Lecture 6 - Control of the CVS Flashcards
what happens if total peripheral resistance falls?
arterial pressure falls
venous pressure rises
what happens if total peripheral resistance rises?
arterial pressure rises
venous pressure falls
what happens if cardiac output falls?
arterial pressure fall
venous pressure rises
what happens if cardiac output rises?
arterial pressure rises
venous pressure falls
define end diastolic volume
volume of blood in the ventricle at the end of diastole
define end systolic volume
volume of blood in the ventricle at the end of systole
define stroke volume
difference between end diastolic and systolic volume
what determines how much the ventricles fill during diastole?
venous pressure
fills until walls stretch until ventricular pressure equals venous pressure
define pre load
end diastolic stretch of myocardium (determined by venous pressure)
define after load
force necessary to expel blood into the arteries
how does end diastolic volume affect force of contraction?
the more the heart fills, the more it contracts, so the bigger the stroke volume
what is the relationship between venous pressure and stroke volume?
as venous pressure increases, stroke volume increases up to the point where the heart is over filled and the myocardium over stretched
define contractility
the gradient of the slope of the relationship between venous pressure and stroke volumenot the force of contraction but the stroke volume for a given venous pressure
what is the effect of the sns on contractility?
increases
makes the heart more susceptible to venous pressure
what happens to cardiac output when venous pressure rises?
rises
what happens to cardiac output when venous pressure falls?
falls
what happens to cardiac output when arterial pressure rises?
falls
what happens to cardiac output when arterial pressure falls?
rises
how does the cardiovascular system respond to a meal?
increased activity of the gut so released metabolites and local vasodilation
tpr falls so arterial pressure falls and venous pressure rises
venous pressure causes rise in co
arterial pressure causes rise in heart rate and co
extra heart pumping lowers venous and raises arterial to meet demand
how does the cardiovascular system respond to exercise?
increase in demand
muscle pumping forces extra blood back to the heart
venous pressure rises and arterial pressure falls
risk of pulmonary oedema if at the top of the starling curve so left heart cant respond to right so blood accumulates in lungs
overfilling of ventricles is prevented by rise in heart rate
when venous rises, hr is already high
stroke volume kept down but co increases
demand met
how does the cardiovascular system respond to standing up?
blood pools in superficial veins of legs central venous pressure falls co falls arterial pressure falls which baroreceptors detect hr rises but venous is still low tpr rises to defend arterial pressure
how does the cardiovascular system respond to haemorrhage?
reduced blood volume so venous pressure falls
co falls
arterial pressure falls which baroreceptors detect
hr rises, tpr rises
hr rise means venous falls further
venoconstriction rises venous
need blood transfusion to replace lost volume
how does the cardiovascular system respond to long term increase in blood volume?
blood volume is under renal control
blood volume increases for days leads to venous pressure rise
co rises
arterial rises
more blood perfuses tissues which autoregulate and increase tpr
arterial rises further and stays up
