Question 1

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

Accepted Answer

It stores and releases $\mathrm{Ca^{2+}}$ ions necessary for muscle contraction.

Question 2

During the sliding filament theory of muscle contraction, tension generated in a muscle fiber is directly proportional to:

Accepted Answer

The number of crossbridges formed between actin and myosin.

Question 3

Which statement correctly explains why the A bands of the sarcomere do not shorten during contraction?

Accepted Answer

The A band corresponds to the length of the thick filaments, which remain constant.

Question 4

A single muscle contraction-relaxation cycle is called:

Accepted Answer

A twitch

Question 5

Compare the ATP yield for aerobic and anaerobic metabolism of one glucose molecule. Which equation correctly represents the net ATP produced in each pathway?

Accepted Answer

Aerobic: $\approx 30-32$ ATP; Anaerobic: $2$ ATP

Question 6

Which muscle fiber type has the highest myoglobin content and is most resistant to fatigue?

Accepted Answer

Slow-twitch oxidative fibers (Type I)

Question 7

At the molecular level, what determines the tension a muscle fiber can generate?

Accepted Answer

The number of active crossbridges between actin and myosin

Question 8

Which of the following best describes the process of summation in muscle fibers?

Accepted Answer

Increasing the frequency of stimulation so that individual twitches combine to produce greater force

Question 9

Which equation best represents the role of phosphocreatine in muscle ATP regeneration?

Accepted Answer

$\mathrm{Phosphocreatine} + \mathrm{ADP} \rightarrow \mathrm{Creatine} + \mathrm{ATP}$

Question 10

Which of the following is true regarding the difference between isotonic and isometric contractions?

Accepted Answer

Isotonic contractions move a load, while isometric contractions generate force without movement.

Question 11

What is the function of titin in the sarcomere?

Accepted Answer

It stabilizes the position of thick filaments and provides elasticity to the muscle.

Question 12

Which of the following best describes the molecular events of the power stroke in muscle contraction?

Accepted Answer

Myosin heads pivot, pulling actin filaments toward the center of the sarcomere.

Question 13

Which statement about the relationship between sarcomere length and tension generation is correct?

Accepted Answer

Sarcomeres at optimal length generate the greatest tension due to maximal crossbridge formation.

Question 14

Which of the following is a regulatory protein in the myofibril?

Accepted Answer

Troponin

Question 15

Which process is responsible for ending a muscle contraction and initiating relaxation?

Accepted Answer

Active transport of $\mathrm{Ca^{2+}}$ back into the sarcoplasmic reticulum by Ca$^{2+}$-ATPase

Question 16

Which of the following best describes the difference between single-unit and multi-unit smooth muscle?

Accepted Answer

Single-unit smooth muscle cells are electrically connected by gap junctions, while multi-unit cells function independently.

Question 17

Which enzyme is dominant when increased force of contraction is observed in smooth muscle, even though $[\mathrm{Ca^{2+}}]$ has not changed?

Accepted Answer

Myosin light chain kinase (MLCK)

Question 18

Which feature is unique to cardiac muscle compared to skeletal and smooth muscle?

Accepted Answer

Presence of intercalated disks for electrical coupling

Question 19

Which of the following is a correct statement about the series elastic elements in muscle contraction?

Accepted Answer

They allow muscles to maintain tension without changing length during isometric contractions.

Chapter 12

Study Guide - Practice Questions

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