Cardiac Force Generation Flashcards
how does muscles of left ventricle contract
muscles are in circular structure so LV reduces in diameter and mitral valve is pulled towards apex which shortens the heart. this allows blood to be squeezed out
how does muscles of right ventricle contract
pulls free wall towards septum and pull tricuspid valve toward apex shortening heart and circular action of LV pushes septum into RV. all this forcing blood out
Cardiac output equation
Cardiac output = Heart Rate*Stroke Volume
what is pre-load
Force exerted on heart wall by blood in LV at end of Diastole
relationship between EDV and Pressure
increase in EDV, pressure increases
relationship between EDV and stroke volume
as EDV increases so does stroke volume
explain length tension relationship
as pre-load increases the stretch on muscle cells increases which increases tension of sarcomeres
this pulls apart sarcomeres and reduces actin overlap
this reveals more actin for more myosin head to bind to
this increases contraction strength
relationship between EDV and venous return
directly proportional
more EDV
more force of contraction
greater stroke volume
more blood returns to heart
what is the limit of the length tension relationship
2.4um
after this point tension drops quickly
as sarcomere stretches actin and myosin gets further away so cant interact
calcium length tension relationship
the more stretched muscles cells are
the more sensitive they are to calcium due to conformational changes
more calcium binding = greater force of contraction
afterload
force acting against blood leaving heart
what causes afterload and why does it occur
mainly pressure of aorta
but certain pathogenic conditions can cause defects in the aortic valve
afterload stops ventricles from completely emptying
ESV is directly related to contractility of heart and inversely related to afterload
