Summary Homeostasis

Homeostasis:


 To control any system you need:
o A receptor that detects a change (the stimuli).
o A signal that is sent to other cells to communicate the
change.
o An effector which produces an automatic response.
o A processing centre which receives information and
coordinates a response.
 The process can be either positive feedback or negative
feedback.
 Negative feedback:
o A process that brings about a reversal of any change in
conditions.
o It ensures that an optimum steady state can be
maintained.
o There is always some variation around the optimum – as
long as the variation is not too great the conditions
remain acceptable.
Example – Control of Body Temperature:

Increase in temperature caused Effector = Muscles.
by a change in environment or
Action of Effector =
adrenaline or shivering.
Shivering.

Receptor = Hypothalamus Processing Centre =
Optimum = 37°C Hypothalamus
Processing Centre =
Hypothalamus Receptor = Hypothalamus


Effector = Sweat Glands. Decrease in temperature
caused by a change in
Action of Effector = Release
environment or sweating.
beads of sweat.