HOMEOSTASIS STANDARD 3: Feedback & Chemical Processes (HMS3)
How do we maintain internal balance?!!
POWERSTANDARD/HOMESTASIS:
Students will be able to convey an understanding of how the external
environment affects the internal environment of an organism and explain how dynamic equilibrium (homeostasis) is
maintained within a living system normally and during stress.
STANDARD HMS3/ Feedback & Chemical Processes: Students will convey a conceptual
understanding of how homeostasis is maintained by explaining the roll of chemicals and reactions in feedback
mechanisms.
TASK/EXAM: Demonstrate conceptual understanding in an exam format that includes short and extended
responses.
STANDARD HMS3/ Feedback & Chemical
Processes: Students will convey a conceptual
understanding of how homeostasis is maintained by explaining
the roll of chemicals and reactions in feedback mechanisms.
RUBRIC: Demonstrate the following skills during an in-class exam…
4 – Exceeding
3 – Meeting
Complete all requirements for
MEETING (3)
and…
includes some combination of
the following:
o All questions are completely
correct
o Some responses demonstrate
greater understanding than
required for this class
(particularly in extended
responses)
o Greater understanding
demonstrated in the
evolutionary tree diagrams
All exam questions are correct though
answers may show minor errors that do not
affect conceptual understanding.
Demonstrate conceptual understanding of the
content listed below in the practice questions.
2 – Approaching
1 – Beginning
Most exam questions are
correct but one or more
answers shows errors that
demonstrate
misconceptions and/or lack
of understanding.
Some to zero exam
questions are correct.
One or more answers show
errors that demonstrate
misconceptions and/or lack
of understanding.
Review QUESTIONS:
Organisms are continually exposed to changes in their external and internal environments. To be healthy,
organisms must maintain homeostasis, a “dynamic equilibrium” or “steady state,” which keeps their internal
environment balanced within normal limits. Failure to maintain homeostasis may result in disease or death.
To maintain homeostasis, organisms use negative feedback mechanisms that detect changes from the set
point, (the normal state) and trigger appropriate responses that return their body systems to the set point.
1. Use the information in the box above to write definitions for the following words:
a. Homeostasis
b. Negative feedback mechanism
c. Set point
2. Why are feedback mechanisms important?
3. The process of homeostasis is like driving a car at the speed limit (55 miles per hour).
a. What is the set point for driving a car?
b. If you detect that the speed of the car is above the set point, what response should you
make?
c. If you detect the speed of the car is below the set point, what response should you make?
4. What are three homeostatic responses to being overly hot (elevated body temperature) such as
having a fever?
5. What are three homeostatic responses to being overly cold (reduced body temperature) such as
being hypothermic?
6. Match each event in the table with the generic description below:
a. Detects above normal state
b. Controls center triggers response
c. Effect of response from a & b
d. Detects below normal state
e. Control center triggers response
f. Effect of d & e
A
B
C
Hypothalamus signals cause muscles to
shiver and blood vessels to constrict.
Hypothalamus detects decrease in body
temperature.
Hypothalamus detects increase in body
temperature.
D
E
F
Sweating and dilation of skin blood
vessels decreases body temperature.
Hypothalamus signals cause sweat
production and skin blood vessel dilation.
Shivering and blood vessel constriction
increases body temperature.
7. Read the case study on Blood Glucose. Fill in the diagram below, showing how blood glucose is
regulated in extreme conditions. Be sure to have written a response to 1-4 and also to have filled in
the two boxes.
Blood Glucose Homeostasis
The concentration of glucose in the blood affects every cell in the body. Therefore, its concentration is
strictly controlled within the range 80-100 mg of glucose per 100 ml of blood. Very low levels of blood
glucose or very high levels of blood glucose are both serious conditions and can lead to death. Blood
glucose concentration is controlled by the pancreas. The pancreas has glucose receptor cells, which
monitor the concentration of glucose in the blood, and it also has endocrine cells which secrete the
hormones insulin and glucagon. These two hormones have opposite effects on blood glucose.
Glucagon stimulates the release of stored glucose from the liver which increases blood glucose levels.
Insulin stimulates the uptake of glucose by cells which decreases blood glucose levels.
After a meal, glucose is absorbed from the digestive tract and glucose concentration in blood
increases. This increase is detected by the pancreas, which responds by secreting insulin. Insulin causes
glucose to be taken up by the body cells. This reduces blood glucose, which causes the pancreas to stop
secreting insulin. If the glucose level decreases too much, the pancreas detects this change and
responds by secreting the hormone glucagon. Glucagon causes the release of stored glucose from the
liver. This increases blood glucose, which causes the pancreas to stop producing glucagon.
If glucose levels…
2
1
Regulating
Blood
Glucose
3
If glucose levels…
4