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Unformatted text preview: BIO 335 WEEK 5 Lab Activity NAME: ______________________________ ION CHANNELS IV. LAB PROCEDURES Tutorial 1. Chattering Ion Channels. This tutorial assumes that you have experience with Neurons in Action (NIA). It also assumes that you have knowledge of the action potential. The Worksheets have to be handed in either at the end of class or at the beginning of next week’s lab. The Post-Lab Activity worksheets can be done after the lab if necessary. From the Tutorials list, choose Chattering Ion Channels . Follow these instructions and answer all questions . Read the introductory material for this tutorial up to the part entitled “Experiments and Observations”. Some Notes…-The analysis/questions are tightly linked to NIA…make sure you always look at the instructions/discussion there.-Sometimes the K or Na channel does not appear after certain manipulations. If this occurs, quit and restart ‘Chattering ion channels’.-Simple answers will almost always suffice. Equations are also preferred if appropriate.-Now scroll back up to the green button that says “ Start the simulation ” and click once on the button.-Using the default setting and in the RunControl window, hit ‘ Reset and Run ’… O BSERVE S INGLE N a AND K C HANNELS IN A P ATCH . 1. In the ‘Voltage vs. Time’ window, what is the Black line? Why does it show a step function? What is the ‘red’ line? What is the ‘blue’ line? In the Lower window you should see single channels for Na + (red) and K + (blue) channels. If not, hit ‘Reset and Run’ again—you may have to do this multiple times to get examples of both. 2. Why do the current amplitudes occur in different directions (the ‘open’ state is negative or inward for the Na channel and positive or outward for the K channel)? 3. Press ‘Reset and Run’ repeatedly and look at the distribution of the Na + and K + channel during the depolarizing step. a. What is the general relationship between the timing of the Na + channel and that of the K + channel? 1 BIO 335 WEEK 5 b. Which channel has a higher open probability (P open )? Why is this timing relationship important for the action potential? S TUDY A S INGLE K C HANNEL BY ITSELF . 1. In terms of the direction of current amplitude what would be the best way to test if this is a K+ channel? 2. Are there two current amplitudes? As explained in the text there are times at the end of the depolarizing step that you see two amplitudes for the currents. Why is this the case? Can you think of an experiment that can test your hypothesis (think E K )? In this and the following Tutorial, you will ‘voltage clamp’ a membrane and record Na and K currents that arise when the membrane potential is changed. It is critical to track the terms that refer to the Voltage protocol....
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- Fall '08
- Physiology, Post- Lab Activity, current amplitudes