Lecture 9.1: Responses of the Whole System

Question 1

Total peripheral resistance is inversely proportional to…?

Answer 1

..the need for blood

Question 2

At a constant TPR, what effect does an increases in CO on venous pressure?

Answer 2

Decrease venous pressure

Question 3

At a constant TPR, what effect does an increases in CO on arterial pressure?

Answer 3

Increase arterial pressure

Question 4

At a constant cardiac output what effect does a fall in TPR have on venous pressure?

Answer 4

Increase venous pressure

Question 5

At a constant cardiac output what effect does a fall in TPR have on arterial pressure?

Answer 5

Decrease arterial pressure

Question 6

What effect do increases in venous pressure have on cardiac output?

Answer 6

Increase cardiac output

Question 7

What effect do decreases in arterial pressure have on cardiac output?

Answer 7

Increase cardiac output

Question 8

Eating a Meal: What happens to TPR, venous pressure, arterial pressure, local vascular changes?

Answer 8

• Increased activity of the gut leads to local
  vasodilatation
• Total peripheral resistance falls
• Venous pressure rises
• Arterial pressure falls

Question 9

What happens is heart rate increases with no other change? (4)

Answer 9

• Initially cardiac output will tend to rise, but total
  peripheral resistance remains the same
• Rise in cardiac output reduces venous
  pressure
• Stroke volume falls
• Cardiac output back to original value

Question 10

What is the issue with the great increase in venous pressure in exercise? (if only ‘muscle pumping’ which forces extra blood back to the heart and no other changes occur)

Answer 10

• The main problem is that it tends to overfill the
  heart
• Pushes the ventricles onto the flat part of
  the Starling curve
• Risk of pulmonary oedema
• Because the outputs of the right and left ventricles
  cannot be matched

Question 11

How is overfilling of the ventricles prevented in exercise?

Answer 11

• By a rise in heart rate
• Occurs as exercise begins
• Driven by the brain

Question 12

What receptors detect fall in arterial blood pressure?

Answer 12

Baroreceptors (carotid body and aortic arch)

Question 13

What happens during Haemorrhage?

Answer 13

• Reduced blood volume lowers venous pressure
• Cardiac output falls - Starlings law
• Arterial pressure falls
• Rise in heart rate lowers venous pressure further
• Makes problem worse, not better
• Heart rate can become very high

Question 14

What organ controls blood volume?

Answer 14

Kidneys

Question 15

Effects of Long-Term increase in Blood Volume (5)

Answer 15

• Venous pressure increases
• Cardiac output increases
• Arterial pressure rises
• Which forces more blood through tissues
• Which autoregulate and increase total peripheral
  resistance
• So arterial pressure rises further and stays up