From "Principles of Pharmacology" 2nd Ed. by Golan. pg.308-310
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.
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.
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.
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)
The expression gradient of _____ channels in the SA node is partly responsible for the effect of certain _____ drugs on SA node automaticity.