Biology
Name _________________________
Period______
Homeostasis and Feedback Worksheet
Part One – Fill in the blanks.
The cells and organs of living organisms can only exist in a narrow range of conditions. Maintaining this narrow
range of stable conditions is within a living organism in called __ H________________________. The process
that allows organisms to respond to changing conditions and maintain _____________________ is called
__F__________________.
_________________ Feedback produces a change away from the initial condition back to the normal
condition.
________________ Feedback produces a change toward the initial condition.
Part Two: Use the pictures in your notes to identify the following as positive or negative feedback and
answer the questions about them.
The Control of Sugar Levels in the Blood:
Choices for 1 -7: (There are extra choices and one choice may be used twice.)
glucagon, insulin, glycogen, normal, abnormal, glucose, liver, pancreas, positive, negative
1. If the blood glucose (sugar) level raises which organ is stimulated? __________________
2. What chemical is produced by the pancreas? ________________
3. This chemical causes 2 reactions - ____________________ is formed and _________________ is taken
in by cells.
4. This results in blood glucose falling back to _________________ levels.
5. Is this positive or negative feedback. ___________________
6. If you were running in a cross country race and your blood glucose dropped to below normal levels
what chemical would your pancreas produce? _______________________
7. What would the result of number 6 be? Blood glucose would return to _______________ levels.
Childbirth
1. What is the stimulus in this feedback loop?
The ______________ head presses on _P________________ ______________ in the uterus wall.
2. The pressure receptors send a message to the control center / brain which causes a hormone to be
released.
What is this hormone? ____________________
3. What gland stores and releases this hormone? __P___________________
4. What is the effect of this hormone on the muscles of the uterus?
The _____________________ increase.
5. This is an example of ____________________ feedback because the stimulus of the baby’s
_H____________ causes the production of the hormone _________________ which increases the
muscle _C_________________ of the uterus. This increases the pressure of the ____________ head
resulting in the production of more __O_________________.
6. What stops this feedback? The _______________ is born and there is no more _ P_______________
on the uterus wall.
The Control of Body Temperature
1. Based on this diagram what is the ideal normal body temperature? _________
2. If the body temperature raises or lowers out of the normal range what part of the brain senses the
change? _H_______________________
3.
Give one example of the action of an Effector if the body becomes too warm? (See Cooling Mechanisms)
4. If the body temperature rises (to warm) the overall response of the feedback that controls body
temperature is to return the body temperature to _______________.
5.
Give one example of the action of an Effector if the body becomes too cold?(See Warming Mechanisms)
6. If the body temperature lowers (to cold) the overall response of the feedback that controls body
temperature is to return the body temperature to _______________.
7. The feedback that controls body temperature is an example of __________________ feedback. Why?
(Explain this in a complete sentence.)