Question 1

Which of the following best describes the role of calcium ions ($$\mathrm{Ca$$^{2+}$$}) in $$skeletal muscle contraction?

Accepted Answer

They bind to troponin, causing a conformational change that exposes binding sites on actin.

Question 2

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

Accepted Answer

Their body attacks acetylcholine receptors at the neuromuscular junction, reducing muscle cell activation.

Question 3

Which of the following statements about the sliding filament mechanism is correct?

Accepted Answer

Actin filaments slide past myosin filaments, shortening the sarcomere.

Question 4

During a biceps curl, which muscle acts as the antagonist to the biceps brachii?

Accepted Answer

Triceps brachii

Question 5

Which of the following best distinguishes isotonic from isometric muscle contractions?

Accepted Answer

Isotonic contractions shorten the muscle while maintaining constant force; isometric contractions generate force without changing muscle length.

Question 6

Which of the following is a primary source of ATP during the first few seconds of intense muscle activity?

Accepted Answer

Breakdown of creatine phosphate

Question 7

A sprinter relies heavily on which type of muscle fibers during a 100-meter dash, and why?

Accepted Answer

Fast twitch fibers, because they break down ATP quickly and provide rapid, powerful contractions.

Question 8

Which of the following best explains why smooth muscle does not fatigue easily?

Accepted Answer

Smooth muscle contracts slowly, so ATP usage is always less than ATP production.

Question 9

Which of the following is true regarding the arrangement of actin and myosin in cardiac muscle?

Accepted Answer

They are arranged in sarcomeres, giving cardiac muscle a striated appearance.

Question 10

Which of the following best describes the 'all-or-none' principle in muscle contraction?

Accepted Answer

A muscle cell contracts fully when stimulated above threshold; otherwise, it does not contract at all.

Question 11

Which of the following is a function of muscle tone?

Accepted Answer

It stabilizes joints and maintains posture by providing a constant, intermediate level of force.

Question 12

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

Accepted Answer

Isometric contraction

Question 13

Which of the following best explains why cardiac muscle does not fatigue under normal conditions?

Accepted Answer

Cardiac muscle undergoes rhythmic cycles of contraction and relaxation, allowing recovery.

Question 14

Which of the following is a characteristic unique to cardiac muscle compared to skeletal and smooth muscle?

Accepted Answer

It contains intercalated discs with gap junctions for electrical coupling.

Question 15

Which of the following best describes the process of muscle fatigue?

Accepted Answer

A decline in muscle performance due to depletion of ATP and accumulation of metabolic byproducts.

Question 16

Which of the following is the correct sequence of events in skeletal muscle contraction after a motor neuron is activated?

Accepted Answer

Acetylcholine release → T tubule depolarization → Calcium release from sarcoplasmic reticulum → Cross-bridge formation

Question 17

Which of the following best explains why fast twitch muscle fibers fatigue more quickly than slow twitch fibers?

Accepted Answer

They rely on anaerobic metabolism, leading to lactic acid accumulation.

Question 18

Which of the following disorders is caused by a lack of the muscle cell protein dystrophin, leading to muscle cell death?

Accepted Answer

Muscular dystrophy

Question 19

Which of the following best describes the role of recruitment in muscle contraction?

Accepted Answer

It increases muscle force by activating more motor units.

Question 20

Which of the following is a function of smooth muscle in the human body?

Accepted Answer

Regulating blood vessel diameter and moving contents through hollow organs

The Muscular System: Structure, Function, and Disorders

Study Guide - Practice Questions