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made up of mm fibers


made up of myofibrils


prot in Z line, connects Actin to Z line


connects Z line to M line

thin filament

2 globular actin chains wound in to a double helix


sits betw 2 chains actin chains, length of 7 ctins

troponin I

bins to actIn, holds it in place

troponin T

binds to Tropomyosin

troponin C

binds to Ca2+

power stroke

the act of moving myosin and actin toward the M line to shorten the sarcomere

Ryanodine SR Ca2+ channels

open in response to volt-dep Ca2+ channels to further inc intracellular Ca2+


single stimulus of mm

active force

Max F gen by isometric twitch


amt of F in mm before contraction


initial F developed by mm before shortening (F gen to lift load)


measure of myosin ATPase activity (crossbridge rate)


spatial summation, increases proportion of mm fibers stimulated


max freq to get sustained contraction

unfused tetanus

tetanus with slight flux in F betw stimuli

fused tetanus

tetanus with no flux in F betw stimuli

motor unit

all the mm fibers innervated by the bundles of 1 motor neuron + the motorneuron itself

slow (oxidative)

type of motor units that are recruited first

temporal summation

increased frequency of stimuli

spatial summation

increased recruitment of motor units

dense bodies

connect myofibrils to cells in smooth mm

unitary smooth mm

smooth mm that has gap junctions, found in GI, uterus, bladder

multiunit smooth mm

under neural control => fine control, found in iris, bl vessels

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