What are the three components of a homeostatic control system, and what role does each play?

The three components are the receptor, the control center, and the effector. The receptor is a sensor that detects a stimulus and sends input along the afferent pathway to the control center. The control center sets the set point, analyzes input, and sends output along the efferent pathway to the effector. The effector carries out the response, which feeds back to alter the stimulus and restore the variable toward homeostatic levels.

All homeostatic control mechanisms involve at least three cooperating components, as described in Chapter 1. The receptor monitors the environment and responds to changes, called stimuli, by sending information to the control center along the afferent pathway. The control center determines the set point, the level or range at which the variable is maintained, analyzes incoming input, and chooses the appropriate response. It then sends output along the efferent pathway to the effector. The effector provides the means for the response, and the results of that response feed back to either reduce the stimulus (negative feedback) or enhance it (positive feedback), helping return the variable to its homeostatic level or driving a self-perpetuating process.