Taylor NMJ Excitation and Contraction Flashcards
what is absolutely needed for a muscle contraction
calcium
motor neuron that innervates muscle
alpha motor neuron
a specific muscle fiber is only innervated by what
a specific motor neuron
1 alpha motor neuron and all of its fibers it innervates
motor unit
what increases surface area on muscle
post junctional folds
action potential down motor neuron causes what to open
voltage gated calcium channels (p or q)
what allows vesicle to fuse with membrane and Ach to be released
calcium binding to synaptotagmin and then causing conformational change where SNARE complex binds to membrane
parts of the SNARE complex
SNAP 25, synaptobrevin, and syntaxin
what receptor on postjunctional side acts as ligand gated ion channel
nicotinic Ach receptor
what happens after Ach binds its receptor
Na comes in and depolarizes membrane and if enough potential, will cause contraction
Ach is released in discrete packages called
quanta
how many quanta of Ach need to be released to cause contraction
50-300
type of channel that allows sodium to come through and depolarization to happen
fast voltage gated Na channel
Z line is made of this and it borders each sarcomere
alpha actinin
head of myosin filament has what binding sites
actin and ATP and light chain
what allows uncovering of myosin binding site on actin filament in resting state
when calcium binds troponin C
6 steps of cross-bridge cycling for contraction
- myosin is bound to actin
- ATP binds myosin and detaches from actin
- ATP hydrolyzed to ADP and inorganic P
- Ca2+ binds troponin C and myosin is able to bind actin
- inorganic P is released and powerstroke happens
- ADP released and myosin remains attached to actin until ATP binds myosin
what surrounds myofibril
sarcoplasmic reticulum
what stores Ca2+ around myofibril
cisternae of sarcoplasmic reticulum
DHPR and RyR allow calcium to leave sarcoplasmic reticulum and enter where
cytosol
triad:
2 cisternae and 1 T-tubule
Ach goes into T tubule and allows depolarization to happen opening what channels
L-type voltage gated calcium channel (DHPR) and ryanodine receptor (RyR)
when Ca2+ is in cytosol, what can happen
it binds troponin C and allows myosin to bind actin so contraction can happen
what pumps calcium back into sarcoplasmic reticulum
SERCA
what protein keeps calcium in sarcoplasmic reticulum
Calsequestrin
what degrades Ach so you don’t have constant contraction
Ach-ase
