Glossary
receptor
A receptor is the structure that detects a change — the sensor of a feedback loop, reporting temperature, pressure, chemistry or stretch.
A receptor is the part of a control loop that detects a change and reports it. It can be a sensory nerve ending in the skin reading temperature or pressure, a stretch receptor in a muscle reporting its own length, or cells in the pancreas reading the glucose in the blood that passes them. What the receptor does is convert one kind of signal into another — a stretch, a temperature or a concentration into a nerve impulse or a hormone release — so that the control center has something to compare. Receptors are tuned: the one that reports blood pressure does not report blood sugar, and that tuning is why a loop can be specific. In the reflex arc the receptor is the first element and the effector is the last, with the control center between them deciding; a question that names a structure is asking which of the three roles it plays.
Taught in
Related terms
- effector — An effector is what carries out a feedback loop's response — a muscle that contracts or a gland that secretes.
- 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.
- 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.
- nervous tissue — Nervous tissue carries electrical signals: neurons generate and conduct them, and glial cells insulate, feed and support the neurons.
- hormone — A hormone is a chemical messenger released into the blood that changes the activity only of cells that carry a receptor for it.
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)