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16 Cards in this Set
- Front
- Back
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what's the difference between type I & II fibers?
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- type I are slow red fibers, have lots of myoglobin so can contract for long amounts of time, smaller diameter
- type II are fast twitch fibers which are largely anaerobic, larger diameter & higher strength of contraction, fatigue quickly |
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is neuromuscular transmission required in: skeletal, cardiac & smooth muscle?
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- skeletal: yes
- cardiac: no only modulates - smooth: can initiate contraction & in other cases just modulate |
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which muscle cells have gap junctions?
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- cardiac cells have gap junctions - making it functional syncytium
- smooth muscle can sometimes have gap junctions |
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what is the difference between multiunit & unitary smooth muscle innervation? which is more common?
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- multiunit: different motor neurons each innervating different cell
- unitary: gap junctions permit coordinated contraction - unitary is most common |
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Where is the Z line? A band? H zone? I band? M line?
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- H = only myosin
- A = all myosin including overlapping thin filaments - Z line = inbetween the thin filaments - I band = just the actin - M line = in the H zone (middle of myosin filaments) |
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what is the sliding filament hypothesis
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- further you stretch the muscle, less overlap between actin & myosin decreases the tension
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when is optimum force development?
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- there needs to be enough overlap of actin & myosin but not too much
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what blocks the myosin binding site on actin? what is the troponin complex made up of?
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- tropomyosin
- TnT, TnC, TnI |
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what does TnC do? TnI? TnT?
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- TnC binds calcium causes conformational change moves TnI
- TnI moves away from tropomyosin allowing TnT to push myosin away from binding site on actin - TnT moves troponin away from actin tropomyosin to push it away from the binding site on actin |
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how does the crossbridge cycle work?
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- myosin in resting state with hydrolyzed ATP energy & energy stored in head - not released until binds to binding sites
- when calcium influxes & binding sites open up it binds & releases stored energy in head from previous ATP hydrolysis - moves myosin filaments along actin - to get head off you need ATP to bind to myosin to dissociate |
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how many times can the crossbridge cycle happen if calcium is present?
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- unlimited
- eventually when calcium stays high the twitches go into a fused contraction |
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how does the crossbridge cycle differ in smooth muscle?
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- calmodulin binds to Ca interacts with MLCK and phosphorylates actin making it active
- myosin head is not ready to go before Ca - this is what takes so long |
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how do T tubules work when Ca influxes?
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- Ca opens L type Ca channels in the T tubule membrane that interact with the SR
- L type channels are coupled to ryanadine receptors - Ca channel physically changes shape & coupled to ryanadine receptor in SR which opens & Ca pours out |
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how are ryanadine receptors different in cardiac muscle?
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- in cardiac muscle ryanadine receptors also are sensitive to Ca [ ] in cytoplasm
- also uses L type channels for conformational change |
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how does calcium get back into the SR? how does this play into muscle contraction?
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- pumps using ATP get Ca back into SR
- if two APs come down fast enough Ca keeps getting puffed out & not put back in fast enough - get fusion of twitches into contraction |
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what is malignant hyperthermia?
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- AD disorder of ryanadine receptor
- triggered during anesthetics - abnormally sensitive to Ca & releases a ton of Ca from SR --> to pump back in make lots of ATP --> hyperthermia - treat with dantrolene |
