Question 1

Which of the following best describes the main function of the sarcoplasmic reticulum in skeletal muscle fibers?

Accepted Answer

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

Question 2

A patient presents with muscle weakness and drooping eyelids. Laboratory tests reveal antibodies against acetylcholine receptors. Which disease is most likely?

Accepted Answer

Myasthenia gravis

Question 3

During the sliding filament model of contraction, which event occurs at the molecular level?

Accepted Answer

Thin filaments slide past thick filaments, increasing their overlap without changing their length.

Question 4

Which connective tissue sheath surrounds individual muscle fibers?

Accepted Answer

Endomysium

Question 5

What is the primary source of ATP during the first 15 seconds of high-intensity exercise?

Accepted Answer

Direct phosphorylation of ADP by creatine phosphate

Question 6

Which of the following is a characteristic unique to cardiac muscle tissue?

Accepted Answer

It is striated and involuntary.

Question 7

A muscle fiber is stimulated so rapidly that it does not relax at all between stimuli. What is this phenomenon called?

Accepted Answer

Fused (complete) tetanus

Question 8

Which protein directly binds $$\mathrm{Ca$$^{2+}$$} in $$smooth muscle to initiate contraction?

Accepted Answer

Calmodulin

Question 9

Which of the following best explains why rigor mortis occurs after death?

Accepted Answer

ATP is no longer produced, so cross bridges cannot detach from actin.

Question 10

Which type of muscle fiber is most resistant to fatigue and best suited for endurance activities?

Accepted Answer

Slow oxidative fibers

Question 11

A muscle is contracting but not shortening because the load exceeds the tension the muscle can generate. What type of contraction is this?

Accepted Answer

Isometric contraction

Question 12

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

Accepted Answer

Events at neuromuscular junction → Muscle fiber excitation → Excitation-contraction coupling → Cross bridge cycling

Question 13

Which of the following is NOT a function of skeletal muscle?

Accepted Answer

Pumping blood

Question 14

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

Accepted Answer

It degrades acetylcholine, terminating the signal.

Question 15

Which of the following is true regarding the length-tension relationship in skeletal muscle?

Accepted Answer

Maximum force is generated when the muscle is at optimal resting length.

Question 16

Which of the following is a regulatory protein found in thin filaments of skeletal muscle but NOT in smooth muscle?

Accepted Answer

Troponin

Question 17

Which of the following best explains why muscle tone is important?

Accepted Answer

It keeps muscles firm, healthy, and ready to respond.

Question 18

Which of the following is the correct equation for the direct phosphorylation of ADP by creatine phosphate?

Accepted Answer

$$\mathrm{Creatine\ phosphate + ADP \rightarrow Creatine + ATP}$$

Question 19

Which of the following is a unique feature of multi-unit smooth muscle compared to unitary smooth muscle?

Accepted Answer

It consists of independent muscle fibers with few gap junctions.

Question 20

Which of the following best describes the role of dystrophin in skeletal muscle?

Accepted Answer

It links thin filaments to proteins of the sarcolemma.

Muscles and Muscle Tissue: Structure, Function, and Physiology

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