Hyperpolarization (biology)

As hyperpolarization (English hyperpolarization ) or hyperpolarization is called an increase in membrane voltage to a sensory nerve or muscle cell above the resting value. Specifically, the voltage between the inner and outer side of the membrane is more negative. The hyperpolarisation is carried out by activation of inhibitory synapses by the opening or closing of specific ion channels or by the application of voltage of the appropriate polarity to the excitable membrane. Hyperpolarization is the opposite of the depolarization, wherein the potential in the inside of the cell is positive. Raised the threshold for triggering an arousal - This is at the same time - in the sense of inhibition.

Shortly after the opening of the closed depolarization voltage-dependent K channels causes a below the rest potential by about 10 to 30 mV to about -100 mV. The reason for this is that the closing of potassium channels on reaching the rest potential takes a long time and during this time further diffuses potassium. One calls this hyperpolarization also " afterpotential ". This prevents the irritability of the nerve cell for a new impulse for about a millisecond ( absolute refractory period ).

In photoreceptor cells, the resting potential is due to the dark current at about -40 mV. The absorption of photons triggers a signaling cascade that leads to the closing of cGMP-dependent Na channels. This in turn causes hyperpolarization of the membrane, whereby the external stimulus ( light) is translated into an electric signal ( change in membrane potential ).