Action potential Flashcards
What is the threshold potential number?
-55mV
What happens after the cell hits -55mV ?
Massive depolarisation phase, cells goes to around -40mV
Then quickly the cell depolarises, even further to hyper-polarisation and eventually goes back to the resting membrane potential
What is Halle doing at the resting potential?
What opens when the cell reaches the -55mV?
Sodium channels open, moves into the cell
Why does sodium fly in the cell?
Big concentration gradient
When sodium rushes into the cell, what happens to the potential?
Becomes hypopolarised
-40mV
Why does the cell quickly repolarise?
- Voltage gated sodium channels shut off
- Voltage bated potassium channels open (not leaky), potassium moves out of the cell
Why does the cell go beyond depolarisation?
The voltage gated potassium channels are open and take a while to shut. Moving lots of potassium out of the cell. Eventually when they shut, the leaky ones remain open and the cell goes back to the resting potential
What happens to the excitability of the cell when the voltage gated sodium channels are open?
Decreases
Can’t be anymore excited
What is the absolute refractory period?
When the voltage gated sodium channels are open, you won’t be able to fire another action potential
What is the relative refractory period?
When the excitability starts to come back after the refractory period
What is the mechanism of the voltage gated sodium channels?
Ball and chain
How do action potentials reflect stimulus intensity?
By the number of action potentials fired
What limited the frequency of AP fired?
Ball and chain of the V gated sodium channel
How is an AP self-propagating ?
Propagates a new AP as it goes along the membrane
Spread from one end of the axon to the other
All because they are mediated by voltage gated sodium channels as apposed to ligand gated
Why don’t AP go backwards?
Cells behind the AP are always in the refractory period (non-excitory phase)
