The excitation threshold of a neuron is the depolarization level that must be caused by a stimulus to be transmitted as a neural impulse. This value is about –50 mV.
The transmission of the neural impulse along the neuronal membrane obeys an all-or-nothing rule: or it happens with maximum intensity or nothing happens. Always and only when the excitation threshold is reached the depolarization continues and the membrane reaches its maximum possible positive polarization, about +35 mV. If the excitation threshold is not reached nothing happens.
