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16 Cards in this Set

  • Front
  • Back
what's the difference between type I & II fibers?
- 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
is neuromuscular transmission required in: skeletal, cardiac & smooth muscle?
- skeletal: yes

- cardiac: no only modulates

- smooth: can initiate contraction & in other cases just modulate
which muscle cells have gap junctions?
- cardiac cells have gap junctions - making it functional syncytium

- smooth muscle can sometimes have gap junctions
what is the difference between multiunit & unitary smooth muscle innervation? which is more common?
- multiunit: different motor neurons each innervating different cell

- unitary: gap junctions permit coordinated contraction

- unitary is most common
Where is the Z line? A band? H zone? I band? M line?
- 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)
what is the sliding filament hypothesis
- further you stretch the muscle, less overlap between actin & myosin decreases the tension
when is optimum force development?
- there needs to be enough overlap of actin & myosin but not too much
what blocks the myosin binding site on actin? what is the troponin complex made up of?
- tropomyosin

- TnT, TnC, TnI
what does TnC do? TnI? TnT?
- 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
how does the crossbridge cycle work?
- 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
how many times can the crossbridge cycle happen if calcium is present?
- unlimited

- eventually when calcium stays high the twitches go into a fused contraction
how does the crossbridge cycle differ in smooth muscle?
- 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
how do T tubules work when Ca influxes?
- 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
how are ryanadine receptors different in cardiac muscle?
- in cardiac muscle ryanadine receptors also are sensitive to Ca [ ] in cytoplasm

- also uses L type channels for conformational change
how does calcium get back into the SR? how does this play into muscle contraction?
- 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
what is malignant hyperthermia?
- 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