MCDB_151_HW1-NeuralSim

MCDB_151_HW1-NeuralSim - MCDB 151/251 - HOMEWORK #1 Due...

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MCDB 151/251 - HOMEWORK #1 Name____________________ Section_____________ Due Wednesday 10/14/09 in Lecture NeuralSim APSIM is an action potential simulation program that reproduces the active and passive electrical properties of the squid giant axon membrane. It uses the Hodgkin-Huxley equations (Hodgkin and Huxley (1952) J. Physiol. (London) 117, 500-544) to simulate membrane action potentials in response to stimulating current pulses delivered with an intracellular electrode. With this program you will be able to reproduce a number of classic experiments on the electrical properties of axons, including threshold, refractory period, and effects of ionic concentrations and channel conductances on the action potential. The program provides separate windows to view the voltage changes during the action potential, the time-depenendent changes in channel conductances, and the time-dependent opening and closing of the channel gates. In the Start menu, go to Programs, Lifesciences, NeuralSim To start the Action Potential Simulation, Select: APSIM Threshold potential is the value of membrane potential at which an action potential is generated. At this potential, inward (e.g. sodium) current just exceeds outward (e.g. potassium) current. Use this exercise to look at action potential threshold. 1. Threshold potential Determine the normal threshold potential using a 0.5 msec stimulating current pulse (Make sure you are in Active Mode, One Pulse under the Mode menu.) Click Run to start a simulation. Using the Stimulus Strength scroll bar to adjust the strength of the current pulse until the pulse just elicits an action potential. a) What current stimulus strength did you need to generate an action potential? To determine the threshold potential, open the Measure window from the menu bar and use the cross hair to read the voltage at the end of the 0.5 msec stimulus that just fails to elicit an action potential. b)
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MCDB_151_HW1-NeuralSim - MCDB 151/251 - HOMEWORK #1 Due...

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