Question 1

Which of the following best describes the sliding-filament model of muscle contraction?

Accepted Answer

Thin and thick filaments slide past each other, powered by myosin, while maintaining their original length.

Question 2

What is the primary role of Ca$^{2+}$ in skeletal muscle contraction?

Accepted Answer

Ca$^{2+}$ binds to the troponin complex, causing tropomyosin to shift and expose myosin-binding sites on actin.

Question 3

A patient is experiencing muscle weakness due to a defect in the sarcoplasmic reticulum's ability to release Ca$^{2+}$. Which step in muscle contraction is most directly affected?

Accepted Answer

The exposure of myosin-binding sites on actin.

Question 4

Which of the following statements about motor units is correct?

Accepted Answer

A motor unit consists of one motor neuron and all the muscle fibers it controls.

Question 5

During a sustained, high-frequency stimulation of a muscle, which phenomenon is most likely to occur?

Accepted Answer

Summation of twitches leading to tetanus.

Question 6

Which of the following best explains why skeletal muscle appears striated under a microscope?

Accepted Answer

The regular arrangement of sarcomeres in adjacent myofibrils.

Question 7

A muscle fiber is stimulated by a motor neuron, leading to an action potential. Which structure transmits this action potential deep into the muscle fiber?

Accepted Answer

Transverse (T) tubules

Question 8

Which of the following is a key difference between slow-twitch and fast-twitch muscle fibers?

Accepted Answer

Fast-twitch fibers have fewer mitochondria and lower myoglobin content than slow-twitch fibers.

Question 9

Which of the following best describes the function of tendons?

Accepted Answer

They attach muscles to bones, transmitting the force of muscle contraction.

Question 10

A researcher is studying the movement of an earthworm, which uses a hydrostatic skeleton. Which statement best describes how movement is achieved in this organism?

Accepted Answer

Movement is achieved by changing the shape of fluid-filled compartments within the body.

Question 11

Which of the following events occurs first during the process of skeletal muscle contraction?

Accepted Answer

Acetylcholine is released at the neuromuscular junction.

Question 12

Which type of muscle tissue is characterized by being striated and under voluntary control?

Accepted Answer

Skeletal muscle

Question 13

A person is experiencing muscle fatigue after prolonged exercise. Which of the following is a primary cause of this fatigue?

Accepted Answer

Depletion of ATP and dissipation of ion gradients

Question 14

Which of the following best explains why cardiac muscle cells can contract without nervous input?

Accepted Answer

They are electrically connected by intercalated discs, allowing coordinated contraction.

Question 15

Which of the following is true regarding the regulation of muscle contraction by regulatory proteins?

Accepted Answer

The troponin complex binds Ca$^{2+}$, causing tropomyosin to move and expose myosin-binding sites.

Question 16

Which of the following best describes the relationship between the number of motor units activated and the force generated by a skeletal muscle?

Accepted Answer

As more motor units are activated, the force generated by the muscle increases.

Question 17

Which of the following is a characteristic of smooth muscle but not skeletal muscle?

Accepted Answer

Involuntary control and lack of striations

Question 18

Which of the following best explains why oxidative muscle fibers are darker in color than glycolytic fibers?

Accepted Answer

They contain more mitochondria and higher levels of myoglobin.

Question 19

A person is unable to extend their forearm after a nerve injury. Which muscle is most likely affected?

Accepted Answer

Triceps

Question 20

Which of the following best describes the function of ligaments?

Accepted Answer

They hold bones together at joints.

Muscle Structure, Function, and Regulation in Animals

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