exam 1-2 Answer Key - Exam 1 Fundamentals of Neurobiology...

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Sheet1 Page 1 Exam 1 Fundamentals of Neurobiology February 2008 Name: __________________________________________ Choose the answer choice that best answers the question or completes the sentence. 1. Neurons have two types of processes: axons and dendrites. What is the major difference between the two? A) A cell body gives rise to a single dendrite and multiple axons B) Dendrites are of uniform diameter throughout while axons taper to a point C) Axons receive incoming signals from other neurons while dendrites carry the output of the neuron D) Dendrites receive incoming signals from other neurons while axons carry the output of the neuron E) Dendrites travel long distances while axons are rarely more than a few millimeters long 2. What is the definition of an ion's equilibrium potential? A) Difference in concentration between region with high ionic concentration and region with low ionic concentration B) The diffusion force that moves the ion from regions of high concentration to regions of low concentration C) The electrical force that prevents positively charged ions from leaving the negative inside of a neuron D) The difference between the actual membrane potential and the equilibrium potential for that particular ion E) The electrical force that exactly balances the diffusion force in the opposite direction 3. Identify the protein that is involved in anterograde transport, and the direction of this transport. 4. The dorsal roots just outside the spinal cord contain only __________ nerve fibers. These fibers __________
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Sheet1 Page 2 5. How long does an action potential last from the beginning of the rising phase to the end of the undershoot? 6. You are measuring the magnitude of the current through potassium channels that stay open all the time (and we assume that the number of channels in the membrane stay constant). You have previously determined that the equilibrium potential for potassium in this neuron is -80 mV. In which direction will the potassium current go at -100 mV, 80 mV and 0 mV? A) Outward current at -100 mV B) Outward current at -100 mV C) Inward current at -100 mV D) Inward current at -100 mV E) Inward current at -100 mV mV 7. You are in the lab using a patch clamp set-up to record currents through individual ion channels. From previous work on the same type of neurons in the same extracellular solution you know that the equilibrium potential for potassium is -75 mV, equilibrium potential for chloride is -58 mV, equilibrium potential for sodium is +68 mV, and equilibrium potential for calcium is +82 mV. You have a single ion channel in your patch pipette and notice that when you set the voltage to -80 mV you see a large inward current, when you set the voltage to +80 mV you see an outward current, at a voltage of -10 mV you again see the inward current but this time it is smaller than at -80 mV, and at a voltage of +68 mV you see no current at all. What type of channel do you think you have in your patch pipette?
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