2.3 Cardiac Output, HR, SV, Starlings Law Flashcards
What factors determine CO
HR and SV
What factors determine SV?
force of contraction and after load
What is preload?
preload is the end diastolic pressure that stretches the right or left ventricle of the heart to its greatest geometric dimensions under variable physiologic demand
What effect does preload have on SV?
bigger preload - larger SV
what effect does SV have on EDV?
as EDV increases SV increases
how does increased preload lead to increased SV?
decrease effective load - increase shortening velocity - increase ejection - increase SV
what are the functional properties of the cardiac pump?
contractility
fibre thickness
force production and sarcomere length
shortening velocity and force production
relationship between sarcomere length and force production
the longer the sarcomere the greater the force that can be produced
what is contractility dependent on?
Ca stores
sympathetic activity
fibre length at beginning of contraction: stretched fibres = larger force
how does fibre thickness relate to contractility?
greater thickness = greater contractility
with hypertrophy there are more contractile proteins (myofilaments) per myocyte which can produce greater force BUT in hypertrophic cardiomyopathy the changes can lead to decreased force due to remodelling (not in nice bundles)
Define afterload
The average pressure against which the ventricle must contract to eject blood into the aorta
relationship between afterload and SV
increase afterload = decrease SV
how can you increase SV?
increase preload
increase contractility
increase fibre thickness
decrease afterload
