4.3 circulation

Question 1

why do some mammals need a double circulatory system in comparison to fish, that only need a single circulatory system

Answer 1

• they have to move without the aid of water
• they must maintain a constant body temperature that’s usually higher than surroundings, which requires oxygen and glucose which produces a lot of waste that must be removed

Question 2

what are the advantages of a double circulatory system

Answer 2

• it ensures that the oxygenated and the deoxygenated blood do not mix
• so the tissues receive as much blood as possible
• fully oxygenated blood can be delivered to tissues at a high pressure

Question 3

what is the role of plasma

Answer 3

transportation of:
- digested food products to where they are needed for use or storage
- nutrient molecules from storage to where they are needed
- excretory products
- hormones from where they are made to where they cause change

Question 4

what is the role of erythrocytes and how are they adapted

Answer 4

• contain haemoglobin and transport oxygen from the lungs to the cells
• biconcave shape means they have a large surface area to volume ratio and can diffuse in and out
• they have no nucleus which provides more space to carry oxygen and haemoglobin

Question 5

what is the role of leukocytes

Answer 5

• defend the body against infection

Question 6

what are the two types of leukocytes and describe them

Answer 6

• granulocytes, have granules in the cytoplasm in the cells that take up stain -lobed nuclei
• agranulocytes, do not have granules in the cells that take up stain in their cytoplasm - unlobed nuclei

Question 7

state the role of the following and what type of leukocyte are they:
1. neutrophils
2. eosinophils
3. basophils

Answer 7

they are granulocytes
1. part of non specific immune system and engulf and digest pathogens by phagocytosis
2. part f non-specific immune system and are important in response against parasites, allergic reactions, inflammation, developing immunity to disease
3. part of non specific immune system, produce histamines involved in inflammation

Question 8

state the role of the following and what type of leukocyte are they:
1. monocytes
2.lymphocytes

Answer 8

1. part of the specific immune system, move out of blood into tissue to form macrophages
2. important in the specific immune response of the body

Question 9

what are platelets and what is their role

Answer 9

• tiny fragments of megakaryocytes
• involved in the clotting of the blood

Question 10

why does blood need to clot

Answer 10

• we only have a limited amount of blood in our systems and if we lose too much, then our blood volume will fall and we will die
• pathogens can enter the body through an open wound

Question 11

how does a blood clot START to form

Answer 11

• plasma (blood cells and platelets) flow from a cut vessel
• contact between tissue and platelets cause the tissue to break open in large numbers and release
  1. serotonin, making the blood vessel narrow
  2. thromboplastin, an enzyme that sets in the progress of forming a blood clot

Question 12

describe the blood clotting cascade

Answer 12

1. thromboplastin catalyses conversion of prothrombin to active thrombin
2. thrombin acts on soluble fibrinogen and converts it to insoluble fibrin, which forms fibres to cover the wound
3. platelets and blood cells pour from the wound and get trapped in fibrin mesh, forming a clot
4. proteins in platelets contract and form a scab

Question 13

structure of haemoglobin

Answer 13

• haemoglobin is a large globular protein made up of four peptide chains, each with an iron prosthetic group
• picks up 4 oxygen molecules in a reversible reaction to form oxyhaemoglobin

Question 14

how does oxygen bind to haemoglobin

Answer 14

• the first oxygen molecule that binds to haemoglobin alters the arrangement of the molecule, making it easier for the other molecules to bind

Question 15

what’s the Bohr effect? (describe it)

Answer 15

• the changes in the oxygen dissociation curve that result due to the changes in carbon dioxide concentration
• when the partial pressure of carbon dioxide is high, the affinity of haemoglobin for oxygen in reduces e.g. in active tissues where there is a high concentration of carbon dioxide, oxygen is released very readily
• when the partial pressure of carbon dioxide is low, like in the lung capillaries haemoglobin easily binds to oxygen

Question 16

describe Fetal haemoglobin

Answer 16

• only found in the developing fetus
• oxygenated blood from the mother runs through the placenta, close to the deoxygenated fetal blood
• has a higher affinity for oxygen than haemoglobin, so it can remove oxygen from mothers blood
• removes blood through a counter current exchange system to maximise oxygen transfer

Question 17

describe myoglobin (also in comparison with haemoglobin)

Answer 17

• respiratory pigment found in the muscle tissue of vertebrates
• small bright red protein (gives meat strong colour)
• contains a haem group that binds to oxygen
• much higher affinity for oxygen, affinity is not affected by partial pressure of oxygen
• does not give up oxygen easily so is used as an oxygen store and releases oxygen when CO2 levels are high in active muscles

Question 18

what do arteries carry, what are the exceptions

Answer 18

• arteries mostly carry blood away from the heart towards the cells of the body
  except:
• pulmonary artery, carrying deoxygenated blood away from the heart to the lungs
• umbilical artery - carry deoxygenated blood from fetus to placenta

Question 19

describe the structure of an artery

Answer 19

• small lumen when it is unstretched by blood flow
• middle layers consist of elastic fibres and and smooth muscle tissue, to withstand high pressure surges of blood from the heart so they can stretch the accommodate high volume of blood
• has an external layer of tough tissue

Question 20

what do arteries branch off into, then what do they flow into

Answer 20

• arteries branch off into arterioles
• then arterioles flow into capillaries

Question 21

describe the structure of a capillary

Answer 21

• they have very small diameters as they are situated in between cells
• walls are one cell thick, allows for rapid diffusion of substances between cells and blood cells
• wall consists of one layer of epithelial cells

Question 22

what do veins carry, what are the exceptions

Answer 22

• carry blood back to the heart and deoxygenated blood

except:
- pulmonary vein, carries oxygen rich blood back to the heart to be circulated around the body
- umbilical vein, carries oxygenated blood from placenta to the fetus

Question 23

• describe the structure of a capillary

Answer 23

• they have an outer tough layer consisting of collagen fibres
• then a thin layer of smooth muscle with few elastic fibres
• smooth inner surface
• relatively large lumen

Question 24

how is low pressure deoxygenated blood recirculated

Answer 24

1. semilunar valves, valves pass through the veins and are formed from inner folding of the inner vein wall, if blood flows backwards then the valves close
2. some larger veins are between large muscle, muscles contract and squeeze blood out of the veins

Question 25

what the septum of the heart

Answer 25

it’s the thick layer of cardiac muscle in the middle that separates the blood on either side of the heart

Question 26

what is the role of the following and where are they situated on a diagram of the heart
1. inferior vena cava
2. superior vena cava

Answer 26

1. bottom left
   collects deoxygenated blood from the rest of the body
2. top left
   collects blood from the head, neck, arms and chest and delivers it to the right atrium

Question 27

where are the following situated on a diagram of the heart, and what do they do
1. tricuspid valve
2. semilunar valve

Answer 27

1. lower left valve
2. lower right valve
   - they both prevent the backflow of blood into the atria

Question 28

where are the following situated on a diagram of the heart and what do they do
1. semilunar valve
2. semilunar valve

Answer 28

1 AND 2. centre of the heart coming out of the pulmonary artery and the aorta
- they prevent the backflow of blood into the ventricles

Question 29

how do hearts make the beating sound ‘lub dub’

Answer 29

• sound is made by blood hitting out heart valves
  LUB - blood being forced against the atrioventricular valves when the ventricles contract
  DUB - the backflow of blood hitting the semilunar valves in the pulmonary artery and the aorta as the ventricles relax

Question 30

what are other names of
- systole
- diastole

Answer 30

systole - contraction of the heart
diastole - relaxation stage of the heart

Question 31

describe the events of the cardiac cycle

Answer 31

1. atrial systole where the atria contract, which forces the AV valves open and blood flows into the ventricles
2. ventricles contract which causes the AV valves to valves to close and the semilunar valve to open, allowing blood to leave through aorta and pulmonary artery
3. cardiac diastole occurs, atria and ventricles relax, reduces pressure in atria and ventricles, causes valves to close and heart fills with blood

Question 32

why is the left side of the heart thicker than the right side

Answer 32

• because it needs to pump blood out of the arteries at very high pressure to deliver oxygenated blood to the extremities of the body and overcome the elastic recoil of the arteries

Question 33

what is the septum of the heart

Answer 33

the thick wall of muscle and connective tissue between the two sides of the heart the prevents the oxygenated blood mixing with the deoxygenated blood

Question 34

what is an ecg

Answer 34

electrocardiogram, diagram produces to investigate rhythms of the heart by producing records of the electrical impulses of the heart

Question 35

what are other words for
1. fast heartbeat
2. slow heartbeat

Answer 35

1. tachycardia
2. brachycardia

Question 36

what is atherosclerosis

Answer 36

• cardiovascular disease that produces a build up of plaque in the arteries

Question 37

what are the typical stages in the arteries that lead to atherosclerosis

Answer 37

1. damage to the inner endothelial lining of the arteries (caused by smoking, high BP)
2. body’s inflammatory response occurs, WBCs arrive at the site of damage leads to the eventual build up of plaque
3. build up of fibrous tissue, calcium salts build up around atheroma turning it into hardened plaque
4. the lumen becomes a lot smaller due to the buildup of plaque, and this makes it harder for the heart to pump blood around the body
5. this increases blood pressure and makes it more likely for other areas of the endothelial lining to be damaged

Question 38

name and explain the effects of atherosclerosis on health

Answer 38

aneurysms - blood builds up behind plaque blockage, artery bulges and the wall is put under more pressure than normal, weakened artery splits open and internal bleeding occurs
raised BP - narrowed arteries due to plaques cause raised BP, can damage blood vessels
heart disease- angina and myocardial infarction (heart attack)
strokes - caused by an interruption to the normal blood supply to an area of the brain

Question 39

explain the non-modifiable risk factors of atherosclerosis

Answer 39

genes - there is a genetic tendency in some families to develop cardiovascular diseases e.g. arteries may be more easily damaged
age - blood vessels begin to lose their elasticity and narrow slightly as you get older
sex : under the age of 50, men are statistically significantly more likely to develop a CVD, as oestrogen reduces build up of plaque

Question 40

explain the modifiable risk factors of atherosclerosis

Answer 40

smoking - a