Question 1

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

Accepted Answer

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

Question 2

A patient is diagnosed with Duchenne muscular dystrophy. Which protein is most likely deficient or abnormal in this condition, and what is its normal function?

Accepted Answer

Dystrophin; it stabilizes the muscle fiber by linking the cytoskeleton to the extracellular matrix.

Question 3

Which of the following correctly matches the muscle tissue type with its characteristic?

Accepted Answer

Cardiac muscle: striated, involuntary, single nucleus per cell

Question 4

During muscle contraction, which event occurs immediately after calcium ions ($$\mathrm{Ca$$^{2+}$$}) $$bind to troponin?

Accepted Answer

Tropomyosin shifts to expose the active sites on actin.

Question 5

Which connective tissue layer surrounds individual muscle fibers?

Accepted Answer

Endomysium

Question 6

A muscle fiber is unable to contract because ATP is not available. Which step in the cross-bridge cycle is directly affected?

Accepted Answer

Detachment of myosin from actin

Question 7

Which of the following best describes the function of titin in the sarcomere?

Accepted Answer

It provides elasticity and stabilizes the thick filament.

Question 8

A muscle is attached to bone at two points. The point that moves during contraction is called the:

Accepted Answer

Insertion

Question 9

Which of the following is a regulatory protein that binds calcium ions ($$\mathrm{Ca$$^{2+}$$}) to $$initiate muscle contraction?

Accepted Answer

Troponin

Question 10

Which structure transmits the action potential deep into the muscle fiber, ensuring simultaneous contraction throughout the cell?

Accepted Answer

T-tubules

Question 11

A muscle biopsy reveals a lack of striations and a single, centrally located nucleus per cell. Which muscle type is most likely observed?

Accepted Answer

Smooth muscle

Question 12

Which of the following best explains why calcium ions ($$\mathrm{Ca$$^{2+}$$}) $$are essential for muscle contraction?

Accepted Answer

They bind to troponin, causing tropomyosin to move and expose actin's active sites.

Question 13

Which protein forms the thick filaments in a myofibril and contains a head that binds and hydrolyzes ATP?

Accepted Answer

Myosin

Question 14

A patient presents with muscle weakness. Laboratory analysis shows a defect in the protein that covers the active sites on actin during muscle relaxation. Which protein is most likely affected?

Accepted Answer

Tropomyosin

Question 15

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

Accepted Answer

Action potential travels along sarcolemma $$\rightarrow T-$$tubules $$\rightarrow$$ sarcoplasmic reticulum releases $$\mathrm{Ca$$^{2+}$$}$$ $$\rightarrow$$ troponin binds $$\mathrm{Ca$$^{2+}$$}$$ $$\rightarrow$$ tropomyosin moves $$\rightarrow$$ myosin binds actin

Question 16

Which of the following best describes the role of the perimysium?

Accepted Answer

It surrounds bundles of muscle fibers (fascicles).

Question 17

A muscle cell is unable to relax after contraction. Which protein is most likely malfunctioning, and what is its normal role?

Accepted Answer

Troponin; it binds calcium and helps move tropomyosin off the active site on actin.

Question 18

Which of the following is NOT a function of the muscular system?

Accepted Answer

Production of hormones

Question 19

Which of the following best describes the function of the aponeurosis?

Accepted Answer

It is a broad, flat tendon that connects muscle to bone or other muscles.

Question 20

A researcher is studying the effect of a drug that prevents the hydrolysis of ATP by the myosin head. What is the most likely outcome on muscle contraction?

Accepted Answer

The myosin head will not be able to perform the power stroke, preventing contraction.

Muscle Tissue: Structure, Function, and Key Proteins

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