Threshold of excitation

Learning objectives

To analyze the consequences of sub-threshold, threshold and superthreshold stimulations on the value of the membrane potential of a neuron.
To set down the law of « all or nothing » that characterizes the notion of action potential.
To understand that the nerve message is encoded in the frequencies of action potentials.

This activity takes an experimental approach to introduce the notion of the threshold of excitation in nerve cells via electrical stimulation of 5 µA, 10 µA, 20 µA, 40 µA and 80 µA.
One notes in passing the way in which the information is encoded:
Beyond the threshold of excitation, the nerve message is a signal that takes the form of a train of action potentials, the frequency of which is proportional to the intensity of the stimulation.

Click on « Start the Experiment », then select an excitation intensity.
Roll over the oscilloscope screens to obtain values.