Voltage-dependent sodium channel
[Ref: BL5:chp3]
aka "Fast sodium channel"
@@ structure
Blocked by tetrodotoxin
2 gates
Both voltage dependent
m gates (activation gates)
- Triggered when Vm reach about -65mV
- Rapid opening (within 0.1-0.2ms)
- Responsible for rapid sodium influx
* i.e. Phase 0
h gates (inactivation gate)
- Tends to close as Vm becomes less negative
- Inactivation is exponential.
- Initially Na+ influx slows down quickly, then more gradually.
- Complete closure take >100ms
- Stay closed until the cell has partially repolarised during phase 3
