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Glossary - Human Factors

accommodation The ability of the eye to change its refractive power to focus light from either near or distant objects.
acid Compounds which combine with alkalis to form salts. In the body, acidity is determined by the concentration of hydrogen ion H+.
adenosine triphosphate A molecule produced by all cells, which contains high energy phosphate bonds. When these bonds are broken, the body is able to utilise the energy for its needs.
aerobic In the presence of oxygen.
aerodontalgia Tooth pain caused by expanding gas within a cavity of the tooth on ascent to altitude.
alkali (base) A substance which neutralises an acid to form a salt. Bicarbonate ion HCO3- a base which combines with H+ in the body to form carbonic acid.
alveoli Small air sacs in the lungs involved in gas exchange.
anaemia Inadequate red blood cells of haemoglobin in the blood.
anaerobic In the absence of oxygen.
angina (pectoris) Pain in the centre of the chest related to ischaemic heart disease, which usually occurs on exertion.
aorta The main artery providing outflow from the left ventricle of the heart, carrying oxygenated blood to the whole body.
aqueous humour Fluid of the anterior chamber of the eye, between the lens and the cornea.
arterioles A small artery.
artery A muscular walled blood vessel, which carries blood away from the heart.
atelectasis Collapse of alveoli in the lungs.
atria The uppermost chambers of the heart, which receive the inflow from the veins, then help to fill the ventricles prior to their contraction.
autokinesis The apparent motion of a single point source of light.
autonomic nervous system A branch of the nervous system which regulates many unconscious bodily functions such as the constriction of blood vessels and movement of the gastrointestinal tract.
barany chair A rotating chair used for demonstrating or testing the functions of the vestibular system.
barometric pressure The pressure of atmospheric gases.
barometric time release unit Mechanism, which automatically controls the ejection sequence of an ejection seat.
baroreceptor A sensor of arterial blood pressure. Baroreceptors are located in the carotid sinus at the bifurcation of the internal and external carotid arteries.
base See alkali.
bends Pains in the joints as a result of decompression illness.
bronchioles Small airways within the lungs.
bronchus The trachea divides into the right and left bronchi, which conduct air to either the right or left lung.
capillaries Tiny blood vessels one cell thick forming a network through all tissues, supplying them with oxygenated blood. They join arteries to veins.
carbonic acid H2CO3––Formed in the body when carbon dioxide gas reacts with water aided by the enzyme carbonic anhydrase. Carbon dioxide exists in the body almost exclusively in this form.
carotid artery Branch of the aorta coursing upwards in the neck to supply the head and brain with oxygenated blood.
cell Smallest structural division of living tissue which can self-replicate, consisting of an outer cell membrane, cytoplasm, nucleus containing genetic material, and other organelles.
central nervous system That part of the nervous system which consists of the brain and the spinal cord.
cerebral arterial gas embolism Sudden collapse or severe neurological impairment caused by a gas bubble occluding the cerebral circulation following a rapid decompression. Often associated with pulmonary barotrauma.
chemoreceptor A sensory cell which detects the concentration of chemical substances within body fluids.
chokes Respiratory manifestations of decompression illness, usually consisting of shortness of breath, chest pain and a cough.
cochlea The organ of hearing, located in each inner ear.
convergence Movement of the eyes inwards towards the midline when focussing on an object nearer to the observer.
cornea The clear membrane at the front of the eye where light enters and is first refracted.
creeps Cutaneous manifestations of decompression illness, consisting of itching, crawling sensations, or rashes.
cutaneous Pertaining to the skin.
decibel scale dB A logarithmic method of quantifying sound pressure levels.
density Mass per unit volume.
diaphragm Dome shaped muscular partition between the thoracic and abdominal cavities. Responsible largely for inspiration and expiration.
diastole (-ic) The phase of the cardiac cycle where the heart is relaxed. Diastolic pressure is the pressure in the arteries at this time.
diffusion Random collisions between molecules of a gas or solute result in the intermingling and movement of that solute or gas from a region of higher concentration to a region of lower concentration.
ebullism Vaporisation of gas within body tissues which occurs when the ambient pressure around the body equals the water vapour pressure of water in the body at 37°C (47 mmHg).
embolism A bolus of foreign material carried in the blood stream, which may lodge in and block smaller blood vessels.
epiglottis A flap of tissue which seals the top of the trachea at the larynx to prevent the aspiration of foreign material into the lungs.
erythrocytes Red blood cells, containing haemoglobin.
eustachian tube A passage between the middle ear cavity and the pharynx, which allows equalisation of pressures between the two regions.
exosphere The outermost layer of the atmosphere.
flatus A collection of gas in the bowel. Often expelled noisily from the anus during hypobaric chamber runs.
flight level Height above the 1013.2 hPa pressure datum, which is mean sea level barometric pressure in the ICAO standard atmosphere. All aircraft use this value as barometric pressure at sea level when setting their altimeters for flight above 13 000 feet.
freznel manoeuvre A manoeuvre for raising the pressure in the nasopharynx by occluding the glottis, lips and nostrils, and contracting the muscles in the floor of the mouth and pharynx.
glycogen A sugar created by the body for the storage of glucose.
greenhouse effect The warming of the earth’s surface caused by trapping of incoming solar radiation by the atmosphere.
haemoglobin A large molecule contained within red blood cells used for the transport of oxygen. It consists of a protein molecule (globin) and an iron-containing pigment (haem).
homeostasis Maintenance of a constant internal environment.
hyperthermia A rise in core body temperature caused by heat stress.
hyperventilation Breathing in excess of the body’s need to eliminate carbon dioxide, resulting in a decline in the level of carbon dioxide within body fluids.
hypoglycaemia Low blood glucose levels.
hypothalamus A region deep within the brain concerned with the regulation of hormonal function, the autonomic nervous system, and many vital processes such as sleep, hunger, thirst, reproductive activity, and temperature regulation.
hypothermia Low core body temperature resulting in clinical symptoms.
hypoventilation Inadequate ventilation of the lungs to meet the body’s requirements of oxygenation and elimination of carbon dioxide.
hypoxia Lack of oxygen to the tissues sufficient to cause impairment of function.
IMSAFE Illness, Medication, Stress, Alcohol/Drugs, Fatigue, Eating
intercostal muscles Muscl