Depolarization of neuronal plasma membrane

Question

How depolarization of the neuronal plasma membrane is produced? How does the cell come back to its original rest?

Answer 1

Whenever neuron receives a stimulus through the binding of the neurotransmitters to the exact receptors sodium channels open and the permeability of plasma membrane in postsynaptic region is changed. Then sodium ions enter in the cell resulting in the lowering of the membrane potential. In case, this reduction of the membrane potential arrives at a level known as the excitation threshold, or threshold potential, which is around–50 mV, the action potential is produced, that is, the depolarization intensifies up-till reaching its higher level and depolarization current is transmitted all along the remaining length of neuronal membrane. In case, the excitation threshold is attained voltage-dependent sodium channels within the membrane open enabling more sodium ions to go into the cell in favor of concentration gradient and an estimated -35 mV level of positive polarization of the membrane is attained. Then the voltage-dependent sodium channels close and more voltage-dependent potassium channels get open. Then the potassium ions go out through the cell in favor of concentration gradient and potential difference of the membrane reduces, a method known as repolarisation. The action potential triggers the similar electrical mechanism in the neighboring regions of plasma membrane and the impulse is therfore transmitted from dendrites to terminal region of the axon.