A&P 1 101 Module 5 Exam: Muscular System Portage
Learning | 2026/2027 Edition.
Instructions: This is a closed-book examination. Select the best answer for each question.
Total questions: 28.
DOMAIN 1: MICROSCOPIC ANATOMY & MUSCLE TISSUE TYPES (10 Questions)
Sub-Topic: Skeletal Muscle Fiber Organization (3 Questions)
Question 1 (Multiple-Choice)
Which of the following correctly lists the structural hierarchy of skeletal muscle from largest
to smallest?
A) Myofibril → Muscle fiber → Fascicle → Sarcomere
B) Fascicle → Muscle fiber → Myofibril → Sarcomere
C) Muscle fiber → Fascicle → Myofibril → Sarcomere
D) Sarcomere → Myofibril → Muscle fiber → Fascicle
Answer: B) Fascicle → Muscle fiber → Myofibril → Sarcomere [CORRECT]
Rationale: A fascicle is a bundle of muscle fibers (muscle cells) wrapped in perimysium. Each
muscle fiber contains multiple myofibrils, which are long cylindrical organelles composed of
repeating contractile units called sarcomeres. This hierarchical organization—fascicle → fiber
→ myofibril → sarcomere—is fundamental to understanding how the whole muscle generates
force through the coordinated contraction of millions of sarcomeres.
Question 2 (Fill-in-Blank)
A skeletal muscle fiber is a single muscle cell that is multinucleated and contains hundreds to
thousands of thread-like contractile organelles called ______________.
Answer: myofibrils [CORRECT]
Rationale: Myofibrils are the contractile organelles within a skeletal muscle fiber. Each
myofibril is composed of repeating sarcomeres arranged in series and is responsible for the
striated appearance of skeletal muscle. The myofibrils run parallel to the long axis of the
muscle fiber and are composed primarily of the contractile proteins actin (thin filaments) and
myosin (thick filaments).
Question 3 (True/False)
,A single skeletal muscle fiber contains multiple nuclei located at the periphery of the cell, just
beneath the sarcolemma.
Answer: TRUE [CORRECT]
Rationale: Skeletal muscle fibers are multinucleated syncytial cells formed by the fusion of
multiple myoblasts during development. The nuclei are pushed to the periphery of the fiber
by the densely packed myofibrils in the central cytoplasm (sarcoplasm). This peripheral
positioning of nuclei is a distinguishing histological feature of skeletal muscle tissue.
Sub-Topic: Sarcomere Structure (4 Questions)
Question 4 (Multiple-Choice)
During muscle contraction, which band of the sarcomere shortens while the thick myosin
filaments themselves do not change length?
A) A-band
B) H-zone
C) I-band
D) M-line
Answer: C) I-band [CORRECT]
Rationale: The I-band (isotropic band) contains only thin actin filaments and appears light
under a microscope. During contraction, the actin filaments slide inward toward the M-line,
causing the I-band to shorten. The A-band, which contains the full length of the thick myosin
filaments, remains constant in width because the myosin filaments do not shorten during
contraction. The H-zone also shortens as actin filaments overlap more extensively with
myosin.
Question 5 (Labeling / Fill-in-Blank)
Identify the labeled structures on the sarcomere diagram below:
plain
Copy
[Z-disc] ----[I-band]---- [A-band] ----[I-band]---- [Z-disc]
[H-zone]
|
, [M-line]
A) The dark band that contains the entire length of thick myosin filaments: ______________
B) The central region of the A-band that contains only thick filaments (no thin filaments):
______________
C) The protein disc that anchors the thin actin filaments and marks the boundary of each
sarcomere: ______________
D) The line in the center of the H-zone that anchors thick myosin filaments: ______________
Answers:
A) A-band [CORRECT]
B) H-zone [CORRECT]
C) Z-disc [CORRECT]
D) M-line [CORRECT]
Rationale: The sarcomere is the fundamental contractile unit of striated muscle, extending
from one Z-disc to the next. The A-band is the dark-staining region containing the full length
of thick myosin filaments. The H-zone is the lighter central region of the A-band that contains
only thick filaments when the muscle is at rest; it disappears during full contraction as thin
filaments slide inward. The Z-disc (Z-line) is a dense protein disc composed primarily of α-
actinin that anchors the plus ends of actin filaments and defines the lateral boundaries of
each sarcomere. The M-line is a dark-staining line in the center of the H-zone that contains
myomesin and other proteins that stabilize and anchor the thick myosin filaments.
Question 6 (Multiple-Choice)
A student is examining a sarcomere under a microscope and observes a region that appears
dark (anisotropic) and spans the entire length of the thick myosin filaments. This region is the:
A) I-band
B) A-band
C) Z-disc
D) H-zone
Answer: B) A-band [CORRECT]
Learning | 2026/2027 Edition.
Instructions: This is a closed-book examination. Select the best answer for each question.
Total questions: 28.
DOMAIN 1: MICROSCOPIC ANATOMY & MUSCLE TISSUE TYPES (10 Questions)
Sub-Topic: Skeletal Muscle Fiber Organization (3 Questions)
Question 1 (Multiple-Choice)
Which of the following correctly lists the structural hierarchy of skeletal muscle from largest
to smallest?
A) Myofibril → Muscle fiber → Fascicle → Sarcomere
B) Fascicle → Muscle fiber → Myofibril → Sarcomere
C) Muscle fiber → Fascicle → Myofibril → Sarcomere
D) Sarcomere → Myofibril → Muscle fiber → Fascicle
Answer: B) Fascicle → Muscle fiber → Myofibril → Sarcomere [CORRECT]
Rationale: A fascicle is a bundle of muscle fibers (muscle cells) wrapped in perimysium. Each
muscle fiber contains multiple myofibrils, which are long cylindrical organelles composed of
repeating contractile units called sarcomeres. This hierarchical organization—fascicle → fiber
→ myofibril → sarcomere—is fundamental to understanding how the whole muscle generates
force through the coordinated contraction of millions of sarcomeres.
Question 2 (Fill-in-Blank)
A skeletal muscle fiber is a single muscle cell that is multinucleated and contains hundreds to
thousands of thread-like contractile organelles called ______________.
Answer: myofibrils [CORRECT]
Rationale: Myofibrils are the contractile organelles within a skeletal muscle fiber. Each
myofibril is composed of repeating sarcomeres arranged in series and is responsible for the
striated appearance of skeletal muscle. The myofibrils run parallel to the long axis of the
muscle fiber and are composed primarily of the contractile proteins actin (thin filaments) and
myosin (thick filaments).
Question 3 (True/False)
,A single skeletal muscle fiber contains multiple nuclei located at the periphery of the cell, just
beneath the sarcolemma.
Answer: TRUE [CORRECT]
Rationale: Skeletal muscle fibers are multinucleated syncytial cells formed by the fusion of
multiple myoblasts during development. The nuclei are pushed to the periphery of the fiber
by the densely packed myofibrils in the central cytoplasm (sarcoplasm). This peripheral
positioning of nuclei is a distinguishing histological feature of skeletal muscle tissue.
Sub-Topic: Sarcomere Structure (4 Questions)
Question 4 (Multiple-Choice)
During muscle contraction, which band of the sarcomere shortens while the thick myosin
filaments themselves do not change length?
A) A-band
B) H-zone
C) I-band
D) M-line
Answer: C) I-band [CORRECT]
Rationale: The I-band (isotropic band) contains only thin actin filaments and appears light
under a microscope. During contraction, the actin filaments slide inward toward the M-line,
causing the I-band to shorten. The A-band, which contains the full length of the thick myosin
filaments, remains constant in width because the myosin filaments do not shorten during
contraction. The H-zone also shortens as actin filaments overlap more extensively with
myosin.
Question 5 (Labeling / Fill-in-Blank)
Identify the labeled structures on the sarcomere diagram below:
plain
Copy
[Z-disc] ----[I-band]---- [A-band] ----[I-band]---- [Z-disc]
[H-zone]
|
, [M-line]
A) The dark band that contains the entire length of thick myosin filaments: ______________
B) The central region of the A-band that contains only thick filaments (no thin filaments):
______________
C) The protein disc that anchors the thin actin filaments and marks the boundary of each
sarcomere: ______________
D) The line in the center of the H-zone that anchors thick myosin filaments: ______________
Answers:
A) A-band [CORRECT]
B) H-zone [CORRECT]
C) Z-disc [CORRECT]
D) M-line [CORRECT]
Rationale: The sarcomere is the fundamental contractile unit of striated muscle, extending
from one Z-disc to the next. The A-band is the dark-staining region containing the full length
of thick myosin filaments. The H-zone is the lighter central region of the A-band that contains
only thick filaments when the muscle is at rest; it disappears during full contraction as thin
filaments slide inward. The Z-disc (Z-line) is a dense protein disc composed primarily of α-
actinin that anchors the plus ends of actin filaments and defines the lateral boundaries of
each sarcomere. The M-line is a dark-staining line in the center of the H-zone that contains
myomesin and other proteins that stabilize and anchor the thick myosin filaments.
Question 6 (Multiple-Choice)
A student is examining a sarcomere under a microscope and observes a region that appears
dark (anisotropic) and spans the entire length of the thick myosin filaments. This region is the:
A) I-band
B) A-band
C) Z-disc
D) H-zone
Answer: B) A-band [CORRECT]
