system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
Which one of the following is absent in smooth muscles?
assistant
The correct answer is  (C) Troponin> Smooth muscle have no troponin or tropomyosin, but they have actin and myosin.> They have no sarcoplasmic reticulum, No T-tubule.> No Z lines. The contraction is stimulated by extracellular ca+.> Latching - is the characteristic of smooth muscle. Even after the dephosphorylation of myosin, the cross bridges continue to attach in the same position for some time. There is no fixed tension relationship.