Muscles Flashcards
Epimysium
Superficial collagenous connective tissue layer that covers the muscle and separates it from neighboring structures.
Perimysium
The second or middle layer of connective tissue of the muscle. The epimysium folds into the muscle as the perimysium, and divides the muscle fibers into groups called fascicles.
Endomysium
The deep layer of connective tissue of the muscles. Connective tissue fivers of the perimysium extend deep into the fascicles as the endomysium, and surround each muscle fiber (cell)
Fascicle
Group of muscle fivers
Tendon
The connective tissues of the muscle interweave and combine at each ends of the muscle. The tendon and the bone’s periosteum interlace to attach the muscle to the bone.
Belly
The center of the muscle
Sarcolemma
The cell membrane of the muscle
Muscle fiber
Composite of many cells that fused into a single cell during embryonic development
Sarcoplasm
Cytoplasm of a muscle fiber
Transverse tubule
(T tubules) Connect the sarcolemma to the interior of the muscle fiber. Function is to pass contraction stibuli to deeper regions of the muscle fiber
Myofibrils
Proteins that are arranged in thousands of rods inside the muscle fiber. Extends the length of the fiber. Each myofibril consists of several kinds of proteins arranged in about 3000 thin filaments and 1500 thick filaments.
Sarcoplasmic reticulum
Surrounds each myofibril. IT is a modified endoplasmic reticulum where calcium ions are stored.
Terminal cisternae
Branches of sarcoplasmic reticulum fuse to form large calcium ion storage chambers. Lies adjacent to the transverse tubules.
Triad
A “sandwich” consisting of a transverse tubule plus the terminal cisterna on each side of the tubule
Thin filaments
Mostly composed of the protein ACTIN; consists of 2 interwined strands of actin.
Thick filaments
Composed of the protein MYOSIN; made of approximately 300 subunits of myosin. Each subunit consists of 2 strands: 2 intertwined tail regions and 2 globular heads. Bundles of myosin subunits, with tails parallel to one another and the head projecting outward, constitute thick filaments.
Sarcomeres
Repeating patterns of arranged filaments
Z line
Where thin filaments are connected to each other on each end of the sarcomere. Each X line is made of a protein called ACTININ
I band
Areas near the Z line that contain only thin filaments
A band
Area between I bands in a srcomere; containing both thin and thick filaments
Zone of overlap
Edges of the A band where the thick and thin filaments bind during muscle contraction
H zone
The middle region of the A band and contains only thick filaments
M line
A dense line in the center of the A band that attaches the thick filaments
Actin
Consists of 4 protein components: G actin, F actin, nebulin, and active sites
G actin
Individual spherrical molecules
F actin strand
Approximately 300 to 400 G actins twisted together
Nebulin
Holds the G actins in position along the F actin strand
Active site
On each G actin molecule where myosin molecules in the thick filaments bind during contraction
Tropomyosin
Follows the twisted actin strands and blocks active sites to regulate muscle contraction
Troponin
Holds tropomyosin in position and has binding sites for calcium ions. Calcium ions cause troponin to change shape and move tropomyosin away from binding sites for contraction
Titin
Protein that attaches the thick filament to the Z line on the end of the sarcomere.
Myosin
Consists of a head, hinge, and tail. Each head contains a binding site for actin and a region that functions as an ATPase enzyme.
