After an action potential, there is
a short period of time when another action potential cannot be generated. What is this period of time
You may recall that if a neuron,
like the one shown in this diagram, receives a sufficiently strong stimulus, a nerve
impulse, which is also known as an action potential, will be generated. This action potential is conducted
along the length of the axon. In a mammalian axon, an average
action potential lasts for between 0.5 and one milliseconds. If another stimulus is given during
this time, it will not generate another action potential in the neuron. This is because the membrane
potential, the difference in charge between the neuron cytoplasm and the
extracellular space, changes during an action potential. And it takes time for the neuron to
return to its resting state before another action potential can be generated.
If you’ve ever been to the gym, you
probably had to stop and recover between exercises. This is exactly what neurons do
between action potentials. The time taken for a neuron to
recover before another action potential can be generated is called the refractory
period. And in mammals, it’s usually
between 0.5 and one milliseconds in duration.
The refractory period is important
because it ensures that each action potential is a discrete event. In other words, it makes sure they
don’t all merge into one another. It also means that action
potentials can only travel in one direction. This is essential for the
successful and efficient transmission of nerve impulses along neurons.
We have therefore determined that
the short period of time following an action potential when another action potential
cannot be generated is called the refractory period.