Anatomy and Physiology / Unit 1: Body Organization and Homeostasis
1.5 Homeostasis
Notes
Homeostasis is the maintenance of a relatively stable internal environment despite outside changes. It is a dynamic balance around a set point, not a fixed value.
- Every control system has three parts: a receptor (sensor) detects a change (the stimulus), a control center (often the brain) compares it with the set point, and an effector (muscle or gland) produces a response.
- Examples of controlled variables: body temperature (about 37 degrees C), blood glucose, blood pH, water balance, blood pressure.
- Failure of homeostasis can lead to disease. Aging reduces the efficiency of many control systems.
- Example: skin temperature receptors detect cold (receptor), the hypothalamus signals (control center), and skeletal muscles shiver (effector) to produce heat.
Practice
Which of the following is the best definition of homeostasis?
Homeostasis is a dynamic balance in which variables fluctuate around a set point within a normal range.
In a control system, which component detects the change and sends information to the control center?
Receptors sense the stimulus. The control center processes the information and effectors carry out the response.
During exercise, sweat glands release sweat and body temperature stays near 37 degrees C. The sweat glands are acting as the:
Sweat glands carry out the response, so they are the effectors.
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