Depolarization (physiology)

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In neurology, depolarization (also called depolarization ) is a reduction in the membrane potential on a cell membrane .


In electrically excitable cells such. B. nerve cells, the resting potential is present in the unexcited state . The membrane voltage of such a cell can be depolarized above or below the threshold by the release of a transmitter at a synapse . If the threshold value is reached, voltage-controlled sodium ion channels (sometimes also calcium ion channels ) open, which intensifies the depolarization and an action potential is triggered. This means that the cell is excited, which can also be passed on to other cells by means of further action potentials. If the depolarization remains below the threshold, the membrane potential returns to the resting value without an action potential. The effect produced is described in the all-or-nothing law .

In the experiment, the depolarization can also be caused artificially.

At inhibitory synapses , it can also cause a hyperpolarization , an increase in membrane tension come. The inhibition represents the opposite of an excitation generated by depolarization.

Example: The resting membrane potential is −70 mV. A change of 30 mV to −40 mV is a depolarization. In the action potential, the voltage change from −70 mV to 0 mV is a depolarization (= reduction in the polarization of the cell), the wider range from 0 mV to +30 mV is called overshoot . If the resting membrane potential of −70 mV is then restored, one speaks of repolarization , or alternatively of hyperpolarization, depending on the definition of the term.


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