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SDK125 Introducing Health Sciences - Glossary

Flashcards for glossary of level 1 Open University course, SDK125 Introducing Health Sciences
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absorbed dose
A measure of the amount of energy from ionising radiation absorbed per kilogram of tissue. It is measured in units of grays where 1 Gy = 1 joule per kilogram. (CS 4)
absorption
a) A process in which the photon energy is captured by a medium, without transmission or reflection. (CS 7)
b) The process by which the molecules released from digested food pass through the wall of the gut and into the surrounding blood vessels. (CS 3)
abstinence
Deliberately deciding never to drink alcohol. (CS 3)
accommodation
The change of thickness of the lens of the eye so that focal length changes. This allows light from objects at different distances to be sharply focused in turn on the retina. (CS 7)
acidosis
Abnormally high acidity (excess hydrogen ion concentration) of the blood and other body tissues.(CS 5)
action potential
A sudden change in potential difference (voltage) across the cell membrane of neurons, consisting of an increase in the resting potential and a sudden return to the resting value. Transmitted along axons and constitute the principal 'language' of communication within nervous systems. (CS 2 & 3)
acute condition
Disease, disorder or traumatic injury characterised by rapid onset, severe symptoms and short duration, from which the patient either recovers quickly or dies (CS 1 & 6). Some chronic (long-term) conditions can have acute episodes, e.g. exacerbations of COPD (CS 5), sudden worsening of glaucoma (CS 7).
acute effects
A response to a stimulus or substance (such as alcohol) which occurs rapidly and produces severe, possibly life-threatening, symptoms. (CS 3)
acute inflammation
Inflammation with a rapid onset, severe symptoms and short duration. (CS 5)
acute pain
Pain of relatively short duration and associated with actual damage to tissues. (CS 2)
adaptive characteristic
A characteristic of an organism is said to be adaptive if an individual possessing that characteristic has an advantage over other members of the same species in terms of survival or reproduction; e.g. ability to evade predators, attractiveness to the opposite sex. (CS 1)
adaptive value
The value of a characteristic in terms of its contribution to the survival and reproductive chances of an animal. (CS 2)
addiction
An excessive engagement in an activity despite negative consequences and a dependence upon the activity such that when access is denied, craving and withdrawal symptoms are seen. Most usually refers to dependency on a chemical substance but need not do so (e.g. gambling). (CS 3)
additive primary colours
Colours of light (red, blue and green) which, when added together, make white light. (CS 7)
adhesion
The joining of tissues to each other that may occur abnormally during repair.(CS 6)
affect
The dimension of positive and negative feelings, exemplified by, respectively, happiness and pain. (CS 2)
age-related macular degeneration
Degenerative disease of the retina that results in loss of vision in the centre of the visual field. It is caused by an impaired blood supply to the macula. This condition is usually associated with ageing. (CS 7)
age-standardisation
A mathematical adjustment that enables disease and mortality rates to be compared from countries with different age-structures, i.e. different proportions of young, middle-aged and older people in their populations. The method involves taking a very large 'reference population' (e.g. the whole of the world) and using its population age-structure as the 'standard' or reference point to which the different age-structures of individual countries are adjusted to remove the distorting effect. (CS 3, 4, 5 & 6)
agonist
A chemical that has the effect of mimicking the action of a natural substance such as a neurotransmitter. (CS 2 & 3)
agriculture
The cultivation of land for the purpose of crop production and/or the rearing of livestock, primarily for food, but also to provide materials, e.g. for fuel, clothing and shelter. (CS 1)
alcohol myopia
This term indicates alcohol's effect in inducing 'psychological short-sightedness'. Alcohol lowers the range of attention, so that immediate events take on more importance than their future consequences. (CS 3)
alcohol tolerant
The need to drink much more than in the past to achieve the same effect. (CS 3)
alcoholic liver disease
Categorised into three progressive stages: fatty liver, hepatitis and cirrhosis. (CS 3)
alcoholic poisoning
Intoxication so extreme that it leads to unconsciousness that can result in death.(CS 3)
allograft
A graft where the donor tissue comes from another person (as opposed to an autograft where it comes from the same person).(CS 6)
alpha-1 antitrypsin
A protein produced in the liver that circulates around the body and blocks the destructive effects of certain proteinase enzymes such as elastase. (CS 5)
alveolus
A small, thin-walled, air sac in the lungs surrounded by a network of blood capillaries where the exchange of oxygen and carbon dioxide takes place between the lungs and the blood. (CS 5)
amygdale
Brain region involved in processing memories and emotional reactions.(CS 6)
analgesia
The process of reducing pain, e.g. by taking morphine. (CS 2)
analgesics
Substances that have the effect of reducing pain. (CS 2)
antagonist
A chemical that has the effect of blocking the action of a natural substance such as a neurochemical. (CS 2 & 3)
antibiotic resistance
The ability of bacteria which have acquired a resistance gene to survive the action of an antibiotic drug that kills antibiotic-sensitive bacteria from the same strain. (CS 1)
anti-inflammatory
A drug that acts to reduce the signs of inflammation, e.g. swelling, redness, heat and pain.(CS 5)
aqueous humour
The transparent fluid that fills the space between the cornea and the lens of the eye. (CS 7)
arterial blood gas test
A test that measures the levels of oxygen and carbon dioxide in a sample of blood from an artery, e.g. in the wrist. Used to evaluate the efficiency of gas exchange between the blood and the lungs. (CS 5)
arteries
Blood vessels that convey blood away from the heart.(CS 3, 5 & 6)
astigmatism
A condition in which the cornea is irregularly curved.(CS 7)
atmospheric pressure
The pressure exerted by the Earth's atmosphere at a particular location as a result of the mass of the column of air above it. At sea level, it is 760 mmHg or 101.325 kPa. (CS 5)
atom
The smallest unit of an element that still has the properties of the element. Made up of a positively charged atomic nucleus, containing protons and neutrons, surrounded by negatively charged electrons. (CS 1, 2, 3, 4, 5, 6 & 7)
atomic nucleus
Contains protons, each of which carry a single positive electric charge, and neutrons which are uncharged. (CS 3 & 7)
attenuation coefficient
A value which can be used to calculate the degree to which X-rays (or other radiation) are reduced in intensity when passing through a material (e.g. human tissue). (CS 4)
attenuation
A reduction in the number of photons passing through a material. It is caused by both absorption and scattering. (CS 4)
autobiographical memory
Memory for events or issues related to oneself. (CS 6)
autograft
A graft where the donor tissue comes from the same person (as opposed to an allograft where it comes from another person).(CS 6)
autonomic nervous system
That part of the nervous system which exerts an influence over a number of the internal organs of the body, such as the gut, heart and blood vessels. Functions without conscious intervention. (CS 2 & 5)
axon
The part of a neuron that consists of a long wire-like projection, ending in a terminal which participates in a synapse with another cell. Action potentials are transmitted along these. (CS 2, 3, 6 & 7)
axon terminal
The end of an axon which participates in a synapse with another cell.(CS 2 & 3)
bacteria
Microbes living in and around us, most of which are harmless or beneficial but some of which can cause disease. (CS 1, 5, 6 & 7)
bar chart
A simple way of presenting numerical data visually, so as to emphasise the relative size of different numbers. May be arranged vertically or horizontally. (CS 1)
binge drinking
Drinking to get drunk rather than just for pleasure. (CS 3)
bioaccumulation
The build-up of levels of a chemical contaminant in the bodies of animals at successive levels in a food chain. (CS 1)
biomass fuel
Fuel derived from plant matter or animal waste, e.g. wood, straw, dried animal dung.(CS 5)
biopsy
The removal for diagnostic study of a piece of tissue from a living body. (CS 4)
bipedality
The ability to stand, walk and run, supported only by the hind limbs. (CS 1)
blind study
A study in which the participants do not know into which group they have been allocated, e.g. whether they have received a drug or a placebo. (CS 2)
blood pressure
The pressure exerted by blood pressing on the walls of the arteries. This is frequently expressed as two numbers, systolic (higher pressure during heart contraction) and diastolic (lower pressure between heart contractions), measured in mmHg. (CS 6)
blood-alcohol concentration
The concentration of ethanol in blood given in mg per 100 ml. (CS 3)
body mass index
A measure of body weight, taking height into account. Calculated by dividing person's weight (mass) in kilograms (kg) by their height in metres squared (m2). In most assessments, 20.0-24.9 is considered to be a normal healthy weight, 20.0 is categorised as underweight, 25.0 to 29.9 is said to be overweight, and greater than 30 is defined as clinically obese. (CS 1)
body systems
Also known as 'organ systems'; combinations of organs and tissues that function in a coordinated way; e.g. the circulatory system, the nervous system, the respiratory system. (CS 2)
bond dissociation energy
The energy needed to break a bond between two atoms. (CS 3)
bond length
The distance between atoms in a molecule. (CS 3 & 4)
bond
The electrical forces holding two atoms together. (CS 3 & 7)
bone marrow
Tissue in the centre of some large bones that contains cells (including stem cells) which are responsible for the production of white cells, red blood cells and a variety of other cells.(CS 6)
brain imaging
A technique for monitoring the activity of the different regions of the brain. One method involves injecting a radioactive tracer substance and measuring its later appearance in different brain regions; high concentrations correspond to regions of high activity in the neurons located there. (CS 2)
bronchiole
A small airway branching from a bronchus. (CS 5)
bronchodilator
A drug that widens the airways of the lungs and eases breathing by relaxing smooth muscle in the walls of bronchioles.(CS 5)
bronchus
One of the two main branches of the windpipe or trachea, leading to the lungs. (CS 5)
calcium ions
Vital to many chemical reactions in the body. Crystals containing these form an important part of the structure of bones. (CS 6)
cancellous
The type of bone that is less dense (compared with compact bone) and contains struts (trabeculae) to provide strength. It is found within the widened areas inside the ends of the bones. (CS 6)
cancer cell
A cell that is part of a malignant tumour; not subject to the body signals that tell normal cells when to divide or stop dividing, so they multiply in an uncontrolled way. (CS 4)
capillaries
The thinnest blood vessels. (CS 3, 5 & 6)
carboxyhaemoglobin
Haemoglobin bound to carbon monoxide. It is formed in the blood when carbon monoxide is inhaled, reducing the ability of the blood to form oxyhaemoglobin. (CS 5)
carcinoma
A cancerous tumour arising in epithelial tissue that has the ability to metastasise (spread) to other parts of the body. (CS 4)
cardiovascular system
The body system consisting of the heart, blood vessels and blood. It circulates blood throughout the body and is also known as the circulatory system. (CS4, 5 & 6)
cartilage
Tissue that is found at joints and during bone repair. Its structure is a bit like bone without the mineral component, giving a smooth and resilient surface to the ends of bones to aid movement at joints. (CS 6)
cast
A shell, typically made from plaster or fibreglass, which can be put around a limb in order to encase and support a broken bone until it has healed. (CS 6)
catalyst
A molecule that facilitates a reaction but which is left unchanged at the end; catalysis refers to the action of this. (CS 3, 5 & 6)
cataract
A visual impairment in which the lens of the eye loses transparency and exhibits reduced light transmission. (CS 7)
cell membrane
A thin membrane (a double layer of lipids) enclosing the cytosol and organelles of a cell.(CS 2, 3, 4 & 5)
cell
The basic structural unit of all organisms; there are many different kinds in multicellular organisms. In mammals, including humans, they are usually composed of a nucleus containing genetic material, surrounded by the watery cytosol containing various other organelles such as mitochondria. Enclosed by a membrane. (CS 2, 4, 5, 6 & 7)
cellular respiration
The process whereby oxygen is taken up by cells and used in chemical reactions involving the oxidation of nutrient molecules (e.g. glucose) derived from food; these reactions release usable chemical energy for cellular processes. (CS 5 & 7)
centilitre
A subunit of the litre, the standard scientific (SI) unit for measuring volume; there are 100 of these in a litre. (CS 3)
central nervous system
The part of the nervous system consisting of the brain and spinal cord. (CS 2 & 6)
cerebral hemisphere
Much of the brain is divided down its midline into two halves, the left and right of this; also referred to as the 'left brain' and the 'right brain'. (CS 2)
chemical bond
The electrical forces holding two atoms together. (CS 3 & 7)
chemical compound
Often abbreviated to 'compound': a substance made up of two or more elements; it may be composed of molecules or ions. (CS 1, 2, 3 & 7)
chemical formula
Tells you which type of atoms are bonded together to make up a compound or molecule, using symbols for its constituent elements. It also shows how many of each type of atom there are (e.g. the formula for carbon dioxide, CO2, shows it has one carbon and two oxygen atoms). (CS 3 & 5)
chemical symbol
Each element has been assigned one of these - often the first letter, or two of the first letters of the name; for example, H stands for hydrogen, C for carbon, N for nitrogen, Ca for calcium and O for oxygen. (CS 3 & 7)
chemoreceptor
A sensory nerve cell or group of cells that responds to a chemical stimulus. (CS 5)
child mortality rate
The number of children who die under five years of age in a given year, usually expressed as a rate per 1000 live births. (CS 1)
choroid
The layer of the eye, between retina and sclera, which absorbs any light that has not interacted with the rods and cones in the retina. (CS 7)
chronic bronchitis
A condition characterised by inflammation of the walls of the airways and excess production of mucus. It results in a persistent (chronic) cough with production of sputum, obstruction of airflow and increased vulnerability to respiratory infections. (CS 5)
chronic condition
Disease or disorder that often has a gradual onset, involves slowly changing symptoms and lasts for a long time. (CS 1, 5 & 7)
chronic effects
Gradual changes that occur slowly over time and may be irreversible, often in response to repeated exposure to a stimulus or toxic substance (e.g. alcohol).(CS 3)
chronic inflammation
Persistent inflammation over long periods of time that occurs when the tissues are unable to overcome the effects of an injurious agent. (CS 5)
chronic obstructive pulmonary disease
An irreversible lung disease that is a combination of emphysema and chronic bronchitis, in which airway obstruction causes breathing difficulties, including shortness of breath. (CS 5 & 6)
chronic pain
Pain that lasts for months or years and which typically persists beyond the time of tissue healing. (CS 2)
cirrhosis
A gradual change in about 10% of chronic heavy drinkers whereby liver cells are replaced by scar tissue. (CS 3)
classical conditioning
A form of conditioning in which a stimulus with no intrinsic capacity to trigger a particular response acquires such a capacity by being paired with a stimulus that does trigger the response; e.g. a bell can come to trigger salivation in a dog if it is repeatedly presented at the time food is given. (CS 2 & 3)
closed fracture
Any fracture where the skin has not been broken. (CS 6)
closed-angle glaucoma
Type of glaucoma in which the outflow of aqueous humour from the eye is blocked because the gap between the iris and the cornea has closed. (CS 7)
cognition
Certain kinds of activity with which the brain is engaged, i.e. the processing of information that is summarised by the term 'mind'. It is exemplified by thinking, memory, reasoning and interpreting. (CS 2)
cognitive-behavioural therapy
A technique where people learn to change their thought patterns and behaviour to create feelings of coping and self-efficacy; e.g. people in chronic pain might be taught to place a less catastrophic interpretation on their pain. (CS 2)
collagen
A protein that is abundant in the extracellular matrix and can form long thin fibres to provide structure to many tissues.(CS 5 & 6)
colour blind
Condition in which no colour at all can be seen. (CS 7)
colour deficiency
Condition in which the full range of colours cannot be clearly distinguished.(CS 7)
compact bone
The type of bone (sometimes called compact) that is more dense (compared with cancellous bone) and very strong. It is found in the parts of the bone that need to withstand the largest forces. (CS 6)
complementary colours
Colours on opposite sides of the colour circle. (CS 7)
concave
A lens shape with a greater thickness at each end than through the centre. (CS 7)
conditional stimulus
A stimulus that has no intrinsic power to trigger a particular response but which acquires this power after being associated with another stimulus. For example, a bell does not normally trigger salivation but, after pairing with food, it acquires this capacity. The capacity of the conditional stimulus is said to be conditional upon the association. (CS 3)
cones
The photoreceptor cells located in the retina that are responsible for daytime and colour vision. (CS 7)
confounding factor
Any factor which is statistically associated with a particular outcome (e.g. the incidence of a disease), but which is not involved in its causation. The association can disguise the true cause (or causes) of the outcome. (CS 3 & 6)
conjunctivitis
A condition in which the conjunctiva is inflamed.(CS 7)
connective tissue
A tissue made up of cells embedded in a matrix of protein fibres which includes bones, fat and tendons; they connect, support, or surround other tissues and organs. (CS 5 & 6)
contagious
Refers to an infectious disease that can be transmitted by physical contact. (CS 7)
convex
A lens shape with a greater thickness at the centre than at each end. (CS 7)
cornea
The curved transparent layer that covers the front part of the eye. This (together with the lens) refracts light to form of an image on the retina, as well as protecting the eye from frontal damage. (CS 7)
coronary heart disease
This condition occurs when the arteries supplying oxygen and nutrients to the heart muscle become blocked by fatty deposits known as plaques, and areas of muscle die as a result. (CS 3)
cortex
The outer layer of the brain, also known as the 'cerebral cortex'. (CS 2 & 3)
covalent bond
A bond between two atoms formed when an outer electron from each of the atoms is shared between them to form an electron pair bond. (CS 3 & 7)
craving
An intense conscious occupation with thoughts of the object of an addiction. (CS 3)
dementia
A general loss of intellectual abilities including memory, judgement and abstract thinking, as well as personality changes. (CS 3)
deoxygenated blood
Blood that contains very little oxygen.(CS 5)
dependence
A state in which addicts come to depend upon a drug for their 'normal' mental functioning. (CS 3)
dermis
The skin layer that lies beneath the epidermis and provides the strength and elasticity of the skin.(CS 6)
deterministic
The effects of ionising radiation are said to be this if there is a threshold below which there is no effect, and if above that threshold, the severity depends on the amount of radiation received. (CS 4)
developed countries
Countries that provide universal education for their children, with populations that have high rates of literacy, comprehensive health services and which meet certain other development indicators, such as 100% access to safe drinking water and sanitation. Their economies grew rapidly in the early 20th century as a result of industrialisation, and they include all the richest nations on Earth (also known as 'high-income countries'). In some classifications, the countries of the former Soviet Union are included in this group; in others they are classed as 'transitional economies'. (CS 1, 2, 3, 4, 5, 6 & 7)
developing countries
Countries that are only partly industrialised and where national wealth is below that of the developed economies (also known as low- and middle-income countries). They rely to a much greater degree than developed countries on subsistence farming, small industrial businesses and low-paid unskilled or low-skilled labour. Major indicators of development, such as literacy and provision of clean water vary hugely between these countries. (CS 1, 2, 3, 4, 5, 6 & 7)
diabetic retinopathy
Damage to the retina due to the abnormal blood flow that may develop in people with diabetes. (CS 7)
diaphragm
A muscular wall separating the chest (thoracic) cavity from the abdominal cavity in mammals.(CS 5)
diarrhoeal diseases
Diseases involving the frequent passing of liquid faeces; they are caused by a wide variety of pathogens, including viruses, bacteria and protoctists (single-celled organisms). (CS 1)
diastolic blood pressure
The blood pressure that is detected between heart contractions (lower than the systolic blood pressure).(CS 6)
diffusion
The movement of atoms or molecules from a region of higher concentration to a region of lower concentration, until the concentration is the same throughout the available volume. Atoms and small molecules can also move across a permeable cell membrane by diffusion, if a concentration gradient exists (e.g. between the inside and the outside of the cell). (CS 3, 5, 6 & 7)
disability adjusted life year
A measure of the real impact of a particular disease, disorder or disability on people's lives (DALY), combining an estimate of the number of years lived with a reduced quality of life, taking into account the severity of the condition (every condition is assigned a 'weighting factor' to reflect this), and the number of years of life lost if the person dies prematurely, based on their age and the average life expectancy in that population. (CS 1, 3, 5 & 6)
disease risk factors
Often abbreviated to 'risk factors'; anything that is statistically associated with an increased chance of developing a particular disease, disorder or disability in a population; when the incidence of the disease is examined in different populations it is found to occur more frequently in those who have been exposed to the risk factor than in those who have not, or whose exposure level has been lower. (CS 1, 4, 5, 6 & 7)
disinfectant
A chemical that reduces microbial contamination of water, surfaces, etc. (CS 1)
deoxyribonucleic acid
A very long macromolecule found in the cell nucleus, abbreviated to DNA. It is the main component of chromosomes and is the material that transfers genetic characteristics through the generations in all organisms. The genetic information is carried in the sequence of the bases that make up the DNA. This sequence codes for thousands of genes that direct the manufacture of all the proteins in a cell. The form and function of proteins determines the characteristics of an individual organism. (CS 4)
DNA repair protein
Any one of numerous proteins in a mammalian cell that are part of the machinery that detects and repairs mistakes in DNA caused by errors during DNA copying, or by the effects of mutagens. They help to minimise the number of mutations, and when they are inactivated the rate of DNA mutation increases. (CS 4)
double bond
A covalent bond formed by the sharing of four electrons, two from each atom at either end of the bond. (CS 3)
double-blind study
A study in which neither the participants (e.g. patients) nor the experimenters (e.g. therapists) know into which group the participants have been allocated (e.g. either drug or placebo groups). (CS 2)
double-strand break
A break in both of the helical strands of a DNA molecule, caused by ionising radiation. (CS 4)
drainage angle
The structure within the eye where the iris meets the cornea, where excess aqueous humour from the front of the eye can drain. (CS 7)
dry AMD
Most common type of age-related macular degeneration, in which the blood supply to the retina is reduced, resulting in gradual loss of vision. (CS 7)
duct
A tube conveying a body fluid, especially a glandular secretion, for example milk from the lobules of the mammary gland to the nipple. (CS 4)
ecosystems
Recognisable assemblages of plants and animals, such as woodland, grassland, rivers, etc., in which a distinct set of plants and animals live together and interact with one another. (CS 1)
ecotoxicology
The study of the fate of chemical contaminants in the natural environment and their effects on plants, animals and ecosystems. (CS 1)
effective dose
A measure of the dose of ionising radiation to an organism which takes into account the sensitivity to radiation of different organs in the body. Multiplied by a tissue weighting factor for that organ. Then the amounts for all the affected organs are added up to give this for the whole body. Measured in sieverts (symbol Sv). Best measure to use to estimate the likelihood of developing radiation-induced cancer. (CS 4)
elastase
A proteinase (protein-degrading) enzyme that catalyses (facilitates) the breakdown of elastin and other related proteins.(CS 5)
electromagnetic radiation
A form of energy that can be described as either a wave or as a flow of 'packets' of energy. It includes gamma rays, X-rays, ultraviolet, visible light, infrared, microwaves and radio waves. The different types of radiation are distinguished by their wavelength and frequency; radio waves have the longest wavelength and lowest frequency; X-rays and gamma rays have short wavelengths and higher frequencies. See Book 4, Figure 4.2. (CS 4 & 7)
electronegative
An atom that is better than other atoms at attracting electrons to itself; e.g. oxygen (CS 3)
electron
Negatively charged particle of almost no mass that surround the nucleus of an atom.(CS 2, 3, 5 & 7)
electronvolt
A small unit of energy frequently used by physicists and denoted by the symbol eV. (CS 4)
element
A substance that cannot be broken down into simpler substances by chemical reactions. It consists only of the atoms characteristic, e.g. hydrogen (H), oxygen (O), nitrogen (N), sodium (Na), chlorine (Cl), mercury (Hg). There are 92 naturally occurring of these found on Earth. ( CS 1, 2, 3, 4 & 5)
emphysema
A chronic, irreversible disease of the lungs characterised by loss of elastic recoil and enlarged air spaces in the lungs due to destruction of the walls of the alveoli and small airways.(CS 5)
endocrine disruptors
Industrial chemicals, commonly found as environmental pollutants, that disrupt the hormonal systems of animals, including humans. (CS 1)
endocrine system
A system of glands (also known as ductless glands), each of which secretes one or more hormones directly into the bloodstream. (CS 1, 2 & 3)
endothelial cells
The flat cells that line the cardiovascular system.(CS 6)
enzyme
A protein produced by a living organism that functions as a catalyst. It facilitates other molecules entering into chemical reactions with one another, but is itself unaffected by these reactions.(CS 3, 4, 5 & 6)
epidemic
An outbreak of an infectious disease in a community, region or country, characterised by a sharp increase in the number of cases, followed after an interval by a decline to a normal level (CS 1)
epidemiology
The statistical study of the occurrence, distribution, potential causes and control of diseases and disabilities in human populations (CS 1, 3, 4 & 6)
epidermis
The outer waterproof protective layer of the skin. (CS 6)
epinephrine
A hormone secreted by the suprarenal gland (formerly the adrenal gland) upon stimulation by the central nervous system in response to stress, anger, fear or exertion. It has many effects on the body, e.g. increasing heart rate and output. Also known as adrenalin. (CS 2 & 5)
epithelial cells
Cells that cover all surfaces of the body. (CS 3, 4, 6 & 7)
epithelial tissue
A tissue that covers a surface or lines a space inside the body, forming a barrier or interface across which substances are absorbed or secreted, e.g. the skin, gut lining, and various glands. (CS 4 & 6)
equivalent dose
A measure of the dose of ionising radiation to an organ that takes into account the type of radiation used. Some types of radiation are more damaging than others (because they tend to lead to double-strand breaks in the DNA rather than the more easily repaired single-strand breaks) so a radiation weighting factor is used. For X-rays this factor is 1. Measured in sieverts (symbol Sv). (CS 4)
erythrocyte
The type of blood cell that transports oxygen; also known as a red blood cell. (CS 5)
ethanol
One of a family of similar chemicals that have the generic name of 'alcohol', with the chemical formula C2H5OH. (CS 3)
evolutionary trade-off
An aspect of a characteristic that represents an adaptive compromise between two opposing evolutionary pressures; e.g. the human pelvis represents a compromise between being narrow, which is necessary for running at speed, and being wide, which is necessary for giving birth to a baby with a large head. (CS 1)
excitatory synapse
A synapse at which the release of neurotransmitter from a presynaptic neuron has an excitatory effect on a postsynaptic cell, e.g. it excites further action potentials in a second cell. (CS 2 & 3)
excretion
The separation of waste products from the blood. (CS 3)
expiration
The process of expiring or breathing out; the emission of air from the lungs.(CS 5)
extinction
A process whereby a stimulus that owes its power to conditioning loses this power by being repeatedly presented on its own; e.g. the ceasing of the capacity of a bell to trigger salivation occurs if the bell is repeatedly sounded, but without food being given. (CS 2 & 3)
extracellular matrix
The material outside the cells in a tissue in which the cells are embedded. It is mainly made from proteins made by and arranged by the cells. (CS 6)
false negative
In screening, a person whose screening test result is negative (indicating no disease), but who actually has the disease. (CS 4)
false positive
In screening, a person whose screening test result is positive (indicating disease), but who actually does not have the disease.(CS 4)
fatty liver
An early and reversible consequence of excessive alcohol consumption during which fat accumulates within the cells of the liver.(CS 3)
fetal alcohol syndrome
A disorder of the fetus or infant caused by excessive maternal alcohol intake during pregnancy. (CS 3)
forced expiratory volume in one second
The amount of air that can be forcefully expired from fully inflated lungs in the first second of expiration, abbreviated to FEV1. (CS 5)
fibrin
An insoluble fibrous protein that forms clots following tissue damage. (CS 6)
fibroblast
A type of cell that can migrate into wound sites and make new extracellular matrix proteins such as collagen.(CS 6)
fibrosis
The process by which collagen is produced by fibroblasts following tissue damage, often resulting in scar formation.(CS 6)
focal length
The distance between the principle focal point and the centre of a lens. (CS 7)
force
The size and direction of a push or pull. (CS 6)
forced vital capacity
The total amount of air that can be forcefully expired from fully inflated lungs, abbreviated to FVC. (CS 5)
fovea
A small depression in the retina of the eye, with high visual capability, consisting exclusively of cones. (CS 7)
fracture
A break in the continuity of a bone. Classified according to the extent of damage and the subsequent position of the broken pieces. (CS 6)
fulcrum
The pivot point about which a lever rotates.(CS 6)
gas pressure
The pressure exerted by a gas. It is the sum of the partial pressures of each individual gas in a mixture of gases, e.g. oxygen, carbon dioxide, nitrogen and other gases that make up the air in the lungs. (CS 5)
gas transfer test
A method for determining the efficiency of gas transfer between the lungs and the pulmonary blood capillaries.(CS 5)
gate theory
A theory of pain that was first proposed by Patrick Wall and Ronald Melzack in 1965. It suggests that there is, metaphorically speaking, a 'gate' within the spinal cord such that, if the gate is closed, nociceptive messages can be blocked. If the gate is open, the nociceptive signal can gain access to the brain and hence trigger pain. (CS 2)
gene
A segment of this contains the coded information required for a cell to make a particular protein. Humans probably have about 25 000. Different forms or variants of these, called alleles, determine how these characteristics are expressed in a given individual. Undergo mutation when their sequence changes. (CS 3, 4, & 5)
glaucoma
A condition in which the optic nerve becomes damaged, usually because the pressure of fluid within the eye becomes too high, leading to a progressive loss of vision. (CS 7)
granulation tissue
The new tissue formed as a wound repairs, containing tiny new blood vessels that give it a grainy appearance. (CS 6)
grays
The unit of absorbed dose of ionising radiation; 1 Gy = 1 joule per kilogram of tissue. (CS 4)
greenstick fracture
A fracture where the bone bends and only breaks on one side; commonest in children, whose bones tend to bend rather than break completely. (CS 6)
haemoglobin
A complex molecule composed of smaller molecules (globin and haem) and iron atoms. It is a component of erythrocytes and its function is to bind reversibly to oxygen. (CS 5)
hard problem of consciousness
The problem of trying to explain how the subjective feelings of consciousness arise from the physical matter of the brain. (CS 2)
heat capacity
The quantity of heat required to raise the temperature of a body, or a quantity of liquid, by 1 °C, measured in joules (J) per °C. (CS 1)
hepatitis
An inflammation of the liver which can vary in severity. (CS 3)
high-risk screening
A screening programme (sometimes called 'individual screening' or 'targeted screening') that identifies individuals who are likely to be at substantially greater risk of developing a certain condition than others in their population group. These individuals are sought out for regular screening, e.g. people with diabetes are screened for signs of visual impairment more often than non-diabetics. (CS 4)
hippocampus
A brain region with an essential role in the storage and retrieval of memories.(CS 6)
homeostasis
A property of the body in which a number of its important parameters are held near to constant and any deviation from their normal value triggers action that tends to restore normality. It is exemplified by the maintenance of body temperature, or of oxygen concentration in the bloodstream, etc. (CS 1)
hominids
A group of primates, to which modern humans belong, characterised by upright posture and a very large brain in relation to body size. (CS 1)
hormone
A substance produced by an endocrine gland that is carried around the body in the blood, and affects the structure or functions of specifically receptive target organs or tissues. (CS 1, 2, 3, 4, 5 & 6)
hydrogen bond
A type of chemical bond formed between a partial positive charge on a hydrogen atom and a partial negative charge on another atom. In more detail, the bond is formed by the electrical attraction occurring between the partial positive charge remaining on a hydrogen atom that is attached to an electron-attracting atom (usually oxygen or nitrogen), and the partial negative charge on the other atom in the bond (usually oxygen or nitrogen) which is attracting an electron from the hydrogen atom. Responsible for maintaining the complex three-dimensional structure of large organic molecules such as proteins and DNA. (CS 1, 3, 4 & 7)
hydroxyl group
An atom of hydrogen and an atom of oxygen bonded together, which is bonded to an organic molecule; can form hydrogen bonds with other polar molecules. (CS 1, 3 & 7)
hyperopia
The visual condition of long-sightedness in which images of nearby objects cannot be focused sharply. (CS 7)
hyperventilate
To breathe more rapidly and deeply than normal.(CS 5)
hypnosis
A technique in which a person is placed in a particular psychological state and, in response to suggestions made by the hypnotist, can experience alterations in perception, memory and voluntary action. (CS 2 & 6)
hypothesis
A clearly stated provisional explanation for a set of observations or data, devised for the purpose of testing its validity by the collection of additional data or by conducting an experiment. (CS 1)
hypovolaemic shock
A state of inadequate supply of oxygen to the brain and other vital organs, often as a result of severe blood loss.(CS 6)
hypoxia
Insufficient levels of oxygen in the blood or tissue.(CS 5)
image
A two-dimensional map or projection of an object. (CS 7)
immune system
The integrated body system of organs, tissues, cells and proteins that functions to protect the body from potentially pathogenic organisms (microbes) or harmful substances. (CS 4, 5, 6 & 7)
immunodeficiency
A condition in which the immune system fails to respond normally to an infection; it can be caused by a genetic defect and by HIV/AIDS, as well as by malnutrition. (CS 2)
incidence rate
The number of new cases in a given period, usually a year, expressed as a rate per 1000 (or per 10 000, or per 100 000 or per million) population (CS 1)
incidence
Number of new cases of a condition diagnosed in a population in a given period, usually one year. (CS 1, 2 & 4)
incubation period
The time between a pathogen entering its host and the host beginning to show disease symptoms; varies from one infectious disease to another. (CS 1)
infant mortality rate
An internationally recognised health indicator, defined as the number of babies in every 1000 live births who die in their first year of life. (CS 1)
infectious dose
The number of individual pathogens required to cause disease in an infected person; the number varies from one infectious disease to another. (CS 1)
inflammation
A protective reaction of body tissues to irritation, injury, or infection, characterised by pain, heat, redness and swelling. (CS 3, 5, 6 & 7)
inflammatory mediators
Molecules or proteins released by immune system cells in the region of an injury, infection or other damage to the tissues. They have several effects including dilation (widening) of blood vessels to increase blood supply to the region. They also attract other immune system cells. (CS 5)
information processing
The ability of the brain to take information and perform informed calculations (e.g. calculating the width of a space in which to park a car). (CS 3)
inhibitory synapse
A synapse at which the release of neurotransmitter from a presynaptic neuron has an inhibitory effect on a postsynaptic cell, i.e. it inhibits the appearance of action potentials in the second cell.(CS 2 & 3)
inspiration
The process of inspiring or inhaling; the drawing in of air into the lungs.(CS 5)
insufficiency fracture
A fracture that occurs because the bone has been weakened through osteoporosis. (CS 6)
intensity
The number of photons passing through a given area per second. (CS 4)
interneuron
A class of neuron that is neither sensory nor motor. (CS 2)
invasive cancer
A cancer that has the ability to spread or metastasise into healthy tissue. (also known as 'malignant' cancer) (CS 4)
ion
An electrically charged atom or molecule. May be positively or negatively charged; e.g. Na+ (the positively charged sodium ion) and Cl- (the negatively charged chloride ion). (CS 1, 2, 3, 4 & 5)
ionic bonding
Bonding which is due to the electrical attraction of equal and opposite electrical charges and which holds the ions in salt crystals together.(CS 3 & 4)
ionic compound
A substance composed of positively and negatively charged ions, held together by the electrical attraction between opposite charges. Salts such as sodium chloride (NaCl), in which the ions are organised in a regular crystal lattice, are this. (CS 1 & 3)
ionisation
The removal of one or more electrons from an atom or molecule.(CS 3 & 4)
ionising radiation
Radiation which can cause ionisation. From the electromagnetic spectrum this includes gamma rays, X-rays and some high-energy ultraviolet radiation. (CS 4)
iris
A thick ring of muscle that controls pupil size, thereby regulating the amount of light that enters the eye. It forms the coloured portion of the eye. (CS 7)
laser
A device that produces light of a single wavelength which is transmitted in a narrow and powerful beam. (CS 7)
LASIK
Abbreviation of a eye-surgery technique where a flap is cut in the cornea and laser treatment applied beneath. (CS 7)
legal blindness
Visual acuity worse than 6/60. (CS 7)
lens
a) A transparent and flexible convex structure behind the iris that (together with the cornea) refracts light. (CS 7)
b) A transparent object, usually made of glass or plastic, that refracts light. Found in spectacles, magnifying glasses and microscopes. (CS 7)
leukocytes
Immune system cells that circulate around the body helping to protect it from infection and some other types of disease; also known as white cells. (CS 5 & 6)
levers
Rigid structures (such as bones) that can move about a fulcrum in response to forces in order to transfer force from one place to another. They can modify the size of the force and the distance of motion. (CS 6)
ligaments
Tissues that are like tendons in terms of structure but connect bones to each other (rather than bones to muscles). (CS 6)
light ray
A narrow beam of light used to show the direction of travel of light from a source. (CS 7)
litre
The standard scientific (SI) unit for measuring volume; it has the symbol l.(CS 3)
lobule
A subdivision of a rounded mass of tissue. For example, in the breast, this is used to describe an individual branched subsection of the mammary gland. (CS 4)
lock-and-key interaction
The binding that occurs between a signalling molecule and its specific receptor. The specificity of the binding is analogous to that of a particular key in a particular lock; e.g. the binding between a neurotransmitter and its receptor, or a hormone and its receptor. (CS 1, 2 & 4)
low vision
Optimal corrected visual acuity worse than 6/18, i.e. wearing optimal correcting lenses, the individual can distinguish letters on a test chart at 6 metres that a person with normal vision could read at 18 metres (CS 7)
lower respiratory infection
An infection of the lower respiratory tract (the bronchi and lungs), e.g. pneumonia.(CS 5)
lung function test
A test that evaluates how well the lungs work; also known as a pulmonary function test. (CS 5 & 6)
lymph node
A bean-shaped tissue packed with immune system cells found at intervals along the vessels of the lymphatic system. They filter potentially harmful substances and organisms (microbes) from body fluids that drain into the lymphatic system; the filtered fluid (lymph) is returned to the blood stream. (CS 4)
macula lutea
The yellow central area of the retina containing the fovea. (CS 7)
malignant cancer
A cancer that has the ability to spread or metastasise into healthy tissue. (Also called 'invasive' cancer) (CS 4)
mammals
A class of animals characterised by having the body covered in hair, by having a four-chambered heart, and by feeding their young on milk produced by the female. (CS 1)
mammography
X-ray imaging of the breast. (CS 4)
media
Substances in which an interaction or reaction occurs, or in which an event takes place, or chemicals or objects are transported or supported, e.g. a medium through which a wave is transmitted in the refraction of light. (CS 7)
metabolism
The process of breaking down foods in the body into the molecules needed to maintain life.(CS 3)
metastasis
The spread of malignant, cancerous cells to other parts of the body by way of the blood or lymph vessels.(CS 4)
microbes
Microscopic organisms (bacteria, fungi and protoctists), together with viruses, whether pathogenic (disease-causing) or harmless; also known as microorganisms. (CS 1 & 5)
microcalcifications
Tiny particles of calcium that appear as small specks on a mammogram. When clustered in one area of the breast, they may indicate the presence of cancer cells. (CS 4)
millilitres
A subunit of the scientific unit of volume - the litre. One litre can be divided into 1000 of these. (CS 3)
mind
A difficult and controversial term to define, in spite of its everyday use. It describes all the information processing carried out by the brain. (CS 2)
mitochondrio
An organelle (plural: mitochondria) in the cytosol of cells where much of cellular respiration takes place (the release of usable chemical energy from molecules derived from food). (CS 4, 5 & 6)
molecule
Two or more atoms held together by chemical bonds, e.g. hydrogen (H2), water (H2O), carbon dioxide (CO2). (CS 1, 2, 3, 4, 5 & 7)
morbidity rate
The number of cases of a disease, disorder or disability in a population, relative to the total number of people at risk of developing it; usually expressed as the number of cases per 1000 (or per 10 000, or per 100 000 or per million) population. (CS 1)
morbidity
Disease, disorder or disability. (CS 4, 5 & 6)
mortality
Death. (CS 3 & 5)
mortality data
Counts of deaths. (CS 1 & 3)
mortality rate
The number of deaths in a population, either from all causes combined or from a specific cause, expressed as a rate per 1000 (or per 10 000, or per 100 000 or per million) people in the population. (CS 1, 4 & 6)
motor neuron
A class of neurons that convey information from the central nervous system (CNS) to the muscles. (CS 2)
mucus
A slimy, viscous substance secreted as a protective lubricant by the cells in the lining of the nose, throat and airways. Traps microbes and particles and is swept out of the respiratory system into the throat, to be coughed out or swallowed. Also secreted by the gut where it lubricates the passage of food and protects the cells lining the gut. (CS 5)
multifactorial disease
Diseases or disorders that develop as a result of the interaction over time of a combination of different risk factors, none of which on its own would be likely to cause the disease. These may include the inheritance of certain gene mutations from a parent, exposure to chemical and biological agents from environmental sources, and individual characteristics such as age or gender or obesity. (CS 3 & 5)
musculoskeletal system
The system of muscles and bones and their various joints and linkages that facilitates support and movement in the body. (CS 6)
mutagen
An agent, such as a chemical, ultraviolet light, or a radioactive substance that can induce, or increase the frequency of, mutations in DNA. (CS 4)
mutation
A change in the sequences of bases in the DNA of an organism, resulting in an alteration in the manufacture or function of a body protein. Also refers to the process by which such a change in DNA sequence occurs due to the action of a mutagen, e.g. radiation, or DNA-damaging chemicals in the environment. (CS 4)
myofibre
A type of cell that is responsible for contraction in skeletal muscle tissue. They are long and thin and have many nuclei. (Also known as muscle fibre) (CS 6)
myofibrils
The organelles found inside myofibres that run the length of the cell and cause contraction. (CS 6)
myopia
The visual condition of short-sightedness in which images of distant objects cannot be focused sharply. (CS 7)
natural selection
A process causing evolutionary change over time (from one generation to the next). Individuals that hold an advantage in terms of survival and reproduction, in competition with other individuals, will pass on characteristics that contribute to that advantage to successive generations, provided that those characteristics have a genetic basis. As a result, these characteristics become more common in the population over successive generations. (CS 1)
nearwork activity
An activity where the eye is constantly focused on objects nearby (e.g. reading). (CS 7)
negative feedback
A process whereby a parameter is maintained at a nearly constant value because deviations from its normal value tend to trigger actions that 'negate' the deviation and return it to normality; e.g. a fall in body temperature is fed back via the nervous system, which triggers shivering and this tends to raise body temperature back to normal. (CS 2)
negative predictive value
For a screening procedure such as mammography, this value is the number of true negative results expressed as a percentage of the total number of negative results (true or false). It tells (other things being equal) what the chance is that a person with a negative test result actually does not have the disease being screened for. (CS 4)
nephrons
Structures in the kidney that filter the blood and produce the urine.(CS 3)
nerve
A bundle of the axons of neurons in the peripheral nervous system. (Occasionally employed informally to refer to a bundle of axons within the central nervous system.) (CS 2)
neurogenic pain
Pain that arises from damage to neurons either within the central nervous system or in the periphery of the body. (CS 2)
neuron
A type of cell that is found within the nervous system and which is specialised to transmit and process information (colloquially referred to as 'nerve cell'). (CS 2, 3, 4, 6 & 7 )
neurotransmitter
A chemical that is stored within the axon terminal of a neuron and is released in response to electrical activity within that neuron. It passes the short distance to a neighbouring cell (neuron or muscle cell) where it binds to a neurotransmitter receptor, initiating an effect in that cell. The term 'synapse' describes the location of these events. (CS 2, 3, 6 & 7)
neutron
An uncharged particle in the nucleus of an atom.(CS 2 & 3)
nociception
The process of detecting stimuli that cause actual or potential damage to the tissues of the body. (CS 2)
nociceptive pain
Pain that is triggered by a stimulus that causes actual or potential damage to the tissues of the body. (CS 2)
non-communicable diseases
Diseases that cannot be transmitted from person to person (also known as 'non-infectious diseases' or 'chronic conditions' or 'long-term conditions'); they mainly develop slowly over time and persist for a long period, or are irreversible; e.g. cancers, heart disease, respiratory diseases, diabetes, cirrhosis of the liver, and neuropsychiatric conditions such as Alzheimer's disease and other dementias. (CS 1)
noxious stimuli
Stimuli that are associated with actual or potential damage to body tissues. (CS 2)
nucleus
a) Contains protons, each of which carry a single positive electric charge, and neutrons which are uncharged. (CS 2 & 4)
b) An organelle containing the genetic material, found in most animal and plant cells. (CS 2, 4 & 6)
obesity
A condition in which a person exceeds a certain threshold for the proportion of body weight that consists of fat. In most assessments based on body mass index, a BMI of greater than 30 is defined as clinically obese. (CS 1)
oestrogens
A group of steroid hormones produced mainly by the ovaries (some are also produced by fat deposits in the body), which are responsible for promoting the development and maintenance of female sexual characteristics. (CS 4)
open angle glaucoma
The most common type of glaucoma, caused by a partial blockage of trabeculae, which reduces the rate at which the aqueous fluid can drain away from the eye and thus leads to a build up of intraocular pressure. (CS 7)
open fracture
Any fracture where the overlying skin is broken.(CS 6)
ophthalmologist
A qualified doctor who has specialised in the diagnosis and treatment of eye conditions, and who can perform eye surgery. (CS 7)
opiates
A class of substances arising from outside the body, but which bear a close similarity to naturally occurring opioids in their structure and effect; they include heroin derived from the opium poppy and morphine. (CS 2)
opioid
A class of natural neurotransmitters that have a similar structure and action to morphine and heroin. (CS 2)
opportunistic screening
Screening that takes place haphazardly when an opportunity arises, for example, when a patient consults a doctor about something unrelated and is referred for a screening test. (CS 4)
optical power
A measure of the refracting power of a lens. Calculated as: 1 / focal length of the lens (in metres). The unit used is dioptres (symbol D). The power of a convex lens is positive; for a concave lens it is negative. (CS 7)
optician
An eye care professional who makes spectacles or contact lenses and advises on suitable frames or lens choices. (CS 7)
optometrist
An eye care professional qualified to perform eye tests and record the findings in a lens prescription.(CS 7)
organ
Complex structures in the body formed from a number of different tissues, which form a distinct structure and serve a particular function, e.g. the heart, the brain, the lungs. (CS 2 & 4)
osteoblasts
The cells that produce new bone.(CS 6)
osteoclasts
The cells that resorb (disassemble) bone.(CS 6)
osteoporosis
A disease in which an excessive loss of bone structure occurs.(CS 6)
oxidation
A chemical reaction involving the addition of oxygen.(CS 3 & 5)
oxygenated blood
Blood that contains a high level of oxygen and in which most of the haemoglobin has been converted into oxyhaemoglobin by bonding to oxygen.(CS 5)
oxyhaemoglobin
Haemoglobin bound to oxygen molecules. Transports oxygen from blood vessels in the lungs to the cells in the rest of the body. (CS 5)
pain matrix
A collection of different brain regions that is activated in response to painful stimuli and is associated with the experience of pain. (CS 2)
pain
An unpleasant sensory and emotional experience traditionally associated with actual or potential tissue damage and which normally is felt to arise in a particular location in the body. The term can also be used to refer to experiences triggered by social loss. (CS 2)
pandemic
An epidemic on a world-wide scale. (CS 1)
partial pressure
The pressure that one component of a mixture of gases would exert if it were alone in a container. (CS 5)
particulates
Fine particles of a solid suspended in the air. (CS 5)
pathogens
Microbes that cause disease. (CS 1, 5 & 7)
period
The time between one peak of a wave and the next . (CS 4)
peripheral nervous system
That part of the nervous system that is not within the central nervous system. It is made up of nerves throughout the body. (CS 2)
pH scale
A scale from 0 to 14 describing the acidity or alkalinity of a solution, where 7 is neutral, greater than 7 is more basic (alkaline) and less than 7 is more acidic. (CS 5)
phagocyte
Any cell that ingests and destroys foreign particles, bacteria and cell debris. (CS 5)
phantom pain
Pain that appears to arise in a part of the body that no longer exists, e.g. in a limb that has been amputated. (CS 2)
photon
An alternative way of modelling the energy from an electromagnetic wave; small packets of energy and the energy of each depends on the frequency of the electromagnetic wave. (CS 4 & 7)
physiology
The study of the relationship between the structure and the function of body systems. (CS 1)
placebo effect
A beneficial effect deriving from a procedure with no intrinsic benefit. It relies upon the context in which the intervention is made; e.g. a sugar pill might serve as a placebo if the patient believes that it will bring some benefits. (CS 2 & 3)
plasticity
A term that refers to the fact that the connections between neurons are not static. Rather, they are subject to change as result of activity within the neurons concerned. It can mean, over a period of time, increased sensitivity of connections between neurons in the circuits that give rise to pain and hence increasing levels of pain. (CS 2)
PM10
Particulates suspended in air that are less than 10 micrometres in diameter. (CS 5)
point-of-use' strategy
A method of purifying water, e.g. filtering, that involves individual people treating water as they use it, rather than having purified water delivered to them from a remote water-treatment plant in pipes. (CS 1)
polar molecule
A molecule that has both negatively and positively charged regions. (CS 1)
polyatomic ions
A small group of atoms bonded together which carry an overall electrical charge; e.g. the bicarbonate ion and the nitrate ion. (CS 1)
polymer
A long chain molecule made up of many repeating units. (CS 7)
population age-structures
The proportion of young, middle-aged and older people in a population. In developing countries, tends to be 'younger' than that of developed countries. (CS 3)
population screening
A screening programme (sometimes called 'mass screening') that aims to screen everyone in a particular population group (rarely every citizen), e.g. everyone over the age of 50 years, or all newborn babies. Attempts are made to screen everyone in that category, sometimes at regular intervals. (CS 4)
positive predictive value
For a screening procedure such as mammography, the number of true positive results expressed as a percentage of the total number of positive results (true or false). It tells (other things being equal) what the chance is that a person with a positive test result actually has the disease being screened for. (CS 4)
postsynaptic neuron
The neuron that has receptors for the neurotransmitter released by a presynaptic neuron at the junction (synapse) between these adjacent cells. (CS 2 & 3)
post-traumatic stress disorder
A condition that may develop following exposure to an extremely stressful situation, typically where a person witnesses the violent death of someone else, or believes their own life is in danger. Symptoms include disordered sleeping, a dread of situations that remind of the original event and the experiencing of flashbacks, in which the distressing scenes are remembered as if really happening again. To be classed as PTSD these symptoms must be present more than a month after the precipitating event. (CS 6)
potential difference
An electrical difference across the membrane of cells that arises from an unequal concentration of ions on either side. It is also termed 'voltage'. (CS 2)
powers of ten
A form of notation (also known as 'scientific notation') used for expressing very large or very small numbers. (CS 1 & 7)
prefrontal cortex
A region of cortex at the front of the brain, where the activity of neurons is associated with voluntary control of behaviour (self-control) and restraint. Biological evidence suggests that mild to moderate doses of alcohol selectively depress the activity of neurons in the PFC, relative to other brain regions. (CS 3)
presbyopia
A decreasing ability of the lens of the eye to accommodate, often associated with increasing age. (CS 7)
presynaptic neuron
The neuron that stores and releases neurotransmitter at a synapse with another neuron or a muscle cell.(CS 2 & 3)
prevalence rate
The total number of people who have a disease, disorder or disability at a particular point in time, expressed as a rate per 1000 (or per 10 000, or per 100 000 or per million) population. (CS 1)
prevalence
The total number of people who have the condition (disease, disorder or disability) at a particular point in time, regardless of how long they have been affected. (CS 1, 2, 4 & 5)
primates
A group of mammals including monkeys, apes and humans, with limbs adapted for climbing, leaping and swinging, reflecting their arboreal (tree-living) habits or origins, and characterised by having large brains in relation to body size, a short snout and large eyes that point forwards, providing stereoscopic vision. (CS 1)
principal focal point
A single point on the optical axis of a lens onto which all light rays parallel to that axis are directed. (CS 7)
priority eye diseases
Leading global causes of visual impairment that have been identified by the WHO's Vision 2020 project as targets that can be prevented or treated. They include refractive errors and low vision, cataract, glaucoma, AMD, diabetic retinopathy and trachoma. (CS 7)
photorefractive keratectomy
An eye-surgery technique where the epithelial layer of the eye is removed and laser treatment applied to the tissues exposed beneath (abbreviated to PRK). (CS 7)
proportional morbidity
The share of the total morbidity in a population which is due to a particular cause; it is usually expressed as a percentage. (CS 1)
proportional mortality
The share of all deaths in a population which is due to a particular cause; it is usually expressed as a percentage. (CS 1)
proteins
Long chain-like molecules (polymers) made from smaller molecules called amino acids joined by chemical bonds. The chains fold up into complex shapes giving them a wide range of functions. Major constituent of all organisms. (CS 1, 2, 3, 4, 5, 6 & 7)
proteinase
A group of enzymes that degrade proteins by splitting the protein chain into smaller molecules; also called a 'protease'. (CS 5)
protons
Positively charged particles found in the nucleus of atoms. In a neutral atom the number of these balances the number of negatively charged electrons surrounding the nucleus. (CS 2, 3, 5 & 7)
proxy measure
A readily measured statistic or parameter that can be used in place of a more complex statistic, or to 'stand in for' one that is impossible to measure directly; e.g. disease statistics are often used as this for the 'health' of a population; the number of prescriptions for antidepressants can be used as this for the number of people with depression in a population. (CS 1 & 2)
psychobiological approach
An approach to explanation which implies two closely related things: (i) both biological and psychological sciences have central roles in the explanation, and (ii) a given phenomenon to be studied within this perspective, such as pain, has both biological and psychological aspects. (CS 2 & 3)
psychogenic pain
Pain that arises from psychological triggers such as social loss; e.g. bereavement, marital breakdown. (CS 2)
psychogenic stimuli
Stimuli to pain that are associated with social loss such as bereavement, marital breakdown. (CS 2)
psychological trauma
Severe psychological shock.(CS 6)
pulmonary hypertension
High blood pressure in the blood vessels supplying the lungs - a sign that blood flow is restricted in some way. (CS 5)
pulmonary rehabilitation
A multi-disciplinary programme of care for patients with chronic respiratory conditions, which is tailored to the individual and combines exercise and education to address all aspects of living with the condition.(CS 5)
pulse oximetry
A non-invasive method of measuring the level of oxygenation of the blood by using light absorption to calculate the relative levels of haemoglobin and oxyhaemoglobin.(CS 5)
pupil
The opening at the centre of the iris that allows light to enter into the eye. (CS 7)
pyloric sphincter
A muscular structure at the junction of the stomach and small intestine that constricts and closes when food is present in the stomach, preventing it from passing into the small intestine.(CS 3)
radiographer
Qualified to employ a range of equipment such as X-rays, MRI scanners, etc. to produce images to diagnose an injury or disease. They will then have undergone further specialist training in mammography. (Two types, diagnostic and therapeutic; the latter have undergone training to enable them to operate radiotherapy machines that treat cancer and to calculate (or plan) the arrangement of X-ray beams for the treatment.) (CS 4)
radiologist
A medically qualified person who has chosen to specialise in clinical radiology - the use of imaging to diagnose, treat and monitor various disease processes. (CS 4)
receptor
A complex specialised molecule embedded in the outer membrane of a cell, or in its internal structure, which has a unique three-dimensional shape and patterns of electrical charge that enable it to bind specifically to a particular signalling molecule (e.g. a hormone or neurotransmitter). (CS 1, 2, 3, 4, 5 & 6)
referred pain
Pain that arises from tissue damage in one part of the body, but which is felt to be arising in a different part of the body. It is said to be 'referred to' a part that is not damaged. (CS 2)
reflection
A process at an interface of two media in which light is returned into the original medium without transmission or absorption. (CS 7)
reflex
The mechanisms in the nervous system underlying an automatic and unconscious reaction to a particular stimulus, i.e. a reaction that cannot be controlled by will-power. (CS 2 & 7)
refraction
A process at an interface of two media in which the direction of light is deviated within the new medium. (CS 7)
refractive errors
Visual defects caused by imperfections in the cornea and/or lens of the eye. (CS 7)
regenerative medicine
The clinical approach to tissue repair that seeks to build new tissues in a similar manner to the way in which they form naturally (rather than the way in which they repair after damage). (CS 6)
reinforcer
A factor that strengthens a tendency to engage in a particular behaviour.(CS 3)
relative risk
An estimate of the probability of developing a particular disease or disorder in a population that has been exposed to a particular risk factor, relative to the probability of developing the condition if the risk factor was not present. (CS 4)
residual volume
The volume of air remaining in the lungs after a maximum expiration (abbreviated to RV). (CS 5)
respiration
The total process in an organism by which oxygen is conveyed to tissues and cells, oxidation of nutrient molecules releases useable energy, and the oxidation products (carbon dioxide and water) are given off. (CS 5)
respiratory centres
The areas of the medulla region in the brain that integrate sensory information from chemoreceptors monitoring the level of oxygen and carbon dioxide in the blood. They send out appropriate signals to regulate the rate of contraction of the respiratory muscles (including the diaphragm and rib muscles). (CS 5)
respiratory system
The system of organs and structures in which gas exchange takes place. In mammals it consists of the airways, the lungs and the muscles that mediate the movement of air into and out of the lungs. (CS 5)
retina
The light-sensitive tissue at the back of the eyeball that contains the visual receptor cells (rods and cones). (CS 7)
reward
An event that follows a particular behaviour and which strengthens the tendency to repeat that behaviour. For example, if relaxation follows drinking alcohol it would be said to reinforce the tendency to drink alcohol. (CS 3)
risk factor
Anything that is statistically associated with an increased chance of developing a particular disease, disorder or disability in a population; when the incidence of the disease is examined in different populations it is found to occur more frequently in those who have been exposed to this than in those who have not, or whose exposure level has been lower. (CS 1, 4, 5, 6 & 7)
rods
Photoreceptor cells that are responsible for night vision. These cells provide no information about colour. (CS 7)
SAFE
A global strategy to combat trachoma, involving eyelid surgery, antibiotic treatment, attention to facial cleanliness and environmental changes. (CS 7)
scar
The tissue that forms following healing, which is not the same in structure as the original tissue. (CS 6)
scatter plot
A graphical method of showing whether two numerical variables are related to one another. They are called 'variables' because they can each have a range of possible values. Each data point represents a particular entity, such as a country, for which the two variables have been measured. (CS 1)
Schwann cells
The cells associated with peripheral neurons that wrap themselves around the axons. (CS 6)
screening
The systematic application of a test or investigation to people who have not sought medical attention, in order to identify those whose risk of developing a particular disease is sufficient to justify further action. (CS 4)
selection pressure
The environmental factors impacting on survival and reproduction in a population of organisms in which there is variation between individuals in their ability to withstand adverse conditions or benefit from advantageous circumstances. The result of this (e.g. exposure to antibiotics in bacterial populations) is that individuals who are best adapted to withstand it or benefit from it leave a larger proportion of offspring in the next generation, while those who are less well adapted suffer reproductive disadvantage. (CS 1)
sensory neuron
A class of neuron that detects the presence of stimuli in the world, such as tactile events, heat, cold or tissue damage. (CS 2)
SI Units
The term given to those units of measurement that scientists all over the world have agreed to use in their publications; e.g. the second (s), the kilogram (kg), and the metre (m). (CS 1)
side-effects
Any unintended and undesirable consequences of medical treatment; also known in medicine as an adverse effect or reaction. (CS 2 & 5)
sievert
The unit used to measure equivalent dose and effective dose (Sv). (CS 4)
single bond
A covalent bond formed by the sharing of two electrons, one from each atom at either end of the bond.(CS 3)
single-strand break
A break in one of the helical strands of a DNA molecule, caused by ionising radiation. (CS 4)
skeletal muscle
The type of muscle tissue that is responsible for moving parts of the musculoskeletal system. (CS 6)
Snellen letter chart
The eye chart used to determine how well a person can see at various distances. Named after a 19th-century Dutch ophthalmologist Hermann Snellen (1834-1908) who devised a test for visual acuity. (CS 7)
solvent
A substance (usually liquid) in which other substances dissolve. (CS 1)
somatic nervous system
That part of the nervous system that exerts control over the skeletal muscles and thereby over behaviour. (CS 2)
specificity
A screening procedure has high of this if, in people who do not have the disease being screened for, the procedure is very likely not to detect disease, that is, to give a negative result. Numerically, this is calculated by expressing the number of true negative results as a percentage of the total number of people (true negatives + false positives) that actually do not have the disease. (CS 4)
spectrum
The entire range or extent of some quantity, arranged in order; e.g. electromagnetic or visible light. (CS 4 & 7)
spinal cord
A collection of neurons and other cells that is located within the protection of the backbone. (CS 2)
spirogram
A graph recording breathing, which is made with a spirometer. (CS 5)
spirometer
An instrument that can be used to measure the volume of air entering and leaving the lungs. (CS 5)
spirometry
The use of a spirometer to measure the volume of air entering and leaving the lungs. (CS 5)
splint
Immobilisation of a broken bone using something rigid. (CS 6)
sputum
Matter formed from saliva mixed with mucus and any foreign material such as dust, which is coughed up (expectorated) from the lower respiratory tract and usually ejected from the mouth. (CS 5)
stem cells
Cells that can divide to produce daughter cells, which can then differentiate to become any of a range of different cell types. (CS 6)
stochastic
This refers to a random effect of ionising radiation. There is no radiation threshold at which the effect inevitably occurs, but the probability of an effect occurring increases with the amount of radiation received. (CS 4)
stress response
A physiological reaction occurring in the body, triggered by the perception of aversive or threatening situations. (CS 1)
stress
The experience of being in an unpleasant situation, over a period of days, weeks or longer, in which one is unable to exert control over circumstances which are not of one's choosing. The coping resources necessary to meet the demands of this unpleasant situation are lacking. (CS 1)
stroma
The corneal tissue consisting mainly of collagen fibres arranged in a manner that permits light transmission. (CS 7)
structural formula
A representation using chemical symbols that shows the order in which the atoms are joined together; e.g. the structural formula of water is shown as H\O\H. (CS 3 & 5)
stunting
Being shorter at a given age by a specified amount below the population average. (CS 1)
subjective experience
An experience which is accessible only to the person who experiences it in terms of the contents of his or her conscious mind. Such experience is not open to objective observation or measurement by any other individual and hence is contrasted with 'objective experience'. (CS 2)
sweat glands
Ducts lined with epithelial cells that originate in the dermis and release sweat onto the surface of the skin.(CS 6)
synapse
The junction where a neuron influences another cell, the latter being either another neuron or a muscle cell. (CS 2 & 3)
systolic blood pressure
The blood pressure that is detected during heart contractions, which is higher than the diastolic pressure. (CS 6)
tendons
The tissues that attach muscles to bones.(CS 6)
threshold of excitation
The level of intensity of stimulation of a neuron at which it first shows activity. The term is used particularly in the context of sensory neurons. (CS 2)
tidal volume
The volume of air inhaled and exhaled at each breath when resting (abbreviated to TV). (CS 5)
tissue engineering
Building replacement tissues to aid repair following damage. (CS 6)
tissue
A group of specialised cells that work together to fulfil a specific function in the body, e.g. muscle.(CS 4, 5 & 6)
tolerance
Over time, a need for an increasing amount of drug to obtain the same level of effect, e.g. the amount of alcohol required to produce intoxication. (CS 3)
total lung capacity
The total volume of gas contained in the lungs after a full inspiration (it is equal to vital capacity plus residual volume). (Abbreviated to TLC) (CS 5)
toxicology
The study of toxins and their effects on living organisms. (CS 1)
toxin
A poisonous substance produced by a living organism, usually injurious to potential prey, predators or competitors. (CS 1)
trachea
The tube descending from the larynx to the bronchi and carrying air to the lungs; also known as the windpipe. (CS 5)
trachoma
A painful eye condition caused by repeated infections with the bacterium Chlamydia trachomatis .(CS 7)
transcutaneous electrical nerve stimulation
A therapeutic technique where low-level stimulation is given to the skin and which has the effect of reducing pain (abbreviated to TENS). (CS 2)
transmission
A process in which light passes through a medium unaffected, e.g. light passing through clear glass. (CS 7)
transpiration
The release of water vapour by plants. (CS 1)
trauma
Any physical injury or severe psychological shock. (CS 6)
traumatic injury
Injury causing physical damage to the body. (CS 6)
trichiasis
A symptom of trachoma in which eyelashes grow inwards and scratch the conjunctiva, causing pain, scarring and eventually blindness. (CS 7)
trichromacy
The production of any colour by varying the relative intensities of the subtractive primaries (cyan, magenta and yellow). (CS 7)
true negative
In screening, a person whose screening test result is negative (indicating no disease), and who actually does not have the disease. (CS 4)
true positive
In screening, a person whose screening test result is positive (indicating disease), and who actually has the disease. (CS 4)
urbanisation
The process of urban development, i.e. of towns and cities, and the movement of an increasing proportion of a country's population from rural to urban environments. (CS 1)
vacuum
A volume in which there are no atoms or molecules. (CS 7)
vasodilation
The expansion of narrow blood vessels immediately beneath the skin; as they dilate they can carry more blood. (CS 3)
veins
Large blood vessels that carry blood towards the heart. (CS 3, 5 & 6)
venous return
The flow of blood back to the heart in the veins. (CS 6)
visual acuity
A measure of how well a person sees, determined by the minimum distance at which two lines (or points) can be distinguished at a test distance. (CS 7)
visual disability
A visual impairment that interferes with day-to-day functions that an affected person considers to be normal. (CS 7)
visual impairment
A variety of conditions associated with eyesight, from total loss of sight (blindness) to partial sight loss. (CS 7)
vital capacity
The total amount of air that can be taken in to the lungs during a maximum inspiration, or expelled during a maximal expiration. (Abbreviated to VC) (CS 5)
vitreous humour
The transparent gelatinous fluid within the eyeball (between the lens and the retina). (CS 7)
water-borne infectious diseases
Diseases in which the pathogen causing the disease lives part of its life cycle in water; e.g. cholera, cryptosporidiosis. (CS 1)
wave
A constantly repeating variation of some quantity that transfers energy from one position in a medium to another. (CS 4 & 7)
wavelength
Distance between one peak of a wave and the next peak, measured in metres (m). (CS 4 & 7)
wave-particle duality
The behaviour of electromagnetic radiation cannot be adequately described in all situations by any one model. In some situations the wave model is appropriate, in others the particle model, which describes the radiation as photons, must be used. (CS 4 & 7)
wet AMD
A type of age-related macular degeneration (AMD) in which new blood vessels form in an attempt to restore the blood supply to the retina. The new vessels are fragile, and may leak blood into the eye. (CS 7)
wind-up
A form of plasticity within the connections between the neurons that underlie nociception and pain, such that, over time, increasing levels of pain are experienced even though the stimulus remains unchanged. (CS 2)
withdrawal symptoms
Characteristic signs that follow the termination of taking a drug, most usually associated with a negative mood. There can also be characteristic physiological signs associated with particular drugs, e.g. sweating and shivering. (CS 3)
xenobiotic
Literally meaning 'alien to nature', the term is commonly used to refer to chemicals in the natural environment that are of human origin. (CS 1)
vasopressin
A hormone which is normally secreted by the brain in response to decreased water levels in the body. When alcohol is drunk, ethanol acts on the brain and inhibites the release of this, allowing the kidneys to make more urine.