Describe the development and propagation of an action potential in response to a stimulus (6 marks)

1.     stimulus excites membrane so Na+ channels open, membrane becomes more permeable to Na+ so Na+ diffuse into neurone down electrochemical gradient. Inside of neuron becomes less -ve 2.     Depolarisation: if potential difference reaches threshold (c55mV) more Na+ channels open, more Na+ diffuses into neurone 3.      Repolarisation: at +30mV Na+ channels close and K+ channels open. Membrane is more permeable to K+ so K+ diffuses out of neuron down its concentration gradient. This pushes the membrane back to resting potential4.     Hyperpolarisation: K+ channels close too slowly so overshoot, too much K+ leaves the neuron and it becomes more negative than resting potential 5.     Resting potential: ion channels reset, sodium potassium pump returns membrane to resting potential (-70mV) by pumping Na+ out and K+ in.  

Answered by Simmy W. Biology tutor

2477 Views

See similar Biology A Level tutors

Related Biology A Level answers

All answers ▸

How is selective reabsorption acheived in the kidneys?


What is a cytoskeleton? What are its main components in animal cells?


List three differences in the composition of tissue fluid at the arterial end of the capillaries to the tissue fluid at the venous end of the capillaries.


What are sinusoids?


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences