Identify The Phases Of An Action Potential
undersboer
repularization phase
depolarization phase
The Correct Answer and Explanation is :
An action potential is the rapid rise and fall in the membrane potential of a cell, which allows for communication between nerve cells, muscle cells, and other excitable tissues. It occurs in several distinct phases, which can be summarized as follows:
Phases of an Action Potential:
- Resting Potential (Resting State):
The resting membrane potential is the stable, negative charge inside the cell compared to the outside (typically around -70mV). During this phase, the cell is not actively sending an electrical signal. - Depolarization Phase:
Depolarization begins when a stimulus causes the cell’s membrane potential to become more positive. Voltage-gated sodium (Na⁺) channels open, allowing sodium ions to rush into the cell. This influx of positive ions causes the inside of the cell to become less negative and eventually reach a positive value, typically around +30mV. This is the depolarization phase. The influx of sodium ions continues to propagate the action potential along the axon. - Repolarization Phase:
After the depolarization peak, the sodium channels close and voltage-gated potassium (K⁺) channels open. Potassium ions move out of the cell, causing the inside of the cell to become more negative again, which is called repolarization. This phase restores the cell’s membrane potential back toward the resting state. The potassium channels remain open for a short time after the membrane potential reaches its resting value, causing an overshoot known as hyperpolarization, where the inside of the cell becomes slightly more negative than the resting potential. - Hyperpolarization (Undershoot) Phase:
During this phase, the cell becomes more negative than the resting potential due to the slow closing of potassium channels. The membrane potential eventually returns to its resting state as the potassium channels close completely, and the sodium-potassium pump restores the ion gradients.
The repolarization phase and depolarization phase are crucial for the propagation of action potentials along neurons and for the effective communication between cells in tissues like muscle. The precise timing and coordination of ion channel openings and closings in these phases enable the action potential to travel down the neuron and trigger physiological responses such as muscle contraction.