what happens during the hyperpolarization stage of a neuron action potential?
The correct answer and explanation is:
During the hyperpolarization stage of a neuron’s action potential, the membrane potential becomes more negative than the resting potential. This occurs after the repolarization phase when potassium (K+) ions continue to exit the neuron through voltage-gated potassium channels, even after the membrane potential has returned to near resting levels. This excess loss of positive charge makes the inside of the neuron even more negative compared to the outside, causing hyperpolarization.
Hyperpolarization is typically caused by the continued flow of potassium ions out of the cell after the voltage-gated potassium channels have closed. Sometimes, chloride (Cl-) ions can enter the cell, further increasing the negativity inside. The membrane potential drops below the resting potential, which is typically around -70 millivolts, and can reach values as low as -80 to -90 millivolts.
This phase plays an important role in regulating the firing of action potentials. The neuron becomes less likely to fire another action potential during this period, known as the refractory period. There are two types of refractory periods: the absolute refractory period, when no action potential can be initiated, and the relative refractory period, when a stronger-than-usual stimulus is required to initiate an action potential. Hyperpolarization is part of the relative refractory period.
Once hyperpolarization is complete, the cell’s membrane potential returns to its resting state. This process is assisted by the sodium-potassium pump, which actively transports three sodium ions out of the neuron and two potassium ions back into the neuron, restoring the resting potential. This ensures that the neuron is ready for the next action potential when needed.
Hyperpolarization serves to maintain the proper functioning of neurons and ensures that signals are transmitted in a controlled manner.