Andrea Studivant - Unit 3: Muscle Assignment
1. Describe the organization of skeletal muscle at the tissue level.
Our bodies contain numerous skeletal muscle organs the muscles that
move and support our body are attached to bones at each end by what
we call tendons. These tendons are composed of connective tissue, which
not only attaches the bone to the muscle, but also wraps around inside
the muscle that separates the organ into smaller components. Inside
each skeletal muscle fibers are organized into individual bundles, called
a fascicle, by a middle layer of connective tissue called the perimysium.
This fascicular organization is common in muscles of the limbs; it allows
the nervous system to trigger a specific movement of a muscle by
triggering a subset of muscle fibers within a bundle, or fascicle of the
muscle. Inside each fascicle, each muscle fiber is encased in a thin
connective tissue layer of collagen and reticular fibers called
the endomysium. The endomysium contains the extracellular fluid and
nutrients to support the muscle fiber. These nutrients are supplied by
blood to the muscle tissue.
2. Describe and provide a function for muscle's associated connective
tissues.
Muscles have 3 layers of connective tissues
the epimysium-an exterior collagen layer connected to the deep
fascia which separates the muscle from surrounding tissues.
the perimysium- surrounds bundles of muscles fibers called
fascicles. Perimysium holds the blood vessels and nerves that
supply the fascicles.
the endomysium- surrounds individual muscle cells (the muscle
fibers), contains the capillaries and nerve fibers that link the muscle
cells. Endomysium also has stem cells that repair damaged
muscles.
At each end of the muscle, the endomysium, perimysium and epimysium
come together to form a connective tissue attachment to the bone
matrix, either a tendon (a bundle) or an aponeurosis (a sheet). Skeletal
muscles are voluntary muscles, operated by nerves from the central
nervous system. An extensive vascular system supplies large amounts of
oxygen to muscles and carries away wastes.
3. How is a muscle attached to the bone? Describe the structures and
their functions.
Muscle is attached to the bone by tendons. Skeletal muscles are attached
to the ends of bones that meet at a joint. These muscles span the joint
and connect the bones. When the muscles contract, they pull on the
bones, causing them to move.
.
4. Identify the structural components of a sarcomere.
, Sarcomeres (the contractile units of muscle) are structural units of
myofibrils that form the organization or pattern of thick (Myosin) and thin
(Actin) filaments within the myofibril. Sarcomeres in the skeletal muscles
appear striped or striated because of the arrangement of alternating dark,
thick filaments (A bands) and light, thin filaments (I band) within their
myofibrils. The center of the A band is the midline or M line of the
sarcomere. The centers of the I bands are Z lines. One sarcomere is
measured from one Z line to another. Thick filaments and thin filaments
overlap in the zone of overlap, which is the densest, darkest area on a
light micrograph. Around the M line are thick filaments but no thin
filaments this is called the H zone. Strands of protein (titin) reach from
the tips of the thick filaments to the Z line and stabilize the filaments.
5. Describe the structural components of a thin filament and a thick
filament.
The thin filaments (Actin) are approximately 7-9 nm in diameter. They
are attached to the Z discs of the striated muscle. Each thin filament is
made up of three proteins: (1) actin, (2) troponin, and (3) tropomyosin.
Actin - composed chiefly of actin proteins, within the filament, each
globular actin monomer (G-actin) contains a myosin binding site and is
associated with the regulatory proteins, troponin and tropomyosin.
Troponin - a globular protein comprised of three complex proteins
involved in muscle contraction and occurs at about every 40 nm along
the filament.
Tropomyosin - rod-shaped protein that is about 40 nm in length. Two
strands of tropomyosin molecules run along the helical actin filaments
and is associated with troponin. Troponin and tropomyosin run along
the actin filaments and control when the actin binding sites will be
exposed for binding to myosin.
Thick filaments (Myosin) are composed of myosin protein complexes,
which are composed of six proteins: two myosin heavy chains and four
light chain molecules.
Heavy chains consist of a tail region, flexible hinge region, and
globular head which contains an Actin-binding site and a binding site
for the high energy molecule ATP.
Light chains regulate the hinge region, but the heavy chain head
region interacts with actin and is the most important factor for
generating force.
6. What role does Calcium play in the activation of muscle contraction?
Calcium binds protein and triggers contraction by reaction with regulatory
proteins that, in the absence of calcium, prevent interaction of actin and
myosin.
7. What role doe Magnesium plain in overall muscle activity?
1. Describe the organization of skeletal muscle at the tissue level.
Our bodies contain numerous skeletal muscle organs the muscles that
move and support our body are attached to bones at each end by what
we call tendons. These tendons are composed of connective tissue, which
not only attaches the bone to the muscle, but also wraps around inside
the muscle that separates the organ into smaller components. Inside
each skeletal muscle fibers are organized into individual bundles, called
a fascicle, by a middle layer of connective tissue called the perimysium.
This fascicular organization is common in muscles of the limbs; it allows
the nervous system to trigger a specific movement of a muscle by
triggering a subset of muscle fibers within a bundle, or fascicle of the
muscle. Inside each fascicle, each muscle fiber is encased in a thin
connective tissue layer of collagen and reticular fibers called
the endomysium. The endomysium contains the extracellular fluid and
nutrients to support the muscle fiber. These nutrients are supplied by
blood to the muscle tissue.
2. Describe and provide a function for muscle's associated connective
tissues.
Muscles have 3 layers of connective tissues
the epimysium-an exterior collagen layer connected to the deep
fascia which separates the muscle from surrounding tissues.
the perimysium- surrounds bundles of muscles fibers called
fascicles. Perimysium holds the blood vessels and nerves that
supply the fascicles.
the endomysium- surrounds individual muscle cells (the muscle
fibers), contains the capillaries and nerve fibers that link the muscle
cells. Endomysium also has stem cells that repair damaged
muscles.
At each end of the muscle, the endomysium, perimysium and epimysium
come together to form a connective tissue attachment to the bone
matrix, either a tendon (a bundle) or an aponeurosis (a sheet). Skeletal
muscles are voluntary muscles, operated by nerves from the central
nervous system. An extensive vascular system supplies large amounts of
oxygen to muscles and carries away wastes.
3. How is a muscle attached to the bone? Describe the structures and
their functions.
Muscle is attached to the bone by tendons. Skeletal muscles are attached
to the ends of bones that meet at a joint. These muscles span the joint
and connect the bones. When the muscles contract, they pull on the
bones, causing them to move.
.
4. Identify the structural components of a sarcomere.
, Sarcomeres (the contractile units of muscle) are structural units of
myofibrils that form the organization or pattern of thick (Myosin) and thin
(Actin) filaments within the myofibril. Sarcomeres in the skeletal muscles
appear striped or striated because of the arrangement of alternating dark,
thick filaments (A bands) and light, thin filaments (I band) within their
myofibrils. The center of the A band is the midline or M line of the
sarcomere. The centers of the I bands are Z lines. One sarcomere is
measured from one Z line to another. Thick filaments and thin filaments
overlap in the zone of overlap, which is the densest, darkest area on a
light micrograph. Around the M line are thick filaments but no thin
filaments this is called the H zone. Strands of protein (titin) reach from
the tips of the thick filaments to the Z line and stabilize the filaments.
5. Describe the structural components of a thin filament and a thick
filament.
The thin filaments (Actin) are approximately 7-9 nm in diameter. They
are attached to the Z discs of the striated muscle. Each thin filament is
made up of three proteins: (1) actin, (2) troponin, and (3) tropomyosin.
Actin - composed chiefly of actin proteins, within the filament, each
globular actin monomer (G-actin) contains a myosin binding site and is
associated with the regulatory proteins, troponin and tropomyosin.
Troponin - a globular protein comprised of three complex proteins
involved in muscle contraction and occurs at about every 40 nm along
the filament.
Tropomyosin - rod-shaped protein that is about 40 nm in length. Two
strands of tropomyosin molecules run along the helical actin filaments
and is associated with troponin. Troponin and tropomyosin run along
the actin filaments and control when the actin binding sites will be
exposed for binding to myosin.
Thick filaments (Myosin) are composed of myosin protein complexes,
which are composed of six proteins: two myosin heavy chains and four
light chain molecules.
Heavy chains consist of a tail region, flexible hinge region, and
globular head which contains an Actin-binding site and a binding site
for the high energy molecule ATP.
Light chains regulate the hinge region, but the heavy chain head
region interacts with actin and is the most important factor for
generating force.
6. What role does Calcium play in the activation of muscle contraction?
Calcium binds protein and triggers contraction by reaction with regulatory
proteins that, in the absence of calcium, prevent interaction of actin and
myosin.
7. What role doe Magnesium plain in overall muscle activity?
