4. Why Doesn't the Action Potential Go Backwards?

4. Why Doesn't the Action Potential Go Backwards?

Aug 24, 2026·
Xander Chu
Xander Chu
· 1 min read
psychology

Key Question

If depolarisation spreads in both directions, why does the action potential normally move forward?

What You’ll Learn

  • What the absolute refractory period is
  • What the relative refractory period is
  • Why voltage-gated sodium channels become inactivated
  • Why recently activated membrane cannot immediately fire again
  • How refractory periods support one-way propagation

Key Takeaway

The membrane just behind an action potential is temporarily unable, or less able, to fire again.

This refractory state makes forward propagation much more likely than backward propagation.

Next

Continue to Why Is Myelin Basically Biological Fibre Optic Cable?

Xander Chu
Authors
Xander Chu (they/them)
Founder, XC Psych
Psychology student at UNSW exploring psychology and neurobiology from first principles, with a background in data science, machine learning, software engineering, and tennis coaching.