heart function curves

Question 1

what is the relationship between cardiac output and venous return

Answer 1

venous return is equal to cardiac output

Question 2

what compartments make up the venous system

Answer 2

central (great veins of the thorax and right heart) and peripheral venous compartments(peripheral veins of the body)

Question 3

what is the venous return

Answer 3

the rate at which blood return to the right atrium of the heart from the body

Question 4

what is CO

Answer 4

the rate at which blood s ejected from the left ventricle and moves through the aorta and systemic circulation

Question 5

what is the central venous compartment

Answer 5

• volume of blood enclosed by the right atrium and the great veins of the thorax

Question 6

how can the volume of blood in the central venous compartment be measured clinally

Answer 6

• as the right ventrical preload
• right atrial pressure(preload)
• and central venous pressure

Question 7

cardiac and vascular function curve:
- what does the cardiac function curve ( cardiac output curve) demonstrate
- what law is this
When does it plateau

Answer 7

• demonstrates the direct relationship between central venous pressure (right atrial pressure) on cardiac output
• as central venous pressure increases up to 4mmhg CO increases but beyond 4mmhg CO reaches a steady state because the heart has reached its limit
• Frank Starling law of the heart

Question 8

cardiac and vascular function curve:
- what does the vascular function curve demonstrate ( venous return curve).

Answer 8

• demonstrates the inverse (negative effect) of central venous pressure on venous return
• as central venous pressure increases venous return decreases

Question 9

what is the mean systemic (circulatory) pressure

Answer 9

• the volume of blood in the total systemic circuit, when the heart is in cardiac arrest and no blood is flowing through the system

Question 10

what is the equilibrium point

Answer 10

is the point which cardiac output and venous return are always equal and stabalized

Question 11

what does the venous return back to the heart depend on

Answer 11

• a pressure gradient between the central and peripheral venous compartment

Question 12

what happens to venous return as the right atrial pressure falls below 0

Answer 12

the intrathorasic pressure is higher, which will cause a collapse of the veins and a plateu of the venous return

Question 13

what may decreases in peripheral venous pressure result from

Answer 13

• blood loss by hemorrhage
• loss of body fluid through severe sweating, diarrhea or vomiting
• venodialation ( decrease sympathetic stimulation)

Question 14

what may increased peripheral venous pressure be a result from

Answer 14

• blood transfusion
• fluid retention in the kidneys
• increases in circulating blood volume
• venoconstriction ( increased sympathetic stimulations)
• venous compressions
• exercise
• wearing elastic stockings

Question 15

what may mean systemic pressure be affected by

Answer 15

can be affected by changes in circulating Blood volume, venous reserve, and venous tone ( venous constriction or dilation)

Question 16

what deoes a positve and negative inotropic drug do to the cardiac function curve
( increasing and decreasing contractility)

Answer 16

• postive: decreases atrial pressure and increases cardiac output and venous return( equib pt is also higher
• negative: increases right atrial pressure because reduced contractile force and decreased CO and venous return

Question 17

what happens to the vascular function curve when you increase and decrease BV

Answer 17

• increase BV: increase in right atrial pressure and increase in CO and venous returnBV: decrease right atrial pressure and decrease CO and venous return

Question 18

what happens to mean systemic pressure when you increase and decrease BV

Answer 18

• when you increase BV mean systemic pressure increases and when you decrease BV it

Question 19

what does it mean when you increase TPR

Answer 19

• youre increases resistiance to flow via vasoconstriction

Question 20

what happens to the cardaic function and venous return curves when you increases and decrease TPR
and why

Answer 20

• when you increases TPR venous return and cardiac output decreases but right atrial pressure stays the same (because rate of blood flow is descreassinf)
• when you decrease TPR venous return and CO increases and right atrial pressure stay the same ( bc rate of blood flow is increasesing- vasodilation)

Question 21

what happens to mean systemic pressure when you increases and decrease TPR and why

Answer 21

• it stay the same because blood volume isn’t changing

Question 22

what do work (solid and fluid) equal ?

Answer 22

work(solid)= force (F) x distance
work (liquid)= volume x pressure

Question 23

what is the the work being performed during a normal HR and what is the definsiton

Answer 23

• the worked being performed is called stroke work
• and it is the work of the ventricles oto eject blood out of the aorta

Question 24

via which formula can stroke work be calculated

Answer 24

Question 25

what is stroke work performed by init time called

Answer 25

power

Question 26

what is the power of the heart known as? and how can it be calculated

Answer 26

-

Question 27

into what components can stroke work and cardiac minute work be divided into

Answer 27

• pressure work (aortic pressure)
• volume work ( CO anf stroke volume)

Question 28

how does pressure work diffir from volume work

Answer 28

pressure work consumes more energy

Question 29

what is the enrgy consumed by the heart known as

Answer 29

myocardial oxygen consumption (MVO2) ans is the amount of oxygen consumed by the heart per minute

Question 30

what is the relationship between myocardial ocygen consumption and stroke work and cardiac minute work

Answer 30

directly proprotional

Question 31

what is mechanical efficency

Answer 31

the ratio between work of the heart and oxygen consumption

Question 32

what is the mechanical efficency eqn

Answer 32

= external worked performed/ O2 consumption

Question 33

what happens with pressures and SV with an increased afterload?
- what happens to oxygen consumptions and mechanical efficenty

Answer 33

• with an increased afterload ( hypertension or aortic stenosis) high pressures are required to eject SV
• o2 consumption increases and mechanical efficiency decreases

Question 34

how does strenous exercise effect CO

Answer 34

increases CO

Question 35

how oxygen consumptionduring exercise compare to the Mechancial efficiency during elevated afterload

Answer 35

• although oxygen consumption increaes it is a smaller change when compared to the reduction in mechanical efficiency with an elevated afterload
• thus mechanical efficiency is reduced but to a lesser extent

Question 36

how does left ventricular presure work comapre to the right
- how does pressure work effect ventricular thickenss

Answer 36

• left ventricular pressure work is greater and pressure work increases ventricular wall thickness thus the left is thicker than the right

Question 37

how does the work of the right heart compare to the left and why (numerical)

Answer 37

• work done by the righ heart is 1/6 of the rok of the left heart because the mean pulmonary pressure is 1/6 of the aortic

Question 38

what happens to tension as pressure and volume work increase

Answer 38

• wall stress/tension increases

Question 39

what is the law of laplace

Answer 39

• the tension of the wall is the product of the pressure and the radius of the chamber and the tension is inverselt related to the thickness of the wall

Question 40

what is thw eqn for the law of laplace

Answer 40

Question 41

what happens to the heart moprpholgy as you increase pressure or volume

Answer 41

• with increased pressure or volume load, the heart will undergi hypertrophy to reduce wall stress

Question 42

what is the effect of excessive preload on heart morphology

Answer 42

eccentric hypertorphy

Question 43

what is the effct of excessive afterload on heart morphology

Answer 43