cardiac muscle structures 2 Flashcards
contraction and relaxation cycle
- Action potential leads to calcium release.
- Calcium binds to troponin C.
- Troponin complex undergoes structural change, moving tropomyosin out of the way.
- Myosin binds actin and crossbridge moves.
- Calcium is released, tropomyosin reblocks binding site - relaxation
crossbridge is
myosin binding actin, which ultimately generates force
Cross bridges are initially in a
weakly bound, non-force-generating “rest” state (state 1) during diastole.
The triggering of force generation and contraction is governed by
Ca2+ fluxes determined by the dynamics of electrochemical coupling of Ca2+ release and Ca2+ binding to cTnC.
4 state cross bridge cycle model
- rest state
- transition state
- active state
- active state
rest state
- no ca2+
- weakly bound
- non force generating
transition state
- Ca2+ bound
- XB weakly bound
- non force generating
- active state
- calcium bound
- XB strongly bound
- force generating
- active state
- no calcium bound
- XB strongly bound
- force generating
Contractility describes the
relative ability of the heart to eject a stroke volume (SV) at a given pre- vailing afterload (arterial pressure) and preload (end-diastolic volume; EDV).
during contraction, what occurs
I band and H band decrease
A band does not change!!
titin forms
an elastic spring
one of the major proteins responsible for passive elastic properties of the cell (and thus for the diastolic properties of the heart)
titin isoforms
- N2B
2. N2BA
CO =
SV x HR
stroke volume is
how much blood is pumped out with each beat
after load
pressure that ventricles are pushing against
Aortic (left side) or pulmonary pressure (right side)
preload
volume in ventricle before ejection
what special features allow heart to beat?
the organization of the muscle, they wrap around the heart in a very coordinated fashion
contraction starts in the
apex and squeezed coordinately in a spiral way up.
which are mechanical adhesions?
desmosomes
which are electrical adhesions?
gap junctions
thin filament contains
actin
thick filament contains
myosin
troponin I is typically located
on the actin and it covers the myosin binding site
contraction is
systole
relaxation is
diastole
where does regulation of the myofilament activation occur?
on the thin filament or thick filament
on the thin filament, regulation is
force, active contraction or sensitivity to calcium
TnC, TnT, TnI, Tm
on the thick filament, regulation is
relaxation kinetics, diastole, passive tension
MLC1, MLC2 or MyBP-C
in sliding filament, the length of actin or myosin
do not change
but titin does become more or less coiled
