Tuesday, October 19, 2010

Electrophysiology

Also known as the axon's electrical response, there are several features that are key to the functioning of an action potential.

1. It's all or nothing - either you're going to have an action potential, or you're not. The membrane depolarization must reach a certain threshold (commonly quote in textbooks as -50mV). If subthreshold, electrotonus occurs (no response far from the point of stimulation), but if above the threshold, a wave of excitations will occur, with each peak potential non-determined by the input stimulus.

2. action potentials move at a constant speed of 0.1 to 120 m/s.

3. Action potential peaks are independent of distance, though the decaying behaviour of hyperpolarization or subthreshold stimuli are. This is to say, one input of stimulus can send an action potential along the longest axon (very important, think of your leg)

4. action potential shape remains constant over time.

5. afterhyperpolarization is where the membrane potential overshoots, become more negative than at rest.

6. The neuron is harder to stimulate during what is known as the refractory period.

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