Integration of the heart and blood vessels

Question 1

Changes in cardiac output can be both physiological
e.g. ?
Or pathophysiological
e.g. ?

Answer 1

exercise/change in posture

heart failure, haemorrhage

Question 2

Key component in

cardiovascular regulation:

Answer 2

• Cardiac function
• Vascular function
• Blood volume (via kidneys)

Question 3

coupling factors?
cardiac factors?
of cardiac output

Answer 3

Preload and Afterload: in
part dependent on Vascular
Function

HR and myocardial contractility

Question 4

Cardio-centric view:

CO =

Answer 4

SV x HR

Question 5

Integrated view:
(proposed by Arthur Guyton)
CO =

Answer 5

Total tissue blood flow

= ΔP/TPR

Question 6

Arthur Guyton Demonstrated that in most cases the need for oxygen in ____tissues determined ______ ______rather than the pumping ability of the heart itself.

Answer 6

body

cardiac output

Question 7

Cardiac Output Curve

Plateau determined by?

Answer 7

Plateau determined by heart strength

contractility x HR

Question 8

Cardiac output is
dependent on ____
return

Answer 8

venous return
(preload)

Question 9

what determines venous return?

Answer 9

Venous return is dependent on the
pressure gradient (Pa-Pv) and vascular
resistance……. i.e. vascular function

Question 10

Venous return formula=

Answer 10

Pa-Pv/R

Pa-Pv: The pressure gradient for flow
• Pv (right atrial pressure) is very
dependent on degree of filling (i.e.
blood volume and venous capacitance)
~ mean systemic filling pressure
• R: Systemic vascular resistance

Question 11

Pa-Pv pressure gradient is dependent on?

Answer 11

cardiac output

Question 12

Increasing “pump speed” (cardiac
output) will increase arterial and
reduce ____ ________ pressure

Answer 12

right atrial

Question 13

the pressure in the system when

cardiac output = 0

Answer 13

Mean Systemic Filling Pressure (MSF)

Question 14

MSF usually about

Answer 14

7 mmHg

Question 15

Vascular function curve (Venous return)

Answer 15

Mean systemic filling pressure at venus return (y-axis)=0
Above Right atrial pressure (x-axis)=0 is down slope. As right atrial pressure increases venous return decreases (due to pressure gradient)
The plateau left of 0 is caused by the large veins collapsing as they enter the
chest if the pressure is lower than
atmospheric

Question 16

Vascular function curve (Venous return)
Usual right atrial pressure is 0-2
mmHg, resulting in a venous
return of about ?

Answer 16

5 L/min

Question 17

Mean Systemic Filling Pressure

Major determinants are:

Answer 17

1. Blood Volume:
   5000 mL ~ 7mmHg MSFP
   4000 mL ~ 0 mmHg MSFP
2. Venous compliance (sympathetic tone)

Question 18

Increasing blood volume or increasing
sympathetic stimulation dramatically
increases ?

MCFP ~ MSFP (pulmonary circulation
only contains about 10% of BV)

Answer 18

MSFP

Mean Systemic Filling Pressure

Question 19

At any given right atrial pressure, as
mean systemic filling pressure (MSFP)
increases venous return will ?

Answer 19

increases

Question 20

Increase blood volume = _______MSFP
Decrease in capacitance (C) (i.e.
increased venous tone) = _______MSFP

Answer 20

increased

increased

Question 21

Altering vascular resistance e.g. vascular
tone alters venous return:
- An increase in peripheral resistance
results in ?

Answer 21

a reduction in venous return at
any given right atrial pressure

Note there is no major effect on mean
systemic filling pressure (Psf) i.e. when no
flow)

Question 22

increased ___leads to
increased vascular resistance and
increased venous tone, increasing
Psf

Answer 22

SNA

Question 23

______ -_____ _______
Represents Frank-Starling
relationship i.e. dependence of cardiac
output on preload (i.e right atrial pressure)

Answer 23

Cardiac function curve.

Question 24

Cardiac function curve
-increased sympathetic stimulation results
in increased output at any filling pressure
due to increase in _____and _________

Answer 24

inotropy

heart rate

Question 25

Guyton Analysis
At steady state:
Cardiac output =

Therefore the equilibrium point will be
where what curves intercept?

Answer 25

Venous return

cardiac function curve and vascular function curve intercept

Question 26

Venous return response to Sympathetic stimulation -

Answer 26

Increased mean systemic filling
pressure as a result of decreased
capacitance
• Decrease in systemic resistance
• Also assisted by increased
ventilation and muscle pumps
assist venous return

Question 27

Heart failure can be viewed as a _____________ in which the
compensatory mechanisms ultimately
contribute to the further deterioration of
the cardiovascular system.

Answer 27

positive

feedback system

Question 28

Diuretic in Treating Heart Failure

Answer 28

• reduce venous pressure (RAP)
• Reduce oedema
- but will reduce output!

Question 29

Treating Heart Failure aims to

Answer 29

: to reduce afterload/inotropy

to reduce the work of the heart!

Question 30

ACE inhibitors/ARB in Treating Heart Failure

Answer 30

• Vasodilation (reduce afterload thus work)
• Reduces remodelling
• Reduces blood volume (MSFP)

Question 31

Beta blockers in Treating Heart Failure

Answer 31

Reduce energy demand by reducing cardiac
function (also reduces chance of arrhythmias)

Question 32

A healthy heart pumps out what goes in: Cardiac

output is dependent on ?

Answer 32

tissue needs.

Question 33

Blood volume, venous capacitance and arteriolar

resistance are key determinants of ?

Answer 33

venous return

Question 34

The cardiovascular system is ________.

Answer 34

integrated

meaning blood vessels are important

Question 35

Right atrial pressure=

Answer 35

preload