Q: Which equation correctly represents the activation of myosin in smooth muscle contraction?

$$\text{Myosin} + \text{ATP} + \text{Phosphate} \rightarrow \text{Phosphorylated Myosin}$$

Q: Which equation best represents the relationship between muscle length change and tension generation in smooth muscle?

$$\text{Length change} \approx 150\% ($$from half to twice resting length)

Question 1

Which structural feature allows smooth muscle cells to contract in a corkscrew manner, unlike the linear contraction seen in skeletal muscle?

Accepted Answer

The diagonal (spiral) arrangement of thick and thin filaments

Question 2

During smooth muscle contraction, which protein binds to Ca$$^{2+} to $$initiate the activation of myosin light chain kinase?

Accepted Answer

Calmodulin

Question 3

Which of the following best describes the function of varicosities in smooth muscle innervation?

Accepted Answer

They release neurotransmitters into a wide synaptic cleft called a diffuse junction

Question 4

A patient is experiencing difficulty with peristalsis in the intestines. Which layer of smooth muscle is most directly responsible for constricting the lumen and propelling contents forward?

Accepted Answer

Circular layer

Question 5

Which equation correctly represents the activation of myosin in smooth muscle contraction?

Accepted Answer

$$	ext{Myosin} + 	ext{ATP} + 	ext{Phosphate} ightarrow 	ext{Phosphorylated Myosin}$$

Question 6

Which of the following is TRUE regarding the source of Ca$$^{2+}$$ for smooth muscle contraction?

Accepted Answer

Most Ca$$^{2+}$$ enters from the extracellular space via caveolae

Question 7

Which statement best explains why smooth muscle can maintain contraction for prolonged periods with little energy cost?

Accepted Answer

Myofilaments may latch together, and ATPases are slower

Question 8

Which of the following is a distinguishing feature of multiunit smooth muscle compared to unitary smooth muscle?

Accepted Answer

Multiunit smooth muscle consists of independent muscle fibers with few gap junctions

Question 9

Which process is required to stop smooth muscle contraction, but not skeletal muscle contraction?

Accepted Answer

Dephosphorylation of myosin

Question 10

A hormone binds to a G protein–linked receptor on a smooth muscle cell, causing contraction without an action potential. Which mechanism is most likely involved?

Accepted Answer

Direct increase in Ca$$^{2+}$$ influx into the sarcoplasm

Question 11

Which equation best represents the relationship between muscle length change and tension generation in smooth muscle?

Accepted Answer

$$	ext{Length change} \approx 150\% ($$from half to twice resting length)

Question 12

Which statement about muscle development is correct?

Accepted Answer

Skeletal muscle cells are multinucleated due to fusion of myoblasts

Question 13

Which of the following is a consequence of defective dystrophin in Duchenne muscular dystrophy?

Accepted Answer

Sarcolemma tears during contraction, allowing excess Ca$$^{2+}$$ entry

Question 14

Which equation best describes the process of muscle hypertrophy in adults?

Accepted Answer

$$	ext{Muscle fiber size increases} ightarrow 	ext{Hypertrophy}$$

Question 15

Which of the following best explains why smooth muscle tone is maintained without fatigue?

Accepted Answer

Smooth muscle has low energy requirements and uses aerobic respiration

Question 16

Which statement accurately describes the effect of neurotransmitter binding in smooth muscle?

Accepted Answer

The effect depends on the neurotransmitter and the type of receptor present

Question 17

Which equation represents the process of excitation-contraction coupling in smooth muscle?

Accepted Answer

$$	ext{Ca}^{2+} ightarrow 	ext{Calmodulin activation} ightarrow 	ext{Myosin kinase activation} ightarrow 	ext{Myosin phosphorylation} ightarrow 	ext{Cross bridge formation}$$

Question 18

Which feature allows unitary smooth muscle to contract as a single unit?

Accepted Answer

Gap junctions electrically couple the cells

Question 19

Which statement best describes the regenerative ability of smooth muscle compared to skeletal and cardiac muscle?

Accepted Answer

Smooth muscle regenerates throughout life, while skeletal and cardiac muscle have limited regenerative abilities

Smooth Muscle: Structure, Function, and Developmental Aspects

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