BIO121NeuralSignalingProblemSet - Neural Signaling &...

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Activity 1. Polarization* The inside of a neuron is typically -60 mV (resting membrane potential) which means that it is more negative than the extracellular fluid by 60 mV. This means the cell is polarized. When a ligand-gated Na + channel opens, Na + diffuses down its concentration gradient and enters the cell. Since Na + ions are positively charged, the inside of the cell becomes more positive. As the inside of the cell gains more positive charge, the membrane potential begins to move from the resting potential toward “0” (from –60 mV, to –59 mV, to –58 mV, etc.). This is called depolarization . If the cell then opens a K + channel (which will allow K + to exit the cell) the positive charge inside the cell will begin to decrease (or move back toward the resting membrane potential). This is called repolarization , and only occurs as the membrane voltage returns to the resting membrane potential after a depolarization. If the K + channel stays open too long, the membrane potential will actually become more negative that –60 mV (it’s like an overshoot). This is called hyperpolarization . Divide into groups. In the situations below, indicate whether the membrane potential is becoming more positive, or more negative. Then indicate whether the membrane is depolarized, polarized, repolarized, or hyperpolarized. Assume that the cell is starting off at the resting membrane potential for each scenario. Each group will complete two of the rows in the table below then share their answers with the group. Na
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This note was uploaded on 01/14/2012 for the course BIO 121 taught by Professor Druger during the Fall '05 term at Syracuse.

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BIO121NeuralSignalingProblemSet - Neural Signaling &...

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