CARDIAC ACTION POTENTIAL

Phase 4

This phase of where the resting membrane potential

Phase 4

This is the period that the cell remains in until it is stimulated by an external electrical stimulus (typically an adjacent cell)

difference in ionic concentrations: conductance

The resting membrane potential in phase 4 is caused by the _____ and____ across the membrane of the cell during phase 4 of the action potential.

About -85 to -95 mV

Change under the phase 4

Phase 4

The membrane is most permeable to K+ and relatively impermeable to other ions

Phase 4

This phase is related to diastole

Phase 0

The rapid depolarization phase

Vmax

The slope of phase 0 represents the maximum rate of depolarization of the cell and is known as ____.

Phase 0

This phase is due to the opening of the fast Na+ channels causing a rapid increase in the membrane conductance to Na+ (GNa) and thus a rapid influx of Na+ ions (INa) into the cell; a Na+ current.

Phase 1

Early-fast repolarization phase

Phase 1

Very short period when sodium ions will equalize inside and outside of the cell.

Phase 1

Occurs with the inactivation (CLOSING) of the fast Na+ channels

Phase 2

“Plateau” phase of the cardiac action potential

Phase 3

Sustained by a balance between inward movement of Ca2+ through L-type calcium channels and outward movement of K+ through the slow delayed rectifier potassium channels

Phase 3

Slow Repolarization phase

Phase 3

The L-type Ca2+ channels close, while the slow delayed rectifier K+ channels are still open.

Phase 3

This ensures a net outward current, corresponding to negative change in membrane potential, thus allowing more types of K+ channels to open

only K+ can permeate

Channel occurance of Phase 4 (Polarized state)

Na+ opens

Channel occurance of Phase 0 (Rapid depolarization)

Na+ closes

Channel occurance of Phase 1 (Early fast repolarization)

Ca2+ and K+ open

Channel occurance of Phase 2 (Plateau)

Ca2+ closes, K+ still open

Channel occurance of Phase 3 (Slow repolarization)