Question 1

Which statement best describes the relationship between sarcomere length and contraction force in skeletal muscle?

Accepted Answer

Maximum force is generated when the sarcomere is at an optimal length, neither too short nor too long.

Question 2

A muscle fiber receives two action potentials in rapid succession, resulting in a stronger contraction than a single twitch. What is this phenomenon called?

Accepted Answer

Summation

Question 3

Which of the following best explains why the tension generated by a muscle fiber is directly proportional to the number of crossbridges formed?

Accepted Answer

More crossbridges allow for greater overlap between actin and myosin, increasing force production.

Question 4

During a sustained maximal contraction, the muscle eventually loses tension despite continued stimulation. What is this phenomenon called?

Accepted Answer

Fatigue

Question 5

Which equation best represents the relationship between force ($F$), lever arm length ($r$), and torque ($	au$) in the context of muscle movement?

Accepted Answer

$	au = F 	imes r$

Question 6

A patient is unable to convert glycogen to glucose-6-phosphate in their muscle cells, leading to exercise intolerance. Which inherited disorder is most likely responsible?

Accepted Answer

McArdle’s disease

Question 7

Which type of muscle contraction occurs when the muscle generates force without changing its length?

Accepted Answer

Isometric contraction

Question 8

What is the primary function of synchronous recruitment of motor units during muscle contraction?

Accepted Answer

To prevent muscle fatigue by allowing different motor units to take turns maintaining tension

Question 9

Which of the following is TRUE regarding smooth muscle compared to skeletal muscle?

Accepted Answer

Smooth muscle uses less energy and can maintain contractions for extended periods.

Question 10

Which of the following best describes the role of calcium in smooth muscle contraction?

Accepted Answer

Calcium initiates a cascade ending with phosphorylation of myosin light chain and activation of myosin ATPase.

Question 11

Which type of smooth muscle is most likely to be found in the walls of the gastrointestinal tract and contracts as a single unit?

Accepted Answer

Single-unit (visceral) smooth muscle

Question 12

A muscle is stimulated at a frequency that allows slight relaxation between contractions, resulting in a wavelike increase in tension. What is this called?

Accepted Answer

Unfused tetanus

Question 13

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

Accepted Answer

Cardiac muscle cells are electrically linked by gap junctions in intercalated disks.

Question 14

Which of the following best describes the effect of increased phosphatase activity on myosin’s response to $Ca^{2+}$ in smooth muscle?

Accepted Answer

It desensitizes myosin to $Ca^{2+}$, decreasing contraction.

Question 15

Which of the following is TRUE regarding the source of calcium for smooth muscle contraction?

Accepted Answer

Calcium is released from both the extracellular fluid and the sarcoplasmic reticulum.

Question 16

Which type of action potential is characterized by always depolarizing to threshold, leading to rhythmic contractions in smooth muscle?

Accepted Answer

Pacemaker potential

Question 17

Which neurotransmitter or paracrine agent causes relaxation of smooth muscle in blood vessels?

Accepted Answer

Nitric oxide

Question 18

A muscle contraction in which the muscle lengthens while generating force is called:

Accepted Answer

Eccentric contraction

Question 19

Which of the following best describes the mechanism of calcium-induced calcium release (CICR) in cardiac muscle?

Accepted Answer

Calcium entry through voltage-gated channels triggers release of more calcium from the sarcoplasmic reticulum.

Question 20

Which of the following is a consequence of muscle atrophy?

Accepted Answer

Decreased muscle size and strength

Ch 12 B Muscle Physiology: Contraction Force and Summation

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