6. Control of the Cardiovascular System

Question 1

At a constant cardiac output, a rise in total peripheral resistance does what to arterial and venous pressures?

Answer 1

Arterial pressure rises

Venous pressure falls

Question 2

At a constant total peripheral resistance, a rise in cardiac output does what to arterial and venous pressures?

Answer 2

Arterial pressure rises

Venous pressure falls

Question 3

At a constant total peripheral resistance, a fall in cardiac output does what to arterial and venous pressures?

Answer 3

Arterial pressure falls

Venous pressure rises

Question 4

How can stroke volume be increased?

Answer 4

Increase end diastolic volume by increasing ventricular filling
Decrease end systolic volume by ejecting more blood

Question 5

What is preload?

Answer 5

The end diastolic stretch of the myocardium, determined by venous pressure

Question 6

What is after load?

Answer 6

Force required to expel blood into the arteries

Question 7

Describe Starling’s law of the heart

Answer 7

The more the heart fills, the harder it contracts

Question 8

Describe a stroke volume against venous pressure graph

Answer 8

Stroke volume increases as venous pressure increases, it then peaks and falls due to overfilling and over stretching

Question 9

What is contractility and how is it increased?

Answer 9

Contractility is the stroke volume that occurs for a given venous pressure (the gradient of the stroke vol against venous pressure graph)
It is increased by sympathetic activity

Question 10

At a constant cardiac output, a fall in total peripheral resistance does what to arterial and venous pressures?

Answer 10

Arterial pressure falls

Venous pressure rises

Question 11

What is the response of the cardiovascular system after consuming a meal?

Answer 11

Increased activity of the gut leads to local vasodilatation
TPR falls, arterial pressure falls, venous pressure rises
Rise in venous pressure causes a rise in cardiac output
Fall in arterial pressure triggers a rise in heart rate and cardiac output
Extra pumping of the heart reduces venous pressure and increases arterial pressure

Question 12

How does the cardiovascular system respond to exercise without overfilling the heart?

Answer 12

Enormous increase in demand
Muscles force extra blood back to the heart (venous pressure increases)
Increase in heart rate allows cardiac output to increase without stroke volume increasing to the point of over stretching
Demand met

Question 13

How does the cardiovascular system respond to standing up?

Answer 13

Upon standing blood pools in superficial veins in legs
Venous pressure falls
Cardiac output falls
Arterial pressure falls
Baroreceptors detects all in arterial pressure
Heart rate increases, venous pressure still low
TPR increases to defend arterial pressure

Question 14

What is the condition known as when baroreceptor reflex to standing up doesn’t work?

Answer 14

Postural hypotension

Question 15

What is the cardiovascular response to haemorrhage?

Answer 15

Reduced volume of blood lowers venous pressure
Cardiac output falls
Arterial pressure falls
Baroreceptor cause increase in heart rate and TPR
Rise in heart rate further decreases venous pressure
Heart rate continues to increase
Venous pressure needs to be increased to solve problem
Venoconstriction and blood transfusion/auto transfusion

Question 16

What is the cardiovascular system response to long term blood volume increase?

Answer 16

Blood volume controlled by kidneys
If blood volume increases for days, venous pressure increases
Cardiac output rises
Arterial pressure rises
More blood to tissues which cause increase in TPR
Arterial pressure rises further and stays up