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skeletal muscle
voluntary, striated
cardiac muscle
involuntary, striated
smooth muscle
involuntary, unstriated
functions of skeletal muscle
movement of body, posture, generation of body heat, movement of substances(ie.urinary tract), nutrient reserves, support soft tissues and organs
what is skeletal muscle linked to bones by
tendons
muscle cell is also called a
muscle fiber
components of muscle fiber
sarcoplasm, sarcolemma, and myofibril
what are myofibrils
contractile elements of the muscle fiber that are composed of myofilaments
thick filaments are composed of
myosin
thin filaments are composed of
actin
motor unit
single motor neuron and all the muscle fibers it innervates
motor end plate
area of sarcolemma where the motor neuron stimulates skeletal muscle
sarcomere
functional unit of contraction
what do myosin heads do
form cross bridges between thick and thin filaments
what is on myosin heads
actin binding sites, ATP binding site, ATPase
thin filaments regulatory proteins
troponin and tropomyosin
tropomyosin
resting, covers myosin binding sites blocking interaction
troponin
bind to tropomyosin, bind to actin, and bind to calcium
what do each actin have
special binding site for attachment with myosin cross bridges—> binding results in contraction of muscle fiber
Sliding FIlament Mechanism
contraction is accomplished by thin filaments from opposite sides of each sarcomere sliding closer together between thick filaments
Power Stroke
swiveling of myosin heads
sliding filament mechanism steps
attachment of myosin cross bridge to a thin filament
swiveling of myosin heads - power stroke
detach of the cross bridge from thin filament
reattach to a new actin binding site
repeat cycle
Cross Bridge cycle steps
resting fiber; CB is not attached to actin
CB bind to actin
P is released causing conformational change in myosin
Power stroke causes filaments to slide; ADP is released
a new ATP binds to myosin head allowing it to be released from actin
ATP is hydrolyzed causing CB to return to normal orientation
Functions of ATP in contraction
energizes CB providing energy for powerstroke
binding of ATP disassociates CB from actin
do myosin and actin interact at rest
no
how does muscle excitation switch on CB cycling
Calcium
calcium is ___ at rest and is stored in the ____
low, sarcoplasmic reticulum
what happens to calcium for a contraction to happen
it is released from SR —→ increase in calcium —→ contraction
how is calcium released from the SR
AP propagated into interior by transverse tubules—> Ca2+ goes through voltage-gated channels in SR-—> release of calcium
tension
force exerted on an object by contracting muscle
load
force exerted on muscle by weight of an object
twitch
response of a single muscle fiber to a single AP
Muscle contraction phases
latent period, contraction time, relaxation time
force velocity curve
for muscle to contract they must generate force that is greater than opposing forces
the greater the force the slower the contraction
two types of muscle contraction
isotonic and isometric
isotonic
change in muscle length
two types of isotonic contractions
concentric and eccentric contractions
concentric contractions
muscle shortens
eccentric contractions
muscle lengthens
isometric contractions
muscles cant shorten because load is too great, can be voluntary
nervous system in muscle tension
frequency of stimulation and motor unit recruitment
frequency of stimulation
because muscle twitch is fairly slow compared to AP many AP arrive before twitch occurs, generation of force is greater than a single twitch , summation
muscle summation
muscle stimulated again before relaxation leads to summation
tetanus
contraction is usually 3-4 greater than a single twitch
motor unit recruitment
increasing the number of active motor units, increase tension and velocity
formation of ATP by muscle
phosphoralation of ADP by creatine phosphate
oxidative phosphoralation
glycolysis
creatine phosphate