1. homeostasis

2. maintenance of a constant state within a living organism
definition
maintenance of
a constant state
within a
living organism

3. Control systems needed to achieve this have the following:
Sensor / Receptor
to monitor the factor to be controlled
Corrective mechanism
to bring about changes to regulate the factor
Negative feedback mechanism
to stop the corrective process and prevent over-correction

4. change from ‘norm’ level (excess) ‘norm’ ‘norm’ change from
Corrective mechanism. Effectors bring about a return to ‘norm’
detected by receptors
change from
‘norm’ level
(excess)
‘norm’
‘norm’
Corrective mechanism. Effectors bring about a return to ‘norm’
change from
‘norm’ level
(deficiency)
detected by receptors

5. Each system needs DIFFERENT mechanisms to raise/lower the factor
Each system needs DIFFERENT mechanisms to raise/lower the factor. This causes the factor to fluctuate about a norm. The process is called NEGATIVE FEEDBACK

6. In homeostasis, deviation from the norm acts as the signal that sets off the corrective mechanism.
This negative feedback keeps variable factors within the narrow ranges suitable for life.

7. and returns the factor towards its norm
any change from the
norm is a deviation.
The deviation acts as
a signal to the control
centre
level of
factor
deviations outside the norm
may not be controlled
by homeostasis
this is the
range of
this factor
that can
be controlled by
homoeostasis.
Cells work
well within
this range
Control centre
sets off the
correct response
response cancels
out the deviation
and returns the factor towards its norm
This is the norm or set point
for the homeostatic control
system. This would be the
ideal level of this
factor for cells to work

8. and returns the factor towards its norm
any change from the
norm is a deviation.
The deviation acts as
a signal to the control
centre
level of
factor
deviations outside the norm
may not be controlled
by homeostasis
this is the
range of
this factor
that can
be controlled by
homoeostasis.
Cells work
well within
this range
Control centre
sets off the
correct response
response cancels
out the deviation
and returns the factor towards its norm
This is the norm or set point
for the homeostatic control
system. This would be the
ideal level of this
factor for cells to work

9. and returns the factor towards its norm
any change from the
norm is a deviation.
The deviation acts as
a signal to the control
centre
level of
factor
Control centre
sets off the
correct response
response cancels
out the deviation
and returns the factor towards its norm

10. and returns the factor towards its norm
any change from the
norm is a deviation.
The deviation acts as
a signal to the control
centre
level of
factor
Control centre
sets off the
correct response
response cancels
out the deviation
and returns the factor towards its norm