Physiology 534 Final: Cardiac Output 1

Front 1

The volume of blood pumped by the heart per unit time

Back 1

Cardiac output

Front 2

The volume of blood ejected from the heart with each beat

Back 2

Stroke volume

Front 3

Cardiac output =

Back 3

SV x HR

units ml/min or L/min

Front 4

The ventricular volume at the moment diastole ends when the mitral valve has just closed

Back 4

End diastolic volume

Front 5

The ventricular volume after ventricular systole

Back 5

End systolic volume

Front 6

SV

Back 6

EDV-ESV

Front 7

The ventricular wall is made up of 3 layers

Back 7

1. myocaridum
2. epicardium-outside heart and contains loose CT, nerves, and blood vessels
3. endocarium-layer on the inside of the heart (nearest to the blood)

Front 8

The tissue that separates the atrial muscle from the ventricular muscle

Made up of dense fibrous CT, annulus fibrosis, the muscle of the heart inserts on this fibrous skeleton

Back 8

Fibrous skeleton

Front 9

Endothelium

Back 9

-Innermost layer
-Simple squamous cells, continuous with vascular intima

Front 10

Subendocarium

Back 10

-contains the specialized conducting system called purkinje fibers

Front 11

Characteristics of purkinje fibers

Back 11

Do not have prominent striations (contractile proteins), have a lot of glycogen (not stained), larger than cardiac myocytes

Front 12

Myocardium

Back 12

-spiral layer
-attached to the cardiac skeleton

Front 13

What are the factors that determine SV

Back 13

1. preload
2. afterload
3. contractility

Front 14

The force on the ventricular wall acting to stretch the ventricular muscles at the end of diastole

Stretching the muscle out as the ventricle fills

Back 14

Preload

Front 15

The force-length relationship in regards to preload.

Back 15

As the preload increases, the muscle cell lengthens and the longer the cell lengthens the more forcefully they will contract.

Front 16

What are other proxies for preload?

Back 16

1. EDV
2. EDP
3. Ventricular filling
4. L atrial pressure
5. End diastolic wall tension

Front 17

La Place's Law

Back 17

The force acting on the ventricular wall is related to the ventricular pressure and the radius

T = Ventricular P x Ventricular radius

Front 18

How is compliance related to preload?

Back 18

The more compliant the ventricle is, the more the fibers will be stretched and the higher the EDV

Front 19

What are the names given to the relationship between preload and SV?

Back 19

Starlings Law of the Heart (heterometric autoregulation)

Front 20

Preload has an effect on what?

Back 20

End diastolic fiber length which is the core determinant of SV.

Front 21

How is end diastolic fiber length related to SV?

Back 21

Increased filling of the heart-->increased length of the sarcomeres-->increased force of contraction-->increases SV

Front 22

Heart disease does what to compliance?

Back 22

It dec complaince-->larager inc. in wall force-->larger inc. in EDP to get the same inc. in stretch to inc. muscle fiber length.

Front 23

What is the best correlate of the degree of stretch of ventricular muscle?

Back 23

The end diastolic volume because you don't have to worry about compliance unlike EDP.

Front 24

The ability of cardiac muscle to develop contractile force at a given diastolic fiber length

Back 24

Contractility

Front 25

The relationship between SV and ED fiber length

Back 25

Increased contractility is an incr. in stroke volume at a constant end-diastolic fiber length.

Front 26

With increased contractility, there is increased?

Back 26

1. Force of contraction
2. Speed of contraction
3. Rate of relaxation

Front 27

Inc. contractility caused by inc. Epinephrine or NE

Back 27

Both bidn to B adrenergic receptors-->inc. contractility-->inc. cytosolic Ca +2.

Front 28

Increased HR has what effect on contracitlity?

Back 28

Small effect bc there isn't enough time to clear out all the calcium between beats so the cytosolic Ca goes up a little more.

Front 29

How does digitalis increase contractility?

Back 29

Inhibits Na/K ATPase--> dec. NaATPAase--> inc. [Na]-->inc. [Ca]

Front 30

Decreased contractility is caused by what physiologial mechansim?

Back 30

Decreased SNS activation
Small effect of inc. PNS activation

Front 31

What pharmacological mechanism causes decreased contractility?

Back 31

1. Calcium antagonist
2. Beta adrenergic receptor antagonists

Front 32

What other mechanisms cause decreased contractility?

Back 32

1. Dec. supply of energy
2. Altered expression of cardiac muscle proteins

Front 33

The force which ventricular muscle must develop in order to eject blood

Back 33

Afterload

Front 34

If the ventricular muscle has to develop more force to eject blood (afterload) it tends to eject more/less blood?

Back 34

Less blood-->less SV

(throwing a heavy pen vs. light pen)

Front 35

How can afterload be increased?

Back 35

1. By an inc. in ventricular systolic pressure

2. Radius (think balloon example where the limpy part has less tension). The bigger the ventricle, the more force that must be developed to eject the bllod.

Front 36

When inc. afterload dec. SV, how does the heart restore the SV?

Starling's Law (heterometric autoregulation)

Back 36

less SV-->more bld left in ventricle-->heart starts o fill and the R heart will deliver the same volume that it delivered for the previous beat--> inc. in EDV-->inc. SV

Front 37

Chronic inc. in afterload

Myocaridal hypertrophy (long arm)

Back 37

Causes hypertrophy

Hypertrophy caused by activation of cell adhesion molecules

Front 38

Another way to restore dec. SV caused by inc. afterload

Homeometric autoregulation

Back 38

Increases contractility