Glossary
homeostasis
Homeostasis is the maintenance of a stable internal environment while conditions outside the body change — a loop that keeps correcting, not a fixed state.
Homeostasis is the maintenance of a stable internal environment while the world outside the body changes: temperature near 37 °C, blood pH inside a narrow band, water and glucose held within limits. It is not a fixed state but a loop that keeps correcting, and the loop has three parts. A receptor detects the change, a control center compares the reading with the set point, and an effector carries out the response. In negative feedback the response reverses the change — a rising temperature produces sweating and widened skin blood vessels, which bring it down — and that is the pattern most of the body's loops follow. In positive feedback the response amplifies the change, which is useful only where a process has to finish quickly: oxytocin in labor and clotting factors at a wound both work this way. A failed loop is what a disease state often looks like from the inside: the effector still works, but the correction no longer brings the reading back to the set point.
Taught in
Related terms
- negative feedback — Negative feedback is a loop in which the response reverses the change that triggered it, bringing the value back toward its set point.
- positive feedback — Positive feedback is a loop in which the response amplifies the change that triggered it, so a process runs to a finish instead of settling.
- receptor — A receptor is the structure that detects a change — the sensor of a feedback loop, reporting temperature, pressure, chemistry or stretch.
- effector — An effector is what carries out a feedback loop's response — a muscle that contracts or a gland that secretes.
- tissue — A tissue is a group of similar cells with a shared job and the material between them — the level between a cell and an organ.
- nephron — A nephron is the functional unit of the kidney: a filtering corpuscle followed by the tubule that turns the filtrate into urine.
Source: The anatomy and physiology guide in this course, whose organ and tissue descriptions follow the US National Cancer Institute's SEER Training Modules and MedlinePlus consumer health pages. Both are US federal government material, not subject to copyright in the United States. The definition above is written for this course in our own words. (SEER Training Modules accessed 2026-10-26; definition written 2026-10-27)