5.2 control of cardiac output

Question 1

Equation for cardiac output ?

Answer 1

CO (ml/min)= SV (ml) X HR (bpm)

Question 2

What is typical CO value ?

Answer 2

4900 ml/min because typical SV = 70ml and typical HR = 70bpm
~ 5L/min

Question 3

CO is what ?

Answer 3

volume of blood ejected from the ventricle each minute

Question 4

what is SV ?

Answer 4

stroke volume is volume of blood ejected from the ventricle with each heartbeat

Question 5

CO is not fixed, what is it effected by ?

Answer 5

increases with exercise
increases with pregnancy
eating

Question 6

What equation can be used to calculate SV ?

Answer 6

EDV - ESV
end diastolic volume - end systolic volume

Question 7

what is preload ?

Answer 7

tension in the myocardial fibres at the end of diastole

Question 8

What is known as the ventricular compliance curve ?

Answer 8

relationship between venous pressure and ventricular volume

Question 9

1. In diastole what relationship with ventricle, arteries and veins ?
2. when do the ventricles fill until ?

Answer 9

1. the ventricle is isolated from the arteries, and connected to the veins
2. the walls stretch enough to produce an intra-ventricular pressure equal to venous pressure

Question 10

Link between the venous pressure and volume of blood in the ventricles ?

Answer 10

The higher the venous pressure, the greater the volume of blood in the ventricles

Question 11

what is compliance of the ventricles ?

Answer 11

ease with which the ventricles expands when filled with blood

Question 12

For the ventricles what gives a measure of stiffness ?

Answer 12

opposite of compliance curve (C = change in V/ change in P) so change in pressure / change in volume

where measure of stiffness is opposite of compliance and as volume increases so does stiffness

Question 13

What is starlings law of the heart ? [change]

Answer 13

the greater that ventricular muscle is stretched, the harder it contracts (within limits)

so the more it fills = the more it contracts = the greater the stroke volume

the more in , the more out

Question 14

The slope (gradient) of frank-starling curves is a measure of what ?

where stroke volume on y-axis
and ventricular end-diastolic volume on x-axis

Answer 14

contractility of the ventricles

Question 15

What is cardiac contractility?

Answer 15

cardiac work performed independent of pre-load or after-load

Question 16

Approximately what percentage of available actin-myosin cross bridges are active during contraction at rest?

Answer 16

40%