Topic 4.4 Circulation

Question 1

Relate the structure of the hearts chambers to their function

Answer 1

• Atria: thin-walled and elastic, so they can stretch when filled with blood
• Ventricles: thick muscular walls pump blood under high preasure. The left ventricle is thicker than the right side because it has to pump blood all the way around the body

Question 2

Relate the structure of the arteries to their function

Answer 2

Thick muscular walls to handle high pressure without tearing. Elastic tissue allows recoil. Narrow lumen to maintain pressure.

Question 3

Relate the structure of veins to their function

Answer 3

Thin walls due to lower pressure. Require valves to ensure blood doesn’t flow backwards. Have less muscular and elastic tissue as they don’t have to control blood flow.

Question 4

Relate the structure of capillaries to their function

Answer 4

• Walls only one cell thick; short diffusion pathway
• Very narrow, so can permeate tissues and red blood cells can lie flat against the wall, effectively delivering oxygen to tissues
• Numerous and highly branched, providing a large surface area

Question 5

Why are two pumps (left and right) needed instead of one?

Answer 5

To maintain blood pressure around the whole body. When blood passes through the narrow capillaries of the lungs, the pressure drops sharply and therefore would not be flowing strongly enough to continue aroun the whole body. Therefore it is returned to the heart to increase the pressure.

Question 6

Describe what happens during cardiac diastole

Answer 6

The heart is relaxed. Blood enters the atria, increasing the pressure and pushing open the atrioventricular valves. this allows blood to flow into ventricles. Preasure in the heart is lower than in the arteries, so semilunar valves remain closed.

Question 7

Describe what happens during atrial systole

Answer 7

The atria contract pushing blood into the ventricles.

Question 8

Describe what happens during ventricular systole

Answer 8

The ventricles contract. The pressure increases, closing the atrioventricular valves to prevent backflow, and opening the semilunar valves. Blood flows into the arteries.

Question 9

What does myogenic mean?

Answer 9

The heart’s contraction is initiated within the muscle itself, rather than by nerve impulses.

Question 10

Name the nodes involved in the heart contaction and where they are situated

Answer 10

• Sinoatrial node (SAN) = wall of right atrium
• Atrioventricular valve (AVN) = in between the two atria

Question 11

Explain how the heart contracts

Answer 11

• SAN initiates and spreads impulse across the atria, so they contract
• AVN recieves, delays, and then conveys the impulse down the bundle of His
• Impulse travels into the Purkinje fibres which branch across the ventricles, so they contract from the bottom up

Question 12

Why does the impulse need to be delayed?

Answer 12

If the impulse spreads straight from the atria into the ventricles, there would be not enough time for atrial systole to complete.

Question 13

What is an ECG?

Answer 13

A graph showing the amount of electrical activity in the heart during the cardiac cycle

Question 14

What does each element of an ECG represent?

Answer 14

• P-wave shows atrial systole caused by the SAN
• QRS complex shows ventricular systole
• T-wave shows systole as the ventricles repolarise

Question 15

Describe the function of the blood

Answer 15

• Transport of nutrients and waste
• Forms tissue fluid
• Defend against foreign bodies

Question 16

What are the main components of blood?

Answer 16

1. Erythrocytes (red blood cells)
2. Leucocytes (white blood cells)
3. Plasma

Question 17

Describe the structure of erythrocytes and their function

Answer 17

Biconcave shape, no nucleus, contain lots of haemoglobin. Function is to carry oxygen.

Question 18

Give types of leucocytes

Order them into granulocytes and agranulocytes

Answer 18

Granuloctyes:
* Basophill
* Neutrophill
* Eosenophill

Agranulocytes:
* Lymphocytes
* Monocytes

Question 19

What are granulocytes?

Answer 19

These leucocytes have granules in the cytoplasm of the cells that take up stain and are obvious under the microscope. They have lobed nuclei

Question 20

What are agranulocytes?

Answer 20

These leucoytes don’t have granules to take up stain in their cytoplasm. They have unlobed nuclei

Question 21

Describe the structure of neutrophill and their function

Answer 21

Part of the non-specific immune system, they engulf and digest pathogens by phagocytosis. They have multi-lobed nuclei.

Question 22

Describe the structure of eosinophill and their function

Answer 22

Part of the non-specific immune system. They are stained red by eosin stain. They are important as they contain enzymes that detoxify proteins.

Question 23

Describe the structure of basophill and their function

Answer 23

Part of the non-specific immune system. They have a two-lobed nucleus. They produce histimines involved in inflammation and allergic reactions.

Question 24

Describe the structure of monocytes and their function

Answer 24

Part of the specific immune system. They’re the largest of the leucocytes. They can move out of the blood and into the tissues to form macrophages, that also play an important part of the specifc immune response. they engulf pathogens by phagocytosis.

Question 25

Describe the structure of lymphocytes and their function

Answer 25

Small leucocytes with very large nuclei that are vitally important in the specific immune response of the body.

Question 26

Describe the function of plasma

Answer 26

Contains water, proteins, ions, nutrients, gases, and hormones. Delivers them to cells. Makes up 55% of blood.

Question 27

Why does blood need to clot?

Answer 27

* Prevents blood loss * Prevents entry of harmful bacteria * provides a framewrok for repair

Question 28

Explain the process of blood clotting

Answer 28

1. Platelets release thromboplatin in response to damage 2. Causes prothrombin to change to its active form, thrombin (calcium and vitimin K are involved in creating thrombin) 3. Turns soluble fibrinogen into insoluble fibrin, forming a mesh that traps blood cells

Question 29

What causes atherosclerosis?

Answer 29

Build-up of fibrous plaque. Endothelium becomes damaged which can cause a blood clot. Cells, salts cholesterol and other substances build up and harden, forming a plaque that narrows the artery.

Question 30

How does atherosclerosis affect health?

Answer 30

Increases risk of cardiovascular diseases such as hearth attack, stroke and angina

Question 31

Give factors that increase risk of atherosclerosis

Answer 31

Age, genetics, smoking, alcohol, lack of exercise, obesity, cholesterol levels.

Question 32

What conditions can atherosclerosis lead to?

Answer 32

* Anuerism * Raised blood preasure * Angina * Heart attack * Stroke

Question 33

What is an aneurism?

Answer 33

Where the increased preasure of blood caused by a blockage can lead to the artery bursting, and internal bleeding.

Question 34

What is angina?

Answer 34

Narrowing of coronary arteries reduces blood flow to the heart and causes chest pain on exercise