Summary
Maintenance of a stable internal environment through negative feedback control.
In depth
A control loop has a receptor, a control centre and an effector. Negative feedback reverses change (temperature, glucose, blood pressure); positive feedback amplifies (childbirth, clotting). Claude Bernard introduced the idea of the internal environment and Walter Cannon named homeostasis.
Failures cause disease: diabetes is failed glucose control.
Set points can shift (fever, pregnancy). Feedback needs a sensor, comparator and effector. Disturbance leads to a corrective response.
Key idea: variables are kept within narrow limits, not fixed values.
Claude Bernard described the constancy of the internal environment in the 1800s, and Walter Cannon coined the word homeostasis in 1926. Variables kept near set points include body temperature (about 37 degrees), blood glucose, pH (7.35 to 7.45), blood pressure, water content and ion concentrations. Positive feedback is rarer and amplifies change, as in blood clotting, childbirth contractions (oxytocin) and the rising phase of the action potential.
Control is distributed: nervous reflexes act in milliseconds, and hormones act over minutes to hours. Many variables show daily rhythms rather than fixed values. Disease can be seen as failure of homeostasis, as in diabetes or heart failure. Allostasis describes stability through change, such as the body adjusting set points under stress.
Example: when you are too warm, skin blood vessels dilate and sweating starts, restoring temperature; this is negative feedback.
Frequently asked questions
What is Homeostasis?
Maintenance of a stable internal environment through negative feedback control.
Which area of biology covers Homeostasis, and how advanced is it?
Homeostasis is one of the 51 topics in Human Physiology. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Cardiovascular Disease Mechanisms, Diabetes Mellitus, Excretory System.
Can you give an example of Homeostasis?
Body temperature is held near 37 °C by sweating or shivering.
What should I learn before Homeostasis?
Homeostasis is a Beginner topic, so no earlier topic is required. Other Beginner topics in Human Physiology that pair well with it include Tissues and Organs, Skeletal System, Muscular System.
What topics are related to Homeostasis?
The closest topics to Homeostasis are Cardiovascular Disease Mechanisms, Diabetes Mellitus, Excretory System, Thermoregulation. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Homeostasis?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Homeostasis. To practise the whole of Human Physiology, use the Human Physiology quiz.
How is Homeostasis different from Cardiovascular Disease Mechanisms?
Homeostasis: Maintenance of a stable internal environment through negative feedback control. Cardiovascular Disease Mechanisms: Atherosclerosis builds plaques from cholesterol and inflammation, narrowing arteries and risking clots. Read both side by side and note what each one explains.
How should I study Homeostasis step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Cardiovascular Disease Mechanisms and explain the difference aloud. Finally, take the Human Physiology quiz and come back to this page for any question you miss.