PY12.1-10 | Integrated Physiology — Glossary

The physiological process of maintaining core body temperature within a narrow range (36.5-37.5 degrees C) through a negative feedback loop involving the hypothalamus

The target temperature maintained by the hypothalamic thermostat; normally 37 degrees C, raised in fever by PGE2 action on EP3 receptors

A regulated elevation of body temperature caused by raised hypothalamic set-point in response to pyrogens; responds to antipyretics

An unregulated rise in body temperature when heat production or environmental heat load overwhelms the body's cooling mechanisms; set-point is normal; does not respond to antipyretics

A medical emergency defined by core temperature above 40 degrees C with CNS dysfunction (confusion, seizures, coma); classical type features cessation of sweating

A substance that causes fever; exogenous (bacterial LPS) or endogenous (IL-1, IL-6, TNF-alpha, IFN-gamma released by macrophages)

The mediator that raises the hypothalamic set-point in fever, produced from arachidonic acid by COX-2 in the OVLT; target of antipyretic drugs

Heat production by brown adipose tissue via UCP1 (thermogenin) which uncouples the mitochondrial proton gradient, dissipating energy as heat instead of ATP

Specialised thermogenic tissue rich in mitochondria containing UCP1; prominent in neonates (interscapular), declining with age but present in adult supraclavicular depots

Dynamic exercise with muscle length change and joint movement (e.g., running, swimming) producing a volume load on the heart

Static exercise with increased muscle tension without significant length change (e.g., wall push) producing a pressure load with significant BP elevation

The exercise intensity above which blood lactate rises exponentially, typically at 60-70% VO2 max in untrained and 80-85% in trained individuals

Maximal oxygen consumption — the gold standard measure of cardiorespiratory fitness, limited primarily by cardiac output in healthy individuals

Excess Post-Exercise Oxygen Consumption (oxygen debt) — elevated VO2 after exercise for replenishing ATP, phosphocreatine, and myoglobin O2, and metabolising lactate

Reversible physiological adaptation to a sustained environmental change (heat, cold, altitude), developing over days to weeks

A cluster of five risk factors (central obesity, hypertriglyceridaemia, low HDL, hypertension, hyperglycaemia) driven by insulin resistance, conferring high cardiovascular and diabetes risk

Age-related loss of skeletal muscle mass and strength, declining 3-8% per decade after age 30, primarily affecting Type II fast-twitch fibres

Irreversible cessation of all brain functions including the brainstem, diagnosed by absent brainstem reflexes and apnoea test; legally equivalent to death in India

The definitive test for brain death: ventilator disconnection with O2 insufflation, allowing PaCO2 to rise above 60 mmHg; no respiratory effort confirms absent medullary function

The negative feedback reflex regulating blood pressure via arterial baroreceptors; operating point shifts upward during exercise to permit higher BP

The enhanced cooling effect of wind, which increases convective heat loss by continually replacing the warmed air layer adjacent to the skin

Hormone produced by renal peritubular cells in response to hypoxia, stimulating erythropoiesis; increases at high altitude causing polycythaemia

2,3-diphosphoglycerate — an allosteric effector in RBCs that right-shifts the Hb-O2 dissociation curve, facilitating O2 release to tissues; increases at high altitude

Beat-to-beat variation in heart rate reflecting autonomic balance; increased HRV indicates greater parasympathetic (vagal) tone and is a marker of cardiovascular health

Reduced sensitivity of target tissues (muscle, liver, adipose) to insulin's metabolic actions; the central pathogenic mechanism of metabolic syndrome and type 2 diabetes