Explain how an action potential is generated in a sensory neurone.

DIAGRAM
At rest, there is a potential difference across the cell surface membrane of -60mV maintained by sodium-potassium ion pumps which pump 3 Na+ ions out of the cell for every 2 K+ ions pumped in. When a stimulus is detected by a receptor some of the sodium ion channels open, allowing Na+ ions to diffuse into the cell down the concentration gradient. This causes a depolarisation of the membrane known as a generator potential. If this generator potential exceeds the threshold potential (-50mV), voltage-gated sodium ion channels will open triggering diffusion of more Na+ ions into the neurone and the membrane will depolarise, generating an action potential of +40mV.
Once the action potential is reached, the sodium ion channels close and potassium ion channels open. K+ ions diffuse out of the cell causing repolarisation of the membrane. However this overshoots leading to hyperpolarisation. At this point the potassium ion channels also close and the sodium-potassium ion pumps return the potential difference to -60mV via active transport.

AM
Answered by Alastair M. Biology tutor

2382 Views

See similar Biology GCSE tutors

Related Biology GCSE answers

All answers ▸

Name the three structures found in a plant cell that are not found in a neurone


In the case of cystic fibrosis, two parents don't suffer from the disease but both carry the recessive cystic fibrosis allele. What is the probability that a child of the parents will suffer from cystic fibrosis.


Name 4 organelles within an animal cell


What is a heart attack?


We're here to help

contact us iconContact ustelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

MyTutor is part of the IXL family of brands:

© 2025 by IXL Learning