Skeletal Muscle Tissue - TU-F2017

Triad

combination of a pair of terminal cisternae (on either side of a T tubule, the tubules of the SR enlarge, fuse, and form expanded chambers) plus a transverse tubule

Thick filaments

composed primarily of myosin, enable muscle contraction to occur

Titin

in the core of thick filaments, either end of the thick filament, a strand of titin continues across the I band to the Z line on that side, become tense when some external force stretches the sarcomere

H band

resting sarcomere= lighter region on either side of the M line, contains thick filaments, but no thin filaments

Muscle Fiber (cell)

sheathed in a delicate endomysium that contains capillaries, myosatellite cells, and axons of the neurons that control the muscle fibers

Zone of overlap

the point where actin myofilaments overlay the myosin myofilaments as it (actin) gets pulled towards the m-line (mid-point of sarcomere), increases during muscle contraction, resulting in the shortening of the muscle

Endomysium

thin layer of areolar CT that surrounds each muscle fiber, loosely interconnects nearby muscle fibers

Tropomyosin

cover the active sites on G-actin and prevent actin-myosin interactions, double stranded protein that is bound to one molecule of troponin midway along its length

Sarcoplasm

cytoplasm of skeletal muscle, acting as a medium for various cellular reactions to take place which are necessary for muscle contraction and general cellular metabolism

Myosatellite cells

stem cells that function in the repair of damaged muscle tissue

F-actin

twisted strand composed of two rows of 300-400 individual molecules of G-actin, primarily involved in crucial cellular processes like morphogenesis, cell division, and migration

T tubules

AKA transverse tubules, narrow tubes that are continuous with the sarcolemma and extends into the sarcoplasm at right angles to the surface, form passageways through the muscle fibers

Troponin

consists of three gloubular subunits, one subunit binds to tropomyosin, locking them together as a troponin-tropomyosin, the second subunits binds to one G-actin holding the troponin-tropomyosin complex in position, third subunit has a receptor that binds two calcium ions

M line

connects the central portion of each thick filament

G-actin

contain active site where myosin can bind (like a substrate binding to an enzymes active site),

I band

contains thin filaments but no thick filaments, extends from the A band of one sarcomere to the A band of the next

Muscle Fascicle

bundle of skeletal muscle fibers surrounded by perimysium, a type of connective tissue, allow for an extended range of motion

Thin filaments

composed primarily of actin, help support the structure of the cell, or cytoskeleton

Epimysium

dense layer of collagen fibers, surrounding the entire muscle, separates the muscle from surrounding tissues/organs, connected to the deep fascia (a dense CT layer), supporting CT

A band

dense region of the sarcomere that contains thick filaments

Myoblasts

embryonic cells, fuse forming multinucleate cells, develop into distinctive skeletal muscle fibers, how muscle fibers develop

Aponeurosis

ends of skeletal muscles, collagen fibers of the connective tissue layers form a broad sheet, provides attachment over a broad area that may involve more than one bone

Perimysium

fibrous layer that divides the skeletal muscle into a series of compartments, collagen fibers and elastic fibers, contains blood vessels and nerves that maintain blood flow/innervate (supply) the muscle fibers w/in the fascicles

Sarcoplasmic reticulum

forms tubular network around each individual myofirbril, found in smooth and striated muscle fibers whose function is to store and release calcium ions

Actinin

is a microfilament protein, necessary for the attachment of actin filaments to the Z-lines in skeletal muscle cells,[1] and to the dense bodies in smooth muscle cells

Nebulin

large protein that extends along the F-actin stand in the cleft between the rows of G-actin molecules, holds the F-actin strand together

Myofibril

long, bundled tubes of cytoskeleton that run the length of striated muscle fibers, function in cellular support, movement, and intra-cellular transport

Z line (disc)

mark the boundary between adjacent sarcomeres, consists of proteins called actinins, which interconnect thin filaments of adjacent sarcomeres

Myofilaments

myofibrils consist of these bundles of protein filaments, most abundant are thin filaments but contains thick filaments, play an important role in muscle contraction and relaxation

Sarcomere

myofilaments w/in each myofibril arranged into repeating contractile units, one myofibril= 10,000 sarcomeres, align end to end, resting length = 2 micrometers, smallest contractile unit of striated muscle cells

Sarcolemma

plasma membrane of the skeletal muscle, acts as a barrier between the extracellular and intracellular compartments, defining the individual muscle fiber from with its surroundings

Myosin

protein component in thick filaments, all the molecules are arranged with their tails pointing towards the M line, heads are arranged in a spiral, no myosin heads in a small area on either side of the M line