Download Extra credit: Questions

Bi 212, Extra Credit Assignment (15 pts)
Due Monday, March 8, 2004
Use your text as well as the article, “Don’t Stress” to answer these questions. Some of the answers are
not directly given in either the text or article, and require you to think carefully about the topics at hand.
1.
A review of adrenal cortex hormones.
a.
Draw a diagram that shows, step by step, the endocrine pathway that leads to the “longterm” (i.e. adrenal cortex-mediated) stress response, including specific hormones
produced/released from particular organs and their effects along the way. (HINT: start
with the hypothalamus and the hormone(s) it releases). Be sure you include the targets and
effects of the adrenal cortex hormones themselves.
b.
Indicate where feedback occurs in the system. [NOTE: While feedback mechanisms are
not explicitly described for these hormones, you should assume that feedback mechanisms
are similar those see in the thyroid hormone (T3 and T4) pathway...]
2.
The development/role of glucocorticoid receptors in the hippocampus.
a.
What are some key functions of the hippocampus (refer to text as well as paper). To what
larger brain “system” does the hippocampus belong?
b.
Do the number glucocorticoid receptors in the hippocampus increase or decrease with early
experience of stress? Briefly describe the experimental results from the paper that support
your answer.
c.
Hypothesize as to how (mechanistically) an increase in number of receptors for the
glucocorticoids in the hippocampus could lead to a decrease in the amount of CRH
released from the hypothalamus. [HINT: Think about feedback mechanisms.]
d.
Discuss why this type of feedback would occur (i.e. why, in terms of the action of
glucocorticoids, should an increase in receptors for glucocorticoids lead to a decrease in
CRH?)
3.
GABA
a.
GABA general acts as an inhibitory neurotransmitter throughout the nervous system.
Explain what these means in terms of its effects on the post-synaptic neuron to which it
binds. Be as specific as possible.
b.
Besides being associated with “fear”, what are some other functions of the amygdala?
c.
Hypothesize as to how (mechanistically) an increase in number of GABA receptors in the
amygdala and locus coeruleus could lead to a decrease in the amount of CRH released
from the hypothalamus. [HINT: Think about feedback mechanisms.]
d.
Given this information, do these brain regions when activated (i.e. not inhibited) stimulate
or inhibit the release of CRH?
4.
Add to your diagram (Question #1) any connections between the hypothalamus and other brain
regions involved in the stress response. Indicate whether (according to this article) activation of
those regions increases (+) or decreases (-) release of CRH. [HINT: Refer to questions 3 and 4.]
5.
Positive vs. deleterious effects of glucocorticoids
a.
One long-term effect of high levels of glucocorticoids is the redistribution of energy stores
from muscle to fat. What might be the original “adaptive” value of this redistribution?
Think in terms of the lifestyles and challenges of our human ancestors in pre-industrial
societies.
b.
Would there be any adaptive value for individuals subjected to greater stress (specifically
greater isolation) early in life to have higher than normal responses to stress hormones?