Sliding Filament Theory

Myofilament

Contractile proteins known as actin and myosin

Actin

Thin filament

Myosin

Thick filament

Sarcomere

The functional unit of the Myofibril - where contraction takes place

ATP

when this molecule binds, the myosin heads release from the actin

H Zone

Myosin only; Shortens/gets smaller during muscle contraction

Z Line

Border that separate sarcomere

I band

thin filaments only; gets smaller as a contraction

A band

where actin and myosin overlap; stays the same size druing contraction

Troponin

calcium binding site on actin

Tropomyosin

covers myosin binding sites on the actin molecules

calcium

binds to the troponin; pulls the tropomyosin out of the way to reveal myosin binding sites

Crossbridges

myosin heads attach to actin

sliding filament theory

the concept that a sarcomere shortens as the thick and thin filaments slide past one another

Acetylchoine

An excitatory neurotransmitter secreted by motor neurons innervating skeletal muscle is ________.

action potential

nerve impulse