Neuron Behavior Modeling in Cognitive Science 107A: Resting Potential & Ionic Currents, Assignments of Physiology

Download Neuron Behavior Modeling in Cognitive Science 107A: Resting Potential & Ionic Currents and more Assignments Physiology in PDF only on Docsity! COGNITIVE SCIENCE 107A Exercise #3 : MODELING THE NEURON The Electrophysiology of the Neuron program can be run on the IBM PC computers in room 101. Instructions on how to run it will be given by TAs. There are two types of experiments that can be modeled: 1) current clamp (C-CLAMP) and 2) voltage clamp (V-CLAMP) experiments. C-CLAMP experiments involve injecting current into a cell (and holding it constant or "clamped",) and recording what happens to the membrane potential. V-CLAMP experiments involve varying the current you inject into a cell in order to hold the membrane potential (voltage) constant. This allows you to see what happens with the different ionic currents. There are, therefore, two modeling programs that can be executed by typing either C-CLAMP or V-CLAMP at the DOS prompt. For questions 1-4 execute C-CLAMP. After executing each program you will see a menu appear on your screen. These are parameters for the experiment. They can be changed by moving the cursor through these menus with the arrow keys and typing in new values. Begin simulation by pressing the B key. Use the R key to return to the menu screen. The O key can be used to open files that have established parameters for observing the resting membrane potential (REST.CCS) or the passive properties of the cell (PASSIVE.CCS) 1. Open the REST.CCS file. Begin simulation to see the resting membrane potential. What happens to this resting membrane potential when you change the K+ or Na+ leak currents (i.e., pKleak or pNaleak) to 0 (one at a time)? 2 pts 2. What happens to the resting membrane potential as you increase the concentration of Na+ or K+ outside the cell (i.e., [Na]o and [K+]o) without changing Mg++, Ca++, or Cl- levels - again, change them one at a time? 2.5 pts 3. Open the PASSIVE.CCS file. Increase the amount of injected current to 2.0 (this should now simulate an action potential). You can also get an action potential by loading the ACTIVE.CCS file. What happens to the action potential when you vary the extra- and intra-cellular concentration of Ca++, K+, Na+, and Cl-(one at a time)? Which ions have a greater role in the generation of the action potential? 3 pts 4. Explain the reasons why the membrane potential changes the way it does in question #2. 2.5 pts