Deck 8: Excitation and Contraction of Smooth Muscle

Question 1

Which of the following best describes a major source of calcium that initiates contraction of smooth muscle?

A)Extracellular fluid
B)Longitudinal tubules
C)Mitochondria
D)Sympathetic nervous system
E)Terminal cisterna

Answer 1

A

Question 2

The contraction of smooth muscle can be attenuated even when intracellular calcium levels are high. This unique ability of smooth muscle can be attributed to variations in the activity of which of the following?

A)Actin
B)Adenosine triphosphate
C)Calcium-calmodulin complex
D)Calmodulin
E)Myosin light chain phosphatase

Answer 2

E

Question 3

The effect of autonomic nerve stimulation on smooth muscle contractile behavior depends on the types of receptors on the smooth muscle fibers. Which of the following best describes the effects of acetylcholine and norepinephrine on various types of smooth muscle? $\begin{array}{ll}\underline{\text { A. Acetylcholine} } &\underline{ \text { Norepinephrine }} \\\text { B. Contraction only } & \text { Relaxation or contraction } \\\text { C. Contraction only } & \text { Relaxation only } \\\text { D. Relaxation only } & \text { Contraction only } \\\text { E. Relaxation only } & \text { Relaxation only } \\\text { F. Relaxation or contraction } & \text { Contraction only } \\\text { G. Relaxation or contraction } & \text { Relaxation or contraction }\end{array}$

Answer 3

F

Question 4

Multiple elements can regulate the contraction of smooth muscle, including endocrine, neurocrine, and paracrine factors. This level of diversity in the control of smooth muscle contraction can be attributed to a diversity of which of the following?

A)Actin-myosin arrangement
B)Calcium sensitivities
C)Cell-surface receptors
D)Motor end plates
E)Subneural cleft architecture

Question 5

Smooth muscle can maintain a contraction for a relatively long time with minimal energy usage because the latch mechanism is present in smooth muscle.

A)Both the statement and the reason are correct and related.
B)Both the statement and the reason are correct but not related.
C)The statement is correct, but the reason is not.
D)The statement is not correct, but the reason is correct.
E)Neither the statement nor the reason is correct.

Question 6

Which of the following factors are important for initiating smooth muscle contractions? $$\begin{array} { l l l } \underline{\text { Hormones }} &\underline{ \text { Paracrine Factors }} &\underline{ \text { Autonomic Nervous System} } \\\text { A. No } & \text { No } & \text { No } \\\text { B. No } & \text { No } & \text { Yes } \\\text { C. Yes } & \text { No } & \text { Yes } \\\text { D. Yes } & \text { Yes } & \text { No } \\\text { E. Yes } & \text { Yes } & \text { Yes }\end{array}$$

Question 7

The sensitivity of the smooth muscle contractile apparatus to calcium can increase. This increase in calcium sensitivity can be attributed to a decrease in the levels of which of the following substances?

A)Actin
B)Adenosine triphosphate
C)Calcium-calmodulin complex
D)Calmodulin
E)Myosin light chain phosphatase

Question 8

Unlike skeletal muscle, the contraction of smooth muscle requires which of the following?

A)Activation of ryanodine receptors
B)Phosphorylation of myosin light chains
C)The presence of intracellular calcium
D)Troponin binding of calcium
E)Voltage activation of dihydropyridine receptors

Question 9

The control mechanism of smooth muscle contraction is considered to be myosin-based because the calcium-calmodulin complex binds to myosin light chain kinase.

A)Both the statement and the reason are correct and related.
B)Both the statement and the reason are correct but not related.
C)The statement is correct, but the reason is not.
D)The statement is not correct, but the reason is correct.
E)Neither the statement nor the reason is correct.