PHGY 215 Module 4 Study Guide Exam
Fully Solved 2026 Updated.
Which neurotransmitter innervates the muscle at the neuromuscular junction? - Answer ACh
A whole skeletal muscle is made up of individual _________ _________, each of which runs the
entire length of the muscle. - Answer muscle fibers
Muscles fibers run parallel to each other and are surrounded by what? - Answer connective
tissue
TRUE OR FALSE: a muscle fibre is actually a single muscle cell - Answer True
TRUE OR FALSE: muscle cells are multinucleated and have a very large number of
mitochrondria. - Answer True
Along the length of a muscle fibre, the cell is divided into discrete contractile elements called...?
- Answer myofibrils
Looking at a cross section of a ___________ you can see a highly organized cytoskeletal patter
of ______ and _____ filaments, which are myosin and actin, respectively. - Answer myofibril,
thick and thin
What bands (that are also called dark bands) are made up of stacked thick and thin filaments
that are aligned parallel to each other. Its borders are defined by the length of the thick
filaments. - Answer A band
The middle of the A band is slightly lighter because the thin filaments do not reach this far from
the ends. What is this lighter portion also called? - Answer H zone
What bands (also called light bands) are made up of the portion of thin filaments that do not
extend into the A band? - Answer I band
What is found in the middle of the I band? - Answer a vertical line called the Z line
Myosin is composed of 2 heavy chains and 2 light chains. The H zone only contains the _______
chains. - Answer heavy
,What does the H zone contain? - Answer the M line that contains proteins that hold thick
filaments (myosin) in a stack
The proteins that hold the thick filaments together in a stack are seen as the ____ line. - Answer
M line
The ____ line runs down the centre of the H zone. - Answer M line
The distance from one ____ line to the next is called a sarcomere. - Answer Z line
What is considered the functional unit of skeletal muscle? - Answer a sarcomere
When muscles are growing, they extend the length of the muscle fibre by adding new
______________ onto the ends. - Answer sarcomeres
When relaxed, a sarcomere is about how many micrometres? - Answer 2.5
The area in the A band where the thick and thin filaments overlap contains ________________,
that extend from the thick filaments and form when thin filaments bind. - Answer cross-
bridges
Myosin is a _________ protein, in that it uses ATP to move along actin filaments. - Answer
motor
TRUE OR FALSE: each molecule of myosin is a dimer of two subunits. - Answer True
TRUE OR FALSE: each subunit of actin looks like a golf club, in that it has a long shaft with a
globular head. - Answer False, each subunit of MYOSIN looks like a golf club.
TRUE OR FALSE: within a thick filament, two dimers come together in a tail-to-tail formation and
then these stack up with other myosin molecules. the heads stick out and contain two
important sites which are...? - Answer -actin binding site
-myosin ATPase site
What 3 things make up the thin filament? - Answer actin, tropomyosin, and toponin
Actin filaments are made up of individual spherical actin molecules that come together to form
a ________ __________ structure. - Answer double helix
, What is a regulatory protein that covers the active binding sites, preventing the interaction of
actin and myosin? - Answer Tropomyosin
What is a thin, double helix protein that lies end to end along the actin helix structure? - Answer
Tropomyosin
What is a regulatory protein complex made of three polypeptides. Where do the three
polypeptides bind? - Answer -troponin
-one binds to tropomyosin, one binds to actin, one binds to Ca2+
Cross-bridge formation forms the basis of the sliding filament mechanism which brings about...?
- Answer muscular contraction
Sarcomere goes from z-line to z-line & has __________ in the middle with ________ on the
sides. - Answer myosin, actin
During contraction, the thin filaments move inwards over the thick filaments. When this
happens, the _________ move closer together. This occurs simultaneously along the fibre & all
_____________ shorten to the same degree. - Answer z-lines, sarcomeres
What is a concentric contraction? - Answer the whole muscle shortens
What does the power stroke refer to? - Answer the interaction btwn myosin & actin that leads
to a shortening of the sarcomere
What are the four steps of the power stroke? - Answer Binding
-myosin cross-bridge binds to actin molecule
Power stroke
-the myosin head bends, pulling thin myofilament inward
Detachment
-cross-bridge detaches at end of power stroke & returns to original conformation
Binding
-cross-bridge binds to more distal actin molecule; cycle repeats
Fully Solved 2026 Updated.
Which neurotransmitter innervates the muscle at the neuromuscular junction? - Answer ACh
A whole skeletal muscle is made up of individual _________ _________, each of which runs the
entire length of the muscle. - Answer muscle fibers
Muscles fibers run parallel to each other and are surrounded by what? - Answer connective
tissue
TRUE OR FALSE: a muscle fibre is actually a single muscle cell - Answer True
TRUE OR FALSE: muscle cells are multinucleated and have a very large number of
mitochrondria. - Answer True
Along the length of a muscle fibre, the cell is divided into discrete contractile elements called...?
- Answer myofibrils
Looking at a cross section of a ___________ you can see a highly organized cytoskeletal patter
of ______ and _____ filaments, which are myosin and actin, respectively. - Answer myofibril,
thick and thin
What bands (that are also called dark bands) are made up of stacked thick and thin filaments
that are aligned parallel to each other. Its borders are defined by the length of the thick
filaments. - Answer A band
The middle of the A band is slightly lighter because the thin filaments do not reach this far from
the ends. What is this lighter portion also called? - Answer H zone
What bands (also called light bands) are made up of the portion of thin filaments that do not
extend into the A band? - Answer I band
What is found in the middle of the I band? - Answer a vertical line called the Z line
Myosin is composed of 2 heavy chains and 2 light chains. The H zone only contains the _______
chains. - Answer heavy
,What does the H zone contain? - Answer the M line that contains proteins that hold thick
filaments (myosin) in a stack
The proteins that hold the thick filaments together in a stack are seen as the ____ line. - Answer
M line
The ____ line runs down the centre of the H zone. - Answer M line
The distance from one ____ line to the next is called a sarcomere. - Answer Z line
What is considered the functional unit of skeletal muscle? - Answer a sarcomere
When muscles are growing, they extend the length of the muscle fibre by adding new
______________ onto the ends. - Answer sarcomeres
When relaxed, a sarcomere is about how many micrometres? - Answer 2.5
The area in the A band where the thick and thin filaments overlap contains ________________,
that extend from the thick filaments and form when thin filaments bind. - Answer cross-
bridges
Myosin is a _________ protein, in that it uses ATP to move along actin filaments. - Answer
motor
TRUE OR FALSE: each molecule of myosin is a dimer of two subunits. - Answer True
TRUE OR FALSE: each subunit of actin looks like a golf club, in that it has a long shaft with a
globular head. - Answer False, each subunit of MYOSIN looks like a golf club.
TRUE OR FALSE: within a thick filament, two dimers come together in a tail-to-tail formation and
then these stack up with other myosin molecules. the heads stick out and contain two
important sites which are...? - Answer -actin binding site
-myosin ATPase site
What 3 things make up the thin filament? - Answer actin, tropomyosin, and toponin
Actin filaments are made up of individual spherical actin molecules that come together to form
a ________ __________ structure. - Answer double helix
, What is a regulatory protein that covers the active binding sites, preventing the interaction of
actin and myosin? - Answer Tropomyosin
What is a thin, double helix protein that lies end to end along the actin helix structure? - Answer
Tropomyosin
What is a regulatory protein complex made of three polypeptides. Where do the three
polypeptides bind? - Answer -troponin
-one binds to tropomyosin, one binds to actin, one binds to Ca2+
Cross-bridge formation forms the basis of the sliding filament mechanism which brings about...?
- Answer muscular contraction
Sarcomere goes from z-line to z-line & has __________ in the middle with ________ on the
sides. - Answer myosin, actin
During contraction, the thin filaments move inwards over the thick filaments. When this
happens, the _________ move closer together. This occurs simultaneously along the fibre & all
_____________ shorten to the same degree. - Answer z-lines, sarcomeres
What is a concentric contraction? - Answer the whole muscle shortens
What does the power stroke refer to? - Answer the interaction btwn myosin & actin that leads
to a shortening of the sarcomere
What are the four steps of the power stroke? - Answer Binding
-myosin cross-bridge binds to actin molecule
Power stroke
-the myosin head bends, pulling thin myofilament inward
Detachment
-cross-bridge detaches at end of power stroke & returns to original conformation
Binding
-cross-bridge binds to more distal actin molecule; cycle repeats
