Control Of Cardiac Output

Question 1

What happens if total peripheral resistance rises and cardiac output remains constant?

Answer 1

The arterial pressure will rise and the venous pressure will fall

Question 2

What happens if cardiac output rises and the total periphral resistance remains constant?

Answer 2

Atreial pressure will rise and the venous pressure will fall

Question 3

What happens if the cardiac output fall and the total peripheral resistance remains constant?

Answer 3

Atreial pressure will fall and the venous pressure will remain constant

Question 4

How are changes in demand for blood met after a meal?

Answer 4

The gut needs more blood, so local vasodilators dilate the arterioles and the total peripheral resistance falls

Question 5

Describe the proccess of demand led pumping.

Answer 5

If the body needs more blood, the heart needs to pump more

Question 6

What is starlings law of the heart?

Answer 6

If the ventricle is stretched before contracting the heart contracts harder

Question 7

How does starlings law happen?

Answer 7

Rises in venous pressure leads to a rise in stroke volume, and this fills the ventricles, causing them to stretch and therefore contract harder

Question 8

Describe some of the features of the starling curve

Answer 8

Relates the stroke volume to the venous pressure, the slope is known as the contractility of the ventricle

Question 9

What does how much the ventricle empty depend on?

Answer 9

How hard it contracts and how hard it is to eject blood

Question 10

What determines the force of contraction?

Answer 10

The end distoolic volume and the contractility

Question 11

How do you increase contractility?

Answer 11

Sympatheic activity to the heart

Question 12

What is preload?

Answer 12

The volume of blood in the ventricles at the end of diastole

Question 13

What is afterload?

Answer 13

The resistance the left ventricle must overcome to pump blood

Question 14

How is the heart rate controlled?

Answer 14

The autonomic outflow is controlled by signals from the baroreceptors, and the carotid sinus sense the Aterial pressure, sends signals to the medulla which controls the heart.

Question 15

What happens if there is a rise in venous pressure?

Answer 15

It is sensed in the right atrium, leading to reduced parasympatheic activity and a raise in the heart rate known as the Bainbridge reflex

Question 16

How is a fall in aterial pressure contered?

Answer 16

Increase in heart rate by increasing the Sympatheic activity, and a increase in contractility by increasing the Sympatheic activity

Question 17

What happens if total peripheral resistance falls and the cardiac output remains constant?

Answer 17

Aterial presure will fall and venous pressure will rise

Question 18

What is the normal cardiac output of the heart and the output during excercise?

Answer 18

At rest, 5l/min, from 5-15 during excericse.

Question 19

What are the different groups of baroreceptors found in the body?

Answer 19

The aortic arch, and the carotid body

Question 20

What are the baroreceptors?

Answer 20

The major blood pressure sensors

Question 21

What pressures of increase firing of the aortic arch?

Answer 21

Pressures> 100mmHg

Question 22

What pressures increase firing of the cartoid body increase firing?

Answer 22

Pressures > 50mmHg

Question 23

What is the normal blood pressure and what are the important features of the blood pressure?

Answer 23

It is 95mmHg, and this provides adequate pressure to perfuse and drive blood throug the CVS, there is a significant functional resevere available with many capillary beds not fully perfused, and if the blood presusre goes below 60 mmHg this can be singificaantly damaging to the CVS

Question 24

What is the acute effect of standing up on the CVS?

Answer 24

Mean arterial pressure falls by 20-25mmHg by starlings law, with both the arterial and venous pressure falling acutely, and tis causes RA filling to drop which reduces the stroke volume of the heart.

Question 25

How does the CVS respond to standing up?

Answer 25

Th ANS causes the TPR to increase to offset theMABP by increasing the arterial and venous smooth muscle tone, and the ans control causes the heart rate to rise. The leg veins have low distensible to limit the gravity pooling, and there are muscle pumps to pump blood up the legs

Question 26

How much does GI demand for blood increase after eating?

Answer 26

It goes from about 30 ml/min/100g to up to 250 ml/min/100g

Question 27

What is the effect on the CVS of eating a large meal/

Answer 27

Locl GI vasodilation reduces the TPR, the initial fall in arterial pressure leads to an increase in cardiac output before the CVS goes back to normal and the MABP adjusts

Question 28

What are the acute effects of excercise on the cardiovacular system

Answer 28

There is a marked increase in TPR and a marked increase in vasodilators, can lead to a decreased blood pressure which can lead to rapid excersie induced hyperaemia.

Question 29

How does the CV deal with excercise?

Answer 29

Heart rate increases in anticipation of excericise to help avoid CVP overfilling, baroreceptors signal the decrease in blood pressure, nd the SNS output increases to keep the blood pressure u, adn there is an increase in captivity to the gut

Question 30

What is a haemorrage.

Answer 30

This is a rapid loss of blood, with lossess of between 10-30% being very potentially damaging

Question 31

What is the effect of a heamorrage on the cardiovascular system?

Answer 31

Rapid loss of blood lowers the CVP drastically, and tissues react badly with a build up of metabolites and so vasodilate, producing a conflict as the MABP needs to be maintained

Question 32

How does the CVS respond to a haemmorage?

Answer 32

Very large SNS output for the TPR maintainance , and there is tachcardia of 120-150, caused again by a large SNS output, and blood supply is diverted to the brain and heart, other organs such as the kidneys lose their supply

Question 33

What are the potential outcomes of a haemorage?

Answer 33

There is either a gradual recovery in MABP or a loss in ability to maintain the MABP resulting in inadequate perfusion and therefore death