What happens when sodium channels open in response to an excitatory impulse?

When sodium channels open in response to an excitatory impulse, sodium ions flow into the cell. This influx of sodium occurs because the opening of these channels reduces the membrane potential, making the inside of the cell less negative compared to the outside. As sodium ions enter the cell, this causes depolarization, which is a critical step in the generation of an action potential in neurons.

The depolarization caused by an influx of sodium is essential for the propagation of electrical signals along nerve fibers. This process allows for communication between neurons and the transmission of signals in the nervous system. The subsequent stages of action potential propagation involve further changes in membrane permeability and the opening of other ion channels, but the initial event of sodium influx is what triggers the rapid rise in membrane potential associated with depolarization.