What produces the plateau (phase 2) of the ventricular myocyte action potential?
Answer and explanation
Correct answer: A. Inward L-type calcium current balanced by outward potassium current
- Step 1: Rapid sodium influx causes phase 0. Step 2. In phase 2, calcium enters through L-type channels while potassium leaves, so the membrane potential stays near zero. Answer: inward calcium balanced by outward potassium. Why not the others: sodium influx is phase 0, potassium alone causes repolarization in phase 3, and chloride does not carry the plateau.
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