READ THIS PAGE BEFORE YOU BEGIN THE EXAM.

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1 BIPN 100B MAMMALIAN PHYSIOLOGY 1 - Fall 2009 Page 1 First midterm exam Name ID number General Instructions: READ THIS PAGE BEFORE YOU BEGIN THE EXAM. 1. Write your name on every page. (5 points off for EACH unnamed page.) 2. For your own benefit, write your answers LEGIBLY in the space allotted. If we cannot read your handwriting, we cannot give you credit for your answer. 3. Do NOT write on the BACK of any page unless you get a TA s permission FIRST. 4. About writing answers: All questions can be answered briefly. Answer the question that is asked specifically, precisely, and accurately. For full credit, show any calculations you did. Problems that ask for an answer and for a reason, most credit will be given for a correct reason. If you are asked for one reason, be sure you write down only the best one. 5. About grading: we give credit for correct and relevant answers; we ignore true, but irrelevant statements; but we deduct points for statements that are both incorrect and irrelevant. (We need to let you know that you have some wrong ideas.) 6. Use either pen or pencil, but do NOT use RED INK or RED PENCIL and do not use white-out. POTENTIALLY USEFUL EQUATIONS: E ion = 61 z log[x] out [X] in V = IR w T = nrt dv V 1 Ix = Gx (Vm-Ex) E ions = 61 log Σ{P X[X] out } Σ{P X [X] in } 2 SCORE: Page 2 /33 Page 3 /30 Page 4 /22 E = mc 2 R = 8ηl πr 4 Page 5 /15 R total = ΣR individual 1 R total = Σ 1 R individual TOTAL /100 WAIVER: By signing this waiver I give permission that this exam can be left for me to pick up in the hall on the third floor of Pacific Hall. (Your exam will be folded over and stapled so that only your name and ID number show.) I realize that this procedure could expose my grade to public scrutiny and my exam to theft. If I do not sign this waiver, I understand I will be able to get my graded exam back only as described in both the Course Outline and on the course Web site. Signature Date

2 Page 2 1. (13 points total) An incompetent electrician hooked up the thermometer controlling an air conditioner improperly, so that whenever the temperature went up, the reading on the thermometer went down. (The rest of the system functions normally.) A. (8 pts) Complete the feedback circuit below to show how this system would work. B. (5 pts) Does this system produce negative feedback or positive feedback? Briefly explain. 2. (20 points) How would the response to muscle stretch be modified (both in the stretched muscle and in its antagonist) if: A. (5 pts) you injected a drug that made the resting potential of the sensory neuron more depolarized than normal without changing its spike threshold? B. (5 pts) there was a genetic defect in the channels for K + that normally open during the generator potential, so that stretching the sensory terminals opened only Na + channels? C. (5 pts) all inhibitory synapses in the spinal cord were blocked? D. (5 pts) the entire peripheral nervous system was exposed to curare?

3 Page 3 3. (18 points total) A neuron in the thalamus was found to have the following characteristics: E Na = 0 mv [Na + ] o = 100 mm V rest = -60 mv E Ca = +100 mv [Ca ++ ] o = 4 mm V EPSP = 0 mv E Cl = -60 mv [Cl - ] o = 110 mm E K = -80 mv [K + ] o = 6 mm A. (6 pts) Can you tell what is the [Na + ] inside the neuron? If not, what additional information do you need? Be brief; show any appropriate calculations. B. (6 pts) Can you tell which ion channels are responsible for an EPSP? If not, what additional information do you need? Be brief; show any appropriate calculations. C. (6 pts) Action potentials in this neuron are overshooting; the peak of each action potential is +30 mv. What ion channel is likely to be responsible for the rising phase of the action potential? If you cannot answer, what additional information do you need? Briefly explain. 4. (12 points total) There was a major car crash on I-5. As the primary neurologist at a trauma unit, you evaluate four patients from the crash who have different symptoms. Based on their responses to your tests, which part of the nervous system is likely to be damaged in these four patients? a. (3 pts) Patient #1 has numbness in the lower left leg, running along the outside of his hip down to the ankle; he has no difficulty in moving any part of the body. b. (3 pts) Patient #2 cannot move the right leg, but has full and normal sensation everywhere. c. (3 pts) Patient #3 has loss of pain and temperature sense in the right leg, but no problem with 2-point discrimination or response to touch in either leg. d. (3 pts) Patient #4 can walk and move the arms normally, but cannot make fine finger movements; he has no problems with somatosensory perception anywhere on the body.

4 Page 4 5. (12 points total) For the following three groups of statements, circle every letter that is a TRUE statement. Note that any number of statements may be true (including none of them), so leaving this part blank means that you think that all statements are false. A. (4 pts) Transduction: is the transformation of energy from one form to another. of light is accomplished by photoreceptors called rods and cylinders in the retina of your eyes. of sound is done by the basilar membrane bending the stereocilia of hair cells in your inner ears. by receptor neurons in the semicircular canals signals which way your head is moving. B. (4 pts) Pain: is sensed by free nerve endings in the skin. can be lessened by drugs called analgesics, such as aspirin and opiates. is relieved by acupuncture, probably by causing the release of endogenous opioids. in internal organs, is often referred to an external body part. C. (4 pts) In the spinal cord: dorsal horn and dorsal root are alternative names for the same structure. each spinal nerve primarily innervates one region of the body called its dermatome. the dorsal columns carry temperature and pain information to the medial lemniscus. some axons from the primary motor cortex terminate on motor neurons in the ventral horn. 6. (10 points total) A neuron C receives synaptic input from two other neurons, A and B. Shown below are the responses of neuron C to input from neurons A and B individually, followed by A and B at the same time (A + B), then to a pair of inputs from A at a short interval (A A). A. (5 pts) Explain how the response to A and B together can be less than simply adding the individual responses to A and B. Be brief; show any appropriate calculations. B. (5 pts) On the diagram, draw the predicted response to stimulating Neuron B twice in quick succession (at the times of the two arrows marked B B at the end of the recording). Briefly explain.

5 Page 5 7. (15 points total) Androgens such as testosterone are a class of steroid hormones that produce male body characteristics (e.g., body and facial hair, bigger skeletal muscles). Androgens are normally produced in small quantities in the adrenal cortex. In males, the amount of androgens produced in the testes is so large that the androgens produced in the adrenal cortex are negligible. In females, however, the adrenal cortex is the only source of androgens. (These androgens are required for the growth of axillary (arm pit) and pubic hair in females, as well as being required to experience sexual arousal.) The androgens in the adrenal cortex are released in response to ACTH (adrenal corticotropin hormone), which also causes the release of cortisol. (Cortisol targets numerous organs to help us cope with many kinds of stress.) Cortisol inhibits neurons in the hypothalamus that produce corticotropin releasing hormone (CRH). CRH causes anterior pituitary cells to release ACTH. Androgens have no effect on the release of CRH. a. (5 pts) Draw the feedback system that shows how ACTH, CRH, androgens, and cortisol interact. (Indicate the source of the ACTH.) b. (5 pts) There are genetic defects that eliminate the synthesis of cortisol. Such animals (including human females) become hyper-masculinized, with bulging muscles and large amounts of hair all over their faces and bodies. Referring to the diagram that you drew, explain how a loss of cortisol could produce hyper-masculinization. c. (5 pts) Also refer to your diagram to propose an effective treatment for the hyper-masculine condition.