Q: What is the optimal sarcomere length for generating maximum tension in skeletal muscle?

$$2.0\ \mathrm{\mu m}\ \text{to}\ 2.25\ \mathrm{\mu m}$$

Question 1

Which of the following best describes the physiological basis of the 'treppe' or stairway effect observed in skeletal muscle contractions?

Accepted Answer

It is caused by a gradual increase in calcium ion concentration in the sarcoplasm with repeated stimulation.

Question 2

A muscle fiber is stimulated at a frequency that allows partial relaxation between contractions. What is this phenomenon called?

Accepted Answer

Incomplete tetanus

Question 3

During heavy exercise, which substrate do skeletal muscles primarily rely on for energy production?

Accepted Answer

Glycogen

Question 4

Which of the following factors does NOT directly influence the strength of skeletal muscle contraction?

Accepted Answer

The amount of myoglobin present in the muscle fiber

Question 5

A patient’s muscle fibers reach maximal tension in approximately 100 ms and are highly resistant to fatigue. Which fiber type is most likely predominant?

Accepted Answer

Type I (slow-twitch, red fibers)

Question 6

What is the optimal sarcomere length for generating maximum tension in skeletal muscle?

Accepted Answer

$$2.0\ \mathrm{\mu m}\ 	ext{to}\ 2.25\ \mathrm{\mu m}$$

Question 7

Which of the following best explains why muscle tension decreases when sarcomere length exceeds $$2.25\ \mathrm{\mu m}$$?

Accepted Answer

There is less overlap between actin and myosin filaments, reducing cross-bridge formation.

Question 8

During a short, moderately intense exercise, which energy substrates are used by skeletal muscle for aerobic respiration?

Accepted Answer

Fatty acids and glycogen to the same extent

Question 9

Which process allows muscle cells to rapidly regenerate ATP during intense, short-duration exercise?

Accepted Answer

Combining ADP with phosphate derived from phosphocreatine

Question 10

A muscle is stimulated at a frequency of 60 shocks per second, resulting in a sustained contraction with no visible relaxation. What is this state called?

Accepted Answer

Complete tetanus

Question 11

Which of the following is a physiological adaptation to exercise that increases glucose uptake by skeletal muscle cells?

Accepted Answer

Increased production of glucose transporters into the sarcolemma

Question 12

Which type of muscle fiber has the greatest rate of ATP and phosphocreatine consumption?

Accepted Answer

Type IIx (fast glycolytic fibers)

Question 13

If a muscle fiber’s sarcomere length is less than $$2.0\ \mathrm{\mu m}$$, what happens to the force generated by muscle contraction?

Accepted Answer

Force decreases due to excessive overlap of actin and myosin filaments

Question 14

Which of the following best describes muscle fatigue during high-frequency stimulation?

Accepted Answer

It occurs after motor subunits are unable to maintain the rate of neural firing and typically recovers in less than a minute.

Question 15

Which equation best represents the calculation of maximal oxygen consumption ($$VO_2$$ max) in skeletal muscle physiology?

Accepted Answer

$$VO_2$$\ 	ext{max} = \frac{	ext{ml of } $$O_2$$}{	ext{min} \cdot 	ext{kg}}$$

Question 16

Which of the following is TRUE regarding graded contractions in vivo?

Accepted Answer

They are produced by variations in the number of motoneurons activated.

Question 17

A sprinter experiences rapid muscle fatigue after a short burst of activity. Which muscle fiber type is most likely responsible for this fatigue?

Accepted Answer

Type IIx (fast glycolytic fibers)

Question 18

Which of the following best describes the difference between isometric and isotonic muscle contractions?

Accepted Answer

Isometric contractions generate tension without changing muscle length, while isotonic contractions change muscle length with constant tension.

Question 19

Which of the following statements about the energy requirements of skeletal muscle during exercise is CORRECT?

Accepted Answer

During light exercise, fatty acids are the primary fuel for aerobic respiration.

Physio: Muscle II

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