11. Control of Cardiac Output

Question 1

What is the venous pressure determined by?

Answer 1

A balance between rate at which blood enters the veins and the rate at which the heart pumps it out.

Question 2

If cardiac output remains constant, and total peripheral resistance falls, what happens to arterial and venous pressure?

Answer 2

Arterial pressure falls and venous pressure increases.

Question 3

If cardiac output remains constant, and total peripheral resistance rises, what happens to arterial and venous pressure?

Answer 3

Arterial pressure increases and venous pressure falls.

Question 4

If total peripheral resistance remains constant, and cardiac output rises, what happens to arterial and venous pressure?

Answer 4

Arterial pressure rises and venous pressure falls.

Question 5

If total peripheral resistance remained constant, and cardiac output falls, what happens to arterial and venous pressure?

Answer 5

Arterial pressure falls and venous pressure rises.

Question 6

How is total peripheral resistance linked to the body’s need for blood?

Answer 6

They are inversely proportional. If metabolism changes, the TPR changes too and this is controlled by signals in the form of changes in arterial and venous pressure.

Question 7

What is meant by demand led pumping of the heart?

Answer 7

If the body needs more blood, it needs to pump more to meet the demand. The demand is expressed as changes in arterial and venous pressure.

Question 8

What is stroke volume the difference between?

Answer 8

End diastolic volume and end systolic volume.

Question 9

What does the ventricular compliance curve show the relationship between?

Answer 9

Venous pressure and ventricular volume.

Question 10

What does Starlings law of the heart say about the force of contraction of ventricles?

Answer 10

Is the ventricular muscle is stretched more before contracting, so the end diastolic volume is larger, it will contract harder.

Question 11

What determines the extent at which the ventricles empty?

Answer 11

How hard the ventricle contract and how hard it is for blood to be ejected.

Question 12

What is force of contraction determined by?

Answer 12

The end diastolic volume, following Starlings law, and contractility.

Question 13

What increases contractility?

Answer 13

Sympathetic activity.

Question 14

What does the difficulty of ejecting blood mainly depend on?

Answer 14

Total peripheral resistance.

Question 15

What happens to stroke volume if arterial pressure falls?

Answer 15

It rises as it is easier to eject blood so more comes out.

Question 16

What happens to stroke volume if venous pressure rises

Answer 16

It rises.

Question 17

What is the preload?

Answer 17

Volume of blood in ventricles at the end of diastole.

Question 18

What is the afterload?

Answer 18

Resistance left ventricle must overcome to circulate blood.

Question 19

What are the effects on heart rate and contractility of falling arterial pressure?

Answer 19

Increased heart rate by reducing parasympathetic activity and increasing sympathetic activity. Increased contractility by increasing sympathetic activity.

Question 20

Where are rises in venous pressure detected?

Answer 20

In the right atrium, leads to reduced parasympathetic activity so a rise in heart rate. This is the Bainbridge reflex.

Question 21

What is arterial pressure determined by?

Answer 21

Cardiac output and total peripheral resistance.