Q: Which of the following equations represents the overall aerobic breakdown of glucose in muscle cells?

$$C_6H_{12}O_6$ + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{energy (as ATP)}$$

Question 1

Which of the following best describes the function of the sarcoplasmic reticulum in skeletal muscle fibers?

Accepted Answer

It stores and releases calcium ions ($$Ca^{2+}) $$necessary for muscle contraction.

Question 2

During the cross-bridge cycle, what event is directly triggered by the release of inorganic phosphate ($$Pi) $$from the myosin head?

Accepted Answer

The power stroke, where the myosin head pivots and pulls actin toward the M line.

Question 3

A patient is exposed to curare, which competitively binds to nicotinic acetylcholine receptors at the neuromuscular junction. Which symptom is most likely to occur?

Accepted Answer

Diaphragmatic paralysis

Question 4

Which connective tissue sheath surrounds individual muscle fibers?

Accepted Answer

Endomysium

Question 5

What would happen if the sarcoplasmic reticulum (SR) failed to actively transport $$Ca^{2+}$$ back into its lumen after contraction?

Accepted Answer

Muscle relaxation would not occur, leading to sustained contraction.

Question 6

Which of the following is true regarding the A band of a sarcomere during muscle contraction?

Accepted Answer

The A band remains the same length.

Question 7

Which of the following best explains why ATP is required for muscle relaxation?

Accepted Answer

ATP binds to myosin, causing it to detach from actin.

Question 8

Which of the following is a characteristic unique to cardiac muscle tissue?

Accepted Answer

Branching chains of cells with intercalated discs

Question 9

A muscle fiber is stimulated to contract but lacks sufficient ATP. What is the most likely physiological consequence?

Accepted Answer

The myosin heads will remain bound to actin, resulting in rigor.

Question 10

Which of the following best describes the role of troponin C (TnC) in skeletal muscle contraction?

Accepted Answer

It binds $$Ca^{2+}$$, causing a conformational change that moves tropomyosin away from actin's myosin-binding sites.

Question 11

Which of the following equations represents the overall aerobic breakdown of glucose in muscle cells?

Accepted Answer

$$C_6H_{12}O_6$ + 6O_2 ightarrow 6CO_2 + 6H_2O + 	ext{energy (as ATP)}$$

Question 12

Which of the following is the correct sequence of events for skeletal muscle contraction?

Accepted Answer

Motor neuron action potential → Neurotransmitter release → Muscle cell action potential → $$Ca^{2+}$$ release from SR → ATP-driven power stroke → Sliding of myofilaments

Question 13

Which of the following best explains the effect of dantrolene in treating malignant hyperthermia?

Accepted Answer

It inhibits $$Ca^{2+}$$ release from the sarcoplasmic reticulum, reducing muscle contraction and heat production.

Question 14

Which of the following is a function of the sodium-potassium ATPase ($$Na^+/K^+$$ pump) in skeletal muscle fibers?

Accepted Answer

It restores ionic gradients after excitation-contraction coupling by pumping $$Na^+$$ out and $$K^+ in.$$

Question 15

Which of the following best describes the difference between isometric and isotonic muscle contractions?

Accepted Answer

Isometric contractions generate tension without changing muscle length, while isotonic contractions change muscle length.

Question 16

Which of the following is the primary source of ATP during the first 10 seconds of intense muscle activity?

Accepted Answer

Direct phosphorylation of ADP by creatine phosphate

Question 17

Which of the following would most likely occur if a patient had a genetic defect in the dystrophin gene?

Accepted Answer

Progressive muscle weakness due to impaired structural integrity of muscle fibers

Question 18

Which of the following best explains why the inside of a resting skeletal muscle cell is negatively charged relative to the outside?

Accepted Answer

There is a higher concentration of $$K^+$$ inside and $$Na^+$$ outside, and the membrane is more permeable to $$K^+$$, allowing more positive charge to leave the cell.

Muscle Tissue: Structure, Function, and Physiology

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