Question 1

Which of the following properties is unique to skeletal muscle tissue compared to cardiac and smooth muscle tissue?

Accepted Answer

It is voluntary and must be stimulated by the nervous system.

Question 2

A patient presents with muscle weakness, a waddling gait, and difficulty climbing stairs. Genetic testing reveals a defective gene for dystrophin. Which process is most directly affected in this disease?

Accepted Answer

Transmission of muscle tension from the sarcolemma to the endomysium and myofibrils.

Question 3

During the sliding-filament mechanism of muscle contraction, which of the following changes occurs in the sarcomere?

Accepted Answer

The I band and H zone narrow.

Question 4

Which equation correctly represents the immediate source of ATP regeneration in skeletal muscle fibers using creatine phosphate?

Accepted Answer

$$ADP + Creatine\ Phosphate \rightarrow ATP + Creatine$$

Question 5

Which of the following best explains why the resting membrane potential of a muscle fiber is negative?

Accepted Answer

Potassium ions diffuse out of the cell more easily than sodium ions enter, resulting in a net loss of positive charges.

Question 6

A muscle fiber is stimulated 90 times per second and cannot relax between stimuli, resulting in a sustained contraction. What is this phenomenon called?

Accepted Answer

Fused (complete) tetanus

Question 7

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

Accepted Answer

Action potential arrives at axon terminal → Calcium enters axon terminal → Acetylcholine released → Acetylcholine binds to motor end plate → End-plate potential generated → Action potential propagated along sarcolemma → Calcium released from SR

Question 8

Which type of muscle fiber is most resistant to fatigue and why?

Accepted Answer

Type I fibers, because they have abundant myoglobin and mitochondria for oxidative catabolism.

Question 9

A person lifts a 10-lb weight by flexing their forearm, then slowly lowers it back down. Which type of muscle contraction occurs during the lowering phase?

Accepted Answer

Isotonic eccentric contraction

Question 10

Which of the following best describes the role of acetylcholinesterase (AChE) at the neuromuscular junction?

Accepted Answer

It degrades acetylcholine in the synaptic cleft, terminating the signal for muscle contraction.

Question 11

Which of the following is a direct effect of botulinum toxin exposure on skeletal muscle?

Accepted Answer

Prevention of muscle contraction due to blocked acetylcholine release.

Question 12

Which process is responsible for the majority of ATP production during sustained, moderate-intensity exercise lasting several minutes?

Accepted Answer

Oxidative (aerobic) catabolism in mitochondria

Question 13

A muscle fiber is overly stretched before contraction. What is the expected effect on tension production and why?

Accepted Answer

Tension decreases because the zone of overlap is too short for effective crossbridge formation.

Question 14

Which of the following best explains the phenomenon of rigor mortis?

Accepted Answer

ATP is no longer available, so myosin heads cannot detach from actin, resulting in sustained muscle contraction.

Question 15

Which of the following is a major cause of delayed-onset muscle soreness (DOMS) after unaccustomed exercise?

Accepted Answer

Minor structural damage to myofilaments caused by isotonic eccentric contractions.

Question 16

Which of the following best describes the role of the sodium-potassium pump ($$Na^+/K^+$$ ATPase) in muscle fibers?

Accepted Answer

It moves three sodium ions out and two potassium ions in, maintaining the resting membrane potential.

Question 17

Which of the following adaptations is most likely to occur in skeletal muscle fibers after several weeks of endurance training?

Accepted Answer

Increase in oxidative enzymes, mitochondria, and blood vessels.

Question 18

A muscle fiber is unable to relax and remains in spasm. Which of the following is most likely impaired?

Accepted Answer

Active transport of calcium ions back into the sarcoplasmic reticulum.

Question 19

Which of the following best describes the process of recruitment in motor units?

Accepted Answer

Activation of additional motor units as greater force of contraction is needed.

Muscle Tissue and Physiology: Overview and Types of Muscle Tissue

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