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Flashcards in control of cardiac output Deck (52):
1

the cardiac output is controlled mainly by

the sum of all the local tissue flows

2

cardiac output

the quantity of blood pumped into the aorta each minute

3

venous return

the quantity of blood flowing from the veins into the right atrium each minute

4

CO =

HR x SV

5

SV =

EDV - ESV

6

EF =

SF/EDV = EDV-ESV/EDV

7

end diastolic volume - end systolic volume =

stroke volume

8

which affects CO more? HR or SV?

HR. changes in HR alone inversely affect stroke volume

9

at low HR, increase in HR is greater than

decrement in SV

10

Bowditch (Treppe or staircase phenomenon)

an increase in HR will also cause positive ionotrpy duets an increase in intracellular Ca+++ with a higher HR

11

preload

the initial stretching of the cardiac myocytes prior to contraction. it is related to the sarcomere length at the end of diastole.

12

what are the indirect ways to measure preload

LVEDV, LVEDP, PCWP, CVP

13

determinants of preload

venous BP, vasomotor tone, venous volume, venous retur, total blood volume, respiration, excerise, filling time (HR), ventricular compliance, atrial contraction, inflows outflow resistance, ventricular systolic failure

14

Frank-Starling Mechanism

When venous return to the heart is increased, ventricular filling increases, as does preload. This stretching of the myocytes causes an increase in force generation, which enables the heart to eject the additional venous return and thereby increase stroke volume.
(the heart pumps the blood that is returned it)

15

increasing venous return and ventricular preload leads to

increase in stroke volume

16

Afterload is closely related to

aortic pressure

17

afterload is

the "load" that the heart must eject blood against

18

LaPlace's Law is for which concept

after load

19

what is LaPlace's Law

wall stress = Pr/h. p is ventricular pressure, R is ventricular radius, h is wall thickness

20

aortic pressure does what to afterload

increased aortic pressure increases afterload

21

SVR does what to afterload

increased SVR increases afterload

22

aortic valve stenosis effect on afterload

increases

23

ventricular dilation effect on afterload

increases

24

Anrep effect

an abrupt increase in afterload can cause a modest increase in inotropy

25

contractility

the inherent capacity of the myocardium to contract independently of changes in afterload or preload.

26

alternative name for contractility

iontropy

27

changes in contractility are caused by

by intrinsic cellular mechanisms that regulate the interaction between actin and myosin independent of sarcomere length.

28

decreased iontropy does what to stroke volume and LVEDP?

decrease SV and increases LVEDP

29

increased iontropy does what to stroke volume and LVEDP

increase SV and decrease LVEDP

30

increased afterload does what to contractility

increases - anrep effect

31

what are the four major determinants of CO

contractility, stroke volume, HR, preload

32

to increase stroke volume, ____ End-diastolic volume

increase

33

to increase stroke volume ___, End-systolic volume

decrease

34

preload is directly related to _____ because of frank starling

CO. preload increases, CO increases. preload decreases, CO decreases

35

What physiologic relationship keeps cardiac output of the ventricle matched with venous return?

Frank starling mechanism – allows the heart to readily adapt to changes in venous return. Increasing venous return and preload leads to an increase in SV.

36

What physiologic relationship keeps the cardiac output of the right and left ventricles matched?

Frank starling – outputs of the two ventricles are matched over time, otherwise blood volume would shift between the pulm and systemic circulations

37

what parameter is on the y axis of starling curve

SV

38

what parameter is on the x axis

LVEDP

39

what factors can cause an increased after load?

Increased aortic pressure, increased SVR, aortic valve stenosis, ventricular dilation

40

Increasing afterload ____ SV

decreasese

41

decreasing afterload ______ sv

increases

42

q: during the phase of rapid ventricular filling

mitral valve open

43

q: rv preload is increased by ___ HR

decreased HR. more time is available for filling at reduced heart rates; therefore preload is increased.

44

effect on decreased atrial contractility, decreased blood volume, and decreased ventricular compliance on preload

reduced ventricular filling, reduced preload

45

increase in preload is a _____ in sarcomere length

increase

46

as the preload on a ventricular myocyte is increased,

active tension development increases

47

LVEDP is ____ by ventricular hypertrophy

increased

48

ventricular stroke volume is ____ by decreased ionotropy

reduced

49

ventricular stroke volume is ___ by reduced HR

increased - more filling

50

left ventricular end-systolic volume is ___ when iontrophy is impaired

increased

51

increasing afterload decreases ejection velocity and stroke volume, which leads to an ___ in end-systolic volume

increase

52

an increase in end diastolic volume will ____ SV, but stroke volume changes are about 1/4 as effective in changing myocardial oxygen consumption compared to changes in HR, MAP, or ventricular radius

increase