Lecture 1 - Cardiovascular Physiology - Introduction

Question 1

Why do we need a cardiovascular system?

Answer 1

• To provide tissues with an adequate supply of oxygen and nutrients
• To remove unwanted by-products of metabolism from the tissues (CO2, H+ ions)
• And to transport all of these substances by bulk flow, since diffusion is not enough by itself

Question 2

What are the types of blood vessels found in the CVS?

Answer 2

• arteries
• arterioles
• capillaries
• venules
  
  • veins

The body holds 4-6L of bood

Question 3

What is different about pulmonary veins compared to the veins throughout the rest of body?

Answer 3

Pulmonary veins are oxygenated (since they are leave the lungs and are returning to the heart). Whereas veins around the rest of the body are deoxygenated.

Pulmonary arteries are deoxygenated.

Question 4

What are the benefits of having a pulmonary circulation?

Besides getting O2 of course

Answer 4

• lungs do not have to compete with the organs in systemic circulation for blood flow
• The lungs are close to the heart (requires a smaller force of contraction from right ventricle)
  
  • The smaller size of the pulmonary circuit allows it to have a lower resistance to flow, thus making it a low energy circuit in comparison to the symstemic circuit
• The pulmonary circuit allows for a low energy circuit that allows blood to be oxygeated and returned to the heart to be pumped around the body

Question 5

What does the systemic circulation do?

Answer 5

Carries blood from the heart to the body organs and tisssues and back.

In the capillaries O2 is offloaded and CO2 is picked up.

The deoxygenated CO2 rich blood is then returned to the heart via the venous system

Question 6

How do the lungs recieve blood supply from the systemic circulation?

Answer 6

Via bronchial arteries to provide O2 to lung tissue

Question 7

How is most of the systemic circulation arranged, in series or in parallel?

Answer 7

Parallel

(Except for splanchnic circulation, where blood leaves the GI organs and passes through the liver)

Question 8

What are the benefits of have the systemic circulation arranged in parallel branches?

Answer 8

• The total resistance is reduced (due to having multiple resistances 1/R_T=1/R₁+R₂)
• Blow flow to individual organs can be independently controlled (blood flow can be redirected to organs which require more supply for O2 consumption/their function)
• Reduces competition for O2 before organs

Question 9

Which organs have an increased perfusion between exercise and rest? And which one maintains the same blood flow

Answer 9

Brain stays the same

Question 10

Where is most of the blood in the blood at any given time?

Answer 10

Most blood is in the venous circulation

60-70%

The highest volume of blood is found in the veins and venules, they hold most of the blood because they are capacitance vessels

Question 11

Describe the changes in blood pressure through the body

Answer 11

The blood pressure varies throughout the body. There is pulsitile flow of blood in the arteries, whilst there is smooth laminar flow in the capilliries and venous system.

If order for blood to move anyway it must be moving down a pressure gradient. The ventricles act like chair lifts, increasing the pressure from 0 to max to create a large enough pressure difference to direct blood flow throughout the body.

Question 12

Describe how arteries change as you move away from the heart

Answer 12

The number of arteries increase as one moves away from the heart, and the diameter of each arterie falls.

The diameter of the aorta is ~2.5cm, whilst the diameter of a capillary is ~8μm. The number of arteries increase, and the diameter of each artery decreases as you move away from the heart as a way to decrease total resistance. (Many small resistances reduce the overall resistance).

Question 13

Describe the change in the vessels in the venous system as they move towards the heart

Answer 13

On the venous side as one approaches the heart the number of vessels fall, and their diameter increases

There are more blood vessels in the venous system than in the arterial system

Question 14

Why is there such a large cross-sectional area of the arteries and venous vessels?

Answer 14

To decrease the velocity of the blood, as we need slow blood flow in the capillaries so that we get efficent diffusion

The cross sectional area graph is inverse to the blood flow velocity graph

Question 15

Does blood flow change at all in the body? And does blood velocity?

Answer 15

Blood flow reamins the same in all parts of the CVS, however blood velocity varies.

In the arteries the mean velocity is ~20cm/sec, and then in the capillaries it decreases to 0.05cm/sec, and then in the veins it speeds up to 15cm/sec