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33 Cards in this Set
- Front
- Back
Skeletal muscle histo
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Striated, multinucleate, longitudinal fibers;
endomysium around individual fibers, perimysium around bundles of fibers, epimysium around entire muscle. |
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tendons
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Heavy, parallel collagenous fibers that are site of muscle attachment, Musculotendinous junction = common injury site
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skeletal muscle blood supply
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Rich circulation pierces the epimysium and run parallel to perimysium. Capillary system can increase 45% during strenuous exercise.
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skeletal muscle nerve supply
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Afferent and efferent fibers; each nerve fiber is distributed to a group of muscle fibers (1 to 200)
-precision = small motor unit -gross = large motor unit |
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Parts of a sarcomere
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Sarcomere runs from Z line to Z line
-I band: thin filaments only -A band: length of thick filaments -M line: middle of sarcomere -H zone: thick filaments only |
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sarcomere during contraction and stretching
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contraction: shortens up to 50%; H zone and I band get shorter; A band always stays the same
stretching: lengthens up to 120%; limited by collagenous tissue |
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what tells a skeletal muscle to contract
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-voluntary impulse from cortex or a reflex impulse arising in upper/lower MN
-all-or-nothing response |
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RMP and depolarization
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Nerve cell has RMP of -85. When a nerve cell fires, Na permeability increases and then K efflux restores RMP.
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4 insoluble proteins that make up myofibrils
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myosin + actin + tropomyosin + troponin
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thick filament
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Myosin chain has 2 globular heads that bind Actin have ATPase activity in the presence of Ca
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Thin filament
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Actin + Troponin + Tropomyosin
-G actin binds ATP and polymerizes to form F actin, which binds Ca tightly |
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tropomyosin and troponin
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Tropomyosin complexes w/ F actin and prevents myosin crossbridges from binding. Ca binds troponin and induces tropomyosin shift that allows actin/myosin to interact
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role of ATP
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attaches to myosin heads and produce cross-bridge w/ actin. Very sensitive to Ca
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Steps in contraction
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Action potential >> Ca released from Sarcoplasm >> crossbridge are made/broken under Ca regulation >>
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Type I skeletal muscle
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Slow twitch, red fibers are rich in mitochondria and myoglobin, do lots of oxidative phos. Good for endurance exercise.
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Type IIa skeletal muscle
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mixture of glycolytic and oxidativ enzymes; intermediate twitch time, fatigue resistant
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Type IIb skeletal muscle
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White fibers, glycolytic pathway, fast-twitch, fatiguable
-weight training causes hypertrophy of type II |
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muscle fiber recruitment
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more motor units recruited as physical effort increases. Type I provide first 20% of strength, then type II are recruited as effort increases. Type II still fatigue first.
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fiber type ratio
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Ratio is set, have some ability to convert btw type II's, but effort must be severe/sustained.
Fiber type depends on MN supplying it, and if a nerve is changed, the muscle fiber may change type. |
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fatigue
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MN unable to maintain firing rate; muscle contractile mechanism becomes less efficient.
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skeletal muscle hypertrophy
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number of fibers stays constant but size of myofibrils increases. Isometric exercises are best.
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atrophy
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occurs due to disuse. Type II fibers are particularly prone.
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myositis ossificans
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non-neoplastic proliferation of bone and cartilage w/in skeletal muscle at the site of previous injury. if it remains symptomatic, can excise it once it is mature (1-2yrs)
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CO
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HR x SV
-early increase in CO w/ exercise is due to increase in SV, then mainly due to increased HR. |
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training and lactic acid
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training increases lactic acid threshold and increases oxidative capacity (by increasing SV and decreasing resting HR)
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isometric exercise
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joint doesn't move during contraction; good for arthritic joints. Ex: straight leg raise. Don't build as much strength but are more tolerable.
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isotonic exercise
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fixed resistance; mainstay of weight-lifting regimen.
-concentric: force applied as muscle shortens -eccentric: force applied as muscle lengthens |
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isokinetic exercise
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joint moves at same speed throughout motion; better at improving muscle strength but machines are $$$
**only positive (concentric), so decrease soreness -most efficient way to train |
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DOMS
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exacerbated by eccentric muscle contractions; collagen/CT injury
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anabolic steroids
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androgenic effect produces muscle hypertrophy but linked to renal and hepatic malfunction.
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creatine
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helps build muscle and reduces recovery time. side effects related to water loss. Purity is a concern.
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maximum HR
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220-age; train btw 55% and 90% max HR for 30 min
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recommendations for sedentary patients
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poor CV reserve that can't tolerate rapid increase in HR. start w/ 55-65% of max HR
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