Understanding the Phases of the Action Potential Waveform: A Comprehensive Analysis of Voltage Changes during Cell Membrane Activation

What will a plot of action potential voltage versus distance look like?

A plot of action potential voltage versus distance typically follows a specific pattern, known as the action potential waveform

A plot of action potential voltage versus distance typically follows a specific pattern, known as the action potential waveform. This waveform can be divided into several distinct phases: the resting phase, the depolarization phase, the overshoot/peak phase, the repolarization phase, and the hyperpolarization phase.

Let’s break down each phase and their corresponding voltage changes:

1. Resting phase: At rest, the membrane potential of a cell is typically around -70 millivolts (mV). This phase is represented as a horizontal line at the resting membrane potential, indicating no change in voltage.

2. Depolarization phase: When a stimulus triggers an action potential, the membrane potential rapidly depolarizes. The voltage increases from the resting potential to a peak value of about +30 mV. In the plot, this phase appears as an upward spike from the resting potential.

3. Overshoot/peak phase: Following depolarization, the voltage reaches its maximum value, usually around +30 mV. This phase is represented as the highest point of the spike in the plot.

4. Repolarization phase: After reaching its peak, the voltage starts to rapidly decrease towards the resting potential. This phase is caused by the opening of voltage-gated potassium channels, allowing the efflux of potassium ions, resulting in the repolarization of the membrane. In the plot, the voltage rapidly drops back down, forming a downward slope.

5. Hyperpolarization phase: In some cells, the voltage temporarily overshoots the resting potential and becomes more negative than the initial resting potential. This phase is known as hyperpolarization and is caused by the prolonged opening of potassium channels. In the plot, it appears as a slight downward dip following the repolarization phase before returning to the resting potential.

Overall, the plot of action potential voltage versus distance appears as a sharp spike followed by a rapid decline, ultimately returning to the resting membrane potential. This pattern represents the electrical activity that occurs during the propagation of an action potential along a neuron or muscle cell.

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