A&P 1 101 - Portage Learning
Module 5 Exam: The Muscular System (Tissue &
Physiology)
Questions & Rationale
Q1: Which of the following is a defining characteristic of skeletal muscle tissue?
A. Involuntary control, intercalated discs, single nucleus
B. Involuntary control, spindle-shaped cells, non-striated
C. Voluntary control, multinucleated, striated [CORRECT]
D. Voluntary control, branched cells, single central nucleus
Correct Answer: C
Rationale: Skeletal muscle is characterized by voluntary nervous system control,
multiple peripheral nuclei (multinucleated fibers), and striated appearance due to
organized sarcomeres. Option A describes cardiac muscle (involuntary, intercalated
discs); Option B describes smooth muscle (involuntary, spindle-shaped, non-striated);
Option D incorrectly combines voluntary control with cardiac muscle features.
Q2: The functional unit of skeletal muscle contraction, extending from one Z-disc to
the next, is called the:
A. Myofibril
,B. Sarcomere [CORRECT]
C. Sarcoplasmic reticulum
D. Motor unit
Correct Answer: B
Rationale: The sarcomere is the basic contractile unit of skeletal muscle, defined as the
region between two successive Z-discs (Z-lines). It contains the thick (myosin) and thin
(actin) filaments arranged to create the striated pattern. A myofibril (A) is a long
cylindrical organelle composed of many sarcomeres in series; the sarcoplasmic
reticulum (C) is the calcium-storing membrane system; a motor unit (D) is one motor
neuron plus all muscle fibers it innervates.
Q3: According to the sliding filament theory, during muscle contraction:
A. The thin filaments shorten while thick filaments remain unchanged
B. The thin filaments slide past the thick filaments toward the M-line, shortening the
sarcomere [CORRECT]
C. The thick filaments shorten while pulling thin filaments together
D. Both thick and thin filaments shorten equally
Correct Answer: B
Rationale: The sliding filament theory states that neither thick nor thin filaments shorten
during contraction. Instead, the thin (actin) filaments slide inward over the stationary
thick (myosin) filaments, powered by cross-bridge cycling. This pulls the Z-discs closer
, together, shortening the sarcomere and the entire muscle fiber. The H-zone and I-band
narrow, while the A-band remains constant width.
Q4: In the sarcomere, the region that contains ONLY thick (myosin) filaments and no
thin filaments is the:
A. I-band
B. A-band
C. H-zone [CORRECT]
D. Z-disc
Correct Answer: C
Rationale: The H-zone (Hensen's zone) is the central region of the A-band that contains
only thick (myosin) filaments and no overlapping thin filaments. During contraction, as
thin filaments slide inward, the H-zone narrows or disappears. The I-band (A) contains
only thin filaments; the A-band (B) contains the entire length of thick filaments plus
overlapping thin filaments; Z-discs (D) are the boundary structures anchoring thin
filaments.
Q5: The protein that binds to calcium ions during muscle contraction, initiating the
movement of tropomyosin away from myosin-binding sites on actin, is:
A. Myosin
B. Tropomyosin
C. Troponin [CORRECT]
Module 5 Exam: The Muscular System (Tissue &
Physiology)
Questions & Rationale
Q1: Which of the following is a defining characteristic of skeletal muscle tissue?
A. Involuntary control, intercalated discs, single nucleus
B. Involuntary control, spindle-shaped cells, non-striated
C. Voluntary control, multinucleated, striated [CORRECT]
D. Voluntary control, branched cells, single central nucleus
Correct Answer: C
Rationale: Skeletal muscle is characterized by voluntary nervous system control,
multiple peripheral nuclei (multinucleated fibers), and striated appearance due to
organized sarcomeres. Option A describes cardiac muscle (involuntary, intercalated
discs); Option B describes smooth muscle (involuntary, spindle-shaped, non-striated);
Option D incorrectly combines voluntary control with cardiac muscle features.
Q2: The functional unit of skeletal muscle contraction, extending from one Z-disc to
the next, is called the:
A. Myofibril
,B. Sarcomere [CORRECT]
C. Sarcoplasmic reticulum
D. Motor unit
Correct Answer: B
Rationale: The sarcomere is the basic contractile unit of skeletal muscle, defined as the
region between two successive Z-discs (Z-lines). It contains the thick (myosin) and thin
(actin) filaments arranged to create the striated pattern. A myofibril (A) is a long
cylindrical organelle composed of many sarcomeres in series; the sarcoplasmic
reticulum (C) is the calcium-storing membrane system; a motor unit (D) is one motor
neuron plus all muscle fibers it innervates.
Q3: According to the sliding filament theory, during muscle contraction:
A. The thin filaments shorten while thick filaments remain unchanged
B. The thin filaments slide past the thick filaments toward the M-line, shortening the
sarcomere [CORRECT]
C. The thick filaments shorten while pulling thin filaments together
D. Both thick and thin filaments shorten equally
Correct Answer: B
Rationale: The sliding filament theory states that neither thick nor thin filaments shorten
during contraction. Instead, the thin (actin) filaments slide inward over the stationary
thick (myosin) filaments, powered by cross-bridge cycling. This pulls the Z-discs closer
, together, shortening the sarcomere and the entire muscle fiber. The H-zone and I-band
narrow, while the A-band remains constant width.
Q4: In the sarcomere, the region that contains ONLY thick (myosin) filaments and no
thin filaments is the:
A. I-band
B. A-band
C. H-zone [CORRECT]
D. Z-disc
Correct Answer: C
Rationale: The H-zone (Hensen's zone) is the central region of the A-band that contains
only thick (myosin) filaments and no overlapping thin filaments. During contraction, as
thin filaments slide inward, the H-zone narrows or disappears. The I-band (A) contains
only thin filaments; the A-band (B) contains the entire length of thick filaments plus
overlapping thin filaments; Z-discs (D) are the boundary structures anchoring thin
filaments.
Q5: The protein that binds to calcium ions during muscle contraction, initiating the
movement of tropomyosin away from myosin-binding sites on actin, is:
A. Myosin
B. Tropomyosin
C. Troponin [CORRECT]
