Pacemaker cells are what type of response?

Pacemaker cells are what type of response?

• A. Slow-response
• B. Fast-response
• C. Mixed-response
• D. No-response

Answer: (A)

Pacemaker cells generate automatic rhythmic impulses with slow-response action potentials. Their upstroke is slower because it relies on calcium influx (mainly L-type, with some T-type) rather than fast sodium channels. They also show diastolic depolarization during phase 4, gradually reaching threshold to trigger the next impulse. This Ca2+-mediated, slowly rising upstroke distinguishes them from fast-response cardiac myocytes (atrial/ventricular muscle and Purkinje fibers), which depolarize rapidly via fast Na+ channels. So, pacemaker tissue is best described as slow-response.

Pacemaker cells generate automatic rhythmic impulses with slow-response action potentials. Their upstroke is slower because it relies on calcium influx (mainly L-type, with some T-type) rather than fast sodium channels. They also show diastolic depolarization during phase 4, gradually reaching threshold to trigger the next impulse. This Ca2+-mediated, slowly rising upstroke distinguishes them from fast-response cardiac myocytes (atrial/ventricular muscle and Purkinje fibers), which depolarize rapidly via fast Na+ channels. So, pacemaker tissue is best described as slow-response.