Part 9/14:
Action Potentials and Their Role in Muscle Function
Muscle contractions are initiated by electrical signals called action potentials, which are rapid depolarizations and repolarizations of the cell membrane potential. In skeletal muscles, these are driven by motor neuron activity—neurogenic contractions—whereas in cardiac and smooth muscles, contractions are often myogenic but can also be modulated by autonomic nerves.
Action Potential Dynamics
Cells maintain a negative internal charge relative to outside.
Depolarization occurs when sodium ions flood into the cell.
Repolarization restores the negative charge.
Hyperpolarization makes the cell more negative than resting potential, inhibiting firing.