regulation of cardiac contraction Flashcards
frank starling mechanism
refers to the ability of the heart to increase its force of contraction when stretched (occur at increase venous return)
how heart can descend to accomadate increased volume
systole in the L-T relation
active tension - cross bridge cycling
any given length = certain output of pressure therefore producing more force
no descending phase due to titin and connective tissue
diastole in the L-T relation
ventricles being filled
passive tension - helps prevent over stretching of the heart
higher passive tension because hight volume
titin
increased ventricular filling
proportional to EDV
increase force of contraction
heart muscle adapts to changes in venous return
factors increasing EDV
increase venous return
exercise
venous constriction
decrease HR (more filling time)
preload
stretch
end of diastole
force that stretches relaxed fibers
increases resting length
proportional to length of sarcomere which is proportional to EDV
afterload
proportional to aortic pressure - when the heart is pumping harder
= blood pressure
force that muscle must overcome
opposing force and arterial pressure
factors it must overcome as it ejects blood during systole
increased preload
increased force of contraction
increased afterload
increased isometric contraction
decrease velocity of contraction
decrease time of shortening
isometric contraction
contraction against constant load
Fmax
independent of rate of X-bridge cycling
Vmax
is adapted to match maximal HR
