Notes to Instructors
Chapter 45 Hormones and Endocrine System
What is the focus of this activity?
This activity requires students to review their understanding of the general mechanisms
What is this particular activity designed to do?
Activity 45.1 How do hormones regulate cell functions?
This activity is designed to help students understand how hormones act within cells to
produce a response.
Answers
Activity 45.1 How do hormones regulate cell functions?
Building the Model
Working in groups of three or four, construct a dynamic (claymation-type) model of
hormone action in cells. You may use the materials provided in class or devise your own.
Step 1. Use chalk on a tabletop or blackboard to draw a eukaryotic cell. Your cell should
be at least 18 inches in diameter. Be sure your drawing includes the cell membrane, the
nuclear membrane, and the DNA inside the nucleus.
Step 2. Answer the following questions.
1. What structures or components do you need to add to your model to allow hormone
1 to react and increase production of substance X?
Because hormone 1 is protein derived, you need to add a signal-transduction
2. What structures or components do you need to add to your model to allow hormone
2 to decrease production of substance Y?
Hormone 2 is a cholesterol-derived hormone, so it can freely cross the plasma and
Step 3. Using claymation, demonstrate how each of the two hormones is likely to
produce its response.
Use the understanding you gained from your model to answer the questions.
3. In medical applications, the type of hormone dictates the mode of administration—
for example, oral versus injection, and so on.
a. How would you need to administer hormone 1 to an organism deficient in this
hormone?
Because hormone 1 is protein derived, it is likely to be digested if taken orally.
b. How would you need to administer hormone 2?
Cholesterol-derived hormones are generally not digested. If taken orally, they
302 Activity 45.1
4. Hormones often act in an antagonistic fashion. That is, one hormone will initiate a
certain response while another inhibits that response. Illustrate this process using
insulin and glucagon as examples of antagonistic hormones.
Insulin and glucagon act to regulate blood sugar concentrations within a fairly
Activity 45.1 303
45.1 Test Your Understanding
1. Assume you are trying to characterize one of the hormones that is involved in the
neuroendocrine regulation of milk production. You make extracts of blood and
mammary tissues of normal, lactating (milk-producing) animals and assay these
extracts by injecting them into animals (each of whose hypothalamus has been
surgically removed) and look for restoration of milk production. Indicate whether
each of the following findings is consistent with the hormone being a steroid, a
peptide, or either type. Explain your reasoning.
a. It is found in blood.
b. It is found in the cytoplasm of mammary tissue cells.
c. It is found associated with receptors.
d. It is found associated with protein complexes that contain G protein.
e. It is found in nuclear extracts of cells.
Only steroid hormones are able to enter the cell and the nucleus.
2 to 4. Glucagon and insulin are hormones that act homeostatically to maintain glucose
levels in the body. Are the following statements True or False concerning insulin
and glucagon. Explain your reasoning.
T/F2. Their production and release is stimulated by trophic hormones from the
anterior pituitary.
False—The pancreas itself monitors levels of glucose in the blood and
304 Activity 45.1