Skeletal Muscle Contraction Flashcards
epimysium
CT around entire muscle
Muscle
formed by multiple fascicles
perimysium
CT around each fascicle
fascicle
bundle of myofiber
endomysium
CT around each myofiber
sarcolemma
muscle fiber cell membrane = plasmalemma
myofiber
individual multinucleated muscle cell
myofibril
chain of sarcomeres in a myofiber
myofilament
actin/myosin filaments that make sarcomere
Z lines
anchor actin, at each end of sarcomere
I bands
solely actin, width changes on contraction
A bands
actin and myosin. No width change
H bands
solely myosin. width changes on contraction
Sliding Filament Mechanism Events
- action potential arrives at terminal end of nerve. 2. Ca channel opens. 3) release of Ach from synaptic vesicles to cleft. 4) sarcolemma Na channels open. 5) action potential generated on sarcolemma/ 6)raynodine receptor on SR interact with VGC on T tubules. 7)ryanodine-sensitive Ca release channels open. 8) cytosol increases Ca ion. 9) sliding filament mechanism is activated.10) Ca ion bind with troponin. 11) tropomysin opens actin binding site. 12)ATPase heads of myosin, split ATP to bind actin. 13)deformation of myosin heads allows thick/thin sliding. 14)2nd ATP binds myosin->releasing actin. 15) repeating process. 16) contraction stops Ca pumps move Ca ions back to SR.
Dihydropyridine Receptors
1)quadruplet L-type Ca channels. 2) located @sarcoleme T-tubules. 3) cause conformation change in ryanodine receptors. 4)Ca flows to cytosol in channel
Ryanodine Receptors
1) located on cisternae of SR. 2)open bc of change in DHP. 3) Ca allowed into cytosol from SR. 4) Calsequestrin maintains optimum [Ca]
Where is ATP required for muscle contraction?
1)sliding filament mechanism. 2)pumps Ca from sarcoplasm to SR. 3)Na-K pump to establish the RP(-90)
[ATP] in muscle fiber??
4mmol, contracts for 1-2 seconds
Phosphocreatine
1)rapid energy release 2) reconstitutes ATP 3) combination provides 5-8 second contraction.
Glycolysis
causes lactic acid build up, only good for 1 second.
How much energy is provided by Oxidative Metabolism?
95% for long term contractions.
Isometric Muscle Contraction
increase in tension but not length.
Isotonic muscle contraction
Eccentric: lengthening of muscle.
Concentric: shortening of muscle.
Fast-twitch fibers
1)fewer mitochondria 2) anaerobic respiration->build up of pyruvic acid. 3) little myoglobin. 4) large [ATPase] 5) aka ‘white’
Slow-twitch fibers
1) more mitochondria 2) aerobic respiration 3) more myoglobin 4) small [ATPase]
How do muscles increase in size?
increase the mass of myofiber and muscle
Summation
electrical events occur faster than mechanical. 2)extra spike occur before previous Ca ion return to SR. 3)Increases Ca ion in cytosol and increases rate of cycling between myosin and actin. Increasing muscle tension.
Tetany
high frequency causing muscle to stay contracted
A lever is?
rigid bone rotating around pivot point
In-lever arm
distance from in-force to fulcrum
out-lever arm
distance from the out-force to fulcrum
First class lever system
1) fulcrum is in the middle. 2) raising chin using sternoclediomastoids. (atlas-axis=fulcrum) 3) in-force& out-force move oppositely
Second class lever system
Both in/out forces are in same direction. (resistance is in middle)
raise body on ball of feet. fulcrum= ball of foot
Third class lever system
both in/out forces on same side of fulcrum. effort is in middle. Lift wt in palm of hand.
