$$\text{Muscle Strength}_{t} = \text{Muscle Strength}_{0} \times (1 - 0.05$$)^{t}$$

$$\text{Total Ca}^{2+} = \text{Ca}^{2+}_{\text{extracellular}} + \text{Ca}^{2+}_{\text{SR}}$$

Question 1

Which structural feature distinguishes smooth muscle from skeletal muscle at the cellular level?

Accepted Answer

Smooth muscle cells are single, spindle-shaped, and lack striations.

Question 2

A patient with Duchenne muscular dystrophy (DMD) is likely to experience which of the following physiological changes?

Accepted Answer

Loss of muscle regenerative capacity and increased apoptosis of muscle cells.

Question 3

Which equation best represents the relationship between muscle strength decline and disuse atrophy?

Accepted Answer

$$	ext{Muscle Strength}_{t} = 	ext{Muscle Strength}_{0} 	imes (1 - 0.05$$)^{t}$$

Question 4

Which of the following is a consequence of rigor mortis?

Accepted Answer

ATP is unavailable, resulting in myosin heads remaining bound to actin.

Question 5

Which statement correctly describes the source of Ca$$^{2+}$$ for contraction in smooth muscle?

Accepted Answer

Ca$$^{2+}$$ enters primarily from the extracellular fluid via caveolae.

Question 6

A patient exposed to botulinum toxin would most likely experience which effect?

Accepted Answer

Blocked acetylcholine release, resulting in muscle paralysis.

Question 7

Which of the following best explains why skeletal muscle contraction is voluntary?

Accepted Answer

Skeletal muscle contraction is controlled by somatic nervous system motor neurons.

Question 8

Which of the following conditions is characterized by an autoimmune attack on acetylcholine receptors?

Accepted Answer

Myasthenia gravis

Question 9

Which equation describes the influx of Ca$$^{2+} in $$smooth muscle contraction?

Accepted Answer

$$	ext{Total Ca}^{2+} = 	ext{Ca}^{2+}_{	ext{extracellular}} + 	ext{Ca}^{2+}_{	ext{SR}}$$

Question 10

Which of the following is a plausible effect of a demyelinating disorder such as multiple sclerosis?

Accepted Answer

Visual disturbances, muscle weakness, and loss of muscular control.

Question 11

Which of the following toxins blocks voltage-gated Na$$^+$$ channels, preventing action potential propagation?

Accepted Answer

Tetrodotoxin

Question 12

Which statement best describes the arrangement of myofilaments in smooth muscle?

Accepted Answer

Actin and myosin filaments are randomly arranged, resulting in no striations.

Question 13

Which clinical scenario best illustrates the effect of disuse atrophy?

Accepted Answer

A patient immobilized in a cast experiences rapid muscle mass loss.

Question 14

Which of the following is true regarding the regulation of contraction in smooth muscle?

Accepted Answer

Contraction is involuntary and regulated by hormones, stretch, and local chemicals.

Question 15

Which of the following best describes the effect of nerve gas on the neuromuscular junction?

Accepted Answer

It inhibits acetylcholinesterase, causing prolonged muscle contraction.

Question 16

Which of the following is a characteristic of cardiac muscle not shared with skeletal or smooth muscle?

Accepted Answer

Branching chains of cells with intercalated discs.

Question 17

Which of the following best explains why muscle strength declines rapidly during disuse atrophy?

Accepted Answer

Muscle fibers are replaced by fibrous connective tissue.

Question 18

Which of the following best describes the effect of curare at the neuromuscular junction?

Accepted Answer

Curare blocks chemically-gated Na$$^+$$ channels, preventing muscle contraction.

Question 19

Which of the following is a plausible effect of a neurotoxin that blocks neurotransmitter release?

Accepted Answer

Muscle contraction is inhibited, resulting in paralysis.

Skeletal and Smooth Muscle: Structure, Function, and Disorders

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