chapter 10

Question 1

What are the smallest functional units of a muscle fiber?
A. Myofibrils
B. Sarcomeres
C. Fascicles
D. Myofilaments

Answer 1

B. Sarcomeres
Explanation: Sarcomeres are the basic units responsible for contraction.

Question 2

Which band contains both thick and thin filaments?
A. I band
B. H band
C. A band
D. Z line

Answer 2

A band
Explanation: The A band includes the full length of thick filaments and overlap.

Question 3

Which band contains only thin filaments?
A. A band
B. H band
C. I band
D. M line

Answer 3

C. I band
Explanation: I bands contain only thin (actin) filaments.

Question 4

What structure marks the boundary of a sarcomere?
A. M line
B. Z line
C. H band
D. A band

Answer 4

B. Z line
Explanation: Sarcomeres extend from one Z line to another.

Question 5

What happens to the H band during contraction?
A. It widens
B. It disappears or narrows
C. It stays the same
D. It becomes darker

Answer 5

B. It disappears or narrows
Explanation: Thick filaments slide, reducing the H zone.

Question 6

What remains constant during contraction?
A. I band
B. H band
C. A band
D. Z line distance

Answer 6

C. A band
Explanation: Thick filament length doesn’t change

Question 7

Which protein covers active sites on actin?
A. Troponin
B. Myosin
C. Tropomyosin
D. Titin

Answer 7

C. Tropomyosin
Explanation: It blocks myosin binding sites on actin.

Question 8

What directly causes contraction to begin?
A. ATP breakdown
B. Ca²⁺ binding to troponin
C. ACh release
D. Oxygen intake

Answer 8

B. Ca²⁺ binding to troponin
Explanation: This exposes active sites for myosin.

Question 8

What binds calcium ions (Ca²⁺)?
A. Actin
B. Troponin
C. Myosin
D. Titin

Answer 8

B. Troponin
Explanation: Ca²⁺ binding moves tropomyosin.

Question 9

What ion enters the muscle fiber to generate an action potential?
A. K⁺
B. Ca²⁺
C. Na⁺
D. Cl⁻

Answer 9

C. Na⁺
Explanation: Sodium influx depolarizes the membrane.

Question 9

What is released at the neuromuscular junction?
A. Dopamine
B. Calcium
C. Acetylcholine (ACh)
D. ATP

Answer 9

C. Acetylcholine (ACh)
Explanation: ACh triggers muscle fiber depolarization.

Question 10

What structure stores calcium ions?
A. T tubules
B. Sarcolemma
C. Sarcoplasmic reticulum
D. Myofibrils

Answer 10

C. Sarcoplasmic reticulum
Explanation: It releases Ca²⁺ during contraction.

Question 11

Which step comes FIRST in contraction?
A. Cross-bridge formation
B. ACh release
C. Power stroke
D. ATP binding

Answer 11

B. ACh release
Explanation: It initiates the entire process

Question 12

What causes cross-bridge detachment?
A. Ca²⁺ binding
B. ATP binding
C. ADP release
D. Power stroke

Answer 12

B. ATP binding
Explanation: ATP breaks the actin-myosin bond.

Question 12

What is wave summation?
A. Decreasing tension
B. Increasing tension from repeated stimuli
C. No contraction
D. Relaxation only

Answer 12

B. Increasing tension from repeated stimuli
Explanation: Stimuli arrive before relaxation ends.

Question 13

Why does rigor mortis occur?
A. No calcium
B. Too much ATP
C. No ATP
D. Too much oxygen

Answer 13

C. No ATP
Explanation: Myosin heads cannot detach without ATP.

Question 13

Maximum tension occurs when:
A. No overlap exists
B. Overlap is optimal
C. Muscle is overstretched
D. Muscle is fully relaxed

Answer 13

B. Overlap is optimal
Explanation: More cross-bridges can form.

Question 13

What are the three phases of a twitch?
A. Start, middle, end
B. Latent, contraction, relaxation
C. Fast, slow, medium
D. Short, long, rest

Answer 13

B. Latent, contraction, relaxation
Explanation: Standard phases of muscle response.

Question 13

What determines the duration of contraction?
A. Muscle size
B. Neural stimulus, Ca²⁺, ATP
C. Bone length
D. Blood pressure

Answer 13

B. Neural stimulus, Ca²⁺, ATP
Explanation: These control how long contraction continues.

Question 14

What is a twitch?
A. Sustained contraction
B. Single contraction
C. Muscle tear
D. Relaxation phase

Answer 14

B. Single contraction
Explanation: One stimulus produces one twitch.

Question 15

Which fiber type has many mitochondria and resists fatigue?
A. Fast fibers
B. Slow fibers
C. Intermediate fibers
D. Smooth fibers

Answer 15

Answer: B. Slow fibers
Explanation: They rely on aerobic metabolism.

Question 15

What is tetanus?
A. No contraction
B. Maximum sustained tension
C. Muscle fatigue
D. Single twitch

Answer 15

: B. Maximum sustained tension
Explanation: Continuous stimulation prevents relaxation.

Question 15

Which fiber type contracts quickly but fatigues fast?
A. Slow fibers
B. Intermediate fibers
C. Fast fibers
D. Cardiac fibers

Answer 15

C. Fast fibers
Explanation: They produce strong, rapid contractions.

Question 16

The connective tissue that surrounds individual muscle fibers is the:
A) Endomysium
B) Perimysium
C) Epimysium
D) Fascia
E) Periosteum

Answer 16

Answer: A. Endomysium
Explanation: Endomysium wraps each muscle cell.

Question 16

What is muscle hypertrophy? A. Muscle loss B. Increase in muscle size C. Decrease in ATP D. Muscle damage

Answer 16

Answer: B. Increase in muscle size Explanation: Caused by training and increased fibers/components.

Question 16

What happens to muscles with aging? A. Increase in elasticity B. Increase in size C. Decrease in elasticity and recovery D. Faster contraction

Answer 16

Answer: C. Decrease in elasticity and recovery Explanation: Aging reduces muscle performance.

Question 17

The dense connective tissue that surrounds an entire skeletal muscle is the: A) Tendon B) Epimysium C) Endomysium D) Perimysium E) Fascicle

Answer 17

Answer: B. Epimysium Explanation: Epimysium covers the whole muscle.

Question 17

Which of the following is a recognized function of skeletal muscle? A) Produce movement B) Maintain posture C) Maintain body temperature D) Guard body entrances and exits E) All of the above

Answer 17

Answer: E. All of the above Explanation: Skeletal muscle performs all these key functions.

Question 18

Interactions between actin and myosin filaments result in: A) Muscle fatigue B) Neural conduction C) Muscle contraction D) Relaxation E) Heat loss

Answer 18

Answer: C. Muscle contraction Explanation: Sliding filaments create contraction.

Question 18

The plasma membrane of a skeletal muscle fiber is called the: A) Sarcolemma B) Sarcomere C) Sarcoplasm D) Sarcoplasmic reticulum E) Myofibril

Answer 18

Answer: A. Sarcolemma Explanation: Sarcolemma is the muscle cell membrane.

Question 18

The repeating functional unit of a muscle fiber is the: A) Myofibril B) Sarcomere C) Sarcolemma D) Fascicle E) Myofilament

Answer 18

Answer: B. Sarcomere Explanation: Sarcomeres are the units responsible for contraction.

Question 19

The A band of a sarcomere contains: A) Thin filaments only B) Thick filaments only C) No filaments D) Thick filaments (and overlap) E) Z lines

Answer 19

Answer: D. Thick filaments (and overlap) Explanation: A band includes the entire length of thick filaments.

Question 20

The I band contains: A) Thick filaments B) Both thick and thin filaments C) Thin filaments only D) No filaments E) M lines

Answer 20

Answer: C. Thin filaments only Explanation: Only actin is present.

Question 21

The H band contains: A) Thin filaments only B) Thick filaments only C) Both filaments D) No filaments E) Z lines

Answer 21

Answer: B. Thick filaments only Explanation: No thin filaments in H zone.

Question 22

During muscle contraction: A) I bands get smaller B) H bands get smaller C) Z lines move closer together D) A band stays the same E) All of the above

Answer 22

Answer: E. All of the above Explanation: Classic sliding filament changes.

Question 23

The Z line functions to: A) Store calcium B) Anchor thick filaments C) Anchor thin filaments D) Produce ATP E) Break down ACh

Answer 23

Answer: C. Anchor thin filaments Explanation: Defines sarcomere boundaries.

Question 24

At rest, active sites on actin are blocked by: A) Myosin B) Troponin C) Tropomyosin D) Calcium E) ATP

Answer 24

Answer: C. Tropomyosin Explanation: Prevents myosin binding.

Question 24

Calcium ions bind to: A) Actin B) Troponin C) Myosin D) Tropomyosin E) ATP

Answer 24

Answer: B. Troponin Explanation: This exposes active sites.

Question 25

The sarcoplasmic reticulum is responsible for: A) Producing ATP B) Storing glycogen C) Releasing neurotransmitters D) Storing and releasing calcium E) Producing proteins

Answer 25

Answer: D. Storing and releasing calcium Explanation: Ca²⁺ triggers contraction.

Question 26

The triad consists of: A) Actin, myosin, troponin B) T tubule and two terminal cisternae C) A band, I band, H band D) Myofibrils and filaments E) Sarcolemma and nucleus

Answer 26

Answer: B. T tubule and two terminal cisternae Explanation: Key for excitation–contraction coupling.

Question 27

Cross-bridges are formed by: A) Actin B) Myosin C) Troponin D) Tropomyosin E) Calcium

Answer 27

Answer: B. Myosin Explanation: Myosin heads attach to actin.

Question 28

The neurotransmitter released at the neuromuscular junction is: A) Dopamine B) Calcium C) Acetylcholine D) ATP E) Serotonin

Answer 28

Answer: C. Acetylcholine Explanation: Starts muscle activation.

Question 29

A single contraction in response to one stimulus is called: A) Tetanus B) Twitch C) Summation D) Recruitment E) Relaxation

Answer 29

Answer: B. Twitch Explanation: Basic muscle response.

Question 29

Action potentials travel into the muscle fiber through: A) Sarcolemma B) Myofibrils C) T tubules D) Sarcomeres E) Tendons

Answer 29

Answer: C. T tubules Explanation: Carry signals deep into the cell.

Question 29

Calcium ions are released when: A) ACh binds receptors B) ATP is used C) Action potentials reach T tubules D) Muscle relaxes E) Oxygen increases

Answer 29

Answer: C. Action potentials reach T tubules Explanation: Triggers SR to release Ca²⁺.

Question 30

Cross-bridge detachment occurs when: A) Ca²⁺ binds B) ATP binds C) ADP is released D) Oxygen enters E) Heat increases

Answer 30

Answer: B. ATP binds Explanation: ATP breaks actin-myosin bond.

Question 31

The first step in muscle contraction is: A) ACh release B) Ca²⁺ binding C) Cross-bridge formation D) ATP binding E) Relaxation

Answer 31

Answer: A. ACh release Explanation: Initiates the process at NMJ.

Question 32

Rigor mortis occurs because: A) ATP is depleted B) Myosin cannot detach C) Calcium remains high D) Muscles stay contracted E) All of the above

Answer 32

Answer: E. All of the above Explanation: No ATP → permanent contraction.

Question 33

Maximum sustained contraction is called: A) Twitch B) Treppe C) Incomplete tetanus D) Complete tetanus E) Recruitment

Answer 33

Answer: D. Complete tetanus Explanation: No relaxation between stimuli.

Question 34

Which muscle fiber type is most resistant to fatigue? A) Fast fibers B) Slow fibers C) Intermediate fibers D) White fibers E) Glycolytic fibers

Answer 34

Answer: B. Slow fibers Explanation: High mitochondria and oxygen supply.

Question 34

Which structure defines the boundary of a sarcomere? A) M line B) H band C) Z line D) A band E) I band

Answer 34

Answer: C. Z line Explanation: Sarcomeres extend from one Z line to the next.

Question 35

What is the function of titin? A) Stores calcium B) Anchors thin filaments C) Provides elasticity and stabilizes thick filaments D) Produces ATP E) Breaks down ACh

Answer 35

Answer: C. Provides elasticity and stabilizes thick filaments Explanation: Titin helps muscle return to resting length.

Question 36

What are thin filaments (F-actin) primarily made of? A) Myosin B) G-actin subunits C) ATP molecules D) Calcium ions E) Collagen

Answer 36

Answer: B. G-actin subunits Explanation: F-actin is a chain of G-actin molecules.

Question 36

Which protein blocks the active sites on actin at rest? A) Troponin B) Myosin C) Tropomyosin D) Titin E) Nebulin

Answer 36

Answer: C. Tropomyosin Explanation: It prevents myosin from binding.

Question 37

How are active sites on actin exposed for contraction? A) ATP binds to myosin B) Calcium binds to troponin C) Sodium enters the cell D) ACh is broken down E) Oxygen increases

Answer 37

Answer: B. Calcium binds to troponin Explanation: This shifts tropomyosin off the binding sites.

Question 38

What is the role of acetylcholine (ACh) in muscle contraction? A) Breaks down ATP B) Releases calcium C) Triggers action potential in muscle fiber D) Binds actin and myosin E) Stores energy

Answer 38

Answer: C. Triggers action potential in muscle fiber Explanation: ACh starts the contraction process at the NMJ.

Question 39

The triad consists of: A) Actin, myosin, troponin B) T tubule and two terminal cisternae C) A band, I band, H band D) Sarcolemma and nucleus E) Myofibril and sarcomere

Answer 39

Answer: B. T tubule and two terminal cisternae Explanation: Important for excitation–contraction coupling.

Question 39

The sliding filament theory states that: A) Filaments shorten B) Thick filaments disappear C) Thin filaments slide over thick filaments D) Sarcomeres expand E) ATP is not required

Answer 39

Answer: C. Thin filaments slide over thick filaments Explanation: This shortens the sarcomere.

Question 40

What is a motor unit? A) A muscle and tendon B) A neuron and all muscle fibers it controls C) A sarcomere and myofibril D) A group of bones E) A type of contraction

Answer 40

Answer: B. A neuron and all muscle fibers it controls Explanation: All fibers contract together.

Question 41

What is recruitment? A) Muscle relaxation B) Increase in ATP C) Increase in number of active motor units D) Breakdown of ACh E) Calcium storage

Answer 41

Answer: C. Increase in number of active motor units Explanation: Produces stronger muscle contraction.

Question 41

What is the main difference between fast and slow muscle fibers? A) Fast fibers have more oxygen B) Slow fibers fatigue quickly C) Fast fibers contract quickly but fatigue fast D) Slow fibers have less mitochondria E) Fast fibers use only aerobic metabolism

Answer 41

Answer: C. Fast fibers contract quickly but fatigue fast Explanation: Slow fibers resist fatigue; fast fibers do not.

Question 42

Which of the following describes isotonic contraction? A) Muscle does not change length B) Muscle tension equals load C) Muscle changes length D) Muscle relaxes completely E) No ATP is used

Answer 42

Answer: C. Muscle changes length Explanation: Includes concentric and eccentric contractions.