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 ($$\mathrm{Ca$$^{2+}$$}) $$necessary for muscle contraction.

Question 2

A patient is diagnosed with a genetic defect in the titin protein. Which of the following muscle properties is most likely to be affected?

Accepted Answer

Elasticity

Question 3

During the sliding filament mechanism, which event directly causes the power stroke?

Accepted Answer

Release of inorganic phosphate ($$\mathrm{P_i}) $$from the myosin head

Question 4

Which of the following best explains why cardiac muscle cells are able to contract in a coordinated manner?

Accepted Answer

They are connected by intercalated discs containing gap junctions.

Question 5

A toxin blocks voltage-gated calcium channels at the axon terminal of a motor neuron. What is the most immediate effect on muscle contraction?

Accepted Answer

Acetylcholine will not be released into the synaptic cleft.

Question 6

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

Accepted Answer

Slow-twitch (Class I) fibers: high resistance to fatigue

Question 7

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

Accepted Answer

It breaks down acetylcholine to terminate the signal at the motor end plate.

Question 8

A muscle is stimulated so rapidly that it does not relax between stimuli, resulting in a sustained contraction. What is this phenomenon called?

Accepted Answer

Fused tetanus

Question 9

Which of the following is true regarding isometric contractions?

Accepted Answer

Muscle length does not change, but tension increases.

Question 10

A patient is unable to perform peristalsis in the digestive tract. Which muscle type is most likely dysfunctional?

Accepted Answer

Smooth muscle

Question 11

Which structure in a skeletal muscle fiber is responsible for propagating the action potential deep into the cell?

Accepted Answer

Transverse (T-) tubule

Question 12

During the contraction phase of a muscle twitch, which of the following occurs?

Accepted Answer

Crossbridges form and the muscle develops tension.

Question 13

Which of the following best describes the role of the sodium-potassium pump in maintaining the resting membrane potential?

Accepted Answer

It moves 3 $$\mathrm{Na^+}$$ ions out and 2 $$\mathrm{K^+}$$ ions into the cell, using ATP.

Question 14

Which of the following is a unique feature of cardiac muscle cells compared to skeletal muscle fibers?

Accepted Answer

Presence of intercalated discs

Question 15

A muscle fiber is unable to relax after contraction. Which enzyme is most likely deficient?

Accepted Answer

Acetylcholinesterase

Question 16

Which of the following best describes the function of the Z-disc in a sarcomere?

Accepted Answer

It anchors thin filaments and defines the boundary of a sarcomere.

Question 17

Which of the following scenarios best illustrates the concept of recruitment in skeletal muscle contraction?

Accepted Answer

Lifting a heavier object by activating more motor units.

Question 18

Which of the following is true regarding the role of troponin in muscle contraction?

Accepted Answer

It binds calcium ions, causing tropomyosin to move and expose active sites on actin.

Question 19

A person is holding a heavy box without moving their arms. Which type of muscle contraction is primarily occurring in their biceps?

Accepted Answer

Isometric contraction

Question 20

Which of the following best explains why smooth muscle can maintain contraction for long periods with minimal energy expenditure?

Accepted Answer

It uses a latch-bridge mechanism that allows sustained tension with low ATP consumption.

Muscle Tissue and Physiology: Comprehensive Study Notes

Study Guide - Practice Questions