6.2.6 Maths Skill: Calculating Maximum Impulse Frequency

Key Concepts

• Refractory period:
  • The time during which a neurone cannot fire another action potential.
  • It includes the absolute refractory period (no impulse possible) and relative refractory period (requires a stronger stimulus to generate an impulse).
• Impulse frequency:
  • The number of action potentials transmitted per second.

Formula for Maximum Frequency:

$$\text{Maximum impulse frequency (Hz)} = \frac{1}{\text{Refractory period (s)}}$$

• Units:
  • Refractory period must be in seconds (s) for the calculation to give frequency in Hertz (Hz).
  • 1 Hz = 1 action potential per second.

Worked Example

If the refractory period is 2 ms (milliseconds):

1. Convert milliseconds to seconds:

• 2 ms = 2 × 10^{-3} s

2. Apply the formula: Answer: The maximum frequency is 500 Hz.

$$\text{Maximum impulse frequency} = \frac{1}{2 \times 10^{-3}} = 500 \, \text{Hz}$$