SDK125 Introducing Health Sciences - Glossary

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Flashcards for glossary of level 1 Open University course, SDK125 Introducing Health Sciences

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)


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)


Deliberately deciding never to drink alcohol. (CS 3)


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)


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)


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)


The joining of tissues to each other that may occur abnormally during repair.(CS 6)


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)


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)


A chemical that has the effect of mimicking the action of a natural substance such as a neurotransmitter. (CS 2 & 3)


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)


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)


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)


Brain region involved in processing memories and emotional reactions.(CS 6)


The process of reducing pain, e.g. by taking morphine. (CS 2)


Substances that have the effect of reducing pain. (CS 2)


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)


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)


Blood vessels that convey blood away from the heart.(CS 3, 5 & 6)


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)


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)


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)


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)


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)


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)


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)


The removal for diagnostic study of a piece of tissue from a living body. (CS 4)


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)


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)


A small airway branching from a bronchus. (CS 5)


A drug that widens the airways of the lungs and eases breathing by relaxing smooth muscle in the walls of bronchioles.(CS 5)


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)


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)


The thinnest blood vessels. (CS 3, 5 & 6)


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)


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)


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)


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)


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)


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)


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)


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)


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)


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)


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)


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)


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)


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)


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)


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)


Refers to an infectious disease that can be transmitted by physical contact. (CS 7)


A lens shape with a greater thickness at the centre than at each end. (CS 7)


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)


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)


An intense conscious occupation with thoughts of the object of an addiction. (CS 3)


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)


A state in which addicts come to depend upon a drug for their 'normal' mental functioning. (CS 3)


The skin layer that lies beneath the epidermis and provides the strength and elasticity of the skin.(CS 6)


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)


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)


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)


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)


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)


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)


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)


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)

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