Q: Which equation best represents the ATP hydrolysis reaction that provides energy for the 'cocking' of the myosin head during muscle contraction?

$$\mathrm{ATP} + \mathrm{H}_2\mathrm{O} \rightarrow \mathrm{ADP} + \mathrm{P}_i + \text{energy}$$

Question 1

Which of the following best describes the structural and functional differences between skeletal, cardiac, and smooth muscle tissue?

Accepted Answer

Skeletal muscle is striated and voluntary, cardiac muscle is striated and involuntary, smooth muscle is non-striated and involuntary.

Question 2

A patient is experiencing muscle weakness due to a defect in the sarcolemma. Which of the following best describes the sarcolemma's function?

Accepted Answer

It is the plasma membrane of the muscle fiber, responsible for conducting action potentials.

Question 3

During muscle contraction, which of the following correctly describes the changes in the sarcomere bands and zones?

Accepted Answer

The A band remains unchanged, the I band shortens, and the H zone disappears.

Question 4

Which equation best represents the ATP hydrolysis reaction that provides energy for the 'cocking' of the myosin head during muscle contraction?

Accepted Answer

$$\mathrm{ATP} + \mathrm{H}_2\mathrm{O} ightarrow \mathrm{ADP} + \mathrm{P}_i + 	ext{energy}$$

Question 5

A muscle fiber is unable to relax after contraction. Which of the following is the most likely cause?

Accepted Answer

Insufficient ATP to detach myosin from actin.

Question 6

Which of the following best describes the role of troponin in muscle contraction?

Accepted Answer

Troponin binds calcium ions, causing tropomyosin to move and expose myosin-binding sites on actin.

Question 7

Which of the following structures is responsible for transmitting the action potential deep into the muscle fiber, triggering calcium release from the sarcoplasmic reticulum?

Accepted Answer

T-tubules

Question 8

A muscle biopsy reveals a deficiency in titin. What is the primary function of titin in muscle fibers?

Accepted Answer

It anchors thick filaments to the Z line and provides elasticity to the sarcomere.

Question 9

Which of the following best explains why muscle cells are considered 'excitable'?

Accepted Answer

They can generate and propagate electrical signals (action potentials) in response to stimuli.

Question 10

Which of the following correctly describes the sequence of events in the crossbridge cycle?

Accepted Answer

Binding, power stroke, release of ADP and Pi, detachment, cocking

Question 11

Which neurotransmitter is released at the neuromuscular junction to initiate muscle contraction?

Accepted Answer

Acetylcholine

Question 12

A patient with a genetic mutation affecting the perimysium would most likely have problems with which of the following?

Accepted Answer

Surrounding and organizing fascicles within the muscle

Question 13

Which of the following best describes the sliding filament model of muscle contraction?

Accepted Answer

Thin filaments slide past thick filaments, causing sarcomere shortening without changing filament length.

Question 14

Which of the following best explains the role of calcium ions ($$\mathrm{Ca}^{2+}) in $$muscle contraction?

Accepted Answer

$$\mathrm{Ca}^{2+}$$ binds to troponin, causing tropomyosin to move and expose myosin-binding sites on actin.

Question 15

Which of the following is true regarding the H zone of the sarcomere during muscle contraction?

Accepted Answer

The H zone shortens and may disappear as thin filaments slide inward.

Question 16

Which of the following best describes the function of tendons in skeletal muscle?

Accepted Answer

Tendons transmit force from muscle to bone, enabling movement.

Question 17

Which of the following is a consequence of the absence of $$\mathrm{Ca}^{2+} in $$the muscle cell cytosol?

Accepted Answer

Tropomyosin blocks myosin-binding sites on actin, preventing contraction.

Question 18

Which of the following best describes the function of the motor end plate?

Accepted Answer

It is the specialized region of the sarcolemma that contains acetylcholine receptors and initiates the muscle action potential.

Question 19

Which of the following best explains why muscle is considered a high-energy-demanding tissue?

Accepted Answer

Muscle cells require large amounts of ATP for contraction, relaxation, and maintaining ion gradients.

Question 20

A patient is diagnosed with a disorder affecting the neuromuscular junction (NMJ). Which of the following is most likely to occur?

Accepted Answer

Impaired release of acetylcholine, leading to reduced muscle contraction.

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