Lecture 6 - Control of the CVS

Question 1

what happens if total peripheral resistance falls?

Answer 1

arterial pressure falls

venous pressure rises

Question 2

what happens if total peripheral resistance rises?

Answer 2

arterial pressure rises

venous pressure falls

Question 3

what happens if cardiac output falls?

Answer 3

arterial pressure fall

venous pressure rises

Question 4

what happens if cardiac output rises?

Answer 4

arterial pressure rises

venous pressure falls

Question 5

define end diastolic volume

Answer 5

volume of blood in the ventricle at the end of diastole

Question 6

define end systolic volume

Answer 6

volume of blood in the ventricle at the end of systole

Question 7

define stroke volume

Answer 7

difference between end diastolic and systolic volume

Question 8

what determines how much the ventricles fill during diastole?

Answer 8

venous pressure

fills until walls stretch until ventricular pressure equals venous pressure

Question 9

define pre load

Answer 9

end diastolic stretch of myocardium (determined by venous pressure)

Question 10

define after load

Answer 10

force necessary to expel blood into the arteries

Question 11

how does end diastolic volume affect force of contraction?

Answer 11

the more the heart fills, the more it contracts, so the bigger the stroke volume

Question 12

what is the relationship between venous pressure and stroke volume?

Answer 12

as venous pressure increases, stroke volume increases up to the point where the heart is over filled and the myocardium over stretched

Question 13

define contractility

Answer 13

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

Question 14

what is the effect of the sns on contractility?

Answer 14

increases

makes the heart more susceptible to venous pressure

Question 15

what happens to cardiac output when venous pressure rises?

Answer 15

rises

Question 16

what happens to cardiac output when venous pressure falls?

Answer 16

falls

Question 17

what happens to cardiac output when arterial pressure rises?

Answer 17

falls

Question 18

what happens to cardiac output when arterial pressure falls?

Answer 18

rises

Question 19

how does the cardiovascular system respond to a meal?

Answer 19

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

Question 20

how does the cardiovascular system respond to exercise?

Answer 20

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

Question 21

how does the cardiovascular system respond to standing up?

Answer 21

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

Question 22

how does the cardiovascular system respond to haemorrhage?

Answer 22

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

Question 23

how does the cardiovascular system respond to long term increase in blood volume?

Answer 23

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