Describe and explain how an action potential is generated (6 marks)

  1. The membrane is at resting potential, -60mV inside compared to outside. It is polarised. 2. Na+ ion channels open and some Na+ ions diffuse into the neurone. 3. The membrane depolarises- it become less negative with respect to the outside and reaches the threshold potential of -50mV. 4. Voltage-gated sodium ion channels open and many Na+ ions enter. As more Na+ ions enter, the inside of the cell becomes more positively charged compared to the outside. 5. The potential difference across the membrane reaches +40mV. The inside is now positive compared to the outside. The Na+ ion channels shut and the K+ ion channels open. 6. K+ ions diffuse out of the cell, bringing the potential difference back to negative compared with the outside - repolarisation. 7. The potential difference overshoots slightly, making the cell hyperpolarised. 8. The original potential difference is restored, so the cell returns to its resting potential.
RE
Answered by Rokshan E. Biology tutor

10744 Views

See similar Biology A Level tutors

Related Biology A Level answers

All answers ▸

Describe the role of tRNA in the production of a protein


Explain why multicellular organisms needs to develop a specialised exchange system and transport system, yet unicellular organisms do not


Describe and explain how temperature affects the rate of an enzyme-controlled reaction?


How does water travel up the stem of a plant from the roots to the leaves, wouldn't gravity prevent this?


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