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Physiology

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Nerve Muscle Physiology

Question
12 out of 19
 

Which of the following is true regarding excitation-contraction coupling in smooth muscle? (LQ)



A Phosphorylation of actin occurs

B Troponin is essential

C Intracellular calcium is essential to cause contraction

D Increased calcium in sarcoplasmic reticulum causes sustained contraction

Ans. C Intracellular calcium is essential to cause contraction

Excitation-contraction coupling (role of calcium ions):

a. The actual contractile process in skeletal muscle is activated by calcium ions Q.

b. This is also true in smooth muscles; however, the source of the calcium ions differs in smooth muscle because the sarcoplasmic reticulum of smooth muscle is poorly developed Q.

c. In ‘some’ types of smooth muscle, almost all the calcium ions that cause contraction enter the muscle cell from the extracellular fluid at the time of the action potential.

d. Because the smooth muscle fibers are extremely small (in contrast to the sizes of skeletal muscle fibers), these calcium ions can diffuse to all parts of the smooth muscle and bring about the contractile process.

Nerve Muscle Physiology Flashcard List

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