CH 18: SA Node Action Potentials

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From "Principles of Pharmacology" 2nd Ed. by Golan. pg.308-310

60, 100

SA nodal cells pace the heart at normal resting heart rates between _____-____ beats/min.

4, 0, 3

The SA node action potential occurs in three phases: phase __, phase __, and phase __ (#s).

Slow, Spontaneous, First

Phase 4: _____ (slow/fast) _____ depolarization. The _____ (First, Second, Third) phase of SA node action potentials.

I_f, Non, Sodium, Greater, Potassium

Phase 4: Mainly driven by _____ channels, which are _____-specific. These channels cause depolarization because at negative membrane potentials, the driving force for ____ entry is _____ (greater/less) than that for _____ efflux.

Fast, Second

Phase 0: _____ (slow/fast) depolarization. The _____ (First, Second, Third) phase of SA node action potentials.

Voltage, Calcium, Threshold

Phase 0: Depolarization mediated mostly by _____-gated _____ ion channels activated once the _____ potential is reached.

Repolarization, Third

Phase 3: _____ of the SA node cells. The _____ (First, Second, Third) phase of SA node action potentials.

Calcium, Potassium, 60, I_f

Phase 3: Repolarization caused by _____ channels slowly closing and _____ channels opening. Repolarization happens until around -___mV, triggering ____ channels which restart the cycle.

Phase 4

This phase is responsible for SA node automaticity.

More, Calcium, More, Sodium

Pacemaker cells in the center of the SA node express _____ _____ channels, and cells at the border of the node express _____ _____ channels. (More/Less, Sodium/Calcium)

Sodium, Antiarrhythmic

The expression gradient of _____ channels in the SA node is partly responsible for the effect of certain _____ drugs on SA node automaticity.

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