and lactate make it unsustainable over long periods of time. This is why high intensity exercise can only last for a few minutes before the intensity must reduce and ATP must go back to being primarily produced by the oxidative (aerobic) system.

Strength training both increases the ability of muscle cells to store more ATP as well as increases the number of enzymes necessary for ATP production.

Creatine Phosphate: Molecule that helps in recycling used ATP. When your body has more creatine in the bloodstream, muscle cells can produce ATP faster. You can get creatine naturally from your diet, but supplementing with a creatine powder is much more efficient, and is dirt cheap.

Anaerobic Energy System: The chemical and metabolic pathways within cells that don’t rely on oxygen to create ATP. The recycling of stored ATP by creatine and glycolysis are both anaerobic energy systems. Fast twitch muscle fibers rely primarily on anaerobic energy systems.

Aerobic Energy System: The chemical and metabolic pathways within cells that rely on oxygen to create ATP. The aerobic energy system depends upon the presence of oxygen and uses fatty acids as well as the products of glycolysis to create ATP. Aerobic energy systems provide ATP at a much slower rate than anaerobic energy systems. Slow twitch muscle fibers rely primarily on aerobic energy systems.

Lactate: Product of glycolysis. Can be used by aerobic energy systems to produce more ATP through a process called the Krebs cycle.

Oxidation: The production of energy from the respiratory process in which you breathe in oxygen and that oxygen then “oxidizes” (or reacts with) fatty acids. This is the same process you see when you cut an avocado in half (avocados are primarily fat) and leave it on the counter. It turns brown through the process of oxidization. The exact same thing happens in our body through the cardio-respiratory process.

Fatty Acids: Lipids used to create ATP when muscle cells are using aerobic energy systems. Oxygen must be present in order for muscle cells to convert fatty acids into ATP.

Glycolosis: The metabolic pathway that converts glucose into ATP/energy.

Glycogen: Glucose stored in your muscles. Used during glycolosis to create ATP/energy.

Hypertrophy: An increase in muscle size.

Atrophy: A decrease in muscle size.

Anabolism: The metabolic process that leads to molecular growth. In the case of strength training, when your body is in an anabolic state, muscle mass increases. Hormones such as testosterone, insulin, and human growth hormone all contribute to anabolism. Strength training, proper diet, and rest help create the positive hormonal adaptation necessary for your body to be in an anabolic state.

Catabolism: The metabolic process that leads to molecular breakdown. In the case of strength training, when your body is chronically in a catabolic state, muscle mass decreases. Hormones such as cortisol and adrenaline contribute to catabolism. Catabolism isn’t entirely bad. In fact, anabolism requires catabolism. Catabolism only becomes a problem when it’s chronic due to over-stress.

Delayed onset muscle soreness (DOMS): Muscular soreness due to inflammation that often occurs 1-2 days after unaccustomed exercise. Also called “myositis.”

Basic Definitions for Exercise Words and Phrases


Activities of Daily Living (ADLs)- Physical tasks of everyday living, such as bathing, and walking up the stairs. ADLs are usually factored in to a person’s basal metabolic rate, so tracking calories burned for these types of movement isn’t recommended when trying to lose weight.

Aerobic exercise Any rhythmic activity that increases the body’s need for oxygen by using large muscle groups continuously for at least 10 minutes. The term aerobic means “with oxygen.”

Agonist muscle- A muscle that is very effective in causing a certain joint movement. Also called the prime mover.On a biceps curl, the biceps is the agonist muscle that flexes the elbow joint.


Amenorrhea- The absence of menstruation, commonly found in women with a very low body fat percentage and/or exercise excessively.

Anaerobic exercise Short lasting, high intensity activity, where the demand for oxygen from the exercise exceeds the oxygen supply.

Angina pectoris- Chest pain due to lack of blood flow (oxygen) to the heart.

Antagonist muscle A muscle that causes movement at a joint in a direction opposite to that of the joint’s agonist (prime mover).

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Beta-blockers Type of medication that reduces heart rate. Exercisers who take beta-blockers will have a lower heart rate at rest and during exercise, so the target heart rate formula cannot be used in this case.

Bioelectrical impedance This method of measuring body composition is based on the fact that the lean tissue of the body is much more conductive due to its higher water content than fat tissue. The more lean tissue present in the body, the greater the conductive potential, measured in ohms.

Body composition Amount of fat vs. lean muscle tissue in the human body.

Body Mass Index (BMI)- Measure of the relationship between height and weight; calculated by dividing weight in kilograms by height in centimeters squared. 

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Caffeine- A stimulant found in coffee, tea, chocolate, and some soft drinks that increases heart contractions, oxygen consumption, metabolism, and urinary output.

Calisthenics Exercising using one’s own body weight which helps develop muscular tone.

Cardiorespiratory fitness- Measure of the heart’s ability to pump oxygen-rich blood to the muscles. Also called cardiovascular or aerobic fitness.

Cardiovascular system- A complex system consisting of the heart and blood vessels; transports nutrients, oxygen, and enzymes throughout the body and regulates temperature, water levels of cells, and acidity levels of body components.

Circuit training Takes the participant through a series of exercise stations (which could also include strength training), with relatively brief rest intervals between each station. The purpose is to keep the heart rate elevated near the aerobic level without dropping off. The number of stations may range from 4 to 10.

Concentric muscle action- Force produced while the muscle is shortening in length.

Continuous training This is the most common type of sustained aerobic exercise for fitness improvement, slowly adding more time to the workout to increase endurance.

Cool down Lowering of body temperature following vigorous exercise. The practice of cooling down after exercise involves slowing down your level of activity gradually.

Core A muscle group comprised of the abdominals, lower back, obliques, and hips.

Cortisol- A hormone secreted by the adrenal gland that makes stored nutrients more readily available to meet energy demands. These hormone levels increase under stress, which can stimulate your appetite, leading to weight gain or difficulty losing weight.

Cross-training– An individualized combination of all aerobic-training methods, characterized by a variety of intensities and modes.

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Detraining Principle This principle says that once consistent exercise stops, you will eventually lose the strength that you built up. Without overload or maintenance, muscles will weaken in two weeks or less.

Diastolic blood pressure- The pressure exerted by the blood on the vessel walls during the resting portion of the cardiac cycle, measured in millimeters of mercury.The diastolic number is the bottom of the fraction. 120/80 is an average value for normal blood pressure (80 is the diastolic number). Mild high blood pressure is considered to be between 140/90 and 160/95. High blood pressure is defined by a value greater than 160/95.

DOMS (Delayed Onset Muscle Soreness)- Muscle soreness or discomfort that appears 12 to 48 hours after exercise. It is most likely due to microscopic tears in the muscle tissue, and it usually requires a couple of days for the repair and rebuilding process to be completed. The muscle tissue grows back stronger, leading to increased muscle mass and strength.

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Eccentric contraction- A lengthening of the muscle during its contraction; controls speed of movement caused by another force.

Ectomorph A body shape characterized by a narrow chest, narrow shoulders and long, thin muscles.

Electrolytes- Salts (ions) found in bodily fluids. Pertaining to exercise, your body loses electrolytes (sodium, potassium) when you sweat. These electrolytes need to be replaced to keep concentrations constant in the body, which is why many sports drinks include electrolytes.

Endomorph A body shape characterized by a round face, short neck , wide hips, and heavy fat storage.

Endorphins- Opiate-like hormones that are manufactured in the body and contribute to natural feelings of well-being.

EPOC (Excess Post-Exercise Oxygen Consumption)- This explains why your breathing rate remains heavy for a few minutes after finishing a workout. Your body needs more oxygen after a workout in order to restore the oxygen stores in the blood and tissues, and to meet the oxygen requirements of the heart rate, which is still elevated.

Epinephrine- Also called adrenaline, a hormone that stimulates body systems in response to stress.

Ergogenic aids A substance, appliance, or procedure that improves athletic performance.

Eustress- “Good” stress that presents opportunities for personal growth. (Exercise is an example of this. It puts stress on the body and its systems, but the results of this stress are positive.)

Exercise metabolic rate (EMR)- The energy expenditure that occurs during exercise.

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Fast twitch muscle fibers Fibers that are better-suited for high-force, short duration activities because they contain more stores for anaerobic energy utilization.

Fixed resistance Strength training exercises that provide a constant amount of resistance throughout the full range of motion. Examples include free weights and resistance bands.

Flexibility- The measure of the range of motion, or the amount of movement possible, at a particular joint.

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Graded Exercise Test (Incremental Exercise Test)- An exercise test involving a progressive increase in work rate over time. Often graded exercise tests are used to determine the subject’s maximum oxygen consumption or lactic threshold.

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Heart Rate Reserve (HRR) Difference between resting and maximal heart rate.

Heat Cramps- Muscle cramps that occur during or following exercise in warm or hot weather.

Heat exhaustion- A heat stress illness caused by significant dehydration resulting from exercise in warm or hot conditions; frequent precursor to heat stroke.

Heat stroke- A deadly heat stress illness resulting from dehydration and overexertion in warm or hot conditions; can cause body core temperature to rise from normal to 100 or 105 degrees Fahrenheit in just a few minutes.

High-density lipoprotein (HDL)- Retrieves cholesterol from the body’s cells and returns it to the liver to be metabolized. Also referred to as “good” cholesterol.

High impact- Activities that place more stress on the bones and joints, where your limbs are actually making contact with the ground or other surface with force. Examples include: walking, running, step aerobics, and sports that involve impact, like basketball or tennis.

Hydrostatic (underwater) weighing This method of measuring body composition is considered the “gold standard” and is based on the assumption that density and specific gravity of lean tissue is greater than that of fat tissue. By comparing test subject’s mass measured underwater and out of the water, body composition may be calculated.

Hyperplasia- An increase in the number of cells in a tissue; usually in reference to fat or muscle cells.

Hypertrophy- An increase in cell size (girth), usually in reference to fat or muscle cells.

Hypothermia- A life-threatening condition in which heat is lost from the body faster than it is produced.

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Incremental Exercise Test (Graded Exercise Test)- An exercise test involving a progressive increase in work rate over time. Often these tests are used to determine the subject’s maximum oxygen consumption or lactic threshold.

Interval training Repeated intervals of exercise interspersed with intervals of relatively light exercise. This type of training provides a means of performing large amounts of high-intensity exercise in a short period of time.

Isokinetic exercise- Exercise in which the rate of movement is constantly maintained through a specific range of motion even though maximal force is exerted.

Isometric exercise Any activity in which the muscles exert force but do not visibly change in length. For example, pushing against a wall or carrying a bag of groceries.

Isotonic exercise Any activity in which the muscles exert force and change in length as they lift and lower resistance. For example, bicep curls or leg extensions.

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Karvonen formula One of the most effective methods used to calculate target heart rate. It factors resting heart rate into the equation.

Ketosis- A condition in which the body adapts to prolonged fasting or carbohydrate deprivation by converting body fat to ketones, which can be used as fuel for some brain activity. The real danger in ketosis is that ketones are acidic, and high levels of ketones make the blood abnormally acid.

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Lactic acid Once thought of as a waste substance that builds up in the muscles when they are not getting enough oxygen, leading to muscle fatigue and soreness. Now, experts believe that lactic acid is beneficial to the body, acting as a “fuel” to help people continue high-intensity (anaerobic) exercise even when oxygen consumption is low.

Lactic threshold The point at which the level of lactic acid in the blood suddenly increases (during exercise). This is a good indication of the highest sustainable work rate. Also known as anaerobic threshold.

Lean mass- Total weight of your muscle, bone, and all other body organs. (Everything in the body besides fat.)

Low-density lipoprotein (LDL)- Transports cholesterol and triglycerides from the liver to be used in various cellular processes. Also referred to as “bad” cholesterol.

Low impact- Activities that place less stress on the bones and joints. These are better for people with joint pain, and overweight individuals whose weight can hurt their joints. Examples include: swimming, elliptical, cycling, and other activities where your feet (or other body parts) aren’t touching the ground with force or where you are somehow supported.

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Max VO 2 (V02 Max) Highest amount of oxygen one can consume during exercise. The higher this number, the more you are cardiovascularly fit and capable of increased levels of intensity.

Mesomorph A body shape characterized by a large chest, long torso, solid muscle structure and significant strength.

MET- An expression of the energy it takes to sit quietly. It is frequently used as a measure of intensity on cardiovascular machines (treadmill, stationary bike, etc.) For example, moderate intensity activities are those that get you moving fast enough or strenuously enough to burn off three to six times as much energy per minute as you do when you are sitting quietly, measured as 3-6 METs.

Moderate intensity Activities that range from 40-60% of max heart rate. These activities cause a slightly increased rate of breathing, and feel light to somewhat-hard. Individuals doing activity at this intensity can easily carry on a conversation.

Muscle fibers Individual muscle cells that are the functional components of muscles.

Muscular endurance The ability of the muscle to perform repetitive contractions over a prolonged period of time.

Muscular strength The ability of the muscle to generate the maximum amount of force.

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Obesity- A weight disorder generally defined as an accumulation of fat beyond that considered normal for a person based on age, sex, and body type.

One-Rep Max (1 RM)- The amount of weight/resistance that can be lifted or moved once, but not twice; a common measure of strength.

Opposing muscles Muscles that work in opposition to the ones you are training. For example, the bicep is the opposing muscle to the triceps; the hamstring is the opposing muscle to the quadriceps.

Osteoporosis- A disease characterized by low bone mass and deterioration of bone tissue, which increases risk of fracture.

Overload Principle This principle says that in order to train muscles, they must work harder than they are accustomed to. This “overload” will result in increased strength as the body adapts to the stress placed upon it.

Overuse Injuries- Injuries that result from the cumulative effects of repetitive (day-after-day) stresses placed on tendons, muscles, and joints.

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Percent grade- Measure of the elevation of a treadmill.

Physical fitness- The ability to perform regular to vigorous physical activity without great fatigue.

Pilates- Exercise programs that combine dynamic stretching with movement against resistance.

Plateau Point in an exercise program where no additional progress is being made (gains in strength, weight loss, increased endurance, etc). One way to break through a plateau is to change the kind of activity you are doing or something about your current activity- adding hills, increasing speed, increasing distance, etc.

PNF stretching– Proprioceptive neuromuscular facilitation (PNF) stretching is a static stretch of a muscle immediately after maximally contracting it.

Primary prevention- Actions designed to stop problems before they start.

Pronation– To turn or rotate (the foot) so that the inner edge of the sole bears the body’s weight.

Plyometric training- Exercises that enable a muscle to reach maximal force production in as short a time as possible. For example, jumping from a 3 ft. stool to the ground and immediately springing back up to another stool.

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Rate of perceived exertion (RPE)- Scale of 1-10 that rates how you are feeling (both physically and mentally) as it relates to exercise fatigue.

Repetition- The number of times an exercise is repeated within a single exercise “set.”

Resistance training- See “Strength training”

Resting HR- Rate at which your heart beats at rest (while sitting or being inactive). Low resting heart rates are a good measure of health and fitness.

Resting Metabolic Rate (RMR)- Number of calories expended to maintain the body during resting conditions. Also referred to as basal metabolic rate.

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Set- A basic unit of a workout containing the number of times (repetitions) a specific exercise is done (e.g. do 3 sets of 5 repetitions with 100 pounds).

Shin splint Generic term used to describe pain in the lower leg, either on the medial (inside) or lateral side (outside) of the shin bone.

Sit and reach test- A common fitness test that determines flexibility (of the hamstrings and lower back).

Skinfold caliper test- A method of determining body fat whereby folds of skin and fat at various points on the body are grasped between thumb and forefinger and measured with calipers.

Skin fold measurements This method of measuring body composition assumes that substantial fat is proportional to overall body fat, and thus by measuring several sites, total body fat may be calculated.

Slow twitch muscle fibers Fibers that are better-suited for low-force, long duration activities because they possess more endurance enzymes.

Specificity of Training Principle This principle says that only the muscle or muscle group you exercise will respond to the demands placed upon it. By regularly doing curls, for example, the muscles involved (biceps) will become larger and stronger, but curls will have no effect on the muscles that are not being trained. Therefore, when strength training, it is important to strengthen all of the major muscles.

Static stretching A low force, high-duration stretch where the muscle is held at the greatest possible length for up to 30 seconds.

Strength training (resistance training)- The process of exercising with progressively heavier resistance for the purpose of strengthening the musculoskeletal system.

Systolic blood pressure The pressure exerted on the vessel walls during ventricular contraction, measured in millimeters of mercury. The systolic number is the top of the fraction. 120/80 is an average value for normal blood pressure (120 is the systolic number). Mild high blood pressure is considered to be between 140/90 and 160/95. High blood pressure is defined by a value greater than 160/95.

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Tai chi- An ancient Chinese form of exercise, widely practiced in the West today, that promotes balance, coordination, stretching, and meditation.

Talk test Method to ensure you are working out at a level where you can answer a question but not comfortably carry on a conversation. This is a good intensity level for weight loss and improved physical fitness.

Tapering- The process athletes use to reduce their training load for several days prior to competition.

Target heart rate (THR)- The recommended range is 60-85% of your maximum heart rate. It represents a pace that ensures you are training aerobically and can reasonably be maintained.

Tension Principle– This principle says that tension is created by resistance, which can come from weights, bands, machines, or body weight.

Testosterone- The steroid hormone produced in the testes; involved in growth and development of muscle mass. Since men have more testosterone than women, they are able to gain muscle mass more easily.

Thyroid- Endocrine gland located in the neck that secretes T3 and T4 (hormones), which increase metabolic rate.

Type I muscle fibers- Fibers that contain large numbers of oxidative enzymes and are highly fatigue resistant (more prevalent in endurance athletes).

Type IIA muscle fibers- Fibers that contain biochemical and fatigue characteristics that are between Type IIB and Type I fibers (the best of both worlds).

Type IIB muscle fibers- Fibers that have a relatively small number of mitochondria, a limited capacity for aerobic metabolism, and are less resistant to fatigue than slow fibers (more prevalent in sprinters and power lifters).

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Variable resistance Strength training exercises that change the amount of resistance throughout the full range of motion.

Vigorous intensity Activities above 60% of max heart rate. These activities cause an increased rate of breathing, sweating, and feel somewhat-hard to hard.

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Waist to hip ratio- A calculation of the proportion of fat stored on your body around your waist and hips. Formula: waist measurement divided by hip measurement. Women should have a ratio of 0.8 or less; men should have a ratio of .95 or less.

Warm up To prepare for an athletic event (whether a game or a workout session) by exercising, stretching, or practicing for a short time beforehand.

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Yoga- A variety of Indian traditions geared toward self-discipline and the realization of unity; includes forms of exercise widely practiced in the West today that promote balance, coordination, flexibility, and meditation.


Neurology – Applied


The brain is highly complex, it contains about 1000 billion neurons, and weighs about 3 lbs in adults.

There are four main areas of the brain:

  1. The brain stem is at the base of the brain where it joins the spinal chord (contains the medulla, pons, and mid brain)
  2. The diencephalon is above the brain stem (contains the thalamus and hypothalamus)
  3. The cerebrum is above the diencephalon and forms the majority of the brain
  4. The cerebellum is the lower back of the brain

The brain has two hemispheres , there are functional differences, for example the left had side of the brain controls the right hand side of the body and visa versa (lateralisation).






Neurotransmitters are substances which excite or inhibit the neurons of the brain, facilitating communication between brain cells. These include endorphins, neuropeptides.

Cerebrospinal fluid circulates around the brain and spinal tracts to provide protection in addition to that provided by the meninges and protective bones of the spine and skull. A lumbar puncture (spinal tap) is where a needle is placed between the vertebra in the lower back. A sample of cerebrospinal fluid might be taken to see if cancerous cells have entered the CNS, or chemotherapy might be administrated to prevent or combat CNS involvement.

The Sensory Systems

A receptor or sense organ picks up stimulus and converts it into a nerve impulse. This impulse is then conducted along a neural pathway to the brain, where the signal is converted into a sensation. There are various receptors:

  • Cutaneous (skin) senses. The skin contains specialist receptors for touch, pressure, vibration, hot, cold, and pain.
  • Proprioceptive (muscle) sensations inform us of the activities and current posture of the muscles.
  • Integrative sensations are not well defined but include memory, sleep, emotions etc.
  • Olfactory sensations (smell). Olfactory neurons have dendrites that are connected to fine hairs in the nose that react to odours.
  • Gustatory sensations (taste) there are about 2000 taste buds, mostly on the tongue and a few in the throat. Taste buds contain gustatory cells which contain sensitive hair like processes.
  • Ophthalmic sensations (sight). The retina of the eye converts light into nerve impulses which are transmitted to the optic nerve. Retinoblastoma is a rare tumour in the cells of the retina.
  • Auditory senses (hearing). Sound waves cause fine hairs in the inner ear to vibrate generating nerve impulses.
  • Equilibrium (sense of balance) the ear also contains receptors that give a sense of static equilibrium (position of the head) and dynamic equilibrium (sudden movements).



The Autonomic Nervous system (ANS)

The nerves of the ANS activate the involuntary smooth muscles, cardiac muscles, and some glands.

Controls our autonomous involuntary functions such as heart rate, perspiration, pupil dilation and digestion. Also controls some voluntary functions such as breathing and swallowing.

Functions of the Nervous System

The complex activities of the body are controlled jointly by the Endocrine and the Nervous systems. As opposed to the Endocrine system the Nervous system has a more or less instant effect on the body via a complex network of nerves and control centres. The Central Nervous System (CNS) includes the brain and spinal cord, while Peripheral Nervous System (PNS) includes nerves connected to the spinal cord. The nervous system can be further divided into sub-systems, all of which are composed of neurons and connective tissue:

Nervous system




Nervous System Chart


About Neurons

Neurons are specialised cells of the nervous system, they vary greatly in appearance and length, but contain a similar structure:

  • Axons are long nerve processes which carry nerve impulses from the Soma to other neurons, they vary in length but can become almost as long as half of the human body.
  • The soma (body) of the neuron contains the nucleus which acts as the cell’s control centre, these contain many small neurofibrils which project from the nucleus into the dendrites.
  • Dendrites are short, thick processes which branch out of the soma in a tree like manor. They conduct nerve impulses to the soma.

The three categories of neurons:

  • Afferent (Sensory) Neurons have the dendrites connected to receptors such as the eyes, ears etc. These receptors change the information they receive into electrical impulses that are transmitted to other neurons. In sensory neurons the axons are connected to other neurons.
  • Efferent (Motor) Neurons have the dendrites connected to other neurons, the axons are connected to effectors. Effectors are either glands or a muscle cell that is the receiving end of the nerve impulse. The nerve, when excited will cause the effector to react (move, contract, or secrete etc).
  • Internuncial Neurons have both the dendrites and the axons are connected to other neurons. They are sometimes referred to as connector neurons. Internuncial neurons are found throughout the body, but especially in the spinal cord and brain.

Properties and characteristics of Neurons:

  • Normally the electrical impulses (messages) travel through a neuron in only one direction.
  • The axon may be surrounded by a ‘coat’ of lipids (fats) and proteins known as the myelin sheath which acts as an insulator.
  • Neurons are specialist cells that have lost the ability to reproduce themselves. Once the soma of a neuron has died the entire neuron dies, and can never be replaced.
  • Repair of damaged neurons only occurs in myelinated neurons.
  • white matter are coloured by myelin, consisting of many neurons supported by neuroglia.
  • grey matter is soma and dendrites or bundles of unmyelinated axons and neuralgia.

Nerves, Neuroglia, and Ganglia

nerve is a bundle of fibres (axons and/or dendrites) outside the CNS.

Neuroglia are cells of the nervous system that help protect and support it.

Ganglia are groups of nerve cell bodies lying outside the CNS.












The Spinal Cord

A spinal tract is a bundle of fibres in the CNS that travel long distances up or down the spinal cord. Ascending tracts carry impulses up the cord to the brain, while descending tracts carry impulses down the cord from the brain. Tracts run along the spinal canal inside the protective spinal column, conveying sensory and motor (movement ) information to and from the brain. Spinal meninges are tough tubes of tissue which protect the cord.

The Nervous System Glossary

absolute refractory period: time during an action period when another action potential cannot be generated because the voltage-gated Na+ channel is inactivated

action potential: change in voltage of a cell membrane in response to a stimulus that results in transmission of an electrical signal; unique to neurons and muscle fibers

activation gate: part of the voltage-gated Na+ channel that opens when the membrane voltage reaches threshold

astrocyte: glial cell type of the CNS that provides support for neurons and maintains the blood-brain barrier

autonomic nervous system (ANS): functional division of the nervous system that is responsible for homeostatic reflexes that coordinate control of cardiac and smooth muscle, as well as glandular tissue

axon hillock: tapering of the neuron cell body that gives rise to the axon

axon segment: single stretch of the axon insulated by myelin and bounded by nodes of Ranvier at either end (except for the first, which is after the initial segment, and the last, which is followed by the axon terminal)

axon terminal: end of the axon, where there are usually several branches extending toward the target cell

axon: single process of the neuron that carries an electrical signal (action potential) away from the cell body toward a target cell

axoplasm: cytoplasm of an axon, which is different in composition than the cytoplasm of the neuronal cell body

biogenic amine: class of neurotransmitters that are enzymatically derived from amino acids but no longer contain a carboxyl group

bipolar: shape of a neuron with two processes extending from the neuron cell body—the axon and one dendrite

blood-brain barrier (BBB): physiological barrier between the circulatory system and the central nervous system that establishes a privileged blood supply, restricting the flow of substances into the CNS

brain: the large organ of the central nervous system composed of white and gray matter, contained within the cranium and continuous with the spinal cord

central nervous system (CNS): anatomical division of the nervous system located within the cranial and vertebral cavities, namely the brain and spinal cord

cerebral cortex: outermost layer of gray matter in the brain, where conscious perception takes place

cerebrospinal fluid (CSF): circulatory medium within the CNS that is produced by ependymal cells in the choroid plexus filtering the blood

chemical synapse: connection between two neurons, or between a neuron and its target, where a neurotransmitter diffuses across a very short distance

cholinergic system: neurotransmitter system of acetylcholine, which includes its receptors and the enzyme acetylcholinesterase

choroid plexus: specialized structure containing ependymal cells that line blood capillaries and filter blood to produce CSF in the four ventricles of the brain

continuous conduction: slow propagation of an action potential along an unmyelinated axon owing to voltage-gated Na+ channels located along the entire length of the cell membrane

dendrite: one of many branchlike processes that extends from the neuron cell body and functions as a contact for incoming signals (synapses) from other neurons or sensory cells

depolarization: change in a cell membrane potential from rest toward zero

effector protein: enzyme that catalyzes the generation of a new molecule, which acts as the intracellular mediator of the signal that binds to the receptor

electrical synapse: connection between two neurons, or any two electrically active cells, where ions flow directly through channels spanning their adjacent cell membranes

electrochemical exclusion: principle of selectively allowing ions through a channel on the basis of their charge

enteric nervous system (ENS): neural tissue associated with the digestive system that is responsible for nervous control through autonomic connections

ependymal cell: glial cell type in the CNS responsible for producing cerebrospinal fluid

excitable membrane: cell membrane that regulates the movement of ions so that an electrical signal can be generated

excitatory postsynaptic potential (EPSP): graded potential in the postsynaptic membrane that is the result of depolarization and makes an action potential more likely to occur

G protein: guanosine triphosphate (GTP) hydrolase that physically moves from the receptor protein to the effector protein to activate the latter

ganglion: localized collection of neuron cell bodies in the peripheral nervous system

gated: property of a channel that determines how it opens under specific conditions, such as voltage change or physical deformation

generator potential: graded potential from dendrites of a unipolar cell which generates the action potential in the initial segment of that cell’s axon

glial cell: one of the various types of neural tissue cells responsible for maintenance of the tissue, and largely responsible for supporting neurons

graded potential: change in the membrane potential that varies in size, depending on the size of the stimulus that elicits it

gray matter: regions of the nervous system containing cell bodies of neurons with few or no myelinated axons; actually may be more pink or tan in color, but called gray in contrast to white matter

inactivation gate: part of a voltage-gated Na+ channel that closes when the membrane potential reaches +30 mV

inhibitory postsynaptic potential (IPSP): graded potential in the postsynaptic membrane that is the result of hyperpolarization and makes an action potential less likely to occur

initial segment: first part of the axon as it emerges from the axon hillock, where the electrical signals known as action potentials are generated

integration: nervous system function that combines sensory perceptions and higher cognitive functions (memories, learning, emotion, etc.) to produce a response

ionotropic receptor: neurotransmitter receptor that acts as an ion channel gate, and opens by the binding of the neurotransmitter

leakage channel: ion channel that opens randomly and is not gated to a specific event, also known as a non-gated channel

ligand-gated channels: another name for an ionotropic receptor for which a neurotransmitter is the ligand

lower motor neuron: second neuron in the motor command pathway that is directly connected to the skeletal muscle

mechanically gated channel: ion channel that opens when a physical event directly affects the structure of the protein

membrane potential: distribution of charge across the cell membrane, based on the charges of ions

metabotropic receptor: neurotransmitter receptor that involves a complex of proteins that cause metabolic changes in a cell

microglia: glial cell type in the CNS that serves as the resident component of the immune system

multipolar: shape of a neuron that has multiple processes—the axon and two or more dendrites

muscarinic receptor: type of acetylcholine receptor protein that is characterized by also binding to muscarine and is a metabotropic receptor

myelin sheath: lipid-rich layer of insulation that surrounds an axon, formed by oligodendrocytes in the CNS and Schwann cells in the PNS; facilitates the transmission of electrical signals

myelin: lipid-rich insulating substance surrounding the axons of many neurons, allowing for faster transmission of electrical signals

nerve: cord-like bundle of axons located in the peripheral nervous system that transmits sensory input and response output to and from the central nervous system

neuron: neural tissue cell that is primarily responsible for generating and propagating electrical signals into, within, and out of the nervous system

neuropeptide: neurotransmitter type that includes protein molecules and shorter chains of amino acids

neurotransmitter: chemical signal that is released from the synaptic end bulb of a neuron to cause a change in the target cell

nicotinic receptor: type of acetylcholine receptor protein that is characterized by also binding to nicotine and is an ionotropic receptor

node of Ranvier: gap between two myelinated regions of an axon, allowing for strengthening of the electrical signal as it propagates down the axon

nonspecific channel: channel that is not specific to one ion over another, such as a nonspecific cation channel that allows any positively charged ion across the membrane

nucleus: in the nervous system, a localized collection of neuron cell bodies that are functionally related; a “center” of neural function

oligodendrocyte: glial cell type in the CNS that provides the myelin insulation for axons in tracts

peripheral nervous system (PNS): anatomical division of the nervous system that is largely outside the cranial and vertebral cavities, namely all parts except the brain and spinal cord

postsynaptic potential (PSP): graded potential in the postsynaptic membrane caused by the binding of neurotransmitter to protein receptors

precentral gyrus of the frontal cortex: region of the cerebral cortex responsible for generating motor commands, where the upper motor neuron cell body is located

process: in cells, an extension of a cell body; in the case of neurons, this includes the axon and dendrites

propagation: movement of an action potential along the length of an axon

receptor potential: graded potential in a specialized sensory cell that directly causes the release of neurotransmitter without an intervening action potential

refractory period: time after the initiation of an action potential when another action potential cannot be generated

relative refractory period: time during the refractory period when a new action potential can only be initiated by a stronger stimulus than the current action potential because voltage-gated K+ channels are not closed

repolarization: return of the membrane potential to its normally negative voltage at the end of the action potential

resistance: property of an axon that relates to the ability of particles to diffuse through the cytoplasm; this is inversely proportional to the fiber diameter

response: nervous system function that causes a target tissue (muscle or gland) to produce an event as a consequence to stimuli

resting membrane potential: the difference in voltage measured across a cell membrane under steady-state conditions, typically -70 mV

Schwann cell: glial cell type in the PNS that provides the myelin insulation for axons in nerves

saltatory conduction: quick propagation of the action potential along a myelinated axon owing to voltage-gated Na+ channels being present only at the nodes of Ranvier

satellite cell: glial cell type in the PNS that provides support for neurons in the ganglia

sensation: nervous system function that receives information from the environment and translates it into the electrical signals of nervous tissue

size exclusion: principle of selectively allowing ions through a channel on the basis of their relative size

soma: in neurons, that portion of the cell that contains the nucleus; the cell body, as opposed to the cell processes (axons and dendrites)

somatic nervous system (SNS): functional division of the nervous system that is concerned with conscious perception, voluntary movement, and skeletal muscle reflexes

spatial summation: combination of graded potentials across the neuronal cell membrane caused by signals from separate presynaptic elements that add up to initiate an action potential

spinal cord: organ of the central nervous system found within the vertebral cavity and connected with the periphery through spinal nerves; mediates reflex behaviors

stimulus: an event in the external or internal environment that registers as activity in a sensory neuron

summate: to add together, as in the cumulative change in postsynaptic potentials toward reaching threshold in the membrane, either across a span of the membrane or over a certain amount of time

synapse: narrow junction across which a chemical signal passes from neuron to the next, initiating a new electrical signal in the target cell

synaptic cleft: small gap between cells in a chemical synapse where neurotransmitter diffuses from the presynaptic element to the postsynaptic element

synaptic end bulb: swelling at the end of an axon where neurotransmitter molecules are released onto a target cell across a synapse

temporal summation: combination of graded potentials at the same location on a neuron resulting in a strong signal from one input

thalamus: region of the central nervous system that acts as a relay for sensory pathways

thermoreceptor: type of sensory receptor capable of transducing temperature stimuli into neural action potentials

threshold: membrane voltage at which an action potential is initiated

tract: bundle of axons in the central nervous system having the same function and point of origin

unipolar: shape of a neuron which has only one process that includes both the axon and dendrite

upper motor neuron: first neuron in the motor command pathway with its cell body in the cerebral cortex that synapses on the lower motor neuron in the spinal cord

ventricle: central cavity within the brain where CSF is produced and circulates

voltage-gated channel: ion channel that opens because of a change in the charge distributed across the membrane where it is located

white matter: regions of the nervous system containing mostly myelinated axons, making the tissue appear white because of the high lipid content of myelin

Neurology Glossary

abdomen- the hindmost of an insect’s three major body sections; the center for digestion and reproduction (M. sexta Wax Model)


abdominal- relating to or involving the abdomen (M. sexta Wax Model)


action potential- an electrical signal that travels along the axon, away from the cell body to the axon terminal where it triggers the release of neurotransmitters (Virtual Neurons, Connect the Neurons)


action potential amplitude- The maximum amplitude of an action potential is a constant value, greater than 0mV. The total amplitude of an action potential is the displacement from the resting potential to the maximum amplitude, usually 70mV or more.


afferent- incoming information or neuronal connection; coming into or towards the central nervous system


amygdala- part of the brain involved in processing the memory of emotional reactions, notably fear and anger (Sheep Brain Dissection)


anterior- toward the front or the head, see also rostral (Sheep Brain Dissection)


arachnoid mater- middle layer of the 3 membranes surrounding and protecting the brain. The space between the arachnoid and pia mater contains many blood vessels that supply the brain.


association cortex- parts of cortex putting together and interpreting sensory information (Motor Learning)


audition- the sense of hearing; the ability to detect information from sound waves


axon- the neuronal process that sends the signal or message away from the cell body toward target cells or neurons (Connect the Neurons, Close-up of the Nervous System, Bead Neuron)


axon terminal- the very end part of an axon that makes a synaptic contact with another cell; the point where neurotransmitters are released (Connect the Neurons, Close-up of the Nervous System)


balance- the sense of body movement with respect to gravity


bilayer- two layers of lipid molecules with their water-liking sides facing outward and their water-hating sides facing each other; lipid bilayers form plasma membranes of cells and membranes of other organelles.


blood volume- the total amount of blood in a body


brainstem- the part of the central nervous system connecting the brain to the spinal cord. The brainstem contains pathways sending information to and receiving information from the spinal cord and peripheral nerves. It also contains neurons that control respiration and regulation of heart rhythms. (Sheep Brain Dissection)


carbohydrate- complex organic molecules composed of carbon, hydrogen, and oxygen that store energy and act as structural components of cells


caudal- towards the tail; the tail end of the nervous system


cell body- the bulbous part of the neuron, also called the soma, that contains the nucleus. Dendrites and axons are processes off of the cell body. (Bead Neuron)


central nervous system- the brain and spinal cord


cerebellum- the highly folded part of the central nervous system above or dorsal to the brainstem that helps control movement, balance, and muscle coordination (Sheep Brain Dissection, Close-up of the Nervous System, Mirror Image)


cerebral cortex- the largest and most complex part of the mammalian central nervous system; appears as tightly packed fat ridges (gyri) and narrow folds (sulci); responsible for all forms of conscious experience, including perception, emotion, thought, and planning. Cortex means barkin Greek; the bark of the cork tree looks a lot like the cerebral cortex. (Sheep Brain Dissection, Close-up of the Nervous System, Memory Items)


cerebral hemispheres- the two halves of the cerebral cortex. The left hemisphere is specialized for initiating speech, language, writing, and calculations. The right hemisphere is specialized for initiating spatial abilities, face recognition in vision, and some aspects of music perception and production




cerebrum- see cerebral cortex (Sheep Brain Dissection, Close-up of the Nervous System)


chemotaxis- when a growth cone follows chemical signals (chemo-) to move toward (-taxis) a desired target (Neuropathfinding, C. elegans + Alcohol, Chemotaxis using C. elegans)


circuit- sets of neurons connected in a pathway that perform a function; a neuronal circuit carries information from one point in the body or nervous system to another. A neuronal circuit is not like an electrical circuit where current must flow in a complete circle. A neuronal circuit uses electrical and chemical energy to carry information along a path. A neuronal circuit can have feedback and feed forward loops within it.


CNS- central nervous system consisting of the brain and spinal cord


corpus callosum- a large bundle of nerve fibers (myelinated axons) that link the right and left hemispheres of the brain; enables the two hemispheres to share information (Sheep Brain Dissection)


cranial nerve- twelve pairs of nerves that arise from each side of the brain stem numbered I to XII from anterior to posterior



declarative memory- see memory, declarative (Mirror Image, Your Incredible Memory)


dendrite- tree-like extension of the neuronal cell body; receives chemical neurotransmitter signals or messages from other neurons (Bead Neuron)


depolarize- movement of membrane potential to a higher (more positive) value

distal- away from, far end


dopamine- a neurotransmitter used in the brain’s reward circuit which signals a positive benefit to an action nor met expectation (Dendritic Spines Lab)



dorsal- toward the back of the body or top of the head (Sheep Brain Dissection)


dorsal horn- dorsal part of the spinal cord gray matter where axons from sensory neurons enter and make their first synapses (Close-up of the Nervous System)


dorsal root ganglion (DRG) neurons- sensory neurons for the skin and muscle; cell bodies of these sensory neurons are grouped in a structure called a ganglion just outside the spinal cord on the dorsal side. Thus they are called Dorsal Root Ganglion Neurons. They have no dendrites. Their axons branch immediately. One branch goes to the periphery (skin or muscle); the other into the spinal cord. Sensory information from the periphery travels from one end of the axon to the other synapsing in the dorsal horn of the spinal cord.


dura mater- tough, leathery outermost layer of the membranes surrounding and protecting the brain and spinal cord; lines the inside of the skull and drapes loosely around the spinal cord. Dura mater is Latin for tough mother. (Sheep Brain Dissection)


electrolytes- charged ions like sodium, potassium, chloride, and bicarbonate


endocrine system- system of glands and groups of cells that secrete hormones to control internal body states


efferent- outgoing information or neuronal connection; going away from or out of the central nervous system


episodic memory- see memory, episodic (Your Incredible Memory)


EPSP- see excitatory post-synaptic potential


excitatory interneuron- an interneuron whose neurotransmitter produces excitation (depolarization) in target cells, helping the target cells to reach threshold


excitatory neuron- see neuron, excitatory (Virtual Neurons)


excitatory post-synaptic potential- short-lived movement of membrane potential to a higher value when neurotransmitter binds to receptors on dendrites; temporary depolarization of post-synaptic membrane potential caused by the flow of positively charged ions into the post-synaptic cell as a result of opening of ligand-gated channels. makes a post-synaptic neuron more likely to generate an action potential; opposite of IPSP


experimental control- the experimental condition which receives no treatments (negative control) or receives treatments already known to cause the desired effect (positive control) (Chemotaxis using C. elegans)


extracellular- outside the cell


feedback- when information from the end is also used to modify the process that produced it; in a feedback loop, information moves backwards to add into an earlier part of the pathway.


feedback loop- in a feedback loop, information moves backwards to add into an earlier part of the pathway.


feed-forward network- occurs when a signal from one point in a neural pathway is transmitted in a forward direction and adds information to the circuit


firing rate- the number of action potentials generated per second


frequency- the rate of a repeated event; usually measured in # of events per second = Hertz = Hz. Frequency = 1 / period


frontal cortex- any part of the frontal lobe; involved in decision making, evaluating, and directing behaviours (Whose Choice Is It Anyway?)


frontal lobe- front region of the cerebrum; the part of the cortex responsible for attention, decision making, abstract thinking, problem solving, emotion, intellect, muscle movements, smell, and personality; motor cortex (Sheep Brain Dissection, Mirror Image, Motor Learning)



ganglion (plural = ganglia)- a group or collection of neuronal cell bodies (Close-up of the Nervous System, M. sexta Wax Model)


gap junction- ion channels in adjoining cells that align to form electrical synapses; gap junctions are turned on and off by calcium and pH.


glands- specialized groups of cells in the endocrine system that secrete hormones, directly into the blood rather than through a duct


glutamate receptor- nonselective cation channels which allows the flow of K+, Na+ and sometimes Ca2+ in response to glutamate binding


graded synaptic potential- small change in membrane potential of the post-synaptic dendrite caused by transmitter released from the pre-synaptic nerve terminal; synaptic potentials are much smaller than action potentials.


gray matter- areas of the brain made up of neuronal cell bodies, dendrites and synapses; without a lot of myelin, these areas appear grayer in freshly dissected brain tissue.
growth cone- the tip of the growing axon that senses and uses chemical signals to find its targets (Neuropathfinding)


gyrus (plural = gyri)- ridges or bumps of folded cerebral cortex


hippocampus- the oldest part of cerebral cortex responsible for spatial localization, formation of declarative memory, and transfer of short-term to long-term memories (Sheep Brain Dissection, Memory Items)


homeostasis- self-regulating process by which a system remains stable by adjusting to changing conditions (Dendritic Spines Lab, Makes Me Sweat, Virtual Neurons)


hyperpolarize- movement of membrane potential to a lower (more negative) value


hypothalamus-part of the brain that processes appetite, thirst, hormone regulation, control of internal body functions, sexual functions, and diurnal rhythms; the hypothalamus is a medial structure below (more ventral than) the thalamus.


inertia- the tendency of a body to remain in a state of rest or uniform motion unless acted upon by an external force (Balance: The Ears Have It)


inhibitory neuron- see neuron, inhibitory (Virtual Neurons)


inhibitory post-synaptic potential- short-lived movement of membrane potential to a lower value when neurotransmitter binds to receptors on dendrites; temporary hyperpolarization of post-synaptic membrane potential caused by the flow of positively charged ions out of the post-synaptic cell (or negatively charged ions moving in) as a result of opening of ligand-gated channels. makes a post-synaptic neuron less likely to generate an action potential; opposite of EPSP


interneuron- a neuron that carries information between sensory neurons and motor neurons; most meurons in the CNS are interneurons; some have special names like projection neurons or Pyramidal cells. (Virtual Neurons)


intracellular- inside the cell


ion channel- a membrane-spanning protein that forms a pore or hole through the plasma membrane; when the ion channel is open, ions move between the inside and outside of the cell. Most ion channels are opened or closed by energy, for example, from a binding reaction, voltage, temperature, or light.


ionotropic- receptor that also is an ion channel


IPSP- see inhibitory post-synaptic potential


labyrinth- an organ in the middle ear that holds the 3 semicircular canals which come together in the vestibule, close to the cochlea (Balance: The Ears Have It)


latency- a property of neurons specifying the time (in milliseconds) between arrival of a stimulus and production of the response; the time between a stimulus and its response


lateral- toward the left or right sides of the body, away from the middle; opposite of medial (Sheep Brain Dissection)


lobe- large division of the cerebral cortex


long-term memory- memories that are stored in a variety of places in the brain over long periods of time (Recency and Primacy Effects)


medial- toward the middle of the body; opposite of lateral (Sheep Brain Dissection)


membrane potential- electrical difference between the inside and outside of a neuron or muscle cell


memory, declarative- type of memory used when recalling (or declaring) facts or experiences, as opposed to skills. Both semantic and episodic memories are declarative memories and can easily be forgotten. (Mirror Image, Your Incredible Memory)


memory, episodic- type of declarative memory used when one talks about events in one’s life (includes time, place and emotions) (Your Incredible Memory)


memory, procedural- type of memory used in performing skills, learned behaviors, or procedures; remembering how to do something like tie a shoelace. Procedural memories are easy to do but difficult to explain to others. For example, it is easy to demonstrate how to ride a bike but it is not easy to describe how to do it. Procedural memories are less likely to be forgotten. (Mirror Image, Your Incredible Memory)


semantic- type of declarative memory used when talking about facts and concepts (Your Incredible Memory)


meninges- three membranes (the dura mater, arachnoid mater, and pia mater) that cover and protect the brain and spinal cord against shocks, knocks, and vibrations; blood vessels run between the arachnoid and pia mater before entering into the cortex. (Sheep Brain Dissection)


merkels discs- small structures in the skin that provide touch information to sensory nerves


metabotropic- receptor that activates a series of intracellular biochemical reactions


metamorphosis- development or transformation of an organism; involves significant changes in physical form (e.g. growth and differentiation) (M. sexta Wax Model)


mnemonic- a device or way (a rhyme, a word) to aid in remembering something (Memory Items)


motor cortex- part of frontal cortex that sends messages to the spinal cord for movement control; see frontal lobe (Mirror Image, Motor Learning)


motor learning- is the process of improving the smoothness and accuracy of movements through practice. During motor learning (and other learning), synapses in neural pathways in the brain are strengthened so that the actions (or thought) progress smoothly with less conscious direction.


motor neuron- see neuron, motor (Virtual Neurons)

muscle fiber- muscle cells fused into a long multinucleated cell which can contract and exert force; motorneurons innervate muscle fibers, not individual muscle cells. Many muscle fibers running in parallel form a muscle.


muscle spindle- senses the stretch of a muscle and sends that information back to the spinal cord and cerebellum to help control muscle length


myelin- compact fatty material that surrounds axons of some neurons; acts as an insulator to enhance electrical conduction of action potentials (Sheep Brain Dissection, Close-up of the Nervous System)


myelinate- to form myelin around an axon


negative feedback- information feeding back which is subtracted from the process thereby slowing the process down


nerve terminal- the end region of an axon; usually a site of synaptic contact with another cell


nervous system- a vast network of cells that carry information to and from all parts of the body (M. sexta Wax Model)


neural circuit- the set of neurons that are connected in sequence to produce a sensation, behavior, or function; neural pathway or network; seecircuit (Bead Neuron)


neural pathway- set of connected neurons that are regularly activated in sequence to produce a specific function; neural circuit or network


neuroethics- questions about ethics raised from neuroscience experiments (Whose Choice is it Anyway?)


neuromuscular junction- a specialized synapse onto a muscle; the place where the neuron connects to the muscle (Virtual Neurons, Connect the Neurons)


neuron- a cell that is specialized for the transmission of information and characterized by long fibrous projections called axons, and shorter, branch-like projections called dendrites; the basic functional unit of the nervous system; also called a nerve cell (Virtual Neurons, Connect the Neurons, Close-up of the Nervous System, Bead Neuron)

neuron, excitatory- a neuron whose neurotransmitter excites, stimulates, or depolarizes (causes the cell membrane to become less negative) another neuron, increasing the probability that the target neuron will fire an action potential; in other words, an excitatory neuron sends a message that may cause another neuron to fire an action potential; excites the next neuron (Virtual Neurons, Connect the Neurons)


inhibitory neuron- a neuron whose neurotransmitter produces inhibition (hyperpolarization) in target cells, making it harder for the target cell to reach threshold


neuron, motor- a neuron that carries information away from the central nervous system to muscles; a motor neuron sends messages to move muscles (Virtual Neurons)


neuron, post-synaptic- the neuron whose dendrites receive the neurotransmitter (Connect the Neurons)


neuron, pre-synaptic- the neuron that releases the neurotransmitter (Connect the Neurons)


neuron, sensory- a neuron that picks up information from the body’s sensory receptors in the skin, muscle, joints, tongue, ear, nose, and eyes and carries it toward the central nervous system; sensory neurons detect environmental information necessary for the body to survive, e.g. touch, pain, temperature, light, sound, taste, smell, balance, and information about muscles and joints. (Virtual Neurons)


neuronal circuit- see circuit


neuronal network- neuronal circuit; see circuit


neurotransmitter- a chemical, released by nerve terminals at a synapse, that crosses the synapse carrying information from the nerve terminal (pre-synaptic cell) to the dendrite (post-synaptic cell). Neurotransmitters, which are stored in synaptic vesicles in the pre-synaptic cell, bind to receptors on dendrites of neighboring neurons. Neurotransmitters relay information across the space between one neuron’s nerve terminal and another neuron’s dendrites. (Connect the Neurons)


nucleotide- See nucleic acid.


nystagmus- an involuntary rhythmic eye movement that occurs when a person is spun around and then suddenly stops (Balance: The Ears Have It)


occipital lobe- the part of the cortex responsible for vision and visual object and face recognition; the most caudal or posterior part of the cerebral cortex. (Sheep Brain Dissection, Mirror Image, Motor Learning)


olfactory bulb- anterior part of the brain concerned with the sense of smell (Sheep Brain Dissection)


optic chiasm- where the optic nerves from the left and right eyes come together. Some nerve fibers cross to the other side and some don’t. All fibers continue in the optic track and synapse in the lateral geniculate nucleus of the thalamus. (Blind Spot)


optic nerve- nerve that connects the retina to the brain (Sheep Brain Dissection)


parietal lobe- region of the cerebrum located in the dorsal and medial region of the posterior cerebrum; processes higher sensory and language functions; association cortex (Sheep Brain Dissection, Motor Learning)


pathfinding- the process of the axons finding the right neuron or target to connect to (Neuropathfinding)


period- the time from the beginning of one event until the beginning of the next; usually measured in seconds; period = 1 / frequency.


peripheral- away from, outside


peripheral nervous system- nerves beyond the brain and spinal cord


pH- a measure of the hydrogen ion concentration in a liquid; pH = -log([H+])


pia mater- innermost layer of the membranes surrounding and protecting the brain that closely follows the bumps and wrinkles of the brain’s surface. The space between the arachnoid and pia mater contains many blood vessels that supply the brain


pioneer axon- the axon that happens to find its connection first and blazes a trail for other like axons to follow (Neuropathfinding)


pituitary gland- gland at the base of the brain; makes and releases growth, reproductive, and other hormones into the blood stream (Sheep Brain Dissection)


PNS- peripheral nervous system consisting of nerves beyond the brain and spinal cord


positive feedback- the information feeding back is added to the process thereby speeding up the process


posterior- towards the back of the head


post-synaptic neuron- see neuron, post-synaptic (Connect the Neurons)


potassium (K+)- element with a single positive charge found mostly inside neurons and muscles; K+ can move through some ion channels.


prefrontal cortex (PFC)- the very most anterior (rostral) part of the cortex which controls planning and thought


pre-synaptic neuron- see neuron, pre-synaptic (Connect the Neurons)


primacy effect- remembering the first information given, see also recency effect (Recency & Primacy Effect)


procedural memory- see memory, procedural (Mirror Image, Your Incredible Memory)


pruning- the process of shortening or reducing number of neuronal synapses, axons, or dendrites in response to use or growth signals (Neuropathfinding)


proprioception- the sense of oneself; where one feels the muscles, limbs, and body are with respect to one’s surroundings. Sensory receptors in the muscles and joints send this information to the brain.


proximal- close to, nearest


purinergic receptor channels- a family of cation-permeable ligand-gated ion channels that open in response to the binding of extracellular purines, like adenosine 5′-triphosphate (ATP).


Purkinje cells- large neurons arranged in a single layer in the cerebellum that send messages to other areas of the brain that influence or refine movement (Close-up of the Nervous System)


reaction time- time it takes to react to a stimulus (Motor Learning)


recall- the act of retrieving memory (Your Incredible Memory)


recency effect- remembering the most recently received information, see also primacy effect (Recency & Primacy Effect)


receptor- a special molecule on a dendrite that tastes each specific neurotransmitter; neurotransmitter and receptor must fit together like a lock and key (Connect the Neurons)


recognition- the act of remembering words or situations that were previously learned or studied. It is also acknowledging and understanding something that is familiar. (Your Incredible Memory)


refractory period- a short time (a few msec) after an action potential when the neuron cannot produce another action potential


rod- photoreceptor cell in the retina of the eye that functions in low light; detects light and dark but not color


rostral- towards the nose or front of the nervous system; see also anterior (Sheep Brain Dissection)


semantic memory- see memory, semantic (Your Incredible Memory)


sensation- the ability to detect chemical or physical changes in the environment


sensory neuron- see neuron, sensory (Virtual Neurons)

short-term memory- an early stage in the processing of information in the brain; information only held for a few minutes. Some of this information will be lost or forgotten, while some will be processed into long-term memory. (Recency and Primacy Effects)


signal transduction pathways- sets of biochemical reactions inside cells that take information triggered by an external event like receptor activation and make that signal bigger or last longer; signal transduction pathways can cause other cellular events to happen including turning on or off genetic processes.


soma- see cell body


somatosensation- the senses of touch, pressure, and pain as localized on the body surface

spinal cord- part of the central nervous system located inside the backbone containing cell bodies and bundles of nerve fibers; connects the brain to different sensory and motor parts of the body (Sheep Brain Dissection, Close-up of the Nervous System, Motor Learning)


sprouting- formation of new branches on axons or dendrites as they grow (Neuropathfinding)


sulcus (plural = sulci)- the valleys or spaces between the folds or gyri of the brain (Sheep Brain Dissection)


synapse- the place where one neuron connects to another. The synapse includes the nerve terminal of the first neuron, the place on the second neuron with receptors, and the space between them. The electrical signal in the axon of the first neuron triggers a chemical signal to be released into the gap that is tasted by receptors in the second neuron. (Connect the Neurons)


temporal lobe- the part of the cortex responsible for hearing, olfaction, object recognition, language, speech, learning, and memory; located in the ventral region of the lateral cerebrum near the temples and ears (Sheep Brain Dissection)


thalamus- interior part of the brain responsible for intermediate processing of motor and sensory functions and sleep


thoracic- relating to or involving the thorax (M. sexta Wax Model)


thorax- the middle section of an insect’s body; the legs and wings attach to the thorax, making it the center for locomotion (M. sexta Wax Model)


threshold- the sum of incoming inputs needed to start an action potential; this value varies and is determined by the number of sodium channels in a neuron’s cell body and the recent firing rate of that neuron. (Virtual Neurons, Close up of the Nervous System, Connect the Neurons)


tract- a bundle of axons in the central nervous system; a pathway


transmitter- short for neurotransmitter


variable- a factor or condition that is subject to change, especially one that is allowed to change in a scientific experiment to test a hypothesis. (Makes Me Sweat)


ventral- towards the front or stomach side of the body and head (Sheep Brain Dissection)


ventral horn- ventral part of spinal cord gray matter containing large motor neuron cell bodies (Close-up of the Nervous System)


ventricle- one of four fluid-filled cavities inside the brain


vertigo- a condition where a person feels as if s/he is spinning when s/he is not (Balance: The Ears Have It)


vestibular system- specialized sensory organs in the inner ear that sense head and body movements, the nerve
that conveys this information into the brain, and the brain stem nuclei that process this information. The vestibular system is responsible for our sense of balance. (Balance: The Ears Have It)


vision- the sense of sight; the ability to detect information from wavelengths of light


visual cortex- see occipital lobe (Motor Learning)


white matter- areas of the brain made up of myelinated axons; the high lipid content of the myelin makes these areas appear whiter in freshly dissected brain tissue.


Energy Systems & Exercise

Energy systems category covers the various ways in which the body generates and uses energy and includes anaerobic respiration, aerobic respiration, krebs cycle, human digestive system, oxygen debt as well as the long term and short term effects of exercise on the body.

Digestive system diagram

The primary function of the digestive system is to break down food both mechanically and by the use of enzymes, so that it can be used by the body for energy and cell growth and repair. It consists of a large number of organs and processes with the combined functions of breaking down our food into smaller molecules which can be used to produce energy and for other nutritional purposes; and excreting the waste consumed and produced by the system.

Anaerobic respiration is when the body produces energy for exercise without oxygen. The anaerobic energy system kicks in in the first few minutes of all exercise, before there is suffiecient oxygen available at the muscles for aerobic metabolism. It is also used for fast, powerful bursts of energy, for which the aerobic system is insufficient. There are two systems within Anaerobic metabolism, which are the ATP-PC system and the lactic acid system.

The aerobic system produces the largest amounts of energy, although at the lowest intensity. At the start of exercise the body cannot deliver oxygen to the muscles fast enough to initiate the complex chemical reactions which occur during aerobic metabolism. Therefore the body relies on anaerobic processes for the first couple of minutes.

When you begin to exercise your body must immediately adjust to the change in activity level. Energy production must increase to meet demand with changes to the predominant energy system and fuel source occuring throughout the exercise in order to maintain the required level of performance.

Exercise affects the circulatory system, respiratory system and the muscles. Short term effects occur immediately as we begin to exercise. Long term effects are more concerned with adaptive changes over time with regular exercise.

What is oxygen debt? When you have a short intense burst of exercise such as sprinting you generate energy for this anaerobically or without oxygen. When you stop exercising you are still breathing heavily. This is your body taking in extra oxygen to ‘repay’ the debt. Well, that is the simple solution but there is a little more to it if you want to look a bit deeper.

What is cellular respiration? Cellular Respiration is the process that takes place in cells to convert food into energy. This process is also known as internal respiration. In order to release the maximal amount of energy, the molecules of Carbon, Hydrogen, Oxygen and Nitrogen which make up our food are stored as a high energy molecule known as ATP or Adenosine Triphosphate.


 Anatomical planes

An anatomical plane- is a hypothetical plane used to transect the human body, in order to describe the location of structures or the direction of movements. In human and animal anatomy, three principal planes are used:

  • The sagittal plane or median plane (longitudinal, anteroposterior) is a plane parallel to the sagittal suture. It divides the body into left and right.
  • The coronal plane or frontal plane (vertical) divides the body into dorsal and ventral (back and front, or posterior and anterior) portions.
  • The transverse plane or axial plane (lateral, horizontal) divides the body into cranial and caudal (head and tail) portions.
    When describing anatomical motion, these planes describe the axis along which an action is performed. So by moving through the transverse plane, movement travels from head to toe. For example, if a person jumped directly up and then down, their body would be moving through the transverse plane in the coronal and sagittal planes.A longitudinal plane is any plane perpendicular to the transverse plane. The coronal plane and the sagittal plane are examples of longitudinal planes.The following terms are defined in reference to the anatomical model being in the upright orientation (standing):
    • transverse (also known as axial or horizontal) plane is an X-Z plane, parallel to the ground, which (in humans) separates the superior from the inferior, or put another way, the head from the feet.
    • coronal (also known as frontal or lateral) plane is a Y-X plane, perpendicular to the ground, which (in humans) separates the anterior from the posterior, the front from the back, the ventral from the dorsal.
    • sagittal (also known as anteroposterior) plane is an Y-Z plane, perpendicular to the ground, which separates left from right. The midsagittal plane is the specific sagittal plane that is exactly in the middle of the body.
    • The midsagittal or median plane is in the midline; i.e. it would pass through midline structures such as the navel or spine, and all other sagittal planes (also referred to as parasagittal planes) are parallel to it. Median can also refer to the midsagittal plane of other structures, such as a digit.

    The axes and the sagittal plane are the same for bipeds and quadrupeds, but the orientation of the coronal and transverse planes switch. The axes on particular pieces of equipment may or may not correspond to axes of the body, especially since the body and the equipment may be in different relative orientations.


    When describing anatomical motion, these planes describe the axis along which an action is performed. So by moving through the transverse plane, movement travels from head to toe. For example, if a person jumped directly up and then down, their body would be moving through the transverse plane in the coronal and sagittal planes.

    longitudinal plane is any plane perpendicular to the transverse plane. The coronal plane and the sagittal plane are examples of longitudinal planes.

The three planes of motion are:

Sagittal Plane

The Sagittal plane passes through the body front to back, so dividing it into left and right. Movements in this plane are the up and down movements of flexion and extension

Frontal Plane

The frontal plane divides the body into front and back. Movements in this plane are sideways movements, called abduction and adduction

Transverse Plane

This plane divides the body into top and bottom. Movements in this plane are rotational in nature, such as internal and external rotation, pronation and supination

Anatomical Position

The anatomical position or neutral position is the starting position for describing any movement. It is important that you know this to be able to understand what is meant by certain movement patterns. It is sometimes also called the anatomical starting position or fundamental starting position.

Anatomical neutral is:

  • Standing upright
  • Legs together and knee straight
  • Toes pointing straight forwards
  • Arms by the side
  • Palms facing forwards


Flexion and Extension

Flexion is a movement in the sagittal plane, which decreases the angle at the moving joint. Extension is the opposite movement, which increases the angle at the joint. Many types of synovial joint are capable of flexion and extension (hinge; ball and socket; saddle; condyloid) including the shoulder, elbow, wrist, hip and knee. Here are some examples:

In the videos above, shoulder flexion is the action of raising the arm above the head. Extension is then the downward movement. In the photo, the shoulder is in an extended position. For the knee, bending the knee is flexion, as the angle is reduced (as shown in the picture) and straightening it is called extension.

Flexion and extension at the ankle joint is called dorsiflexion and plantarflexion. Dorsiflexion is when you point your toes towards the ceiling and plantar flexion is when you point your toes away, towards the floor. Remember to start in the anatomical starting position!

Abduction and Adduction

These are movements in the frontal plane and involve moving the body part away or towards an imaginary centre line. Abduction is taking the body part away from the central line and adduction is moving it towards (remember this by thinking adduction adds the body part to the centre). Adduction can also be moving the body part across the centre line and to the other side of the body, shown in the hip abduction video below. Amongst the joints capable of abduction and adduction are the shoulder and hip.

Other abduction and adduction movements include the fingers. If you splay your fingers and move them apart, this is abduction as they are moving away from the centre position. When you bring the fingers back together, this is adduction, as you are adding them back to the centre line.


Rotation movements are in the transverse plane and include any twisting motion. Joints which permit rotation include the shoulder and hip. These are both ball and socket joints. We can also rotate our necks and backs due to a series of smaller joints, including the atlanto-axial joint which is a pivot joint in the neck between the first two vertebrae (C1 and C2).

Rotation of the hip and shoulder can be broken down into internal or external rotation (also sometimes known as medial and lateral rotation respectively). In the example of the shoulder video below, internal rotation is the movement of the hand either inwards towards the body (when the shoulder is adducted) or down to point towards the floor (when the shoulder is abducted). External rotation is therefore the opposite, when the hand moves away from the body (when the shoulder is adducted) or up towards the ceiling (when the shoulder is abducted).




Circumduction is a combination of all of the movements above. It is possible at ball and socket, condyloid and saddle joints such as the shoulder, hip, wrist and ankle. It involves moving the entire connecting limb through its full range of motion. Here is an example of shoulder circumduction:

Pronation, Supination, Inversion and Eversion

Pronation and supination are specialised movements of the forearm and ankle. In the forearm, pronation is the movement of turning the palm over to face downwards (or backwards if starting in anatomical neutral). Supination is the opposite movement, of turning the palm up or forwards. The movement here comes from the proximal radio-ulnar joint (the joint just below the elbow, between the Radius and Ulna bones) which is a pivot joint, allowing the Radius to move around the Ulna.

At the ankle, supination is the movement of turning the sole of the foot inwards. This is sometimes called inversion. Pronation is the movement of turning the sole of the foot outwards, sometimes called eversion. You will sometimes hear people saying they have over-pronated feet, meaning their sole turns outwards slightly more than it should when they walk or run, giving the appearance of a flat foot, without an arch.





A joint is a place where one bone meets another bone. Joints are a major part of the skeletal system. There are many joints, some of which allow no movement, some allow minor movement, and some allow free movement.

The immovable joints are called synarthroses, or fibrous joints. They are firm in their position to prevent gliding or sliding. There are three major groups of this joint. First there are sutures, like the joints between the bones of the skull. Next, there are syndesmoses, like the membrane that sketches in between tibia and fibula in human beings. Finally, there is gomphosis which are the joints between the teeth and sockets that hold them.

The next group of joints is the cartilaginous joints, or symphyses, which connect two bones with cartilage. Only slight movement occurs between the bones that have this joint connecting them. Two cartilaginous joints are synchondrosis, and fibrocartilaginous joints. The more common of these two joints is the synchondrosis. This joint is a layer of cartilage between two of part of two bones. Fibrocartilaginous joints are bound between the bones of the vertebral column. It is also between the sternum and its inferior.

The final group of joints is synovial joints, or diarthroses. These joints allow various movements depending on the type of joint. Cartilage covers bones near synovial joints so that ligament attachment can occur. Between tow bones in these joints there is a membranous sac called bursa. Bursae produce synovial fluid which covers the ends of bones allowing smooth movement. Bursitis, a condition where the bursa undergo inflammation, causes severe pain.




There are several typed of synovial joints. Plane joints are joints between two flat bones where one bone moves horizontally over the other bone in various directions. An example is the bones in a hand. Pivot joints occur between two bones where one bone is cylindrical in shape and rotates inside a ring shaped bone or ligament. An example is the movement that occurs between the first two bones of the vertebrae where someone shakes his head “no” (Johnson). The hinge joint is like the hinge on a door, and it moves back and forth in one plane. The elbow and knee joints are examples. Condyloid joints, also called ellipsoid joints, occur between two bones where one is football-shaped and fits in its concave complementary “partner.” The movements occur when someone shakes his head “yes” (Johnson) or when he tilts his head side to side. The saddle joint is two saddle shaped joints that can move ninety degrees over each other like a jockey can tilt side to side on a horse, but he cannot tilt too far without falling off. The final joint is the ball and socket joint, which is like an adult hand loosely wrapping one hand around a baby’s hand. Examples of this joint are the joints in the hips and shoulders.






The skeleton has several purposes which are vital to human life. In the human body there are 206 bones of various sizes and shapes that share the same main function, support. But not only does it provide support, but it also stores calcium, a vital mineral to human life, protects the inner organs including the central nervous system, and serves as anchorage points for muscles. The skeleton also allows humans to have an erect posture, an important evolutionary advantage. The skeleton of a human, as in most vertebrates, consists of bone and cartilage connected by ligaments and tendons. The skeletal system as a whole is divided into three parts: the axial (the vertebral column, spine, and most of the skull), the visceral (the jaw and the branchial arches), and the appendicular (the hip and shoulder girdles and the limbs). The different types of bones are also categorized into three groups. There are the long bones (all limbs), short bones (the wrist and ankle bones), flat bones (particular skull bones, ribs, scapula, and sternum), and irregular bones (facial bones and the vertebrae). The bones, joints, cartilage, and ligaments work together to provide humans with structural support and movement.
The human skeletal system is advantageous in the fact that it serves many important functions. However, all of these functions fall within three main categories: the skeleton provides protection, movement, and support; it stores a large quantity of the calcium, fatty tissue, and phosphorous within the body; and it enables other organ systems to function properly.
The rigid skeleton provides a large amount of protection to the many organs and tissues inside the human coelom. The cranium or skull is a worthy example as it protects and cushions the brain. Also, the rigidity of the skeleton contributes support. The rigid skeleton holds the organs and muscles, allows humans to move against the gravitational pull of the earth, and allows humans to stand and sit. The spine, legs, pelvis, and feet provide most of the support within the body. The rigidity of bone also allows movement. Muscle attachment, in conjunction with joints, permits certain bones to move in a variety of different planes and to function as Class One, Two, or Three levers.
Second, the skeletal system houses most of the body’s calcium, fatty tissue, and phosphorous. Although both are stored within the bone matrix, calcium salts are stored as hydroxyapatite, a complex, crystalline molecule. The hydroxyapatite is converted to calcium by osteoclasts during periods in which calcium is needed by the body, and the hydroxyapatite is converted into new bone tissue in times of excess. Fatty tissue is stored in the medullary cavity as yellow bone marrow; the yellow marrow provides the body with energy when the amount of body fat has been reduced.
Lastly, the skeletal system is key the proper function of many of the other organ systems of the body. For example, red bone marrow, which produces erythrocytes, leukocytes, and thrombocytes, which are red blood cells, white blood cells, and platelets, respectively, is the primary source of blood cell production and is essential to the circulatory system although yellow marrow is used to produce erythrocytes in times of anemia. Bones also aid in the respiratory system as the ribs are necessary for the diaphragm to contract, allowing air to enter the lungs. Three small bones, the hammer, anvil, and stirrup of the inner ear, regulate hearing and balance.
In conclusion, the human skeletal system is required for many of the processes that occur within the human body, and it is essential for ultimately maintaining homeostasis and metabolism.
Bone marrow consists of two types, red(vascular) or yellow (fatty) bone marrow. Red bone marrow forms all blood cells, except lymphocytes, in humans. It also destructs old red blood cells. Yellow bone marrow stores fat. It can be converted into red bone marrow under certain conditions, like severe blood loss. All human bone marrow is red until about the age of seven because the need for new blood formation is high. Later, fat tissue slowly replaces the red bone marrow. Red bone marrow is found in adults only in the vertebrae, hips, breastbone, ribs, skull, and the ends of long bones. Yellow bone marrow fills the cavities of these bones.
Cancellous bone is very spongy in structure and appearance. It is made of trabeculae, which are rigid plates. They also have osteocytes with incomplete Haversian systems, so the osteocytes are nourished by a network of canaliculi.
Compact bone is a dense, ivory-like substance that surrounds the cancellous bone. It contains a series of ring deposits of mineral salts and collagen fibers, called lamellae. The lamellae are interlaced with the Haversian canals.
The periosteum is a sheath of tissue that covers the outer bone surfaces. During growth, it contains osteoblasts, and it contains connective tissue cells that can become osteoblasts that form bones in reaction to stress or injury. The periosteum is composed of two layers. One is an outer layer that provides a shield and a point of attachment for ligaments and tendons. The inner layer is called the endosteum, which is a thin membrane that contains bone forming and blood forming cells. It is also needed for bone remodeling.
Cartilage is a dense, connective tissue that covers the ends of bones. It is made of collagen fibers embedded within a substance which resembles plastic. This structure allows cartilage to be very strong, so it can support weight, while still being extremely flexible.
The first type of cartilage is hyaline cartilage which is the most common and it forms the embryonic skeleton. It exists in adults at the ends of bones in free moving joints, at the ends of ribs, and in the nose, trachea, larynx, and bronchi. The second type, fibrocartilage, is very tough, and found in disks which exist in side the vertebrae. The last type is yellow, or elastic, cartilage. It is the most flexible cartilage because it contains elastic fibers in addition to the collagen fibers. It forms the external ear, the auditory tube of the middle ear, and the epiglottis.
Another function of cartilage is to form a model for the growth of the bony skeleton. In the embryo, the fibrous part of the cartilage calcifies, and is replaced by chondrocytes, the cells that form cartilage, or osteocytes. In conclusion, cartilage is vital to the functions performed by the skeletal system.
There are two types of connective tissues. Ligaments are tough fibrous bands of connective tissue that support internal organs and hold bones together at the joints. A ligament is composed of dense fibrous bundles of collagenous fibers and spindle-shaped cells known as fibroblasts. (They are long, flat, spindle-shaped connective-tissue cells. Fibroblasts are vital in the production of collagen.) There are two major types of ligaments: white ligaments and yellow ligaments. White ligaments are rich in collagenous fibers. Yellow ligaments are rich in elastic fibers which allow movement.
At the joints, ligaments form a capsule-shaped sac that encloses bone ends and a lubricating membrane, the synovial membrane. Other ligaments fasten around or across bone ends in bands or act as a tie pieces between bones, such as in the ribs and forearm, restricting inappropriate movement. Tendons are the other type of tissue, that connects bones to muscles.




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