Unit 4 - Wk 2 Physiology

Front 1

Frank Starling Relationship

Back 1

Increase in stroke volume and cardiac output in response to an increase in venous return or end diastolic volume

Increases in end diastolic volume cause an increase in ventricular fiber length, which produces an increase in developed tension; this mechanism matches cardiac output to venous return

Front 2

What mechanisms shift the frank starling relationship up or down

Back 2

Changes in contracility

Increased contractility; increased cardiac output for any level of right atrial pressure or end diastolic volume

Decreased contractility; decrease in cardiac output for any level of right atrial pressure or end diastolic volume

Front 3

Preload

Back 3

End diastolic volume, related to right atrial pressure; increased venous return = increased end diastolic volume = lengthened ventricular fibers

Front 4

Afterload

Back 4

Aortic pressure in the left ventricle; increases in aortic pressure cause an increase in afterload on the left ventricle

for the right ventricle it's pulmonary artery pressure; increases in pulmonary artery pressure cause an increase in afterload on the right ventricle

Front 5

When is the velocity of contraction at a fixed muscle length maximal?

Back 5

When the afterload is zero

Front 6

What decreases the velocity of contraction at a fixed muscle length?

Back 6

Increases in afterload

Front 7

Name the valves!

Back 7

Clinical significance; usually tricuspid/mitral and aortic/pulmonary are simultaneous; if there is a delay that you can hear a difference there may be a pathologic condition involved

Front 8

What is the first heart sound heard during the cardiac cycle?

Back 8

Closure of the AV valves; closes with alot of force due to rapid increase in pressure in the ventricles compared to low pressure in the atria

Their large size = lower pitch "lub"

Front 9

What is the second heart sound heard during the cardiac cycle?

Back 9

Aortic and Pulmonary valves closing; sound is a little sharper and higher pitched then first sound "Dub"

Front 10

What is the 3rd heart sound heard in the cardiac cycle?

Back 10

Very low pitch; caused by blood rushing into ventricles

Front 11

What is the 4th heart sound in the cardiac cycle?

Back 11

atrial contraction late in diastole; hard to hear with stethoscope except in hypertensive patients with a thick left ventricle

Front 12

Stenosis of Valve

Back 12

Stenosis = narrowing of valvular opening and fluid can't flow through as easily

2 problems; turbulent flow through valve (additional noise occuring when normal heart sound would not be heard)
increase in pressure from which the blood is flowing and decrease in pressure in receiving chamber

ex) AV stenosis = increase in atrial chamber, decrease in ventricular chamber

Front 13

Stroke Volume

Back 13

Amount of blood expelled from heart each time it beats

Front 14

Heart rate

Back 14

Number of times the heart beats per minute

Front 15

Cardiac Output

Back 15

Amount of blood pumped out of the heart per minute

Front 16

Why might you have a decreased stroke volume at high heart rates?

Back 16

Ventricles fill less = less output per beat = less stroke volume

Front 17

Cardiac Output = ?

Back 17

Cardiac Output = Stroke Volume x Heart Rate

Front 18

How is cardiac output regulated?

Back 18

Know these relationships well

Front 19

How does standing affect venous return?

Back 19

Decreases it decreasing end diastolic volume, decreasing stroke volume, and decreasing cardiac output

Front 20

What the normal ejection fraction?

Back 20

70%

Front 21

Relationship of contractility and ejection fraction

Back 21

Increase contractility = increased ejection fraction
Decreased contractility = decreased ejection fraction

Front 22

What is a potential complication of aortic stenosis?

Back 22

Left ventricular hypertrophy

Heart is overworked; increased oxygen demand; growth of heart tissue = decreased contractility = decreased cardiac output

Front 23

How might aortic regurgitation affect ventricular pressure?

Back 23

Increases ventricular pressure

Front 24

Mitral Stenosis Complications

Back 24

Increased atrial volume leads to increased atrial fibrillation; increased left atrial pressure could lead to pulmonary edema; increased right ventricular pressure could lead to right vent. failure

left ventricule normal

Front 25

Mitral Regurgitation Complications

Back 25

Increased left atrial pressure can -> pulmonary edema

increased left atrial volume -> atrial fibrillation

Front 26

What is the pressure in the aorta relative to the ventricle during the rapid ejection phase?

Back 26

Aortic pressure is less; this is why blood is flowing through it from the ventricle

Front 27

When does the aortic valve open?

Back 27

When ventricular pressure meets and exceeds aortic pressure

Front 28

Why is blood flow to the heart muscle highest in diastole?

Back 28

The heart contracting also prevents blood from flowing into it; coronary blood flow does not start until heart relaxation (diastole)

Front 29

Back 29

Pressure drops in capillaries as you move from arterial to venous side

Front 30

Ohms Law

Back 30

Q = dP/R

Front 31

Back 31

As the radius increase, the tension on the wall of a vessel increases (assuming constant pressure)

e.g. in the aorta it has a large cross sectional area relative to other vessels, larger radius, at a given pressure the tension on the walls will be greater; if the tension becomes great enough you get a tear in the wall which can cause a dissecting aneurysm

Front 32

Reynolds Number

Back 32

Useful for determining when turbulent flow will occur

Above 200-400 will result in turbulent flow at a branch in an artery

Numbers above 2000 will result in turbulent flow in a straight artery

Re = (V)(d)(p)/n

Front 33

Poiseuille's Law

Back 33

Explains the effect of a radius change relative to blood flow rate

Diameter from 1,2 and 4; radius is a significant factor on the flow rate

F = (pi)dP(r^4)/8nL

Front 34

Effect of Resistance in Series and Parallel

Back 34

Series: the resistance is added

Parallel: As you increase # of capillaries the total resistance will decrease, so you consider conductance

1/Rtot = 1/R1 + 1/R2...etc

Front 35

Distensibility =?

Back 35

Increase in volume/[(Increase in pressure)(original volume)]

Front 36

Relate to arterial pulse pressure

Back 36

Incisura (notch)

Compare pressure in aorta to arterial pulse pressure

Influences: perssure generated by left ventricle and total peripheral resistance by all the arterioles added to together; high resistance = lower runoff slope, lower peripheral resistance = rapid decay in pressure

Front 37

Back 37

MAP = [(systolic-diastolic)/3] + diastolic pressure

MAP = ((120-80)/3) + 80

Front 38

Vascular Filling Pressure

Back 38

Pressure obtained in arteries and veins after heart stops; after heart stops blood flows from arteries into veins until an equilibrium pressure is reached; generally = 7 to 12 mmHg

Front 39

why does systolic pressure increase as we move down the vascular tree from the heart towards the ankles?

Back 39

Rebound from wall of aorta + wave of returning blood bouncing back through oncoming pulse of blood

But we really don't completely understand

Front 40

Relationship Between Heart & Circulatory System

Back 40

Blood flow to tissue is delivered based on need
Cardiac output is determined by the sum of this need
Pressure is controlled by other factors in the body which regulate and control pressure independently

Front 41

Back 41

PDA and AR; high drop off pressure difference; resistance to outflow has been reduced by openings

Front 42

Back 42

Effect of sympathetic inhibition and stimulation on arterial pressure and flow

Front 43

Back 43

Blood Pressure and Age

Hardening of arteries may contribute to this

Front 44

Compliance

Back 44

C = dV/dP

Used to compare how easily a vessel can be distended; you can only make an accurate measure when the vessel is filled and you add volume (otherwise there is no change in pressure); at this volume you reach the capacitance of the vessel and from there you can measure compliance (measure of wall of vessel, need filled vessel)

Front 45

Capacitance

Back 45

Filling the container (what is its capacity)

Front 46

When and only when can you measure compliance?

Back 46

Only after the system is full

Front 47

Volume distribution between venous and arterial

Back 47

2/3 venous
1/3 arterial

Note compliance of arterial side = 6.54 mils, if you add 6.54 mils the bp will increase 1 mmHg
On venous side, youd have to ad 1650 ml of blood to make the bp increase 1 mmHg

Front 48

Back 48

As we increase venous pressure we increase cardiac output

If we stop heart and move cardiac otput to zero, there would be an equilibration of bp at 7 mmHg; where two lines cross gives us a representation of where this system would operate (CO = 5, VP = 2)

Front 49

What happens to venous pressure if you decrease CO to 0

Back 49

equilibration at 5 mmHg; filling pressure has decreased from 7 to 5 because of decreased volume in system; new cardiac output would be 3.8L and venous pressure would be 1.2

Front 50

What happens if you add blood?

Back 50

Filling pressure increases to 9
CO increases from 5 to 6.2 and venous pressure increases from 2 to 2.8

Front 51

Increase total peripheral resistance

Back 51

Done by constricting arterials; since we increase afterload by increasing TPR, CO decreases from 5 to 4, and VP decreases from 2 to 1.4
the decrease in CO is due to decreased VP and that the heart is having to pump against an increased pressure
VP decreases because there is increased resistance to flow from arterial to venous side; more blood from

Front 52

Back 52

CO increases, VP increases, filling pressure remains the same; anytime we change TPR we change the slope of the line
changing blood volume changes filling pressure but does not change the slope

Front 53

Decreasing venous compliance

Back 53

Makes change similar to what occurs if you add blood volume; equivalent to making walls of veins stiffer/thicker; equivalent to reducing the size of the container

amount of blood remains the same but an increase in VP due to the fact that the container is effectively smaller

Front 54

Increase in venous compliance

Back 54

Similar to making wall of vein more distensible; similar to making container larger;

VP decreases, CO decreases, filling volume has decreased; similar to loosing blood

Front 55

Back 55

Increase CO to 6, decrease VP from 2 to 1

the decrease in VP is because were moving more blood from venous to arterial side;

Front 56

Back 56

Decrease in filling pressure from 7 to 6 due to blood loss; resulted in increased sympathetic stimulation pushing curve up to left; increase in total peripheral resistance which changed shape of vascular function curve; now we function where golden and red line cross, right at 0 VP, CO = 3.8

Mistake: central venous pressure should flatten and go straight across at central venous pressure of 0

Front 57

Back 57

Even though we have the ability to stimulate the heart through sympathetic system, the heart can not respond; when this occurs blood pressure decreases