9.2.4 - The action potential Flashcards
What causes the resting potential to change to the action potential?
A stimulus
At the beginning of the action potential what does a stimulus cause to happen?
Na+ channels to open so Na+ diffuse into the axon along their electrochemical gradient.
This is called depolarisation.
When Na+ begin diffusing into the axon, more channels open what is this an example of?
Positive feedback.
What happens when the action potential reaches +40mV?
Na+ channels close and excess Na+ ions are pumped out of the axon by the sodium potassium pump.
What happens after Na+ ions are pumped out of the axon by the sodium potassium pump?
K+ channels open so K+ ions diffuse out of the axon down their electrochemical gradient. Axon is repolarised as the inside becomes more negatively charged.
What is hyper polarisation and how is it caused?
When the inside of the axon is more negative then at resting potential.
This is caused by the outward diffusion of K+ ions.
After hyper polarisation, how is resting potential restablished?
K+ channels close.
The sodium potassium pump causes Na+ ions to move out and K+ ions to move in.
What is the inside of the axon called?
The axoplasm
When is the absolute refractory period?
During depolarisation and repolarisation
When is the relative refractory period.
Between hyperpolarisation and restoring resting poential.
