Regulation of Contraction Flashcards
what are the regulatory proteins in thin filament
troponin
tropomyosin
what does the force of contraction depend on
Ca2+
the higher the Ca2+, the greater the force of contraction
there is 1 tropomyosin every ___ actin subunits
7
there is 1 troponin every ___ actin subunits
7
what is the structure of tropomyosin
alpha helical coiled coil
2 identical chains
40 nm long
what is the structure of troponin
3 subunits
TnC- binds to ca2+
TnI- inhibitory= binds to TnC, TnT, acting
TnT- binds to tropomyosin
what occurs at low ca2+ concentrations
the TnI of troponin is bound to actin/tropomyosin, all myosin binding sites are blocked
what occurs at high ca2+ concentrations
the ca2+ binds to TnC of troponin,
TnI binds to TnC
this causes the tropomyosin to move
myosin binding sites are exposed, myosin binds, forms a cross-bridge
troponin can bind to…
actin
tropomyosin
ca2+
what modulates the ca2+ concentration
ca2+ ions are stored in sarcoplasmic reticulum/
released due to nerve impulse from the nervous system= impulse causes release of neurotransmitter acetylcholine= depolarise the muscle fibre membrane. the electrical impulse travels down the T-tubules and opens the ca2+ stores= ca2+ flow to myofibrils where trigger a muscle contraction
what is DHPR
di-hydro-pyridine receptor
it is an L-type ca2+ vg-channel
where is DHPR located
in the T-tubules
what is RyR
Ryanodine receptor
Ca2+ channel
where is RyR located
Sarcoplasmic reticulum
how do the DHPR and RyR interact
activation of DHPR activates the RyR= releases Ca2+
this activates other RyR’s= a spike of Ca2+ reached at 10 um
