BIOL 251 Anatomy & Physiology I – Exam 3 Review (Chapters 9
& 10): 120 Questions & Correct Answers with Rationales
Comprehensive Exam Q&A Bundle: Operating Systems (180
Qs) + BIOL 251 A&P I Exam 3 (120 Qs) – 2026 Edition
Chapter 9 – Muscular System: Histology and Physiology
Muscle Tissue Overview (Q1–Q10)
1. Which of the following is NOT a primary function of skeletal muscle?
A) Body movement
B) Maintaining posture
C) Generating heat
D) Pumping blood
E) Stabilizing joints
☑ Corect Answer: D) Pumping blood
Rationale: Pumping blood is the function of cardiac muscle (myocardium), not
skeletal muscle. Skeletal muscle is responsible for voluntary movement, posture
maintenance, joint stabilization, and thermogenesis (heat production via
shivering).
2. Which term describes the ability of muscle tissue to respond to a stimulus by
generating an electrical signal?
A) Contractility
B) Excitability
,C) Extensibility
D) Elasticity
☑ Corect Answer: B) Excitability
Rationale: Excitability (also called responsiveness) is the ability to receive and
respond to a stimulus (usually a neurotransmitter or hormone). Contractility is the
ability to shorten forcefully; extensibility is the ability to stretch; elasticity is the
ability to recoil after stretching.
3. Which type of muscle tissue is non-striated, has a single nucleus per cell, and
is under involuntary control?
A) Skeletal muscle
B) Cardiac muscle
C) Smooth muscle
D) Both B and C
☑ Corect Answer: C) Smooth muscle
Rationale: Smooth muscle lacks striations, has a single, centrally located nucleus,
and is controlled involuntarily. It is found in the walls of hollow organs (e.g.,
stomach, bladder, blood vessels). Cardiac muscle is striated and branched with
intercalated discs; skeletal muscle is striated and multinucleated.
4. The sarcolemma is the:
A) Contractile protein in muscle fibers
,B) Cytoplasm of a muscle cell
C) Plasma membrane of a muscle cell
D) Endoplasmic reticulum of a muscle cell
☑ Corect Answer: C) Plasma membrane of a muscle cell
Rationale: The sarcolemma is the specialized cell membrane of a muscle fiber
(myocyte). It conducts action potentials and is surrounded by the endomysium.
The sarcoplasm is the cytoplasm; the sarcoplasmic reticulum stores calcium.
5. Which structure stores calcium ions within a resting skeletal muscle fiber?
A) Sarcolemma
B) T-tubule
C) Sarcoplasmic reticulum (SR)
D) Myofibril
☑ Corect Answer: C) Sarcoplasmic reticulum (SR)
Rationale: The SR is a specialized smooth ER that sequesters Ca²⁺ via active
transport (Ca²⁺ ATPase). Upon excitation, Ca²⁺ is released into the sarcoplasm to
initiate contraction.
6. The functional unit of skeletal muscle contraction is the:
A) Myofibril
B) Sarcomere
, C) Myofilament
D) Motor unit
☑ Corect Answer: B) Sarcomere
Rationale: The sarcomere is the repeating unit between Z-discs that contains the
overlapping thin (actin) and thick (myosin) filaments. Its shortening during the
sliding filament theory produces muscle contraction.
7. Which of the following is the correct order of organizational hierarchy from
largest to smallest?
A) Muscle → fascicle → myofibril → muscle fiber (cell) → myofilament
B) Muscle → muscle fiber → fascicle → myofibril → myofilament
C) Muscle → fascicle → muscle fiber → myofibril → myofilament
D) Muscle → myofibril → fascicle → muscle fiber → myofilament
☑ Corect Answer: C) Muscle → fascicle → muscle fiber → myofibril →
myofilament
Rationale: A whole muscle is composed of fascicles (bundles of fibers). Each
fascicle contains many muscle fibers (cells). Each muscle fiber contains many
myofibrils, and myofibrils are made of myofilaments (actin and myosin).
8. The thin myofilament is primarily composed of:
A) Myosin
B) Actin
& 10): 120 Questions & Correct Answers with Rationales
Comprehensive Exam Q&A Bundle: Operating Systems (180
Qs) + BIOL 251 A&P I Exam 3 (120 Qs) – 2026 Edition
Chapter 9 – Muscular System: Histology and Physiology
Muscle Tissue Overview (Q1–Q10)
1. Which of the following is NOT a primary function of skeletal muscle?
A) Body movement
B) Maintaining posture
C) Generating heat
D) Pumping blood
E) Stabilizing joints
☑ Corect Answer: D) Pumping blood
Rationale: Pumping blood is the function of cardiac muscle (myocardium), not
skeletal muscle. Skeletal muscle is responsible for voluntary movement, posture
maintenance, joint stabilization, and thermogenesis (heat production via
shivering).
2. Which term describes the ability of muscle tissue to respond to a stimulus by
generating an electrical signal?
A) Contractility
B) Excitability
,C) Extensibility
D) Elasticity
☑ Corect Answer: B) Excitability
Rationale: Excitability (also called responsiveness) is the ability to receive and
respond to a stimulus (usually a neurotransmitter or hormone). Contractility is the
ability to shorten forcefully; extensibility is the ability to stretch; elasticity is the
ability to recoil after stretching.
3. Which type of muscle tissue is non-striated, has a single nucleus per cell, and
is under involuntary control?
A) Skeletal muscle
B) Cardiac muscle
C) Smooth muscle
D) Both B and C
☑ Corect Answer: C) Smooth muscle
Rationale: Smooth muscle lacks striations, has a single, centrally located nucleus,
and is controlled involuntarily. It is found in the walls of hollow organs (e.g.,
stomach, bladder, blood vessels). Cardiac muscle is striated and branched with
intercalated discs; skeletal muscle is striated and multinucleated.
4. The sarcolemma is the:
A) Contractile protein in muscle fibers
,B) Cytoplasm of a muscle cell
C) Plasma membrane of a muscle cell
D) Endoplasmic reticulum of a muscle cell
☑ Corect Answer: C) Plasma membrane of a muscle cell
Rationale: The sarcolemma is the specialized cell membrane of a muscle fiber
(myocyte). It conducts action potentials and is surrounded by the endomysium.
The sarcoplasm is the cytoplasm; the sarcoplasmic reticulum stores calcium.
5. Which structure stores calcium ions within a resting skeletal muscle fiber?
A) Sarcolemma
B) T-tubule
C) Sarcoplasmic reticulum (SR)
D) Myofibril
☑ Corect Answer: C) Sarcoplasmic reticulum (SR)
Rationale: The SR is a specialized smooth ER that sequesters Ca²⁺ via active
transport (Ca²⁺ ATPase). Upon excitation, Ca²⁺ is released into the sarcoplasm to
initiate contraction.
6. The functional unit of skeletal muscle contraction is the:
A) Myofibril
B) Sarcomere
, C) Myofilament
D) Motor unit
☑ Corect Answer: B) Sarcomere
Rationale: The sarcomere is the repeating unit between Z-discs that contains the
overlapping thin (actin) and thick (myosin) filaments. Its shortening during the
sliding filament theory produces muscle contraction.
7. Which of the following is the correct order of organizational hierarchy from
largest to smallest?
A) Muscle → fascicle → myofibril → muscle fiber (cell) → myofilament
B) Muscle → muscle fiber → fascicle → myofibril → myofilament
C) Muscle → fascicle → muscle fiber → myofibril → myofilament
D) Muscle → myofibril → fascicle → muscle fiber → myofilament
☑ Corect Answer: C) Muscle → fascicle → muscle fiber → myofibril →
myofilament
Rationale: A whole muscle is composed of fascicles (bundles of fibers). Each
fascicle contains many muscle fibers (cells). Each muscle fiber contains many
myofibrils, and myofibrils are made of myofilaments (actin and myosin).
8. The thin myofilament is primarily composed of:
A) Myosin
B) Actin
