Control Of Cardiac Output

Question 1

Define Afterload

Answer 1

The load the heat must eject blood against (Equivalent) to aortic pressure

Question 2

Define Preload

Answer 2

Amount of blood that fills the ventricles in diastole

Question 3

Define Total Peripheral Resistance

What is it also known as

Answer 3

Resistance to blood flow offered by all the systemic vasculature

Systemic vascular resistance

Question 4

Which vessels have the greatest resistance to blood flow

How does resistance affect the pressure of the blood leaving the stenosis

Answer 4

Arterioles

More resistance-> Less pressure

Question 5

If Cardiac Output is constant and TPR falls, what is the effect on;

Arterial Pressure
Venous Pressure

Answer 5

Arterial pressure- Decreases

Venous pressure- Increases

Question 6

If Cardiac Output is constant and TPR increases, what is the effect on;

Arterial Pressure
Venous Pressure

Answer 6

Arterial pressure- Increases

Venous pressure- Decreases

Question 7

If TPR is constant and Cardiac Output increases, what is the effect on;

Arterial Pressure
Venous Pressure

Answer 7

Arterial pressure- Increases

Venous pressure- Decreases

Question 8

If TPR is constant and Cardiac Output falls, what is the effect on;

Arterial Pressure
Venous Pressure

Answer 8

Arterial pressure- Decreases

Venous pressure- Increases

Question 9

What 2 things does the heart respond to changes in?

Compare the mechanisms by which it does this

Answer 9

aterial Blood Pressure, aBP
Central Venous Pressure, CVP

Intrinsic- Due to Myoarcium + Myocardial cells
Extrinsic- Due to Neurohormonal mechanisms

Question 10

How do you calculate Stroke Volume, SV

In what 2 ways, can you increase SV

Answer 10

SV= EDV-ESV
(End Diastolic Volume- End Systolic Volume)

Increase EDV OR Decrease ESV

Question 11

When filling ventricles, when do the walls stop stretching?

Explain the Ventricular Compliance Curve relationship

Answer 11

When Intraventricular pressure= Venous pressure

Higher venous pressure= Heart fills more
Heart fills more= Higher left ventricle pressure

Question 12

Compare increased and decreased compliance of the heart

Answer 12

Increased- Dilated/ Enlarged heart

Decreased- Smaller heart

Question 13

What is the Frank-Starling Law

On a Starling curve,
What is on the Y and X axis

Answer 13

The more the heart fills, the harder it contracts, up to a limit, leading to a bigger stroke volume

Y- Stroke volume (ml)
X- LV EDP/ LV EDV

Question 14

Define Contractility

Answer 14

The force of contraction for a given fibre length

Question 15

what 2 factors determine Cardiac Output

Answer 15

1. How hard it contracts
   Depends on EDV and Contractility
2. How hard it is to eject blood
   Depends on Aortic impedance (Arterial Pressure) (Afterload)

Question 16

How does exercise cause increased Cardiac Output

Answer 16

Metabolism increases-> TPR Decreases to supply more blood

Arterial pressure falls, venous pressure rises
Heart responds by pumping more

Question 17

Where is the Jugular Venous Pulse measured from?
What angle must patient at, where must they face?
Why from here?

Answer 17

• Right Internal Jugular Vein behind SCM Muscle
• 45 degrees and facing away
• A direct column of blood connected to right atrium

Question 18

Which 3 events increase JVP

Answer 18

• Right side of heart doesn’t pump out blood properly
• Volume overload with IV infusion
• If filling of heart is impaired

Question 19

What 2 ways can you measure JVP

Answer 19

1. Estimate highest visible pulsations+4cm

2. Insert Central line into Internal Jugular Vein