True regarding excitation contraction coupling in smooth muscle is: (A) Presence of troponin is essential, (B) Sustained contraction occurs with high calcium concentration, (C) Phosphorylation of actin is required for contraction, (D) Presence of cellular calcium is essential to cause muscle contraction
Answer is D. Ans. (d) Presence of cellular calcium is essential to cause muscle contraction(Ref: Ganong, 25th ed/p.116)Troponin is absent in smooth muscleSustained contraction (latch) occurs with less use of ATPPhosphorylation of myosin is required for smooth muscle contraction