lecture_10_3

lecture_10_3 - II.B. How does voltage change in the neuron...

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II.B. How does voltage change in the neuron over time? What properties of the CM are responsible for the shape of the V vs. time curve? Voltage change recorded across a cell membrane as current is injected II.B.2 What causes the shape of the voltage vs time graph Injected Current Voltage time 63% Vss resistance of a unit length of membrane (in ohm-cm) magnitude of the injected current (in amps) input (total) resistance of the cell (in ohms) capacitance of a unit length of membrane (in farads/cm) where and is the membrane time constant is the steady state voltage at the injection site V ss is value at t = II.B.3.c Properties of the time constant, τ If we increase the membrane capacitance, c m , will the cell reach its steady state voltage change more quickly or more slowly? ________ If we increase c m , we _______ τ . Therefore by ________ τ, we increase the time it takes for a neuron's voltage to reach a new steady state in response to an injected current. c m Cell responds more quickly Cell responds more slowly r m τ c m r m τ Why? _________________ As an exercise, you might want to fill in the rest of the chart above. In general, increasing τ slows the cell's response to injected current, which is shown on the chart below. The value τ is useful because it gives us a single parameter with which to determine how quickly or slowly a cell's voltage will change in response to current flow. where
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lecture_10_3 - II.B. How does voltage change in the neuron...

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