Homeostasis
Homeostasis
Describes the body's ability to maintain relatively stable internal conditions even though the outside world changes continuously. It indicates a dynamic state of equilibrium, or a balance, in which internal conditions vary, but always within relatively narrow limits.
The Control Center
Determines the set point, which is the level or range at which a variable is to be maintained. Analyses the input it receives and determines the appropriate response or course of action. Information (output) then flows from the control center to the third component, the effector, along the efferent pathway.
Positive Feedback Mechanisms
Intensify the initial stimulus, leading to an enhancement of the response. They rarely contribute to homeostasis, but blood clotting and labor contractions are regulated by such mechanisms.
The Receptor
Monitors the environment and responds to changes, called stimuli, by sending information (input) to the second component, the control center. Input flows from the receptor to the control center along the so-called afferent pathway.
The Effector
Provides the means for the control center's response (output) to the stimulus. The results of the response then feed back to influence the effect of the stimulus, either reducing it (in negative feedback) so that the whole control process is shut off, or enhancing it (in positive feedback) so that the whole process continues at an even faster rate.
Negative Feedback Mechanisms
Reduce the effect of the original stimulus, and are essential for maintaining homeostasis. Body temperature, heart rate, breathing rate and depth, and blood levels of glucose and certain ions are regulated by negative feedback mechanisms.
Homeostatic Control
The nervous and endocrine systems, use neural electrical impulses or blood-borne hormones, as information carriers.
Homeostatic Imbalance
With age, the efficiency of negative feedback mechanisms declines, and positive feedback mechanisms occur more frequently. these changes underlie certain disease conditions.
