19) Which of the following is true about smooth muscle contraction? A) Smooth mu

Question

19) Which of the following is true about smooth muscle contraction? A) Smooth muscle has well-developed T tubules. B) Smooth muscle has sarcomeres C) In smooth muscle the calcium-calmodulin complex activates an enzyme that phosphorilates the head of the myosin. D) Smooth muscle contains high concentration of troponin. 20) In a relaxed smooth muscle fiber the actin active sites are and the myosin heads are A) blocked; non-phospohorilated C) free; non-phosphorilated B) free; phosphorilated D) blocked, phosphorilated 21) What is the most distinguishing characteristic of all types of muscle tissue? A) the ability to transform chemical energy (from ATP) into mechanical energy B) the presence of troponin C) the presence of transverse T tubules D) the presence of sarcomeres 22) The dermis A) is an avascular connective tissue layer C) has blood vessels B) lacks sensory corpuscles and glands D) is where melanocytes are found

Explanation / Answer

19. C.

In smooth musclesthe calcium calmodulin complexactivatesan enzyme that phosphorhylatesthe head of myosin.

20. A.

The actin sites are blocked and myosin head dephosphorhylated.

21. A.

The most distinguishing feature of all muscles is that they use atpinto mechanical energy.

22. Dermis is

C. Has blood vessels.

33.

B.

Lacunae are connected by cannaliculi

34. B.

Bone tissue.

35. C. The chondrocytes and osteocytes are present in lacunae

36. D.

Osteoclasts. They dissolve bony extracellular matrix.

37. A. Calcium ions.

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