4.4 Circulation

Question 1

(i)What kind of muscle is the heart made out of and what are its features?

Answer 1

-Myogenic muscle
-Can contract without nervous or hormonal stimulation
-Doesn’t fatigue, as long as it has sufficient oxygen and glucose.

Question 2

Name the four chambers of the heart

Answer 2

2 Atrium - Right atrium and left atrium
2 Ventricles - Right ventricle and left ventricle

Question 3

What is the function of valves

Answer 3

-To prevent the backflow of blood.

Question 4

What are some adaptations of the atria?

Answer 4

Made from thin tissue as because they only flow blood to short distances (to ventricles)

Question 5

What are some adaptations of the ventricle

Answer 5

Made from thick tissue as they must supply blood to longer distances (lungs or rest of body)

Question 6

How can the AV resist so much pressure?

Answer 6

Strong tendious cords allow them to withstand huge amounts of pressure

Question 7

Describe the structure of an artery and how its related to its function.

Answer 7

-Narrow lumen to maintain high blood pressure
-Elastic fibres which recoil to maintain pressure
-Smooth muscle lining to reduce resistance to blood flow
-Collagen to prevent rupture f artery

Question 8

Describe the structure of a vein and how its adapted to its function

Answer 8

-Large lumen
-Relatively thin layer of muscle and elastic fibres as pressure is low
-Valves to prevent backflow

Question 9

Describe the structure of a capillary to its function

Answer 9

-Cell wall made of one layer of flattened endothelium cells.
-One cell thick
-Allows for short diffusion pathway
-Easy exchange

Question 10

(ii)Describe the circulation of blood in a fish

Answer 10

-Single circulation
-Blood flows from heart to gills
-Blood flows from gills to rest of body
-Blood then flows from body back to heart

Question 11

What are the advantages that the human circulatory system has over the over the fish

Answer 11

1-Blood flows faster and at a higher pressure to the rest of the body
2- Blood flows slower at a lower pressure to the lungs which reduces risk of damage to the lungs

Question 12

(iii)What are the main three stages in the cardiac cycle?

Answer 12

1-Diastole (Relaxation of the heart)
2-Atrial systole(Contraction of the atria)
3-Ventricular systole(Contraction of the ventricle)

Question 13

Why is the mammalian heart divided into a right and left hand side

Answer 13

-To keep oxygenated and deoxygenated blood separated
-Which results in as much oxygen being carried to cells as possible

Question 14

Describe the events which occur in atrial systole

Answer 14

• Atria contract and ventricles are relaxed
• AV valves open to allow blood from a high to low pressure

Question 15

Describe the events which occur in ventricular systole

Answer 15

• Ventricles contract and AV valves close to prevent backflow to the atria. Semi-lunar valves are forced open which allows blood to be pumped out of the heart via aorta and pulmonary artery.

Question 16

iv) What is meant by the term myogenic

Answer 16

-Can contract and relax without nervous or hormonal stimulation(external)
- Brings about depolarisation `

Question 17

What are the three nerves which control the heart ?

Answer 17

-SAN
-AVN
-Bundle of His

Question 18

Explain the process of the cardiac cycle

Answer 18

1-SAN sends a wave of electrical impulse across the myocardial tissue of both atria to the AVN which causes atrial systole
2-AVN sends wave of electrical activity between the ventricles to bundle of His
3-Bundle of His branches into two smaller fibres called the Purkinje fibres.
4-Wave of electrical activity is released by purkinje fibres and causes ventricles to contract at the same time
5- AV close to prevent flow to atria
6- SL opened by pressure and blood is forced into arteries

Question 19

How do you calculate bpm?

Answer 19

1-Duration of one heartbeat then divided by 60.
Eg. 60/0.7 = 85.7 BPM

Question 20

(ix)What is atherosclerosis?

Answer 20

-Hardening of the artery by damage of the delicate endothelium of an artery.

Question 21

What leads to damage of the endothelium layer ?

Answer 21

-High blood pressure, high levels of cholesterol, diabetes ,smoking, obesity and old age.

Question 22

What are the steps involved of atherosclerosis

Answer 22

1-Damage to endothelium wall (eg, via high blood pressure)

2-Inflammatory response occurs and macrophages accumulate in the damaged area

3-Lipids and cholesterol clump together with the macrophages and form fatty streaks or plaque

Question 23

What is an atheroma

Answer 23

-The collection of macrophages, lipids cholesterol and platelets which have formed under the endothelium layer. (plaque)

Question 24

What are the main two types of cholesterol?

Answer 24

High density lipoproteins and low density lipoproteins

Question 25

How are HDL’s formed

Answer 25

-Formed from protein, cholesterol and unsaturated fats
-They transport cholesterol from body tissues to the liver to be broken down
-They may even help remove cholesterol from fatty plaques in the arteries

Question 26

How are LDL’s formed

Answer 26

-Formed from saturated fats, cholesterol and protein

-They bind to cell membranes before being taken up by cells.

-If levels of LDL are high, cell membranes will become saturated so more remain in the blood

-This means blood cholesterol levels are high. This cholesterol can get deposited in artery walls causing an atheroma to form.

Question 27

What is aneurism and how is it an effect of atherosclerosis ?

Answer 27

-If an area of an artery is blocked, pressure builds up behind the blockage

-The artery bulges and weakens the artery wall

-This weakened points can swell up like a balloon

-If it bursts, it leads to a haemorrhage and therefore a loss of blood to a region of the body.

Question 28

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