Summary:
- A nerve impulse is a sudden reversal of the electrical charge across the membrane of a resting neuron.
- The reversal of charge is called an action potential.
- It begins when the neuron receives a chemical signal from another cell.
- The signal causes gates in sodium ion channels to open, allowing positive sodium ions to flow back into the cell.
- As a result, the inside of the cell becomes positively charged compared to the outside.
- This reversal of charges ripples down the axon very rapidly as an electric current.
- An action potential speeds along an axon in milliseconds.