Pacemaker Cells

Pacemaker Cells

Specialized cardiac cells capable of spontaneous depolarization without external stimulation.

SA Node - Primary Pacemaker

• Located in right atrium near SVC

• Fires at 60-100 bpm

• No true resting potential (unstable -60 mV)

Pacemaker Action Potential

Different from ventricular myocytes - has three phases only:

• Phase 4 - Spontaneous depolarization (funny current If)

• Phase 0 - Depolarization (Ca²⁺ influx, not Na⁺!)

• Phase 3 - Repolarization (K⁺ efflux)