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.
Answered by Rokshan E. Biology tutor

8469 Views

See similar Biology A Level tutors

Related Biology A Level answers

All answers ▸

What is the myelin sheath?


Explain how polymerase chain reaction is used in DNA fingerprinting


The allele y occurs with a frequency of 0.8 in a population of clams. Give the frequencies of the genotypes YY, Yy and yy.


How does eutrophication work?


We're here to help

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