WACE ATAR Human Biology flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Negative feedback loop

A control mechanism in which a detected deviation from the set point triggers a response that reverses the deviation, restoring the internal environment toward its normal value.

Positive feedback loop

A control mechanism in which a change stimulates responses that amplify the same change, moving the body further from the set point; examples include childbirth contractions and blood clotting.

Homeostasis definition

The maintenance of a relatively stable internal environment within narrow limits despite external changes, achieved through sensors, control centres, effectors and feedback mechanisms.

Osmosis

The net movement of water molecules across a selectively permeable membrane from a region of lower solute concentration to a region of higher solute concentration, requiring no energy input.

Facilitated diffusion

Passive transport of substances down their concentration gradient through specific membrane channel or carrier proteins, without expenditure of cellular ATP.

Sodium-potassium pump

An active transport protein that uses ATP to move three sodium ions out of and two potassium ions into a cell, maintaining electrochemical gradients and contributing to membrane potential.

Endocytosis

Bulk uptake of material into a cell by invagination of the plasma membrane to form a vesicle; it requires ATP and includes phagocytosis of particles and pinocytosis of fluid.

Exocytosis

Bulk secretion of material from a cell when a vesicle fuses with the plasma membrane and releases its contents outside, an ATP-requiring process used for hormones and neurotransmitters.

Surface area to volume ratio

The ratio of an organism's or cell's exchange surface area to its volume; it falls as size increases, limiting diffusion and requiring specialised exchange and transport systems.

Enzyme active site

The specific region of an enzyme where substrate molecules bind, forming an enzyme-substrate complex; its shape is complementary to the substrate and determines specificity.

Denaturation

Loss of an enzyme's functional three-dimensional shape, especially its active site, caused by excessive heat or extreme pH, permanently reducing or abolishing catalytic activity.

Insulin

A hormone secreted by beta cells of the pancreatic islets that lowers blood glucose by stimulating cellular uptake, glycogen formation and fat storage.

Glucagon

A hormone secreted by alpha cells of the pancreatic islets that raises blood glucose by stimulating glycogen breakdown and glucose synthesis in the liver.

Type 1 diabetes

An autoimmune condition in which beta cells are destroyed, causing little or no insulin secretion; blood glucose rises and must be managed with insulin injections.

Type 2 diabetes

A condition in which cells become resistant to insulin and secretion may later decline; associated with obesity, poor diet and inactivity, and managed through lifestyle and medication.

Bohr effect

The shift of the haemoglobin oxygen dissociation curve to the right when carbon dioxide and hydrogen ion concentrations rise, reducing haemoglobin's affinity for oxygen and aiding release to tissues.

Alveolar gas exchange

Exchange of oxygen and carbon dioxide across thin, moist alveolar walls by diffusion, driven by partial pressure gradients and aided by large surface area and rich blood supply.

Vital capacity

The maximum volume of air that can be exhaled after a maximal inhalation, calculated as tidal volume plus inspiratory and expiratory reserve volumes.

Tidal volume

The volume of air moved into or out of the lungs during one normal, quiet breath; it is much smaller than vital capacity.

Nephron

The functional unit of the kidney, comprising the glomerulus, Bowman's capsule, proximal tubule, loop of Henle, distal tubule and collecting duct, which together filter and modify blood.

Ultrafiltration

Pressure-driven filtration in the glomerulus that forces water, ions, glucose and urea into Bowman's capsule while retaining blood cells and large proteins.

ADH action

Antidiuretic hormone increases the water permeability of the collecting duct, so more water is reabsorbed and a smaller volume of more concentrated urine is produced.

Glomerular filtration rate

The volume of filtrate formed by both kidneys per unit time; it depends on filtration pressure, surface area and permeability of the glomerular membrane.

Thermoregulation

Control of body temperature around a set point by the hypothalamus, using responses such as sweating, vasodilation, shivering and vasoconstriction to balance heat gain and loss.

Vasodilation

Widening of skin arterioles that increases blood flow near the body surface, promoting heat loss by radiation and convection when body temperature rises.

Vasoconstriction

Narrowing of skin arterioles that reduces blood flow near the body surface, conserving heat by limiting radiation and convection when body temperature falls.

Antigen

A molecule, often a protein or polysaccharide on a cell or pathogen surface, recognised as foreign by specific receptors and capable of triggering an immune response.

Antibody structure

A Y-shaped protein produced by plasma cells, with variable regions that bind specifically to an antigen and constant regions that determine the antibody's class and function.

Active immunity

Protection resulting from the body's own production of antibodies and memory cells after exposure to an antigen, either through infection or vaccination; it develops slowly but lasts long.

Passive immunity

Protection from antibodies acquired from another source, such as maternal antibodies across the placenta or injected antiserum; it acts immediately but is short-lived.

Neuron structure

A nerve cell with dendrites receiving signals, a cell body containing the nucleus, and an axon conducting impulses to terminals that release neurotransmitter across a synapse.

Synaptic transmission

A nerve impulse triggers calcium entry and release of neurotransmitter into the synaptic cleft; it binds receptors on the postsynaptic membrane, generating a new impulse.