Question 1

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

Accepted Answer

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

Question 2

A patient is diagnosed with myasthenia gravis. Which of the following best explains the physiological basis of their muscle weakness?

Accepted Answer

Antibodies block acetylcholine receptors, preventing effective stimulation of muscle fibers.

Question 3

During the sliding filament model of contraction, which of the following changes occur in the sarcomere?

Accepted Answer

The I band and H zone both narrow, but the A band remains the same length.

Question 4

Which of the following is the correct order of events in excitation-contraction coupling in skeletal muscle?

Accepted Answer

Acetylcholine release → action potential in sarcolemma → $$Ca^{2+}$$ release from SR → cross-bridge formation

Question 5

Which structure in skeletal muscle is directly responsible for transmitting the action potential deep into the muscle fiber?

Accepted Answer

Transverse (T) tubule

Question 6

What is the primary difference in the regulatory mechanism of contraction between skeletal and smooth muscle?

Accepted Answer

Skeletal muscle uses troponin, while smooth muscle uses calmodulin to bind $$Ca^{2+}.$$

Question 7

A toxin from Clostridium botulinum causes paralysis by which of the following mechanisms?

Accepted Answer

Blocking the release of acetylcholine at the neuromuscular junction

Question 8

Which connective tissue layer surrounds individual muscle fibers within a fascicle?

Accepted Answer

Endomysium

Question 9

Which of the following best describes the function of acetylcholinesterase at the neuromuscular junction?

Accepted Answer

It breaks down acetylcholine, terminating the signal for muscle contraction.

Question 10

Which of the following statements about cardiac muscle is correct?

Accepted Answer

Cardiac muscle fibers are striated, branched, and connected by intercalated discs.

Question 11

A muscle fiber is stimulated by a motor neuron. Which of the following events occurs first?

Accepted Answer

Acetylcholine is released into the synaptic cleft.

Question 12

Which of the following is true regarding the arrangement of myofilaments in a sarcomere?

Accepted Answer

The A band contains thick filaments and overlapping thin filaments.

Question 13

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

Accepted Answer

ATP is needed to detach myosin heads from actin and to pump $$Ca^{2+}$$ back into the sarcoplasmic reticulum.

Question 14

Which of the following is a unique feature of smooth muscle compared to skeletal muscle?

Accepted Answer

Smooth muscle lacks striations and has myofilaments arranged randomly.

Question 15

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

Accepted Answer

It coordinates the release of $$Ca^{2+}$$ from the sarcoplasmic reticulum in response to an action potential.

Question 16

A patient is given a drug that inhibits acetylcholinesterase. What is the most likely effect on skeletal muscle contraction?

Accepted Answer

Prolonged muscle contraction due to increased acetylcholine in the synaptic cleft.

Question 17

Which of the following best explains why the A band does not change in length during muscle contraction?

Accepted Answer

The A band is defined by the length of the thick (myosin) filaments, which do not change length.

Question 18

Which of the following is the correct sequence for the cross-bridge cycle in skeletal muscle contraction?

Accepted Answer

Myosin binds to actin → power stroke → ATP binds to myosin → myosin detaches from actin

Question 19

Which of the following is a function of the connective tissue layer known as the perimysium?

Accepted Answer

It surrounds bundles of muscle fibers (fascicles) within a muscle.

Question 20

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

Accepted Answer

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

Muscle Tissue and Muscle Contraction Physiology: Structured Study Notes

Study Guide - Practice Questions