VPY-0016
QUESTION
Platue in cardiac muscle is due to presence of?
OPTIONS
(A) Fast sodium channels
(B) Fast potassium channels
(C) Slow Na+ – Ca++ channels
(D) Slow chloride channels
ANSWER
(C) Slow Na+ – Ca++ channels
EXPLANATION
Slow Na+-Ca++ channels are the correct option because the cardiac action-potential plateau is produced mainly by prolonged inward Ca2+ current through L-type slow calcium channels, accompanied by reduced outward K+ current. Fast sodium channels are responsible mainly for the rapid upstroke, fast potassium channels promote repolarization, and slow chloride channels do not produce the plateau.