BIPN100B FIRST MIDTERM Fall 2010 Name PID

Transcription

1 General Instructions: READ THIS PAGE BEFORE YOU BEGIN THE EXAM. 1. Write your name and PID 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 your calculations. 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. We deduct points for statements that are both incorrect and irrelevant. (We don't just ignore irrelevant answers because we need to let you know that you have some wrong ideas.) 6. Use a pen or pencil to write your answers, but do NOT use RED INK or RED PENCIL, and do NOT use WHITE-OUT of any kind. POTENTIALLY USEFUL EQUATIONS: 2 E ion = 61 z log[x] out V = IR w [X] T = nrt dv in V SCORE: 1 Page 2 Ix = Gx (Vm-Ex) R total = ΣR individual Page 3 Page 4 R = 8ηl πr 4 E = mc 2 Page 5 1 = Σ 1 R total R individual TOTAL 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. I realize that this procedure may 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 on the course Web site. Signature Date

2 1. (15 points) Below is a diagram showing the relationships among 11 organs. a. How many feedback loops are there? Name them (e.g., A-->B-->C-->A). b. Is each loop positive feedback or negative feedback? Briefly explain. c. If A increases, would the output from C increase, decrease, or remain the same? Explain. (If it is impossible to tell what would happen, explain why.) 2. (15 points) List 3 differences between the Na + channels responsible for action potentials and the Na + channels responsible for receptor potentials.

3 3. (15 points) In a survey of the life in the depths of Lake Baikal in Russia, the world s deepest lake, you dredge up a primitive creature that has neurons with a resting potential of -78 mv that results from the leak across four different kinds of channels: Rb +, Li +, Br -, and I -. You are able to measure the equilibrium potentials for each of the ions; they are: E Rb = -100mV E Li = +61 mv E Br = +61 mv E I = -78 mv a. You measure the concentration of Br - on the outside of the neurons; it is 10 mm. What is the concentration of Br - inside the neurons? (Show your calculations.) b. Calculate how much current flows through I - channels at the resting potential. c. You measure the conductances of each of the channels: G Rb = 70 ps G Li = 1 ps G Br = 10 ps G I = 19 ps Which ion has the strongest effect on the resting potential? Briefly explain your answer. 4. (5 points) Sarin gas has long been used as a weapon, including in 1995 when it was released in a Toyko subway. Symptoms of sarin gas inhalation include skeletal muscle spasms (prolonged contraction) and such a strong bronchiolar constriction (contraction of the smooth muscles in the airway passages to the lungs, which are innervated by postganglionic parasympathetic neurons) that the victim suffocates to death. Sarin is an acetylcholine esterase inhibitor. Explain how sarin causes both skeletal muscle spasm and bronchiolar constriction.

4 5. (12 points total) For the following three groups of statements, circle every letter that makes a TRUE statement. Note that any number of statements may be true (including none of them), and that not circling a letter means that you think that the statement is false. A. Sensory receptor neurons in the human body include: a. nociceptors, which include receptors to sharp pain, dull pain, and itch. b. olfactory (smell) receptors that respond to a limited number (4 or 5) basic odors. c. auditory (hearing) receptors that are specialized mechanoreceptors. d. visual receptors that turn light energy into action potentials that are transmitted by axons of the receptor neurons to the brain through the optic nerve. B. Different pairs of hormones have different kinds of interactions: a. additive: the total effect of two hormones is the sum of the individual effects. b. synergism: the total effect of two hormones is more than the sum of the individual effects. c. permissive: one hormone cannot exert its full effect unless a second ( permissive ) hormone is present. d. antagonistic: two hormones have opposite effects, and one of them totally negates the effect of the other. C. In the autonomic nervous system: a. there are no known antagonists that distinguish between alpha-adrenergic receptors and beta-adrenergic receptors. b. the adrenal medulla is often described as a modified parasympathetic ganglion. c. both sympathetic and parasympathetic postganglionic neurons release their transmitters onto metabotropic receptors. d. unlike the skeletal neuromuscular junction, each postganglionic synaptic ending forms a series of swollen areas called varicosities. 6. (12 points) You accidently pick up a hot frying pan; you quickly pull your hand away, and notice that your heart is beating much faster than normal. List four ways that the reflex pathway responsible for pulling your hand away from the hot pan differs from the reflex pathway responsible for the increase in your heart rate.

5 7. (16 points) When you set up your own neurological practice and research lab in 2025, Transcranial Magnetic Stimulation (TMS) technology has become so precise that you can stimulate small groups of neurons or axon tracts anywhere in the brain. You decide to duplicate the experiments of Wilder Penfield by determining the effects of stimulating specific areas of the CNS and PNS of awake human subjects. You (1) carefully monitor any body movements and (2) ask the subject, after each stimulation, what he/she perceived. What do expect to observe or have him/her report after you stimulate: a. a dorsal root ganglion on the left side in the lumbar region. b. a ventral horn on the right of the spinal cord in the lumbar region. c. the medial lemniscus on the right side. d. the anterolateral tract on the right side of the thoracic spinal cord. e. the primary visual cortex. f. the visual association area. g. the right primary motor cortex, in the arm region. h. the frontal lobe. 8. (10 points) Gastrin is a peptide hormone produced by the stomach. Aldosterone is a steroid hormone produced by the adrenal cortex. Without knowing the targets of these two hormones, tell how gastrin is different from aldosterone both in the time-course of its actions and in the mechanisms it uses to affect its target cells.