• 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.
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