Regulation of stroke volume Flashcards
what is heart rate controlled by
neural activity
What does Starling’s law state?
the energy of contraction is proportional to the initial length of the cardiac muscle fibre
what does the term ‘preload’ mean?
the degree to which the ventricles are stretched prior to contracting
An increase in the volume or speed of venous return (blood returning to heart) will increase preload and, through Starling law, will increase stroke volume
what is preload affected by?
the end diastolic volume - ie the volume of blood that has filled the chambers after contraction
an increased EDV (end diastolic volume) would have what effect on stroke volume
stroke volume would increase
define stroke volume
volume of blood pumped by each ventricle each time heart contracts
decreased venous return would cause
decreased EDV and therefore decreased stroke vol
what does having matched stroke vol of both L and R ventricles ensure?
self-regulation
what is afterload?
the load against which the muscle tries to contract
what affect does hypercalcemia have on curve of stroke volume/EDV graph
shift curves up and left
increased calcium levels enhances contractility and strength of contraction so even if same EDV as before, with more calcium the heart is pumping more of that blood out in one contraction so increased SV
what affect does hypocalcemia have on curve of stroke volume/EDV graph
shifts curve down and right
what affect does ischaemia have on curve of stroke volume/EDV graph
shifts curve down and right
what is the end diastolic
volume of blood in the right and/or left ventricle at end load or filling in
what effect do barbiturates have on curve of stroke volume/EDV graph
shifts curve down and right
what is stroke volume
the amount of blood pumped by the left ventricle of the heart in one contraction.
