An action potential is the change in electrical potential associated with the passage of an impulse along the membrane of a muscle cell or nerve cell. An action potential occurs when a neuron sends information down an axon, away from the cell body. A threshold is the minimum amount of stimulation needed to start a neural impulse. Action potentials generated by neural impulses are “all or nothing”. Meaning the signal reaches the threshold for communication or it doesn’t. No signal is stronger or weaker than another. Depolarization increase in positive charge inside the plasma membrane caused by a depolarizing graded potential causes increasing numbers of voltage gated Na+ channels to open rapidly.