33. During skeletal muscle contraction, what substance does the sarcoplasmic ret

Question

33. During skeletal muscle contraction, what substance does the sarcoplasmic reticulum store and release? A. acetylcholine B. sodium C. potassium D. calciunm 34. What stimulates the sarcoplasmic reticulum (SR) to release this chemical? A. the voltage change from the muscular action potential traveling down the transverse (t) tubules B. the binding of acetylcholine to ligand-gated channels in the transverse tubules C. direct stimulus from the neural action potential D. the binding of myosin to actin 35. Transverse (T) tubules are extensions of the in skeletal muscle. A. sarcoplasmic reticulum B. sarcolemma C. junctional folds D. cytoskeleton E. thick filament 36. Before a myofiber can contract, calcium must first bind to A. calsequestrin B. myosin C. actin D. troponin E. tropomyosin to roll off the active site. A. tropomyosin B. actin-myosin complex C. myosin head D. myosin tail 38. "Power stroke" in skeletal muscle contraction refers to A. flooding the sarcoplasm with calcium B. release of acetylcholine from the motor neuron via exocytosis C. increase in the permeability to sodium following acetylcholine binding D. pulling the tendon on the bone as a whole muscle contracts E. the swiveling of the myosin heads as they connect with and move actin filaments 39. For muscle relaxation to occur, the muscle fiber needs A. presence of acetylcholine (ACh) B. free calcium C. an end plate potential on the myofiber D, an action potential generated from the trigger zone E. ATP

Explanation / Answer

33) Answer is D- Calcium

34) Answer is A-

Generation of end plate potential followed my action potential.

35) answer is B - Sarcolemma

It extends into the cells and form transverse tubules.

36) answer is D -troponin

Calcium binds to troponin and slides away the troponin on tropomyosins complex and thus exposes the binding sites.

37) answer is B

38) answer is E

39) answer is E

Calcium is pumped back into the sarcoplasmic reticulumn by atp dependent calcium-magnesium channels.

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