midterm2009 KEY

midterm2009 KEY - MCDB 111/ Introduction to Physiology -...

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1 MCDB 111/ Introduction to Physiology - Midterm, Winter 2009 Your Name: Perm #: Your TA's name: Discussion section time: 1. (9) ________ 2. (6) ________ 3. (15) ________ 4. (6) ________ 5. (6) ________ 6. (13) ________ 7. (5) ________ 8. (5) ________ 9. (5) ________ 10. (6) ________ 11. (4) ________ total (80) ________ 1. The graph below shows changes of relative K + and Na + permeability with respect to time in a nerve cell as it has an action potential. a. Between about 0.5 ms and 1.5 ms the permeability of ion “A” is dropping quickly. What is ion “A” and what is causing the permeability to drop so suddenly? (3 points) A = Na+; it is dropping because the inactivation (slow) gate on the Na+ channels is closing.
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2 b. Between 0 and about 1.25 ms the permeability of ion “B” is increasing. What is ion “B” and what is the stimulus that is causing the permeability of ion “B” to increase? (3 points) B = K+; the stimulus is the depolarization of the membrane that started the action potential c. At time point 2 ms, would you expect the membrane potential of this nerve cell to be: at the resting potential, more negative than the resting potential (hyperpolarized), or more positive than the resting potential (depolarized). Explain your answer in terms of relative membrane permeability. (3 points) It would be more negative than the resting potential, because of the higher permeability of K+. 2. Refer to the picture of the synapse below. The graph shows the membrane potential in the post-synaptic cell. The post-synaptic cell has three pre-synaptic inputs (A, B, and C). The numbers at the top of the graph of membrane potential versus time indicate different time segments. a. In which of these segments is an inhibitory post-synaptic potential (IPSP) being produced, what neurotransmitter might the presynaptic nerve be releasing, and what
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3 ion current could cause the IPSP [what ion and what direction (in or out of cell)]? (3 points) C; glycine or GABA(other possible correct answers); Cl- moving into the cell (K+ moving out of the cell is OK, too) b. What sort of summation is being displayed in segment 2, and why does segment 2
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This note was uploaded on 02/14/2011 for the course MCDB 111 taught by Professor Smith during the Spring '11 term at UCSB.

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midterm2009 KEY - MCDB 111/ Introduction to Physiology -...

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