microscopic quick review muscles

state the order of the muscle down to microscopic

muscle, fasicle, muscle fiber/cell, myofibril, myofilaments

state the macroscopic order of the skeletal muscle

epimysium, perimysium, fascicles, endomysium, muscle fiber/cell

plasma membrane of the muscle cell

sarcolemma

cytoplasm of muscle cell

sarcoplasm

smallest contractile unit

sarcomere

large, sub cellular structures that extend the length of a skeletal muscle; responsible for muscle contraction

myofibril

also called T tubules, extensions of the sarcolemma that extend into the cell

Transverse tubules

smooth endoplasmic reticulum that stores Ca2+ which is released during contraction; note the terminal cisternae (flattened areas)

Sarcoplasmic Reticulum

a T tubule bounded by two SR terminal cisternae

Triad

myofibrils are made of

actin and myosin

one segment of a sarcomere extends between 2 _?

z discs

what differentiates myosin from actin?

myosin heads

where are myosin heads

myosin-actin overlap

a globular protein which polymerizes to form a filament called F actin; each G actin has a binding site for myosin

G actin

a regulatory protein made of three polypeptides; TnT holds tropomyosin to actin; TnC binds Ca+2 and TnI binds to actin

Troponin

blocks actin’s myosin binding sites when the muscle is resting

Tropomyosin

what filament is made of titin

elastic filament

end of the sarcomere: thin myofilaments and thick myofilaments attach here

z disc

dark band under the microscope that includes thick myofilament and thin myofilament

A band

only thin filament

I band

region of A band containing only thick myofilament

H zone

bisects the H zone and consists of proteins that connect adjacent thick myofilaments

M line