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Feltham Press - Physiology Glossary Category: Earth and Environment > Physiology Date & country: 25/11/2007, UK Words: 136

Abdomen
That part of the body containing the viscera, ie the kidneys, liver, stomach, and intestines; separated from the thorax by the diaphragm.

Acetylcholine
A chemical (neurohormone) released from presynaptic nerve endings, which diffuses across the synapse (gap between the neurones) and stimulates the initiation of an impulse in the post-synaptic membrane. Is rapidly broken down by the enzyme cholinesterase.

Acid
A chemical which dissociates ('splits up') in solution to give hydrogen ions (H+). Have a pH less than 7. Neutralised by alkalis (bases).

Adenosine Triphosphate (ATP)
A compound formed from ADP + P with energy released from Phosphocreatine (PC) and/or the breakdown (oxidation - either aerobic or anaerobic) of energy rich substrates e.g. glucose. Stored in all cells, especially muscle fibres. When it is broken down by enzyme action back into ADP + P the stored energy is made available for chemical or mechanical work. All the body's energy use is via ATP, which is continually broken down and resynthesised (average daily turn-over = body weight).

Adipose tissue
Special tissue within which fat is stored. Found mainly under the skin (sub-cutaneous) and around the major organs.

Adolescence
The period in which a second growth spurt occurs and sexual maturity is achieved.

Adrenal glands
Literally 'on top of the kidneys'. Composed of two distinct regions, an outer cortex, and an inner medulla. The cortex secretes adrenal cortical hormones, e.g. sex hormones, aldosterone, cortisol; the medulla secretes adrenaline and noradrenaline, and is closely linked to the sympathetic nervous system.

Adrenaline
A hormone (chemical transmitter substance) released from the medulla of the adrenal glands and from sympathetic nerve endings, which prepares the body for 'fight or flight'as a result of a 'fright'.

Aerobic Exercise
Exercise during which the energy needed is supplied by aerobic respiration (oxidation) of energy rich substrates e.g. glucose, using the oxygen that is breathed in (fats can only be broken down aerobically). Such exercise can be continued for long periods.

Affinity
Attraction to, 'liking' for; e.g. haemoglobin has an affinity for oxygen, with which it forms oxyhaemoglobin.

Alkali (or base)
A chemical which accepts hydrogen ions, thus neutralising acids. Have a pH greater than 7.

Amphetamine
A synthetic central nervous system stimulant related to adrenaline.

Anabolic Steroids
A group of ergogenic aids (related to the male hormone testosterone) that have an anabolic (protein building) effect, and to a greater or lesser extent an androgenic (development of male characteristics) effect on the body.

Anabolism
That aspect of metabolism involved in the building up (synthesis) of complex substances (e.g. proteins) from simpler substances (e.g. amino acids). Requires energy in the form of ATP.

Anaerobic Exercise (respiration)
Exercise that demands more oxygen than can be supplied at the time, and which therefore results in the depletion of ATP-PC stores, and the incomplete oxidation of glucose with the accumulation of lactic acid.

Anaerobic Glycolysis
The initial stages in the oxidative breakdown of glucose in the cytoplasm of cells and muscle fibres, which does not directly involve oxygen, generates a relatively small amount of ATP from each glucose molecule very rapidly, and which in the shortage of oxygen leads to the accumulation of lactic acid.

Anaerobic Threshold
The 'point' at which, during exercise, the oxygen supply becomes insufficient to maintain aerobic respiration, so that anaerobic respiration becomes predominant, with the accumulation of lactic acid in the blood. Less used than previously, as overlap between aerobic and anaerobic respiration systems at all times in all types of exercise complicate the idea of a simple 'threshold'.

Analgesic
Pain killer e.g. aspirin.

Anoxia
Lack of oxygen in tissues.

Arterioles
Finer branches of arteries, with relatively narrow diameters, and involuntary muscle in their walls, the contraction of which leads to vasoconstriction, and the relaxation of which leads to vasodilation. When constricted (narrowed) there is a greater resistance to the flow of the blood and a raised blood pressure, and vice-versa. Lead into the capillary beds.

Artery
Blood vessels carrying blood away from the heart, eventually dividing into arterioles.

Articulate
To connect by means of a joint.

ATP-PC System (phosphagen system)
An anaerobic energy system in which ATP is regenerated from the breakdown of phosphocreatine (PC). Muscles performing at maximal effort obtain ATP from this system.

Atrophy
Reduction in size and/or mass of cells and tissues, especially relating to muscle fibres.

Autonomic
Self-controlling; functionally independent of voluntary control.

Autonomic Nervous System
That part of the nervous system which works involuntarily (is not under voluntary control), controlling all the autonomic processes in the body, e.g. breathing rate, heart rate, peristalsis in the gut, contraction of the bladder, dilation and constriction of the pupil of the eye. Consists of two opposing (antagonistic) sub-systems, the sympathetic and parasympathetic nervous systems.

Basal Metabolic Rate
The rate of the metabolism, as measured by the energy output of an individual, whilst at rest in optimum conditions 12-18 hours after eating (post-absorptive period).

Biopsy
The extraction of small pieces of tissues for chemical and/or histological studies, e.g. muscle biopsy to study fibre composition, using a hollow needle.

Blood Pressure
The pressure exerted by the blood on the wall of a blood vessel, a function of cardiac output and peripheral resistance (the resistance to flow of the blood in the blood vessels, mainly the arterioles).

Bradycardia
Resting heart rate slower than average.

Buffering capacity
The capacity to prevent changes in pH.

Buffers
Substances which can prevent rapid changes in pH (acidity and alkalinity) within the body, e.g. proteins in the plasma, and haemoglobin in the red cells of the blood.

Calorie
A unit of heat. A thousand so-called small calories equals one large Calorie (kilocalorie or kcal), which is the type used when speaking of human nutrition. 1 Calorie = 4186 joules (4.186 kJ).

Carbohydrates
Organic compound containing only carbon, hydrogen and oxygen in a characteristic ratio, e.g. starch, sucrose (table sugar), and glucose. They are a basic source of energy, circulating as glucose in the blood stream, and being stored as glycogen in virtually all body tissues, but mainly in the liver and muscles. Bread, potatoes, fruits, honey and refined sugars are all excellent sources of carbohydrates. Carbohydrates yield about four Calories per gram when oxidised.

Cardiac Output
The amount of blood in dm3 (litres), pumped by the heart per minute, a function of heart rate and stroke volume. Generally the outputs of the right and left ventricles are the same.

Catabolism
That aspect of metabolism involved in the breakdown of complex substances into simpler substances. For example the oxidation of glucose into carbon dioxide and water (with the release of energy) in aerobic respiration.

Central nervous system
The brain and spinal cord.

Chemoreceptors
Receptors sensing changes in the chemical composition of body fluids e.g. blood glucose levels.

Concentric contraction
Contraction of a muscle reducing its length.

Connective Tissue
Tissues that provide support and cohesion for the body, e.g. white collagen fibres which form tendons, the basis of bone, and fibrous cartilage: yellow elastic fibreswhich form ligaments, and the basis of elastic cartilage; bone and cartilage. Others form sheets or mesenteries which hold organs in place.

Core Body Temperature
The central body temperature, as opposed to that of the limbs, the temperature of which is lower due to their greater surface area to volume ratio .

Coronary
Relating to the blood vessels that supply the cardiac muscle of the heart wall (from their 'crown' like arrangement around the heart).

Dehydration
Excessive loss of water, during exercise mainly as a result of sweating.

Diastole
Relaxation, as in relaxation of the ventricles (ventricular diastole).

Diffusion
The net movement of gases or dissolved substances, as a result of their kinetic energy, from regions of their higher concentration to regions of their lower concentration, down a concentration gradient, until equilibrium is reached.

Eccentric contraction
Contraction of a muscle whilst the length of the muscle increases, e.g. the contraction of the quadriceps in the front of the thigh whilst running downhill.

Electrolytes
Substances that dissociate into ions in solution (ionize). See inorganic ions/mineral salts.

Empty Calories
Calories obtained from foods such as sugar, which are virtually devoid of dietary essentials like amino acids, vitamins and minerals.

Endocrine glands
Ductless glands that produce and release (secrete) hormones directly into the blood, e.g. pituitary gland, adrenal glands, thyroid gland.

Energy
Energy can neither be created nor destroyed. In metabolism, energy in chemical compounds is trapped eventually in ATP, and then either used in synthetic reactions e.g. protein synthesis in growth, or in the sliding filament mechanism in contracting muscle fibres etc.; ultimately all energy is lost as heat.

Enzymes
Complex proteins that are capable of speeding up specific chemical reactions without being changed themselves (ie. organic catalysts), name ends in Ã`-aseÃ`, e.g. sucrase (catalyses the breakdown of sucrose), and maltase (catalyses the breakdown of maltose) etc.

Epithelium
A tissue lining a body surface, e.g. the lungs.

EPOC
Excess post exercise oxygen consumption, the oxygen taken up after the end of a period of exercise. To be preferred to 'oxygen debt', as not all the extra oxygen taken up after a period of exercise excess to normal needs is 'a debt' as such resulting from under supply during the period of exercise.

Ergogenic Aids
Substances, other than naturally occurring foods, that when taken orally or by injection will increase the potential for exercise performance, e.g. anabolic steroids.

Ergometer
A stationary cycle used for training or for laboratory tests to measure work performed.

Fast-Twitch (FT) Muscle Fibres
They have a contraction speed 2-3 times faster than slow-twitch (ST) fibres, and are capable of producing more power than ST fibres.

Fat (lipid)
Fat acts as an energy store, contains fat soluble vitamins, provides heat insulation under the skin (sub-cutaneous), and support and protection for organs. Fat supplies about nine Calories per gram when oxidised. Fat can only be oxidised aerobically.

Fatigue
A subjective experience, not amenable to objective testing, but clearly understood by all sportspersons.

Fatty acids
Long chain organic acids which are one of the end products of the digestion of fats (glycerol being the other), which can be oxidised aerobically as a source of energy, or which can be resynthesised back into fats stored in adipose tissue. Some are essential for certain key metabolic processes e.g. the proper functioning of the nervous system, and must be supplied in the diet (the essential fatty acids).

Fulcrum
The axis of rotation for a lever

Functional residual capacity (FRC)
The volume of air left in the lungs when the respiratory muscles are relaxed.

Glucose (blood sugar)
The simplest carbohydrate in the body (a monosaccharide or 'single sugar'). It may be oxidised aerobically to carbon dioxide and water, or anaerobically to lactic acid. It is the sole source of energy for the nervous system. It may be converted into glycogen or fat.

Glycogen
The form in which carbohydrate is stored in the body, mainly in the muscles and the liver, sometimes known as 'animal starch'.

Glycolysis
The first stages of cellular respiration occurring with or without the presence of oxygen, in which glucose is converted to two molecules of pyruvic acid.

Haemoglobin
The iron-containing pigment in the red blood corpuscles (erythrocytes) that combines with oxygen to form oxyhaemoglobin.

HDL
High density lipoprotein. Lipoproteins are combinations of fat (lipo) and proteins. The greater the proportion of protein (which is more dense than fat) the higher is the density of the lipoprotein (HDL), and vice versa (LDL). The ratio of HDL to LDL in the plasma is of more significance to health than straightforward 'cholesterollevels'. The higher the ratio the Ã`betterÃ`.

Homeostasis
The maintenance of constant internal conditions (mainly of the body fluids) in the face of changing activity and external conditions, to provide optimum conditions for enzyme activity of metabolism. Controlled by negative feed-back loops, in which any change away from the 'goal state' is opposed. The 'ideal state' is never reached, and the metabolism fluctuates or 'hunts' around the optimum within narrow limits, meaning that homeostasis is a dynamic equilibrium, never a static state.

Hormones
Chemical 'messengers' secreted by ductless endocrine glands directly into the blood, which in small amounts stimulate specific processes of metabolism in 'target' organs or tissues, usually at a distance from their site of production and secretion.

Hyperglycaemia
Higher blood glucose level than normal

Hypertension
High blood pressure.

Hypertrophy
Increase in the size and/or mass of cells and tissues, especially relating to muscle fibres.

Hyperventilation
An excessive increase in the rate of breathing, which causes a decrease in the amount of carbon dioxide in the blood, resulting in giddiness, cramps, convulsions, lowered blood pressure, and anxiety.

Hypoglycaemia
Lower blood glucose level than normal.

Hypothermia
Body temperature below normal.

Hypoxia
Low oxygen in the inspired air.

Insulin
Hormone secreted by patches of endocrine cells in the pancreas. Opposes any rise in blood glucose by suppressing breakdown of liver glycogen to blood glucose, and stimulating formation of muscle glycogen from blood glucose. Also has a role in protein synthesis. The actions of insulin are opposed by the hormones glucagon and adrenaline.

Interval Training
A system of training in which intervals of hard exercise are alternated with easier recovery intervals.

Isokinetic Exercise
Contraction of a muscle at constant speed, whilst exerting maximum tension over the full range of movement at all joint angles, rarely achieved without special equipment.

Isometric Exercise
Contraction of a muscle in which shortening is prevented, e.g. when straining against an immovable resistance.

Isotonic drink
Being of the same concentration as the blood.

Isotonic Exercise
Contraction of a muscle during which the force of resistance to the movement remains constant throughout the range of motion.

Kinaesthetic Feedback
The provision of feedback from proprioceptors (internal sense organs) about the position and movement of the body.

Lactic Acid (lactate)
Formed in exercising muscles under anaerobic conditions. It causes the muscular pain associated with intense exercise. It is not a waste product, as it is oxidised as an energy source when oxygen is available. The alternative term 'lactate' is strictly more accurate, as all acids exist in solution in the dissociated form, that is the molecule of lactic acid 'splits up' releasing positively charged hydrogen ions, and the remainder of the molecule, which is negatively charged, is the lactate ion.

Lactic Oxygen Debt
The oxygen necessary after strenuous exercise to remove lactic acid from the blood

LDL
Low density lipoproteins, see HDL.

Ligament
Elastic tissue joining bones to bones.

Lymph
Plasma, minus plasma proteins, is exuded (pushed) through the capillary walls by the blood pressure and bathes the tissues as 'tissue fluid', which is drained into the lymphatic system, where white cells known as lymphocytes are added by the lymph glands that occur throughout the system. The fluid is now known as lymph. It is returned to the circulatory system in the neck region. The lymphocytes help fight infection, if the lymph glands become infected they become swollen and painful (hence 'glandular fever').

Metabolism
All the chemical processes involved in maintaining life.

Mitochondria
Microscopic structures (from 0.001 mm - 0.4 mm) in cells and muscle fibres, just visible under the highest magnification of the light microscope. Centres of aerobic respiration using oxygen, regenerating ATP, and producing carbon dioxide and water as end products of the oxidation of glucose.

Monosaccharide
Literally 'single sugar', the simplest type of sugar molecules e.g. glucose.

Motor unit
All the muscle fibres supplied (innervated) by a single motor neurone.

Myogenic contraction
Initiating contraction without nervous stimulation, although nervous stimulation and hormones are involved in co-ordination and determining rate, e.g. cardiac muscle, and involuntary muscle in the wall of the gut.

Myoglobin
'Muscle haemoglobin', an iron containing muscle pigment, that when oxygenated acts as an oxygen storage compound in Slow Twitch muscle fibres, imparting a red colour, hence red muscle fibres.

OBLA
Onset of blood lactate accumulation. Although there are normally traces of lactate in the blood, it is generally agreed that a level of about 2 - 4 millimoles per dm3 (litre) represents OBLA, which correlates to the term 'anaerobic threshold'.

Optimum
The best possible.

Osmosis
The passage of water from regions of high water potential (pure water or more dilute solutions) to regions of low water potential (more concentrated solutions), across a partially permeable membrane (one that is more permeable to water than to dissolved substances (solutes)), down a water potential gradient until an equilibrium is reached. It is the special case of the diffusion of water. Sea water is more concentrated than blood, therefore if it is swallowed water moves from the blood and tissues by osmosis into the sea water in the gut. Fresh water is less concentrated than blood, therefore when drunk it moves by osmosis from the gut into the blood.

Oxidative potential
The ability to use oxygen in aerobic respiration.

Oxygen Debt
The amount of oxygen required to repay the oxygen deficit, by the removal of lactic acid and other metabolic products that accumulate when the supply of oxygen was below the needs of the individual during intense activity.

Oxygen Deficit
The amount of oxygen that the body is undersupplied with during a period of intense exercise, when oxygen consumption does not equal what is necessary to supply all the ATP from aerobic oxidation, during which time energy is partially supplied from anaerobic stores.

Parasympathetic nervous system
The part of the autonomic (involuntary) nervous system responsible for promoting normal relaxed functioning. Antagonistic to the sympathetic nervous system, e.g. the sympathetic nervous system stimulates an increase in the heart rate, and the parasympathetic nervous system decreases the rate.