Physiology

Physiology is operational excellence at the cellular level. Every term in this category describes how organisms maintain function under varying conditions—the biological equivalent of 'how do we keep the factory running?' Homeostasis, metabolism, thermoregulation: these aren't abstract concepts but operational necessities. The core insight of physiology is that efficiency isn't free. Every optimization comes with trade-offs. A faster metabolism enables quicker response but requires constant fuel. A larger body stores more energy but moves more slowly. A specialized organ handles one function brilliantly but fails catastrophically when that function isn't needed. Business faces identical trade-offs. Physiology vocabulary helps you think about operating constraints. 'Metabolic rate' maps to burn rate. 'Homeostasis' maps to operational stability. 'Allostasis' maps to adaptive capacity. When you understand how organisms maintain function despite environmental chaos, you understand how organizations do too—or fail to. The terms here reveal why some operational strategies that look inefficient are actually robust, and why some that look optimized are actually fragile. A liver that operates at 100% capacity seems efficient until you need surge capacity. A company that runs lean seems smart until demand spikes. After exploring this category, you'll understand that operations isn't about maximizing throughput—it's about maintaining function across conditions you can't predict.

Adrenaline A hormone and neurotransmitter released during stress that prepares the body for 'fight or flight.' Also called epinephr... Angiogenesis The formation of new blood vessels from existing vessels. Essential for growth, wound healing, and unfortunately, tumor... Circadian Rhythm Internal biological cycles with approximately 24-hour periods that regulate sleep, metabolism, hormone release, and many... Cortisol A steroid hormone released during stress that mobilizes energy reserves and suppresses non-essential functions. The body... Countercurrent Exchange A mechanism where fluids flow in opposite directions on either side of a barrier, maximizing transfer efficiency. Used i... Cryptobiosis A state of suspended animation where metabolism drops to undetectable levels. Literally 'hidden life'—the organism shows... Diapause A period of suspended development in insects and some other organisms, typically triggered by environmental cues like da... Digestion The process of breaking down food into molecules small enough to be absorbed and used by cells. Involves mechanical brea... Ectotherm An organism that regulates body temperature primarily through external sources of heat, such as sunlight or warm surface... Ectothermy A metabolic strategy where body temperature depends primarily on external heat sources rather than internal metabolism.... Endotherm An organism that generates body heat internally through metabolic processes, maintaining a relatively constant body temp... Energy Budget The accounting of energy intake, storage, and expenditure in an organism. All energy acquired must be allocated between... Estivation A state of dormancy similar to hibernation but occurring during hot, dry periods. Also spelled 'aestivation.' A survival... Excretion The biological process of eliminating metabolic waste products from the body, including nitrogenous wastes (urea, uric a... Extreme Survival Adaptations enabling organisms to survive conditions lethal to most life: extreme temperatures, desiccation, radiation,... Gastric Relating to the stomach. Gastric juices contain hydrochloric acid and enzymes that break down food; gastric emptying con... Ghrelin A hormone produced by the stomach that stimulates appetite. Often called the 'hunger hormone,' it signals the brain to s... Glucagon A hormone produced by the pancreas that raises blood glucose levels by triggering the release of stored glucose from the... Hibernation A state of prolonged torpor in which body temperature, heart rate, and metabolic rate drop dramatically to conserve ener... Homeostasis The maintenance of relatively stable internal conditions despite changing external conditions. The tendency of biologica... Hormone Chemical messengers produced by glands or cells that travel through the bloodstream to affect distant target cells. Horm... Immune Relating to the body's defense system against pathogens and foreign substances. The immune system distinguishes self fro... Insulin A hormone produced by the pancreas that regulates blood glucose levels by promoting glucose uptake into cells. Essential... Ketosis A metabolic state where the body burns fat for fuel instead of glucose, producing ketone bodies as an alternative energy... Kleiber's Law The observation that metabolic rate scales with body mass to the 3/4 power across species spanning twelve orders of magn... Leptin A hormone produced by fat cells that signals satiety to the brain. Leptin levels indicate energy reserves, helping regul... Melatonin A hormone produced by the pineal gland that regulates sleep-wake cycles. Secretion increases in darkness, signaling nigh... Metabolic Rate The rate at which an organism consumes energy, typically measured as oxygen consumption or heat production per unit time... Metabolic Scaling The mathematical relationship between body size and metabolic rate. Metabolic rate scales with body mass to the 3/4 powe... Photoperiod The relative length of light and dark periods in a 24-hour cycle. Many organisms use photoperiod as a reliable cue for s... Regeneration The ability to regrow lost or damaged body parts. Ranges from wound healing to regrowing entire limbs or body sections. Testosterone A steroid hormone primarily produced in testes (males) and ovaries (females). Drives development of male characteristics... Thermogenesis The production of heat by metabolic processes. Endotherms use thermogenesis to maintain body temperature; various forms... Thermoregulation The ability of an organism to maintain its body temperature within certain boundaries, even when the surrounding environ... Torpor A state of reduced physiological activity, typically characterized by lowered body temperature, metabolic rate, and hear... Vasoconstriction The narrowing of blood vessels, reducing blood flow to specific areas. A response to cold (conserving heat), stress (dir...