Resting and Action Potential in Muscle Cells

Study Notes

Resting Membrane Potential

The resting membrane potential of skeletal muscle is -94 mV.
The resting membrane potential is maintained due to the constant leakage of potassium ions out of the cell.
Potassium ions leak down their concentration gradient from inside the cell to outside the cell.
The outward movement of positive potassium ions leaves the inside of the cell more negatively charged.

Action Potential

The minimum potential required to generate an electrical signal is -70 mV.
An action potential is triggered when acetylcholine binds to a receptor on the muscle cell membrane.
The binding of acetylcholine allows sodium ions to enter the cell.
The influx of sodium ions causes the membrane potential to become more positive.
This is referred to as depolarization.
The peak potential during depolarization is +70 mV.
At the peak, the sodium channels close, while the potassium channels open.
Potassium ions leave the cell, causing repolarization.
The repolarization phase returns the membrane potential to the resting potential of -94 mV.
The membrane potential may briefly drop below the resting potential, known as hyperpolarization.
Hyperpolarization is a built-in mechanism preventing overlapping muscle contractions.
The sodium-potassium pump restores the original ion distribution, maintaining the resting membrane potential.

Absolute Refractory Period

The absolute refractory period is a time when another action potential cannot be generated.
This occurs because sodium channels are either open, closed, or inactivated.
Inactivated sodium channels require time to reset to their original open position.

Description

Explore the fundamentals of resting membrane potential and action potentials in skeletal muscle. Understand how potassium and sodium ions contribute to electrical signaling within muscle cells. Test your knowledge on the processes of depolarization and repolarization.