What is repolarization?
Nerve cells in the nervous system in the nervous system send signals called action potentials during which soma or cellular body of neuron sends an electrical signal of the axon. If there is no signaling, the neuron is hyperpolarized, which means it has a negative charge compared to the outside. When the action potential signal travels through Axon, the cell causes the cell to depolarize or become more positive. At the end of the signal, the cell undergoes repolarization, where the original negative polarization returns.
Neuron is made up of soma or cellular body, from which dendrites address as branches of a tree. At one end of the neuron is a long cable called Axon, which ends in synaptic buttons. Excitative and inhibitory signals travel from other neurons to dendrites and cellular body, and these signals are added to the hill Axon, which lies just before the start of the axon. These signals can hyperpolarize or depolarize a cell. Repolarization returns the cell to its resting state.
hyperpolarization, depolarization and repolarization of neuron are caused by a flow of ions or charged molecules, in and out of the cell. When the cell is at rest, these ion channels remain closed when the membrane potential reaches a certain point, called the threshold potential, opens. The cellular body receives messages from other cells that either depolarize or hyperpolarize the cell, and if enough messages are received, the cell reaches the threshold potential.
When threshold potential is achieved, potassium and sodium channels are open, allowing the cell to enter a positively charged potassium and sodium ions. At the same time, chloride channels allow to leave the cell of negatively charged chloride ions. This causes depolarization where the cell is less negatively charged than when it is calm.
After the action potential depolarizes the cell, the repolarization process begins. Sodium and potassium channels are closing and blocking positioutside charged ions in the entrance to the cell. At the same time, a negatively charged chloride ions returns to the cell.
The first part of the repolarization is called the refractory period and there are two phases of this phase, the absolute refractory period and the relative refractory period. During the absolute refractory period, the cell refuses to generate further action potential. During the relative refractory period, the cell can generate a different action potential, but requires greater than the usual signal. This refractory period of repolarization occurs because hyperpolarization of the cell occurs due to the influx of potassium ions after action potential.