Question 1

Which of the following statements best describes the difference between skeletal, cardiac, and smooth muscle cells?

Accepted Answer

Skeletal muscle cells are striated, multinucleate, and voluntary; cardiac muscle cells are striated, uninucleate, and involuntary; smooth muscle cells are non-striated, uninucleate, and involuntary.

Question 2

A patient is unable to consciously move their arm, but the heart continues to beat and digestion proceeds normally. Which muscle types are functioning involuntarily in this scenario?

Accepted Answer

Cardiac and smooth muscle

Question 3

Which connective tissue layer directly surrounds a single skeletal muscle fiber?

Accepted Answer

Endomysium

Question 4

During muscle contraction, which protein forms cross bridges with actin filaments?

Accepted Answer

Myosin

Question 5

Which of the following best explains the role of calcium ions ($$\mathrm{Ca$$^{2+}$$}) in $$the sliding filament theory of muscle contraction?

Accepted Answer

Calcium ions bind to regulatory proteins on actin, exposing myosin-binding sites and allowing cross bridge formation.

Question 6

Which equation correctly represents the direct phosphorylation of ADP by creatine phosphate (CP) in muscle cells?

Accepted Answer

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

Question 7

A marathon runner relies primarily on which pathway for ATP regeneration during prolonged, moderate exercise?

Accepted Answer

Aerobic respiration (oxidative phosphorylation)

Question 8

Which of the following is TRUE regarding the 'all-or-none' law of muscle fiber contraction?

Accepted Answer

A muscle fiber contracts to its fullest extent when adequately stimulated, but the whole muscle can show graded responses.

Question 9

Which neurotransmitter is released at the neuromuscular junction to stimulate skeletal muscle contraction?

Accepted Answer

Acetylcholine (ACh)

Question 10

What is the primary function of acetylcholinesterase (AChE) at the neuromuscular junction?

Accepted Answer

It breaks down acetylcholine, ending muscle contraction.

Question 11

Which process is responsible for restoring ion balance after a muscle action potential?

Accepted Answer

The sodium-potassium pump moves $$\mathrm{Na^+}$$ and $$\mathrm{K^+}$$ ions back to their original positions.

Question 12

Which type of muscle contraction occurs when the muscle shortens and movement occurs, such as lifting a weight?

Accepted Answer

Isotonic contraction

Question 13

A weightlifter is pushing against an immovable wall with maximum effort, but the wall does not move. What type of muscle contraction is occurring?

Accepted Answer

Isometric contraction

Question 14

Which of the following best describes muscle tone?

Accepted Answer

A state of continuous partial contraction that keeps muscles firm and ready for action.

Question 15

Which of the following is a result of aerobic (endurance) exercise?

Accepted Answer

Stronger, more flexible muscles with greater resistance to fatigue.

Question 16

Which of the following is a correct sequence of events at the neuromuscular junction leading to muscle contraction?

Accepted Answer

Nerve impulse → Calcium influx → ACh release → ACh binds sarcolemma → Na$$^+$$ influx → Action potential

Question 17

Which metabolic pathway produces the most ATP per glucose molecule during muscle activity?

Accepted Answer

Aerobic respiration (about 32 ATP per glucose)

Question 18

A sprinter experiences muscle fatigue after a short, intense burst of activity. Which factors most likely contribute to this fatigue?

Accepted Answer

Ion imbalances, lactic acid accumulation, and decreased ATP supply

Question 19

Which structure in skeletal muscle stores and releases calcium ions necessary for contraction?

Accepted Answer

Sarcoplasmic reticulum

Question 20

If a muscle is stimulated so rapidly that no evidence of relaxation is seen and contractions are smooth and sustained, what is this state called?

Accepted Answer

Fused (complete) tetanus

The Muscular System: Structure, Types, and Function

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