PHGY 215 Module 4 Exam 2026
Questions and Answers
Which type of neurotransmitter when innervates the muscle at the neuromuscular
junction? - Correct answer-acetylcholine
Skeletal muscle is ________ and under _________ control - Correct answer-
striated, voluntary
Muscle Fibre - Correct answer-The muscle fibres run parallel to each other and are
surrounded by connective tissues. A muscle fibre is actually a single muscle cell.
These cells are multinucleated and have a very large number of mitochondria.
Myofibrils - Correct answer-Along the length of a muscle fibre, the cell is divided
into discrete contractile elements called myofibrils. They display a pattern of light
and dark bands, which we call I bands and A bands, respectively
A band - Correct answer-The A bands, also called the dark bands, are made up of
stacked thick and thin filaments that are aligned parallel to each other and its
borders are defined by the length of the thick filaments. The middle of the A band
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,is slightly lighter as the thin filaments do not reach this far from the ends. This
lighter portion is also called the H zone. *remember* the word 'dark' has an A in it
I band - Correct answer-The I bands, also called the light bands, are made up of the
portion of the thin filaments that do not extend into the A band. In the middle of the
I band is a vertical line called the Z line. *remember* the word 'light' has an I in it
H zone - Correct answer-The slightly lighter portion of the A band is called the H
zone. It only contains proteins that hold the thick filaments, myosin, together in a
stack. Myosin is composed of 2 heavy chains and 2 light chains. The H zone only
contains the heavy chains. These proteins are seen as the M line running down the
centre of the H zone. *remember* M line is middle of sarcomere, letter M is in the
middle of the alphabet
M line - Correct answer-The proteins that hold the thick filaments together in a
stack are seen as the M line. The M line runs down the centre of the H zone.
*remember* H is a thick letter, H zone has this filaments.
Z line - Correct answer-In the middle of the I band is a vertical line called the Z
line. The distance from one Z line to the next Z line is called a sarcomere and is
what we consider to be the functional unit of skeletal muscle. *remember* Z line
defines end of sarcomere....z is end of the alphabet
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, The sarcomere - Correct answer-When relaxed, a sarcomere is about 2.5 μ m in
width. When muscles are growing, they extend the length of the muscle fibre by
adding new sarcomeres onto the ends. The area in the A band where the thick and
thin filaments overlap contains cross-bridges, that extend from the thick filaments
and form when thin filaments bind
What are cross-bridges? - Correct answer-cross-bridges are the connection formed
when mobile myosin heads bind to actin molecules in muscles
The thick filament is composed of the protein _________. This is a motor protein,
in that it uses ____ to move along actin filaments. Each molecule of myosin is a
dimer of____ subunits. Each subunit looks like a golf club, in that it has a long
shaft with a globular head.
When the dimers come together, the "shaft" or tail portions wrap around each
other. 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, an _______ site, and a ______ site. - Correct answer-
myosin, ATP, 2, actin binding, myosin ATPase
The thin filament is made up of the proteins _____, ______ and _______. The
main structural component is two _______. - Correct answer-actin, tropomyosin,
troponin, actin filaments
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Questions and Answers
Which type of neurotransmitter when innervates the muscle at the neuromuscular
junction? - Correct answer-acetylcholine
Skeletal muscle is ________ and under _________ control - Correct answer-
striated, voluntary
Muscle Fibre - Correct answer-The muscle fibres run parallel to each other and are
surrounded by connective tissues. A muscle fibre is actually a single muscle cell.
These cells are multinucleated and have a very large number of mitochondria.
Myofibrils - Correct answer-Along the length of a muscle fibre, the cell is divided
into discrete contractile elements called myofibrils. They display a pattern of light
and dark bands, which we call I bands and A bands, respectively
A band - Correct answer-The A bands, also called the dark bands, are made up of
stacked thick and thin filaments that are aligned parallel to each other and its
borders are defined by the length of the thick filaments. The middle of the A band
©COPYRIGHT 2025, ALL RIGHTS RESERVED 1
,is slightly lighter as the thin filaments do not reach this far from the ends. This
lighter portion is also called the H zone. *remember* the word 'dark' has an A in it
I band - Correct answer-The I bands, also called the light bands, are made up of the
portion of the thin filaments that do not extend into the A band. In the middle of the
I band is a vertical line called the Z line. *remember* the word 'light' has an I in it
H zone - Correct answer-The slightly lighter portion of the A band is called the H
zone. It only contains proteins that hold the thick filaments, myosin, together in a
stack. Myosin is composed of 2 heavy chains and 2 light chains. The H zone only
contains the heavy chains. These proteins are seen as the M line running down the
centre of the H zone. *remember* M line is middle of sarcomere, letter M is in the
middle of the alphabet
M line - Correct answer-The proteins that hold the thick filaments together in a
stack are seen as the M line. The M line runs down the centre of the H zone.
*remember* H is a thick letter, H zone has this filaments.
Z line - Correct answer-In the middle of the I band is a vertical line called the Z
line. The distance from one Z line to the next Z line is called a sarcomere and is
what we consider to be the functional unit of skeletal muscle. *remember* Z line
defines end of sarcomere....z is end of the alphabet
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, The sarcomere - Correct answer-When relaxed, a sarcomere is about 2.5 μ m in
width. When muscles are growing, they extend the length of the muscle fibre by
adding new sarcomeres onto the ends. The area in the A band where the thick and
thin filaments overlap contains cross-bridges, that extend from the thick filaments
and form when thin filaments bind
What are cross-bridges? - Correct answer-cross-bridges are the connection formed
when mobile myosin heads bind to actin molecules in muscles
The thick filament is composed of the protein _________. This is a motor protein,
in that it uses ____ to move along actin filaments. Each molecule of myosin is a
dimer of____ subunits. Each subunit looks like a golf club, in that it has a long
shaft with a globular head.
When the dimers come together, the "shaft" or tail portions wrap around each
other. 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, an _______ site, and a ______ site. - Correct answer-
myosin, ATP, 2, actin binding, myosin ATPase
The thin filament is made up of the proteins _____, ______ and _______. The
main structural component is two _______. - Correct answer-actin, tropomyosin,
troponin, actin filaments
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