midterm2010 KEY

midterm2010 KEY - 1 MCDB 111 Introduction to Physiology...

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1 MCDB 111/ Introduction to Physiology - Midterm, Winter 2010 Your Name: Perm #: Your TA's name: Discussion section time: 1. (12) ________ 2. (9) ________ 3. (10) ________ 4. (8) ________ 5. (6) ________ 6. (8) ________ 7. (5) ________ 8. (4) ________ 9. (8) ________ 10. (4) ________ 11. (6) ________ total (80) ________ 1. The short-term regulation of plasma cortisol involves a negative feedback loop shown here: a. In this diagram, where would you expect the integrating center(s) to be, and what is/are the efferent signals? (4 points) the integrating centers would be in the hypothalamus and anterior pituitary the efferents are CRH and ACTH
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2 b. Cortisol is a steroid hormone. One of the effects of cortisol on liver cells is to increase the amount of the enzyme glucose-6-phosphatase. Briefly, describe in words or a diagram the mechanism by which cortisol increases glucose-6-phosphatase. (4 points) cortisol will diffuse into the liver cell and bind a nuclear receptor . The ligand-bound receptor will the bind to the regulatory region of the glucose-6-phosphatase gene . This then recruits the transcriptional machinery to transcribe the gene. The mRNA is then processed and exported to the cytoplasm where it is translated to make more enzyme. c. What is the effect of cortisol in metabolism, and why is this an appropriate response to stress? (4 points) it stimulates: 1)catabolism of protein and triglyceride catabolism; 2) gluconeogenesis (also maintenance of plasma glucose). the metabolic actions will free up stored energy reserves that will be needed for recovering from the stressful situation. 2. The figure below shows two graphs. The top graph is from the text and shows the relative tension in a skeletal muscle fiber as it receives a series of stimuli (S) from a motor neuron. a. The bottom graph needs to be filled in by you. It should show the relative myoplasm [Ca 2+ ] in this same muscle fiber in the same time period as the top graph. (4 points) b. at time point “A” in the top graph the relative tension is falling (i.e., the fiber is
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midterm2010 KEY - 1 MCDB 111 Introduction to Physiology...

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