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What are the "4" phases of cardiac contraction?
4 0 1 2 3 4
Describe phase 4
The resting membrane potential
Describe phase 0
Rapid Depolarization phase.
The movement of what ions brings about this phase?
Na + down its electrochemical gradient into the myocardiocyte.
what gates cause this movement?
Fast Na+ channels on the cell membrane.
Describe Phase 1
Short lived "peak" of depolarization
What ionic movement causes phase 1?
Na+ stops moving. Small "notch" created by K+ and Cl- movement.
Due to the actions of which gates?
Fast Na+ channels close.
Describe phase 2
The plateau phase
What ionic movement causes phase 2?
Ca+ into cytosol from interstitium and sarcoplasmic reticulum. balanced by K+ efflux
Due to which gates?
opening Slow Ca2+ channels and K+ channels
Describe phase 3
Rapid repolerisation phase
What ionic movements cause this phase?
k+ efflux
Due to the action of which gates?
Closure of slow Ca2+ channels.
what happens next?
return to phase 4
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