6.2

Question 1

What are the components of blood?

Answer 1

Plasma
Erythrocytes ( red blood cells)
Leucocytes ( white blood cells )
Platelets

Question 2

What is the function of the plasma?

Answer 2

It dissolves or carries other components of blood, nutrients and waste. Anything that is polar.

Question 3

What is the function of erythrocytes?

Answer 3

Transports oxygen using haemoglobin

Question 4

What is the function of leucocytes?

Answer 4

Two types: phagocytes engulf pathogens and dead cells.

Lymphocytes form the immune system with antibodies and antitoxins

Question 5

What is the function of platelets?

Answer 5

Clotting of blood

Question 6

What is the diameter of arteries, and within this, the thickness of the wall and lumen?

Answer 6

Greater than 10um

Thick wall and narrow lumen due to high pressure

Question 7

How many layers do arteries have in their walls?

Answer 7

3 layers- túnica externa, media and intima

Question 8

What is the direction of flow of arteries?

Answer 8

Away from the heart

Question 9

What is the diameter of capillaries, and the size of their wall and lumen?

Answer 9

Around 10um.

Extremely thin wall and large lumen.

Question 10

How many layers do capillaries have in their walls?

Answer 10

1 layer, the túnica íntima. Endothelium. 1 layer of thin cells.

Question 11

What is the direction of flow of capillaries?

Answer 11

All around

Question 12

What is the diameter of veins and their lumen and walls?

Answer 12

Larger than 10um

Relatively thin wall, wide lumen due to low blood pressure

Question 13

How many layers do the walls of veins have?

Answer 13

3- túnica íntima, media and externa

Question 14

What is the purpose of valves in veins?

Answer 14

If blood flows backwards due to low pressure, it gets caught in the flaps of the pocket valve, which fill with blood, blocking the lumen and thus preventing backflow to capillaries or insufficient return to the heart

Question 15

What did William Harvey prove?

Answer 15

That blood flows in one direction
Proved valves
Proved circulation
Predicted presence of capillaries

Question 16

Why do we have a double circulatory system?

Answer 16

Because we are large and require different pressures

Question 17

What are the different blood pressures needed and where?

Answer 17

Capillaries in lungs need low pressures- in the pulmonary circulation

High pressure is needed for the organs- systemic circulation

Question 18

What is the pulmonary circulation?

Answer 18

To and from the lungs

Question 19

What is systemic circulation?

Answer 19

To and from other organs, including heart muscles

Question 20

Why do we need a double pump in the heart?

Answer 20

It is essential that the 2 blood circulation as do not mix

Question 21

What do the ventricles do?

Answer 21

Pumps blood out into the arteries

Question 22

What do the atria do?

Answer 22

Collects blood from veins and passes to ventricle

Question 23

Where does oxygenated blood flow in the heart?

Answer 23

On the left side through the pulmonary veins from lungs and out the aorta

Question 24

Where does deoxygenated blood flow in the heart?

Answer 24

Into the right side through the vena cava and out in pulmonary arteries

Question 25

What happens in atherosclerosis?

Answer 25

The development of fatty tissue, atheroma, in the artery wall, adjacent to the endothelium. Low density lipoproteins accumulate and phagocytes are attracted by signals from endothelium and smooth muscle. Phagocytes engulf fats and cholesterol by endocytosis and grow large, smooth muscle forming a tough cap over the atheroma. The artery wall bulges into the lumen, narrowing it, impending blood flow.

Question 26

What is myogenic?

Answer 26

The contraction of the heart, meaning that it is generated in the muscle itself- controlled by medulla

Question 27

How does the heart contract?

Answer 27

The membrane of heart muscle cell depolarises when the cell contracts, activating adjacent cells so they also contract. The region of the heart with fastest rate of spontaneous beating is a group of muscle cells in the wall of the right atrium, the sinoatrial node, as it has extensive membranes. Therefore it initiates the heartbeat as membranes of its cells are the first to depolarise in each cardiac cycle.

Question 28

What are the stages of the cardiac cycle?

Answer 28

0-0.1 secs- atria contract, small pressure increase, blood from atria to ventricle through atrioventricular valve.

0. 1-0.15 secs- ventricles contract, rapid pressure increase, AV valves close, semilunar valves remain closed.
1. 15-0.4 secs- pressure in ventricles is greater than the pressure in arteries, so the semilunar valves open, blood pumps from ventricles to arteries, maximum arterial blood pressure, pressure rises in atria as blood drains into them
2. 4-0.45 secs- ventricular muscle contraction wanes, pressure rapidly developing drops in ventricles, semilunar valves close and AV valves are closed.
3. 45-0.8 secs- pressure on ventricles drops below that of atria, AV valves open, blood from veins drains into atria, ventricle pressure increasing

Question 29

Where does the SAN receive signals from?

Answer 29

Branches of two nerves in the medulla called the cardiovascular centre

Question 30

What is the chemical process of the cardiac cycle?

Answer 30

• heartbeat contracts in right atria, sinoatrial node
• wave of excitation across atria
• atrial systole
• stimulus picked up at AVN
• signal related to bundle of his in ventricle
• ventricle contracts
• signal from bundle of his to purkinje fibres