• After an action potential passes through a section of an axon it undergoes a?period of recovery?and is?unresponsive
  • This is known as the?refractory period

   

• The refractory period means that there is a?minimum time between action potentials?occurring at any one place along a neurone
• The?duration?of the refractory period is?key in determining the maximum frequency?at which impulses can be transmitted along neurones (between 500 and 1000 per second)
• In order to find the maximum frequency of impulses within a certain period of time the following equation can be used:

Time ÷ duration of the refractory period

• Questions often ask for the maximum frequency of impulses within one second. This would make the equation:

1 ÷ duration of the refractory period

• Different units are used for these calculations
  • Impulses sec-1
  • Action potentials sec-1
  • Hz (1 Hz is equal to one impulse per second)

   

Step 1: Determine the duration of the refractory period

From the graph: 2.75 milliseconds

Step 2: Convert this to seconds

0.00275 seconds

Step 3: Insert relevant figures into the equation

Time ÷ duration of the refractory period

1 ÷ 0.00275 = 363.63

Answer = 364 action potentials sec-1