Control of Cardiac Output Flashcards
What is afterload
the load the heart must eject blood again (roughly equivalent to aortic pressure/impedance)
What is preload
amount the ventricles are stretched/filled in diastole. related to EDV or central venous pressure
what is total peripheral resistance (systemic vascular resistance)?
resistance to blood flow by all systemic vasculature
what happens to the pressure of fluid in a tube as it encounters resistance
the pressure decreases.
what does constriction of the arterioles do?
increases the resistance causing venous and capillary pressure to fall and arterial pressure to rise.
what will happen to arterial pressure and venous pressure if TPR falls and cardiac output remains the same
arterial pressure will decrease and venous pressure would increase
what will happen to arterial pressure and venous pressure if TPR increases and cardiac output remains the same
arterial pressure will increase and venous pressure will decrease
what effect does changing cardiac output have on arterial and venous pressures if TPR remains the same
if CO increases arterial pressure will increase and venous will decrease. Vice versa if CO decreases
How does the heart react to changes in tissue demand for blood
by detecting changes in the arterial BP and central venous pressure through intrinsic and extrinsic mechanisms.
what is cardiac output
the amount of blood pumped by the heart per unit of time. Usually litres per min. stroke vol x heart rate
what is stroke volume
the amount of blood pumped by the ventricles during systole. end diastolic volume- end systolic volume
what percentage of the normal EDV is the SV
67%
how can the SV change
by increasing the EDV or decreasing the ESV
what causes the ventricles to stop filling
when the venous pressure (pulmonary veins) is equal to the intraventricular pressure
what does the frank-starling law say
stretching a muscle before contraction leads to a greater force of contraction up until a point
