Action Potential Flashcards
Explain in terms of ions what is happening during the cell at rest
-the membrane has a high permeability to K+ due to leak channels
-K+ efflux (chemical > electrical)
-Na+ influx due to both chemical and electrical force however limited by membrane permeability
-Na+K+ATPase maintain gradient
-activation gate closed, inactivation gate open
Explain in terms of ions what happens to the cell when it depolarises
-stimulus causes VGNaC and VGKC to open
-VGNaC open faster causing an influx of Na+ making the cell more positive causing it to depolarise ( towards ENa+)
-if it reaches threshold an action potential is generated
-activation gate and inactivation gate are open
Explain in terms of ions what happens when the cell is repolarised
-VGKC are fully open causing an efflux of K+
-VGNaC become inactive as during depolarisation both inactivation gate and activation gate respond however the response from the inactivation gate is slower
-inactivation gate closes stopping Na+ influx and the channel resets
Explain in terms of ions what happens to the cell membrane when it becomes hyperpolarised
-VGKC stay open for longer causing more K+ to leave the cell
- this causes the Vm to become more negative than RMP
How is RMP restored
By leak channels
Describe the effect lidocaine has in the action potential
-local anaesthetic which enters the cell (as its lipid soluble) and binds to the open VGNaC from the cytoplasmic side and blocks it
-prevents the channel from being reactivated which blocks the action potential
-effect smaller axons as there are more VGNaC present
What effect does TTX (tetrodotoxin) have on the action potential
Block VGNaC
Prevents action potential from being produced which eventually leads to paralysis
What effect does scorpion venom have on the action potential
Prevents Na+ inactivation by keeping channel open
Prolongs depolarisation
