Q: If the sarcomere shortens from $$2.5\ \mu m to$$ $$2.0\ \mu m$$ during contraction, what is the percentage decrease in sarcomere length?

$$\frac{2.5 - 2.0}{2.5} \times 100 = 20\%$$

Q: Which equation best represents the process of ATP hydrolysis by myosin during muscle contraction?

$$\mathrm{ATP} \rightarrow \mathrm{ADP} + \mathrm{P_i} + \text{energy}$$

Question 1

Which of the following statements best describes the role of the sarcoplasmic reticulum in skeletal muscle contraction?

Accepted Answer

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

Question 2

During the crossbridge cycle, what event directly causes the myosin head to detach from actin?

Accepted Answer

Binding of ATP to the myosin head.

Question 3

A patient is experiencing muscle weakness due to impaired acetylcholine release at the neuromuscular junction. Which step in excitation-contraction coupling is most directly affected?

Accepted Answer

Initiation of the muscle fiber action potential.

Question 4

Which protein acts as a molecular spring, providing elasticity and stabilizing the position of thick filaments within the sarcomere?

Accepted Answer

Titin

Question 5

If the sarcomere shortens from $$2.5\ \mu m to$$ $$2.0\ \mu m$$ during contraction, what is the percentage decrease in sarcomere length?

Accepted Answer

$$\frac{2.5 - 2.0}{2.5} 	imes 100 = 20\%$$

Question 6

Which of the following best explains why cardiac muscle cells are resistant to fatigue compared to skeletal muscle cells?

Accepted Answer

Cardiac muscle cells have more mitochondria and a greater blood supply.

Question 7

A toxin blocks the reuptake of $$\mathrm{Ca$$^{2+}$$}$$ into the sarcoplasmic reticulum. What is the most likely effect on muscle contraction?

Accepted Answer

Muscle relaxation will be impaired, leading to prolonged contraction.

Question 8

Which of the following correctly matches the muscle cell structure with its muscle equivalent?

Accepted Answer

Sarcoplasm: Cytoplasm

Question 9

Which event occurs first during excitation-contraction coupling in skeletal muscle?

Accepted Answer

Acetylcholine binds to receptors on the muscle fiber membrane.

Question 10

Which of the following is a function of troponin in muscle contraction?

Accepted Answer

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

Question 11

A patient with a genetic mutation in the nebulin protein would most likely experience which of the following symptoms?

Accepted Answer

Impaired alignment and stability of thin filaments, leading to muscle weakness.

Question 12

Which equation best represents the process of ATP hydrolysis by myosin during muscle contraction?

Accepted Answer

$$\mathrm{ATP} ightarrow \mathrm{ADP} + \mathrm{P_i} + 	ext{energy}$$

Question 13

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

Accepted Answer

Actin and myosin filaments slide past each other, shortening the sarcomere.

Question 14

Which muscle type is responsible for voluntary body movement and is usually attached to bones by tendons?

Accepted Answer

Skeletal muscle

Question 15

In a scenario where ATP is depleted in a muscle cell, what is the most immediate effect on the crossbridge cycle?

Accepted Answer

Myosin heads remain bound to actin, resulting in rigor.

Question 16

Which of the following is true regarding antagonistic muscle groups?

Accepted Answer

They produce opposite movements at a joint, such as flexion and extension.

Question 17

Which structure allows action potentials to rapidly propagate into the interior of the muscle fiber?

Accepted Answer

T-tubules

Question 18

A muscle fiber is stimulated but fails to contract. Which of the following is the most likely cause?

Accepted Answer

Calcium ions are not released from the sarcoplasmic reticulum.

Question 19

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

Accepted Answer

It blocks myosin-binding sites on actin in a resting muscle.

Question 20

Which of the following is the correct sequence of events in excitation-contraction coupling?

Accepted Answer

Action potential → $$\mathrm{Ca$$^{2+}$$}$$ release → Troponin activation → Crossbridge formation

Muscle Structure and Function: Anatomy & Physiology Study Notes

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