COMPONENTS OF CREATING BALANCE
1. STIMULUS- change that occurs in the internal environment
( ex. During exercise, not enough oxygen getting to cells)
2. RECEPTORS -Sensors that monitor the internal environment (ex.
Nerve cells detect the drop in O2 levels in the blood when exercise
begins)
3. CONTROL CENTER (set point)-determines what a particular value
should be, usually determined by the brain.(ex. Brain-identifies O2
levels are low and stimulates change)
3. EFFECTORS-cause responses that alter conditions in the internal
environment, usually they are muscles or glands (ex. Adrenal glands
stimulated by brain to release adrenaline which speeds up the heart
rate to deliver more O2 needed for cells)
5. RESPONSE-how the change is corrected (ex. Heart rate increases)
1.) Negative Feedback
•
Causes conditions to return to normal. Reduces the deviation from the
set-point. The action of the effectors is shut off.
•
Returns the system to normal (lessens the deviation from the set point).
•
The change is opposite to the original change.
Example 1: Blood sugar Increase -Too much sugar in the blood releases
insulin which causes the body to increase storage of sugar
which ultimately decreases sugar levels in the blood.
Example 2: Body Temperature Decrease-if body temperature drops,
muscles begin contracting (shivering) to produce
heat which ultimately increases the body temperature.
Example 3: Body Temperature Increase –if body temperature increases,
blood vessels expand to release heat which ultimately
decreases body temperature.
****Notice that all the examples return the body to its set point. Change is
opposite to the original change.
Negative feedback controls body temperature.
2.) POSITIVE FEEDBACK
• Output of a system turns on or increases the action
of the effectors.
• Moves the system away from normal (increases the
deviation from the set point).
• The change is the same as the original change.
Example 1: Blood clotting- the chemicals (platelets
and fibrin) that carry out the processes of clotting
are turned on to stimulate more clotting in order to
minimize bleeding.
Example 2: Childbirth-increase in uterine contractions
help to push the child out of the womb.