Question 1

Which of the following best describes the structural difference between skeletal, cardiac, and smooth muscle tissue?

Accepted Answer

Skeletal muscle fibers are single, very long, cylindrical, multinucleate cells with obvious striations; cardiac muscle fibers are branching chains of cells with striations; smooth muscle fibers are single, spindle-shaped cells without striations.

Question 2

Which function of muscle tissue is most directly responsible for maintaining body temperature during cold exposure?

Accepted Answer

Generate heat as they contract

Question 3

A patient is unable to move their arm after nerve damage. Which tissue component of skeletal muscle is most likely affected?

Accepted Answer

Nerves and blood supply

Question 4

Which of the following best explains the sliding filament model of muscle contraction?

Accepted Answer

Thin filaments slide past thick filaments, causing actin and myosin to overlap more, resulting in sarcomere shortening.

Question 5

During the cross bridge cycle, what event directly causes the detachment of the myosin head from actin?

Accepted Answer

ATP attaches to the myosin head

Question 6

Which of the following best describes the role of the sarcoplasmic reticulum (SR) in muscle contraction?

Accepted Answer

It releases Ca$^{2+}$ ions in response to an action potential, triggering contraction.

Question 7

A muscle fiber remains relaxed until which of the following occurs?

Accepted Answer

Ca$^{2+}$ binds to troponin, moving tropomyosin away from myosin binding sites on actin.

Question 8

Which phase of a muscle twitch corresponds to the time when Ca$^{2+}$ is re-entering the sarcoplasmic reticulum?

Accepted Answer

Period of relaxation

Question 9

What is the correct sequence of events at the neuromuscular junction leading to muscle contraction?

Accepted Answer

ACh is released from the motor neuron, binds to receptors on the sarcolemma, Na$^+$ channels open, and the end plate potential is generated.

Question 10

If the end plate potential reaches threshold, what is the next event in the generation of an action potential?

Accepted Answer

Voltage-gated Na$^+$ channels open, causing a large influx of Na$^+$ and depolarization.

Question 11

Which equation best represents the ionic movement during depolarization of the sarcolemma?

Accepted Answer

$Na^+_{out} \rightarrow Na^+_{in}$

Question 12

A motor unit consists of:

Accepted Answer

One motor neuron and all the muscle fibers it innervates

Question 13

Which principle explains why small motor units are recruited before larger ones during muscle contraction?

Accepted Answer

Size principle of recruitment

Question 14

Which of the following best describes temporal (wave) summation in muscle contraction?

Accepted Answer

Additional stimuli delivered before relaxation is complete produce increased force with each stimulus.

Question 15

A muscle fiber is exposed to a subthreshold stimulus. What is the expected response?

Accepted Answer

No contraction is seen

Question 16

Which of the following is true regarding the relationship between stimulus intensity and muscle tension?

Accepted Answer

As stimulus intensity increases, more motor units are recruited, increasing muscle tension until maximal stimulus is reached.

Question 17

During excitation-contraction coupling, what is the role of T tubules?

Accepted Answer

They transmit the action potential deep into the muscle fiber, triggering Ca$^{2+}$ release from the SR.

Question 18

Which step in the cross bridge cycle directly uses the energy from ATP hydrolysis?

Accepted Answer

Cocking of the myosin head into a high-energy state

Question 19

A patient is experiencing muscle weakness due to impaired Ca$^{2+}$ reuptake into the sarcoplasmic reticulum. Which phase of the muscle twitch would be most affected?

Accepted Answer

Period of relaxation

Question 20

Which of the following equations best represents the restoration of ionic conditions after an action potential in a muscle fiber?

Accepted Answer

$3 Na^+_{out} : 2 K^+_{in}$ (Na$^+$/K$^+$ pump activity)

Muscles and Muscle Tissue: Structure, Function, and Contraction Mechanisms

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