Action Potential Flashcards
What is the action potential?
This is the fundamental concept of electricity. It fully depends on the ‘resting membrane potential’. In a passive state, energy is expanded to maintain an unstable state. The trigger causes a release of energy which causes a signal to create action potential.
What is activation?
Activation must occur for action potential to take place. The membrane is in an unstable state as if it becomes permeable all the acid would move which would result in a change in the membrane potential.
How do the ions get through the membrane?
Ions are water soluble so they can’t move through fats and so can only get through through a channel in the membrane or a pump such as sodium potassium.
What is a sodium channel?
A sodium channel lets sodium into the cell, or out of a cell. They can move freely from one side to the other, but this doesn’t work for potassium.
What would happen without a channel?
Without a channel, they would suddenly cross the membrane and the cations would flood the cell and rapidly change the membrane potential.
How does action potential start?
Starts with membrane depolarisation, the voltage gated channel opens at -55mV.
What happens when one sodium channel opens?
More also open because of the sodium that is going through into the membrane. This is known as the threshold of excitation.
When is the membrane polarised?
When it is resting at -70mV.
What happens when the membrane is depolarised?
The sodium cations flood into the neurons due to the diffusion, they can do this due to the electrostatic pressure. The membrane potential then becomes less negative.
Why does the membrane potential become positive after being depolarised?
The membrane potential becomes positive because the concentration gradient becomes so huge because of the sodium that keeps coming through into the membrane.
What happens when the membrane hits +40mV?
The sodium channel closes which means sodium can’t continue to come in or leave but the potassium channels are still open?
What happens to potassium since the channels are still open?
There is now more potassium ions on the inside than the outside and less sodium. As the cell is now more positive, the electrostatic pressure is trying to push the potassium out. This causes repolarisation?
What happens when the electrostatic pressure goes?
The membrane potential is still there so potassium continues to leave because of the concentration gradient causing full repolarisation
