PSL 310 -Unit 3 Exam Practice
Questions and Answers Graded A+
2026 Updated.
What are the three different types of muscle found in the human body? - Answer Skeletal,
cardiac, and smooth muscle.
How do each differ from one another structurally and functionally? - Answer Skeletal muscle
is attached to the skeleton, it is striated, and it is under voluntary control. Cardiac muscle is the
muscle of the heart, it is striated, and it is under involuntary control. Smooth muscle is found in
places like the GI tract and the vasculature, it is not striated, and it is under involuntary control
What does the term striated refer to? - Answer Striations seen in muscle under a light
microscope are the "A" and "I" bands of the sarcomeres in myofibrils.
You are a teacher charged with explaining the structural organization of a muscle organ and the
connective tissues associated with it. You decide to start from the smallest level of organization
and work your way up, constructing the entire muscle organ. You take a single strand of red
licorice and wrap a clear piece of plastic wrap around. What does this layer of clear plastic wrap
represent? - Answer The layer of clear plastic wrap represents the endomysium.
You then make several more of these single strands of licorice wrapped with clear plastic wrap,
bundle them all together and then wrap the bundle with a layer of green plastic wrap. What
does this layer of green plastic wrap represent? - Answer The layer of green plastic wrap
represents the perimysium.
Finally, you make several more of these bundles of licorice wrapped by plastic wrap, bundle
them together and then wrap the entire bundle with a layer of white plastic wrap. What does
this layer of white plastic wrap represent? - Answer The layer of white plastic wrap
represents the epimysium.
What is the name of the connective tissue immediately parietal to sarcolemma? - Answer
The connective tissue immediately parietal to the sarcolemma is the endomysium
What type of cell makes endomysium? - Answer Fibroblasts
Can you identify some important things located in the endomysium? - Answer Terminal
knobs, capillaries, and satellite cells are located in this loose connective tissue.
How is a tendon related to muscle? - Answer The tendon attaches the muscle to the bone.
,What is the function of a tendon? - Answer Tendons help in transmitting the force from the
muscle to the load
How is a tendon formed? - Answer It is formed when the perimysium and epimysium
converge.
What is the name for a skeletal muscle stem cell? - Answer Myoblast
What germ layer is the skeletal muscle stem cell derived from? - Answer Mesoderm
Are skeletal muscle cells classified as a true syncytium? Why or why not? - Answer Yes,
because skeletal muscle fibers are formed by the fusion of several individual cells.
What is the resting membrane potential of a typical skeletal muscle cell? - Answer The resting
membrane potential of a typical skeletal muscle is -85 millivolts
Is it more or less polarized than a typical neuron? - Answer It is more polarized (i.e., more
negative) than a typical neuron.
What is a sarcolemma? - Answer A sarcolemma is the plasma membrane of a muscle cell.
What is a T-tubule? - Answer T-tubules are extensions of the sarcolemma.
If you were microscopic and inside of a T-tubule, where would you technically be? - Answer If
you were microscopic and inside of a T-tubule, you would technically be on the outside of the
cell, since a T-tubule is an extension of the sarcolemma.
What is the function of a T-tubule? - Answer The function of a T-tubule is to allow action
potentials to propagate as close to the inside of the cell as possible. This allows the sarcoplasmic
reticulum to release its calcium stores.
What is the function of a triad? - Answer The function of a triad is to turn the excitation of
the sarcolemma into the release of calcium from the sarcoplasmic reticulum
What is sarcoplasm? - Answer The cytoplasm of a muscle cell.
,Unlike a typical soma cell, what unique things are located in the sarcoplasm of a skeletal muscle
cell? - Answer Myofibrils, glycogen, and multiple nuclei are all located in the sarcoplasm of a
skeletal muscle cell
How would you describe a myofilament? - Answer Myofilaments are the protein fibers that
constitute a myofibril.
What are the two major types of myofilaments? - Answer The two major types of
myofilaments are thick and thin filaments.
What are the two major proteins that make up the two major types of filaments? - Answer
Thin filaments are primarily made of actin and thick filaments are made of myosin
What is a sarcomere? - Answer A sarcomere is the smallest structural and functional unit of a
myofibril in striated muscle.
What is a myofibril? - Answer A myofibril is a linear, repeating sequence of sarcomeres.
What is a myofiber? - Answer A myofiber is a skeletal muscle cell.
Which structure of a typical somatic cell is the sarcoplasmic reticulum most analogous to? -
Answer The sarcoplasmic reticulum is most analogous to the smooth endoplasmic reticulum.
What is the specialized function of the sarcoplasmic reticulum in skeletal muscle cells? - Answer
The function of sarcoplasmic reticulum is to store calcium in skeletal muscle.
What is the smooth endoplasmic reticulum ATPase, abbreviated as SERCA, where is it located,
and what is its function? - Answer SERCA is a calcium pump found in the sarcoplasmic
reticulum membrane. It is located in the longitudinal region. Its function is to transfer calcium
from the sarcoplasm to the interior of the sarcoplasmic reticulum.
What is calsequestrin (CSQ), where is it located, and what is its function? - Answer
Calsequestrin is a membrane-bound, calcium-binding protein found in the lateral sacs of the
sarcoplasmic reticulum. Its function is to hold calcium in high concentration in the sarcoplasmic
reticulum
What is the A band? What can you find there? - Answer The A band is the length of the thick
filaments. Myosin, actin, theM line, titin, and myomesin can be found in the A band.
, What is the I band? What can you find there? - Answer The I band is the distance between
thick filaments between two adjacent sarcomeres. Actin, actinin, titin, and the Z line can be
found in the I band.
What is the H zone? What can you find there? - Answer The H zone is the distance between
thin filaments in the center of the sarcomere. Myosin, myomesin, titin, and the M line can be
found in the H zone.
What is the zone of overlap? What can you find there? - Answer The zone of overlap is the
region of the sarcomere where actin and myosin overlap one another. Myosin, actin, and titin
can be found in the zone of overlap.
What is the M line? What can you find there? - Answer The M line is the point of attachment
of the thick filaments.
What is the Z line? What can you find there? - Answer The Z line is the point of attachment of
the thin filaments.
Why is an A band also referred to as a dark band? - Answer The A band is referred to as the
dark band because it contains thick and thin filaments, and therefore picks up a lot of stain.
Why is the zone of overlap arguably the most important region of a sarcomere? - Answer It is
the place where actin and myosin interact.
Why is an I band also referred to as a light band? - Answer The I band is referred to as the
light band because it contains only thin filaments and does not pick up as much stain as the A
band.
How many I bands are present in one sarcomere? - Answer There are zero I bands present in
one sarcomere.
What is the structural organization of actin? - Answer G-actin monomers dimerize and these
dimers assemble into two strings of intertwining beads referred to as F-actin.
What are the two regulatory proteins found within actin? - Answer Troponin and
tropomyosin.
What are their functions? - Answer Tropomyosin prevents the interactions between thin and
thick filaments by blocking the active sites on the G-actin monomers. Troponin is attached to
the protein tropomyosin and binds calcium. With bound calcium, troponin "pulls" tropomyosin
out of the way of the G-actin active sites permitting the myosin heads to bind to actin.
Questions and Answers Graded A+
2026 Updated.
What are the three different types of muscle found in the human body? - Answer Skeletal,
cardiac, and smooth muscle.
How do each differ from one another structurally and functionally? - Answer Skeletal muscle
is attached to the skeleton, it is striated, and it is under voluntary control. Cardiac muscle is the
muscle of the heart, it is striated, and it is under involuntary control. Smooth muscle is found in
places like the GI tract and the vasculature, it is not striated, and it is under involuntary control
What does the term striated refer to? - Answer Striations seen in muscle under a light
microscope are the "A" and "I" bands of the sarcomeres in myofibrils.
You are a teacher charged with explaining the structural organization of a muscle organ and the
connective tissues associated with it. You decide to start from the smallest level of organization
and work your way up, constructing the entire muscle organ. You take a single strand of red
licorice and wrap a clear piece of plastic wrap around. What does this layer of clear plastic wrap
represent? - Answer The layer of clear plastic wrap represents the endomysium.
You then make several more of these single strands of licorice wrapped with clear plastic wrap,
bundle them all together and then wrap the bundle with a layer of green plastic wrap. What
does this layer of green plastic wrap represent? - Answer The layer of green plastic wrap
represents the perimysium.
Finally, you make several more of these bundles of licorice wrapped by plastic wrap, bundle
them together and then wrap the entire bundle with a layer of white plastic wrap. What does
this layer of white plastic wrap represent? - Answer The layer of white plastic wrap
represents the epimysium.
What is the name of the connective tissue immediately parietal to sarcolemma? - Answer
The connective tissue immediately parietal to the sarcolemma is the endomysium
What type of cell makes endomysium? - Answer Fibroblasts
Can you identify some important things located in the endomysium? - Answer Terminal
knobs, capillaries, and satellite cells are located in this loose connective tissue.
How is a tendon related to muscle? - Answer The tendon attaches the muscle to the bone.
,What is the function of a tendon? - Answer Tendons help in transmitting the force from the
muscle to the load
How is a tendon formed? - Answer It is formed when the perimysium and epimysium
converge.
What is the name for a skeletal muscle stem cell? - Answer Myoblast
What germ layer is the skeletal muscle stem cell derived from? - Answer Mesoderm
Are skeletal muscle cells classified as a true syncytium? Why or why not? - Answer Yes,
because skeletal muscle fibers are formed by the fusion of several individual cells.
What is the resting membrane potential of a typical skeletal muscle cell? - Answer The resting
membrane potential of a typical skeletal muscle is -85 millivolts
Is it more or less polarized than a typical neuron? - Answer It is more polarized (i.e., more
negative) than a typical neuron.
What is a sarcolemma? - Answer A sarcolemma is the plasma membrane of a muscle cell.
What is a T-tubule? - Answer T-tubules are extensions of the sarcolemma.
If you were microscopic and inside of a T-tubule, where would you technically be? - Answer If
you were microscopic and inside of a T-tubule, you would technically be on the outside of the
cell, since a T-tubule is an extension of the sarcolemma.
What is the function of a T-tubule? - Answer The function of a T-tubule is to allow action
potentials to propagate as close to the inside of the cell as possible. This allows the sarcoplasmic
reticulum to release its calcium stores.
What is the function of a triad? - Answer The function of a triad is to turn the excitation of
the sarcolemma into the release of calcium from the sarcoplasmic reticulum
What is sarcoplasm? - Answer The cytoplasm of a muscle cell.
,Unlike a typical soma cell, what unique things are located in the sarcoplasm of a skeletal muscle
cell? - Answer Myofibrils, glycogen, and multiple nuclei are all located in the sarcoplasm of a
skeletal muscle cell
How would you describe a myofilament? - Answer Myofilaments are the protein fibers that
constitute a myofibril.
What are the two major types of myofilaments? - Answer The two major types of
myofilaments are thick and thin filaments.
What are the two major proteins that make up the two major types of filaments? - Answer
Thin filaments are primarily made of actin and thick filaments are made of myosin
What is a sarcomere? - Answer A sarcomere is the smallest structural and functional unit of a
myofibril in striated muscle.
What is a myofibril? - Answer A myofibril is a linear, repeating sequence of sarcomeres.
What is a myofiber? - Answer A myofiber is a skeletal muscle cell.
Which structure of a typical somatic cell is the sarcoplasmic reticulum most analogous to? -
Answer The sarcoplasmic reticulum is most analogous to the smooth endoplasmic reticulum.
What is the specialized function of the sarcoplasmic reticulum in skeletal muscle cells? - Answer
The function of sarcoplasmic reticulum is to store calcium in skeletal muscle.
What is the smooth endoplasmic reticulum ATPase, abbreviated as SERCA, where is it located,
and what is its function? - Answer SERCA is a calcium pump found in the sarcoplasmic
reticulum membrane. It is located in the longitudinal region. Its function is to transfer calcium
from the sarcoplasm to the interior of the sarcoplasmic reticulum.
What is calsequestrin (CSQ), where is it located, and what is its function? - Answer
Calsequestrin is a membrane-bound, calcium-binding protein found in the lateral sacs of the
sarcoplasmic reticulum. Its function is to hold calcium in high concentration in the sarcoplasmic
reticulum
What is the A band? What can you find there? - Answer The A band is the length of the thick
filaments. Myosin, actin, theM line, titin, and myomesin can be found in the A band.
, What is the I band? What can you find there? - Answer The I band is the distance between
thick filaments between two adjacent sarcomeres. Actin, actinin, titin, and the Z line can be
found in the I band.
What is the H zone? What can you find there? - Answer The H zone is the distance between
thin filaments in the center of the sarcomere. Myosin, myomesin, titin, and the M line can be
found in the H zone.
What is the zone of overlap? What can you find there? - Answer The zone of overlap is the
region of the sarcomere where actin and myosin overlap one another. Myosin, actin, and titin
can be found in the zone of overlap.
What is the M line? What can you find there? - Answer The M line is the point of attachment
of the thick filaments.
What is the Z line? What can you find there? - Answer The Z line is the point of attachment of
the thin filaments.
Why is an A band also referred to as a dark band? - Answer The A band is referred to as the
dark band because it contains thick and thin filaments, and therefore picks up a lot of stain.
Why is the zone of overlap arguably the most important region of a sarcomere? - Answer It is
the place where actin and myosin interact.
Why is an I band also referred to as a light band? - Answer The I band is referred to as the
light band because it contains only thin filaments and does not pick up as much stain as the A
band.
How many I bands are present in one sarcomere? - Answer There are zero I bands present in
one sarcomere.
What is the structural organization of actin? - Answer G-actin monomers dimerize and these
dimers assemble into two strings of intertwining beads referred to as F-actin.
What are the two regulatory proteins found within actin? - Answer Troponin and
tropomyosin.
What are their functions? - Answer Tropomyosin prevents the interactions between thin and
thick filaments by blocking the active sites on the G-actin monomers. Troponin is attached to
the protein tropomyosin and binds calcium. With bound calcium, troponin "pulls" tropomyosin
out of the way of the G-actin active sites permitting the myosin heads to bind to actin.
