BIO105 Anatomy and Physiology 1 Exam 2 Version
2 Questions with Correct Answers and Expert
Explanation for Each Question
1. Which type of muscle tissue is characterized by being voluntary and striated?
A. Smooth muscle
B. Visceral muscle
C. Cardiac muscle
D. Skeletal muscle
Correct Answer: D
Expert Explanation: Skeletal muscle is the only muscle type that can be controlled
consciously by the somatic nervous system. Its striated appearance is due to the
organized arrangement of actin and myosin filaments within sarcomeres. These
muscles are primarily attached to the skeleton to facilitate movement and maintain
posture. Unlike cardiac or smooth muscle, skeletal muscle cells are multinucleated
and lack intercalated discs. Understanding this classification is foundational for
studying the physiology of human movement and performance.
2. What is the structural and functional unit of a skeletal muscle fiber?
A. Sarcolemma
B. Sarcomere
,C. Myofibril
D. Sarcoplasmic reticulum
Correct Answer: B
Expert Explanation: The sarcomere is defined as the region between two
consecutive Z-lines in a muscle fiber. It contains the contractile proteins actin and
myosin which slide past each other during contraction. This unit is responsible for
the striations observed in skeletal and cardiac muscle tissues under a microscope.
When a muscle contracts, the individual sarcomeres shorten in length, leading to
overall muscle shortening. Mastering the anatomy of the sarcomere is critical for
understanding the sliding filament theory of muscle contraction.
3. Which neurotransmitter is released at the neuromuscular junction to initiate a
muscle contraction?
A. Dopamine
B. Acetylcholine
C. Norepinephrine
D. Serotonin
Correct Answer: B
,Expert Explanation: Acetylcholine is the primary chemical messenger that bridges
the gap between a motor neuron and a muscle fiber. It is stored in synaptic vesicles
and released into the synaptic cleft upon the arrival of an action potential. Once
released, it binds to specific receptors on the motor end plate to trigger
depolarization. This depolarization eventually leads to the release of calcium ions
from the sarcoplasmic reticulum. The enzyme acetylcholinesterase quickly breaks it
down to ensure that muscle stimulation is not continuous.
4. In the sliding filament theory, which ions are necessary to uncover the binding sites
on actin?
A. Sodium ions
B. Calcium ions
C. Potassium ions
D. Magnesium ions
Correct Answer: B
Expert Explanation: Calcium ions play a pivotal role in the regulatory mechanism
of skeletal muscle contraction. When an action potential reaches the sarcoplasmic
reticulum, these ions are released into the sarcoplasm. Calcium binds to troponin,
which causes a conformational change in the tropomyosin molecule. This movement
uncovers the active sites on the actin filament so that myosin heads can attach.
, Without a sufficient concentration of calcium, the muscle remains in a relaxed state
because the cross-bridge cycle cannot begin.
5. What is the name of the connective tissue sheath that surrounds an entire
individual muscle?
A. Endomysium
B. Perimysium
C. Epimysium
D. Fascicle
Correct Answer: C
Expert Explanation: The epimysium is a layer of dense irregular connective tissue
that encases the whole muscle organ. It serves to protect the muscle from friction
against other muscles and bones during movement. Deep to this layer, the
perimysium organizes muscle fibers into groups called fascicles. This hierarchical
arrangement of connective tissue provides structural integrity and allows for the
transmission of force. These layers eventually converge to form tendons that anchor
the muscle to the periosteum of bones.
6. Which molecule provides a rapid source of high-energy phosphates to regenerate
ATP in a contracting muscle?
A. Glucose
2 Questions with Correct Answers and Expert
Explanation for Each Question
1. Which type of muscle tissue is characterized by being voluntary and striated?
A. Smooth muscle
B. Visceral muscle
C. Cardiac muscle
D. Skeletal muscle
Correct Answer: D
Expert Explanation: Skeletal muscle is the only muscle type that can be controlled
consciously by the somatic nervous system. Its striated appearance is due to the
organized arrangement of actin and myosin filaments within sarcomeres. These
muscles are primarily attached to the skeleton to facilitate movement and maintain
posture. Unlike cardiac or smooth muscle, skeletal muscle cells are multinucleated
and lack intercalated discs. Understanding this classification is foundational for
studying the physiology of human movement and performance.
2. What is the structural and functional unit of a skeletal muscle fiber?
A. Sarcolemma
B. Sarcomere
,C. Myofibril
D. Sarcoplasmic reticulum
Correct Answer: B
Expert Explanation: The sarcomere is defined as the region between two
consecutive Z-lines in a muscle fiber. It contains the contractile proteins actin and
myosin which slide past each other during contraction. This unit is responsible for
the striations observed in skeletal and cardiac muscle tissues under a microscope.
When a muscle contracts, the individual sarcomeres shorten in length, leading to
overall muscle shortening. Mastering the anatomy of the sarcomere is critical for
understanding the sliding filament theory of muscle contraction.
3. Which neurotransmitter is released at the neuromuscular junction to initiate a
muscle contraction?
A. Dopamine
B. Acetylcholine
C. Norepinephrine
D. Serotonin
Correct Answer: B
,Expert Explanation: Acetylcholine is the primary chemical messenger that bridges
the gap between a motor neuron and a muscle fiber. It is stored in synaptic vesicles
and released into the synaptic cleft upon the arrival of an action potential. Once
released, it binds to specific receptors on the motor end plate to trigger
depolarization. This depolarization eventually leads to the release of calcium ions
from the sarcoplasmic reticulum. The enzyme acetylcholinesterase quickly breaks it
down to ensure that muscle stimulation is not continuous.
4. In the sliding filament theory, which ions are necessary to uncover the binding sites
on actin?
A. Sodium ions
B. Calcium ions
C. Potassium ions
D. Magnesium ions
Correct Answer: B
Expert Explanation: Calcium ions play a pivotal role in the regulatory mechanism
of skeletal muscle contraction. When an action potential reaches the sarcoplasmic
reticulum, these ions are released into the sarcoplasm. Calcium binds to troponin,
which causes a conformational change in the tropomyosin molecule. This movement
uncovers the active sites on the actin filament so that myosin heads can attach.
, Without a sufficient concentration of calcium, the muscle remains in a relaxed state
because the cross-bridge cycle cannot begin.
5. What is the name of the connective tissue sheath that surrounds an entire
individual muscle?
A. Endomysium
B. Perimysium
C. Epimysium
D. Fascicle
Correct Answer: C
Expert Explanation: The epimysium is a layer of dense irregular connective tissue
that encases the whole muscle organ. It serves to protect the muscle from friction
against other muscles and bones during movement. Deep to this layer, the
perimysium organizes muscle fibers into groups called fascicles. This hierarchical
arrangement of connective tissue provides structural integrity and allows for the
transmission of force. These layers eventually converge to form tendons that anchor
the muscle to the periosteum of bones.
6. Which molecule provides a rapid source of high-energy phosphates to regenerate
ATP in a contracting muscle?
A. Glucose
