Starling Curve

Question 1

pressure work

Answer 1

work needed to move blood from low pressure veins to high pressure arteries. 99% of energy used (volume pressure work or external work)

Question 2

kinetic energy of blood flow

Answer 2

work needed to accelerate blood to its ejection velocity 1% of total work ( can increase to 50% during aortic stenosis). proportional to mass of blood ejected times velocity of ejection.

Question 3

work load of right heart

Answer 3

1/6 of left heart

Question 4

stroke work output

Answer 4

amount of energy converted to work during each beat

Question 5

minute work output

Answer 5

total energy converted to work per minute (stroke work x HR)

Question 6

are within vol. pres. curve

Answer 6

proportional to net external work. since kinetic work is usually small can consider it the stroke work output of heart .

Question 7

total energy

Answer 7

stroke work output plus potential energy

Question 8

potential energy

Answer 8

additional work heart could do if it were able to contract enough to empty ventricle.

Question 9

cardiac efficiency

Answer 9

ratio of energy that is converted to work vs total energy consumed. work output/ total energy used. rest is lost as heat

Question 10

normal cardiac efficiency

Answer 10

20-25%. Heart failure can go as low as 5-10%

Question 11

optimal filling of heart

Answer 11

120-170. after that get increase in diastolic pressure.

Question 12

max pressure generation

Answer 12

250-300 mmHg (60-80 for RV)

Question 13

EDV and EDP

Answer 13

120 mls. 5-7 mmHG

Question 14

ESV AND ESP

Answer 14

50 MLS 2-3 mmHg

Question 15

max CO

Answer 15

15L/min

Question 16

factors affecting HR

Answer 16

para/sympathetic tone of heart

Question 17

factors changing SV

Answer 17

intrinsic contractility (preload), afterload, extrinsic contractility

Question 18

1 mmHg change in preload changes ventricular vol. by…

Answer 18

25 mls

Question 19

1 mmHg change in afterload reduces SV by…

Answer 19

.5 ml

Question 20

fiber cannot shorten as much with increased afterload because…

Answer 20

at end of systole the fibers have to support higher tension which requires longer end systolic length

Question 21

increased contractility affect on graph

Answer 21

left movement of ESV/ESP relationship, same systolic pressure at lower systolic volume. increases slope of line

Question 22

estimation of contactility based on slope of line

Answer 22

change in pressure/ change in volume

Question 23

energy production from heart

Answer 23

70-90% from oxidative metabolism of fatty acids, 10-30% from lactate and glucose (fetal hearts use mostly lactate and glucose to make ATP)

Question 24

myoglobin

Answer 24

heart protein that binds with O2 making it easier for heart to extract O2 (venous sat at 25%)

Question 25

only way to increase o2 supply to heart

Answer 25

increase coronary blood flow

Question 26

basal metabolism of heart

Answer 26

25% of overall o2 use. maintains active transport mechanisms in cell

Question 27

muscle contraction o2 consumption

Answer 27

75% ATP use associated with cross bridges . sequestration of calcium

Question 28

isovolumetric contraction

Answer 28

50% of overall O2 use larget consumer. o2 use related to afterload. related to tension not pressure

Question 29

law of laplace

Answer 29

tension= pressure x radius reduction of preload will decrease o2 use

Question 30

stroke work

Answer 30

volume x pressure. increases in pressure more costly than volume .

Question 31

afterload vs preload. contractilty vs HR on O2 USE

Answer 31

AFTERLOAD AND CONTACTILITY HAVE GREATER EFFECT ON O2 USE