<prompt> Charecteristic of smooth muscle cells in intestineMarch 2005Does not have actin and myosinCannot do sustained contractionIt contracts when stretched in the absence of any extrinsic innervationDoes not require calcium for contraction  <response>: Ans. C: It contracts when stretched in the absence of any extrinsic innervationUnitary smooth muscle as present in a walls of a hollow viscus is characterized by the instability of its membrane potential and by the fact that it shows continuous, irregular contractions that are independent of its nerve supply. This maintained state of contraction is called tonus toneIt does have actin and myosin-II but they are not arranged in regular arrays to give striations as in skeletal and cardiac muscle.They require calcium for initiation of contraction like skeletal and cardiac muscle. 