BIOL 251 Exam #2 Review Ultimate Study Guide
(Updated 2025–2026)
Muscles make up how much of your weight? - correct answer -about 1/2
What are the three types of muscles? - correct answer -skeletal, smooth, cardiac
Muscles are specialized to convert ____ energy to ____ energy. - correct answer -chemical,
mechanical
How many skeletal muscles are in the human body? - correct answer -more than 600
Skeletal muscle includes: - correct answer -skeletal muscle tissue, connective tissues, nerves
and blood vessels
Skeletal muscles do not contract until what occurs? - correct answer -They are stimulated by a
nerve to do so. This is different from cardiac and smooth muscle.
Skeletal muscle cells are also called - correct answer -muscle fibers
What are the connective tissues of muscles? - correct answer -endomysium, perimysium,
epimysium, fascia
Endomysium - correct answer -Thin sleeve that surrounds each muscle fiber, creates room for
capillaries and nerve fibers to reach every muscle cell.
Perimysium - correct answer -Sheath that bundles muscle fibers into units called fascicles.
Larger blood vessels, nerves, and stretch receptors will be found within this sheath.
,Epimysium - correct answer -Fibrous sheath that surrounds the entire muscle and bundles
multiple fascicles together.
Fascia - correct answer -Sheet of connective tissue outside of the epimysium that separates
muscles from one another.
What is direct vs indirect attachment? - correct answer -Direct: looks like directly attached, but
is not, short connection of collagen fibers.
Indirect: attaches by tendon, obvious band.
What are the characteristics of muscle? - correct answer -excitability: muscle cells can become
excited electrically
conductivity: electrical signals will travel along the cell
contractility: muscle cells and shorten when stimulated
extensibility: muscle cells can stretch between contractions
elasticity: when a muscle cell is stretched and then released, it recoils to a shorter length.
Is skeletal muscle voluntary or involuntary? - correct answer -voluntary
Why are there striations in muscle fibers (skeletal muscle)? - correct answer -Due to the
overlapping arrangement of contractile proteins.
Structure of skeletal muscle fibers - correct answer -Sarcolemma: plasma membrane with T
tubules (infoldings).
Sarcoplasm: cytoplasm. Made of long proteins called myofibrils/myofilaments. Myoglobin,
glycogen strorage.
, Sarcoplasmic reticulum: smooth endoplasmic reticulum, surround each myofibril. High amounts
of calcium, which is important for contraction, are stored there.
Sacrolemma - correct answer -Plasma membrane of a muscle fiber that forms T tubules
(tubular infoldings).
Sarcoplasm - correct answer -Cytoplasm of a muscle cell. Made of long proteins called
myofibrils. Contains a large amount of glycogen as well as myoglobin (an oxygen binding
protein).
Sarcoplasmic reticulum - correct answer -Smooth endoplasmic reticulum, surround each
myofibril. High amounts of calcium, which is important for contraction, are stored there.
What are the three kinds of myofilaments? - correct answer -thick, thin, elastic
What is the structure of thin, thick, and elastic myofilaments? - correct answer -Thick: consists
of many molecules of protein myosin
Thin: is made of two intertwined strands of actin. Each bead of the actin has an active site that
can bind to the head of a myosin molecule. Also includes the protein tropomyosin, which covers
these active sites at rest. Each tropomyosin has troponin bound to it.
Elastic: composed of titin, anchors the ends of thick filaments to the Z line.
Overall structure of striations and sarcomere - correct answer -~ Striated muscle has dark A
bands (thick filaments side by side, part of the A band is where thick and thin filaments overlap)
alternating with lighter I bands
~ In the middle of an A band, there is a H band, where thin filaments do not reach
~ In the middle of the H band, the M line links thick filaments together
~ I bands have thin filaments, not thick filaments. Each I band is bisected by the Z line, which
provides anchorage for thin and elastic filaments
(Updated 2025–2026)
Muscles make up how much of your weight? - correct answer -about 1/2
What are the three types of muscles? - correct answer -skeletal, smooth, cardiac
Muscles are specialized to convert ____ energy to ____ energy. - correct answer -chemical,
mechanical
How many skeletal muscles are in the human body? - correct answer -more than 600
Skeletal muscle includes: - correct answer -skeletal muscle tissue, connective tissues, nerves
and blood vessels
Skeletal muscles do not contract until what occurs? - correct answer -They are stimulated by a
nerve to do so. This is different from cardiac and smooth muscle.
Skeletal muscle cells are also called - correct answer -muscle fibers
What are the connective tissues of muscles? - correct answer -endomysium, perimysium,
epimysium, fascia
Endomysium - correct answer -Thin sleeve that surrounds each muscle fiber, creates room for
capillaries and nerve fibers to reach every muscle cell.
Perimysium - correct answer -Sheath that bundles muscle fibers into units called fascicles.
Larger blood vessels, nerves, and stretch receptors will be found within this sheath.
,Epimysium - correct answer -Fibrous sheath that surrounds the entire muscle and bundles
multiple fascicles together.
Fascia - correct answer -Sheet of connective tissue outside of the epimysium that separates
muscles from one another.
What is direct vs indirect attachment? - correct answer -Direct: looks like directly attached, but
is not, short connection of collagen fibers.
Indirect: attaches by tendon, obvious band.
What are the characteristics of muscle? - correct answer -excitability: muscle cells can become
excited electrically
conductivity: electrical signals will travel along the cell
contractility: muscle cells and shorten when stimulated
extensibility: muscle cells can stretch between contractions
elasticity: when a muscle cell is stretched and then released, it recoils to a shorter length.
Is skeletal muscle voluntary or involuntary? - correct answer -voluntary
Why are there striations in muscle fibers (skeletal muscle)? - correct answer -Due to the
overlapping arrangement of contractile proteins.
Structure of skeletal muscle fibers - correct answer -Sarcolemma: plasma membrane with T
tubules (infoldings).
Sarcoplasm: cytoplasm. Made of long proteins called myofibrils/myofilaments. Myoglobin,
glycogen strorage.
, Sarcoplasmic reticulum: smooth endoplasmic reticulum, surround each myofibril. High amounts
of calcium, which is important for contraction, are stored there.
Sacrolemma - correct answer -Plasma membrane of a muscle fiber that forms T tubules
(tubular infoldings).
Sarcoplasm - correct answer -Cytoplasm of a muscle cell. Made of long proteins called
myofibrils. Contains a large amount of glycogen as well as myoglobin (an oxygen binding
protein).
Sarcoplasmic reticulum - correct answer -Smooth endoplasmic reticulum, surround each
myofibril. High amounts of calcium, which is important for contraction, are stored there.
What are the three kinds of myofilaments? - correct answer -thick, thin, elastic
What is the structure of thin, thick, and elastic myofilaments? - correct answer -Thick: consists
of many molecules of protein myosin
Thin: is made of two intertwined strands of actin. Each bead of the actin has an active site that
can bind to the head of a myosin molecule. Also includes the protein tropomyosin, which covers
these active sites at rest. Each tropomyosin has troponin bound to it.
Elastic: composed of titin, anchors the ends of thick filaments to the Z line.
Overall structure of striations and sarcomere - correct answer -~ Striated muscle has dark A
bands (thick filaments side by side, part of the A band is where thick and thin filaments overlap)
alternating with lighter I bands
~ In the middle of an A band, there is a H band, where thin filaments do not reach
~ In the middle of the H band, the M line links thick filaments together
~ I bands have thin filaments, not thick filaments. Each I band is bisected by the Z line, which
provides anchorage for thin and elastic filaments
