Question 1

Which of the following best describes the role of the sarcoplasmic reticulum (SR) in skeletal muscle contraction?

Accepted Answer

It stores and releases $Ca^{2+}$ ions, which trigger muscle contraction when released into the sarcoplasm.

Question 2

During the cross-bridge cycle in muscle contraction, what is the primary function of ATP?

Accepted Answer

ATP binds to myosin, causing it to detach from actin and reset for another contraction.

Question 3

Which structure is responsible for transmitting the action potential deep into the muscle fiber, ensuring all myofibrils contract simultaneously?

Accepted Answer

T-tubule

Question 4

A patient suffers a bone fracture. Which of the following sequences correctly describes the stages of bone repair?

Accepted Answer

Hematoma formation → soft callus formation → hard callus formation → bone remodeling

Question 5

Which protein covers the myosin binding sites on actin in a resting muscle fiber?

Accepted Answer

Tropomyosin

Question 6

What is the function of osteoclasts during bone remodeling?

Accepted Answer

They secrete substances that dissolve the bone matrix, allowing for bone resorption.

Question 7

Which of the following best describes a compound (open) fracture?

Accepted Answer

A fracture in which the skin is broken and bone is exposed.

Question 8

Which event directly triggers the release of $Ca^{2+}$ from the terminal cisterns of the sarcoplasmic reticulum?

Accepted Answer

Action potential traveling down the T-tubules

Question 9

Which of the following is the smallest contractile unit of a skeletal muscle fiber?

Accepted Answer

Sarcomere

Question 10

A patient with a greenstick fracture most likely:

Accepted Answer

Is a child, as their bones are more flexible and partially break rather than completely fracture.

Question 11

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

Accepted Answer

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

Question 12

Which of the following is TRUE regarding the function of voltage-gated channels in the neuromuscular junction?

Accepted Answer

They open or close in response to changes in membrane potential, allowing ions such as $Na^+$ and $K^+$ to flow.

Question 13

Which process is responsible for the deposition of new bone matrix during fracture repair?

Accepted Answer

Ossification

Question 14

A muscle fiber is stimulated by a motor neuron. Which sequence of events leads to contraction?

Accepted Answer

Action potential arrives at axon terminal → $Ca^{2+}$ influx → acetylcholine release → $Na^+$ enters muscle cell → action potential travels down T-tubules → $Ca^{2+}$ released from SR → troponin binds $Ca^{2+}$ → tropomyosin moves → myosin binds actin

Question 15

Which of the following best describes the role of fibroblasts in bone fracture repair?

Accepted Answer

They produce collagen fibers that bridge the gaps between fracture ends.

Question 16

Which of the following is a function of the axon terminal at the neuromuscular junction?

Accepted Answer

It releases acetylcholine into the synaptic cleft to stimulate muscle contraction.

Question 17

Which of the following statements about incomplete fractures is correct?

Accepted Answer

The bone is damaged but not broken all the way through.

Question 18

Which of the following best describes the function of chemically gated channels at the neuromuscular junction?

Accepted Answer

They open in response to neurotransmitters such as acetylcholine, allowing ions to flow across the membrane.

Question 19

Which of the following is TRUE regarding the role of osteoblasts in bone repair?

Accepted Answer

Osteoblasts are responsible for bone deposition and ossification, forming new bone matrix.

Muscle Fiber Structure, Contraction Mechanism, and Bone Fracture Repair

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