Slow Na+ channels underlie which pacemaker current in nodal tissue?

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Multiple Choice

Slow Na+ channels underlie which pacemaker current in nodal tissue?

Explanation:
Slow Na+ channels generate the funny current, I_f, in nodal tissue. This current activates when the membrane hyperpolarizes at the end of repolarization and carries Na+ (with some K+) inward more slowly. The result is a gradual diastolic depolarization that brings the cell to threshold and triggers the next heartbeat, setting the pace for the SA and AV nodes. The upstroke in nodal cells relies mainly on calcium currents, not fast Na+ current, and the plateau and refractory currents are not the pacemaker current.

Slow Na+ channels generate the funny current, I_f, in nodal tissue. This current activates when the membrane hyperpolarizes at the end of repolarization and carries Na+ (with some K+) inward more slowly. The result is a gradual diastolic depolarization that brings the cell to threshold and triggers the next heartbeat, setting the pace for the SA and AV nodes. The upstroke in nodal cells relies mainly on calcium currents, not fast Na+ current, and the plateau and refractory currents are not the pacemaker current.

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