Homeostasis is the manifestation of the characteristic of life known as irritability and responsiveness.





The overwhelming number of homeostatic reactions are facilitated by negative feedback loops. Negative feedback loops have “negative” effects on the stimulus. They “reverse” the stimulus.



The roles of receptor, control center, and effector are not necessarily consigned to one structure.

For instance if a receptor is only sensitive to a change in temperature, then a control center would be required to determine the direction of the change (warmer or cooler)


However if the receptor is only sensitive to a decrease in temperature then there is no need for a control center as the receptor is performing both roles.



Negative feedback loops help maintain a physiological dynamic equilibrium which facilitates a relative internal steady state within optimal limits.



In contrast to negative feedback loops there are a few positive feedback loops.

Positive feedback loops ultimately increase or enhance the stimulus.

Positive feedback loops are most readily described in:


Blood vessel repair

Labor and delivery