Final answer:
Depolarization of nerve membranes by electrical currents produces action potentials, leading to propagation of nerve impulses and muscle contraction, critical for functions like heartbeats.
Step-by-step explanation:
Electrical currents exert their physiological effects by depolarizing nerve membranes, which leads to the production of action potentials.
When a stimulus changes a membrane's permeability, it becomes temporarily permeable to sodium ions (Na+), initiating an influx due to diffusion and the Coulomb force.
This inrush of Na+ depolarizes the nerve cell membrane, making it slightly positive. Subsequently, repolarization occurs as the membrane becomes impermeable to Na+, and potassium ions (K+) move out, returning the cell to its resting potential.
This depolarization and repolarization cycle enables nerve impulses to propagate along neurons and induces muscle contraction in response to these electrical signals.
For example, in the heart, a depolarization wave can travel from the sinoarterial (SA) node across cardiac muscle cells, coordinating the heart's rhythmic contractions necessary for blood circulation.