Muscular Tissue
triad
A transverse tubule and the two terminal cisterns on either side of it form
Tropomyosin
Regulatory protein that is a component of thin filament; when skeletal muscle fiber is relaxed, tropomyosin covers myosin-binding sites on actin molecules, thereby preventing myosin from binding to actin.
Dystrophin
Structural protein that links thin filaments of sarcomere to integral membrane proteins in sarcolemma, which are attached in turn to proteins in connective tissue matrix that surrounds muscle fibers; thought to help reinforce sarcolemma and help transmit tension generated by sarcomeres to tendons
Nebulin
Structural protein that wraps around entire length of each thin filament; helps anchor thin filaments to Z discs and regulates length of thin filaments during development.
actin
The main component of the thin filament is the protein Individual actin molecules join to form an actin filament that is twisted into a helix
sarcolemma
The multiple nuclei of a skeletal muscle fiber are located just beneath
aponeurosis
When the connective tissue elements extend as a broad, flat sheet
filaments
Within myofibrils are smaller protein structures
sarcoplasmic reticulum
a fluid-filled system of membranous sacs
sarcoplasm
cytoplasm of a muscle fiber
H zone
in the center of each A bands contains thick but not thin filaments
Fascia
is a dense sheet or broad band of irregular connective tissue that lines the body wall and limbs and supports and surrounds muscle and othe organs of the body
I band
is a lighter, less dense area that contains the rest of the thin filaments but no thick filaments
Perimysium
is also a layer of dense irregular connective tissue, but it surrounds groups of 10 to 100 or more muscle fibers, separating them into bundles called fascicles (FAS-i-kuls = little bundles).
Myosin
is the main component of thick filaments and functions as a motor protein in all three types of muscle tissue.
Epimysium
is the outerlyer encircling the enitire muscle. it consists of dense irregular connective tissue
M line
middle of the sarcomere.
Endomysium
penetrates the interior of each fascicle and separates individual muscle fibers from one another. The endomysium is mostly reticular fibers.
Z discs
separate one sarcomere from the next
myofibrils
the contractile organelles of skeletal muscle
terminal cisterns
the contractile organelles of skeletal sarcloplasmic reticulum
transverse tubules
tunnel in from the surface toward the center of each muscle fiber. B
A band
which extends the entire length of the thick filaments (Figure 10.3b). Toward each end is a zone of overlap, where the thick and thin filaments lie side by side.
subcutaneous layer
which separates muscle from the skin is composed of areolar connective tissue and adipose tissue.
Troponin
Regulatory protein that is a component of thin filament; when calcium ions (Ca2+) bind to troponin, it changes shape; this conformational change moves tropomyosin away from myosin-binding sites on actin molecules, and muscle contraction subsequently begins as myosin binds to actin
Myomesin
Structural protein that forms M line of sarcomere; binds to titin molecules and connects adjacent thick filaments to one another.
α-Actinin
Structural protein of Z discs that attaches to actin molecules of thin filaments and to titin molecules.
Titin
Structural protein that connects Z disc to M line of sarcomere, thereby helping to stabilize thick filament position; can stretch and then spring back unharmed, and thus accounts for much of the elasticity and extensibility of myofibrils.