Regulation of cardiac contraction and cycle Flashcards
structures that blood passes through starting at vena cava
RA - RV - pulmonary artery - lungs - pulmonary vein - LA - LV - aorta - circulation - vena cava
how much of the ventricular volume fills passively in ventricular diastole
how much does atrial systole add
70%
30%
VENTRICLES
end diastolic volume
end systolic volume
stroke volume
ejection fraction
VENTRICLES
end diastolic volume ~130 mL
end systolic volume ~ 50 mL
stroke volume ~ 80 mL
ejection fraction ~ 65%
(normal range of EF 55-75%)
cardiac output at rest
what is the definition
5 L/min (each ventricle)
flow rate out of one side of the heart
AT REST
heart rate
stroke volume
cardiac output
venous return
AT REST
heart rate: 70 bpm
stroke volume: 70-80 mL
cardiac output: 5-5.5 L/min
venous return: 5-5.5 L/min
how is cardiac output calculated
heart rate X stroke volume
what controls stroke volume
why
venous return
increasing the end diastolic volume stretches the ventricles
this increases the pressure they can generate
frank-starling law
“within physiological limits the heart pumps all the blood it receives”
increased venous return stretches the ventricles and increases the force production until cardiac output matches venous return
contractility
what regulates it
a change in contractility is defined as a change in the work performed by the heart not brought about by a change in initial fibre length
sympathetic NS
isovolumetric contraction
the contraction occurring does not change the volume but does the pressure
what intraventricular pressure is required to open the aorta
why
80 mmHg
normal BP = 120/80, so much increase past diastolic pressure in the arteries
action of sympathetic stimulation
increases cardiac contractility
at rest the heart is under sympathetic tone
effect of parasympathetic stimulation on contractility
little effect
intrinsic regulation of cardiac contraction
venous return
gives a constant ejection fraction
extrinsic regulation of cardiac contraction
what are inotropic agents
autonomic nerves, hormones and drugs that alter force of contraction
agents that alter contractility (SNS stimulation, adrenaline)
