4.3 - circulation

Question 1

what are the 4 features do all mass transport systems have

Answer 1

-a system of vessels which carry the transport medium
-a transport medium which carries all the substances needed to be delivered to cells and and waste products needed to be removed from cells
-a way of making sure that substances are moved in the right direction
-a means of moving substances fast enough to supply the needs of an organism

Question 2

describe a double circulatory system

Answer 2

-includes the systematic circulation where oxygenated blood is transported from the heart to the body
-here O2 diffuses into cells, and CO2 diffuses into the blood
-deoxygenated blood is transported from the body to the heart
-the the pulmonary circulation carries deoxygenated blood from the heart to the lungs to be oxygenated
-then oxygenated blood is transported from the lungs to the heart

Question 3

what are the advantages of a double circulatory system

Answer 3

-makes sure that the oxygenated and deoxygentated blood don’t mix together, so that the maximum amount of oxygen is able to diffuse into cells
-allows blood in different parts of the body to be at different pressures
e.g. blood going through blood vessels in the lungs are at a lower pressure so it doesn’t damage blood vessels and enough time is allowed for O2 to diffuse in and CO2 out
if this low pressure blood was transported to the body blood would move too slowly
-because oxygenated blood from the lungs returns back to the heart, blood can be pumped again and transported around the body

Question 4

describe what is meant by a single circulatory system

Answer 4

-the heart pumps blood to the gas exchange organs and then travels around the body, then returns back to the heart

Question 5

describe the circulatory system in fish

Answer 5

-single circulatory system
-deoxygenated blood is pumped from the heart to the capillaries in the lamellae of the gills where oxygen diffuses into the blood
-oxygenated blood is transported from the lamellae to the systematic capillaries in the body where oxygen diffuses out the blood into cells
-deoxygenated blood returns to the heart

Question 6

why can fish survive with a single circulatory system

Answer 6

-they have a lower energy requirement so need to carry out less respiration
-they don’t need to maintain internal body temperature

Question 7

what are the advantages and disadvantages of the single circulatory system in fish

Answer 7

advantage:
-after blood flows through the gills it is fully oxygenated, so when this blood flows through the body there is a high concentration gradient for increased rate of diffusion
disadvantage:
-when blood passes through the capillaries in the lamellae it loses a lot of pressure so the circulation of blood to the rest of the body is slow, limiting the rate of oxygen delivery

Question 8

describe the circulatory system of insects

Answer 8

-open circulatory system, blood is not contained in blood vessels, it circulates through the body cavity
-the transport medium is haemolymph, blood and lymph are mixed together
-the dorsal muscular pumping organ pumps heamolymph around the body cavity
-this circulatory system transports amino acids, carbohydrates and hormones, it doesn’t transport oxygen efficiently
-so insects rely on their gas exchange system for respiration

Question 9

name the components of blood

Answer 9

-plasma
-platelets
-leukocytes
-erythrocytes

Question 10

describe the roles of the plasma

Answer 10

-the plasma transports:
-digested food products (amino acids + glucose) from the small intestines to parts of the body for immediate use or storage
-nutrient molecules from storage areas to cells
-excretory products (CO2 + urea) from cells to organs (lungs + kidneys) that excrete them from the body
-hormones
-plasma helps to maintain a constant body temperature by transferring heat around the body

Question 11

describe the role of the erythrocytes

Answer 11

-oxygen binds to haemogobin
-so erythrocytes transport oxygen from the lungs to cells

Question 12

where are erythrocytes formed

Answer 12

the bone marrow

Question 13

explain how erythrocytes are adapted to their function

Answer 13

-biconcave disc shape, high surface area to volume ratio, to increase the rate that O2 diffuses in and out of the erythrocytes
-no nucleus, more room for more haemoglobin to increase the amount of O2 they can carry
-haemoglobin carries a small amount of CO2 produced in respiration to be transported back to the lungs

Question 14

are erythrocytes or leukocytes larger

Answer 14

leukocytes are larger
they can still be transported through small blood vessels because they can change shape

Question 15

where are leukocytes formed

Answer 15

in the bone marrow
but some leukocytes mature in the thymus gland

Question 16

where are platelets formed and what are they

Answer 16

in the bone marrow
they are tiny fragments made from megakaryocytes

Question 17

what is the function of the arteries

Answer 17

-carry blood away from the heart to cells
-carry oxygenated blood (except from the pulmonary artery and the umbilical artery)

Question 18

what are the arterioles

Answer 18

the arteries leaving the heart branch off in every direction
the diameter of the lumen gets smaller the further away the artery is from the heart
the very smallest arteries of the arterial system and furthest from the heart are the arterioles

Question 19

what 2 arteries carry deoxygenated blood

Answer 19

-pulmonary artery, carries deoxygenated blood from the heart to the lungs
-umbilical artery carries deoxygenated blood from fetus to the placenta

Question 20

what is the structure of the arteries

Answer 20

-external layer of tough tissue
-middle layer contains smooth muscle and elastic fibres
-elastic fibers allow the artery to stretch to withstand a greater volume of blood without being damaged
-smooth muscle can contract or relax to change the size of the lumen, controlling blood flow
-arteries nearest the heart have more elastic fibres and arteries furthest from the heart have a greater proportion of muscle tissue
-smooth lining lines the lumen, allows for the easiest flow of blood
-lumen, where blood flows through, small when the artery is unstretched

Question 21

what is the function of capillaries

Answer 21

-they link arterioles and venules
-their small diameter slows the flow of oxygenated blood, so oxygen and nutrients can diffuse into cells
-CO2 and waste products diffuse into the blood in capillaries
-every cell is close to a capillary

Question 22

what is the structure of capillaries

Answer 22

-thin walls (1 epithelial cell thick), helps capillaries to fit in between cells and increase rate of diffusion
-lumen is only large enough to fit 1 erythrocyte at a time, slows down the flow of blood to increase rate of diffusion

Question 23

what is the function of the veins

Answer 23

-transports blood back to the heart
-carries deoxygenated blood (except pulmonary vein and umbilical vein

Question 24

what is the structure of the veins

Answer 24

-the capillaries branch into tiny venules, which become larger veins as they get closer to the heart
-tough outer layer made of collagen fibres
-thin layer of smooth muscle and few elastic fibrers
-smooth inner lining
-relatively large lumen

Question 25

what 2 veins don't carry deoxygenated blood

Answer 25

-the pulmonary vein carries oxygenated blood from the lungs into the heart -the umbilical vein carries oxygenated blood from the placenta to the fetus

Question 26

what 2 veins carry deoxygenated blood into the heart

Answer 26

-superior vena cava, carries blood from the upper parts of the body -inferior vena cava carries blood from lower parts of the body

Question 27

at any time which blood vessel holds the highest volume of blood

Answer 27

veins

Question 28

explain why the blood in veins is at low pressure

Answer 28

-when the heart muscle contracts pressure surges in blood can be seen in arteries -but after blood passes through the capillaries pressure surges are eliminated

Question 29

explain how veins return low pressure blood to the heart

Answer 29

-semi-lunar valves -though out the venous system there are one-way valves -these are infoldings of the vein inner wall -blood can pass through the valves, but if blood flows backwards the valves close, preventing the backflow of blood -large veins are situated in between large muscles -during physical activity muscles contract, which squeezes veins, opening the valves and pushing blood through

Question 30

what muscle makes up the heart

Answer 30

cardiac muscle

Question 31

how is cardiac muscle different to other types of muscle

Answer 31

-it can carry on contracting without getting fatigued -contains lots of myoglobin, which stored oxygen needed for respiration -good blood supply through the coronary arteries, which bring oxygenated blood to the cardiac muscle -myogenic

Question 32

what is atrial systole

Answer 32

when the atria contract together forcing blood into the ventricles

Question 33

what is ventricular systole

Answer 33

when the ventricles contract forcing blood out of the ventricles into the pulmonary artery and aorta happens 0.13 seconds after atrial systole

Question 34

what is diastole

Answer 34

between systole the heart relaxes and fills with blood there is atrial diastole and ventricular diastole when there is atrial systole there is ventricular diastole when there is ventricular systole there is atrial diastole

Question 35

what does myogenic mean and what can be described as myogenic

Answer 35

the heart beat is myogenic in that the cardiac muscle can contract without any stimulus from the nervous system

Question 36

what does an ECG measure

Answer 36

the electrical changes on the surface of the heart caused by waves of depolarisation

Question 37

what is bradycardia

Answer 37

when the heart rate drops below 60 beats per minute (60 bpm is the intrinsic rhythm)

Question 38

what is tachycardia

Answer 38

when the heart rate is over 100 beats per minute may be caused by short term effects like fear and exercise long term tachycardia is caused by health problems

Question 39

what is an ectopic heartbeat

Answer 39

-a heart beat that is not a part of the heart's usual rhythm -appears on an ECG

Question 40

why do atheromas develop in the arteries and not in the veins

Answer 40

-blood in the arteries is at higher pressure -so the endothelium is under more strain and can cause small areas of damage

Question 41

explain how an atheroma is formed

Answer 41

-damage to the endothelium caused by high blood pressure -inflammatory response and arrival of macrophages (white blood cells) -deposits of LDL cholesterol and calcium -a hardened plaque forms on the endothelium, causing this area of the artery to harden too, so the artery is less elastic than it should be

Question 42

why does the presence of an atheroma lead to atherosclerosis

Answer 42

-the atheroma means the lumen is much narrower -increasing blood pressure -making it harder to transport blood around the body -high blood pressure makes damage to other areas of the endothelium more likely

Question 43

how are aneurysms formed

Answer 43

-an artery is narrowed by an atheroma -blood builds up behind the blockage creating a bulge -the endothelium is under more pressure than normal, so is weakened -this is an aneurysm -if the endothelium splits open it can cause internal bleeding which is fatal -if the aneurysm is diagnosed before the artery wall splits, surgery can be used to save the patient

Question 44

explain how atherosclerosis can lead to kidney damage

Answer 44

-the atheroma causes arteries to narrow, raising blood pressure -high pressure damages blood vessels which filter out urea from the blood -the high pressure can also force out protein from the blood

Question 45

explain how atherosclerosis can lead to blindness

Answer 45

-the atheroma causes arteries to narrow, raising blood pressure -high blood pressure damages the blood vessels supplying the retina -if these blood vessels are blocked or leak retinal cells are starved of O2 -they die and cause blindness

Question 46

explain how atherosclerosis can lead to angina

Answer 46

-an atheroma forms in the coronary arteries -narrowed coronary arteries restricts blood flow to cardiac muscle cells -so sufficient oxygen isn't delivered to cells for aerobic respiration -the cardiac muscle resorts to anaerobic respiration which produces lactic acid -causing a gripping pain in the chest that can extend to the left arm and jaw -this is most common during exercise when the cardiac muscle requires more oxygen for a higher rate of respiration to produce ATP -thrombosis in one or more arteries causes angina

Question 47

what advice is given by doctors to patients diagnosed with atherosclerosis

Answer 47

-lose weight by doing regular exercise -eat a balanced diet low in saturated fat -don't smoke

Question 48

what medical treatment are given to patients diagnosed with atherosclerosis

Answer 48

-stent -heart bypass surgery -drugs which cause the rapid dilation of the coronary arteries

Question 49

what is another name for a heart attack

Answer 49

myocardial infarction

Question 50

explain what causes myocardial infarction

Answer 50

-when one of the branches of the coronary arteries becomes completely blocked off so part of the heart in permanently starved of oxygen -the main cause of this is thrombosis (blood clot) -if thrombosis occurs towards the bottom of the heart it can cause a small heart attack, if towards the top a large heart attack that can develop into cardiac arrest -a symptom of myocardial infarction is chest pain which can extend to the left arm and jaw -pain may last for several hours -exercise may trigger it or can happen unexpectedly -death may happen very rapidly or after a few days of symptoms

Question 51

explain what causes a stroke

Answer 51

-thrombosis or atherosclerosis mean that oxygenated blood isn't transported to the brain for respiration -the severity of the stroke depends on whether the blockage is in a main artery supplying the brain with oxygenated blood or a small arteriole -symptoms include paralysis down one side of the body, loss of vision in 1 eye, confusion -

Question 52

explain the 3 non-modifiable risk factors for atherosclerosis

Answer 52

genes - there is a genetic tendency in some families/ethnic groups to develop atherosclerosis due to the arteries being more easily damages or cholesterol metabolism may be faulty etc age - as people get older the arteries lose their elasticity and narrow sex - under the age of 50 men are more likely to develop atherosclerosis because oestrogen in women reduces the build up of plaque

Question 53

state the modifiable risk factors for atherosclerosis

Answer 53

-smoking -diet -stress -weight -lack of physical activity -high blood pressure

Question 54

how is weight a risk factor for atherosclerosis

Answer 54

-being overweight doesn't directly affect the risk of developing atherosclerosis -but it is an important factor of risk because other factors that are direct result of being overweight do increase risk of atherosclerosis -including type 2 diabetes and high blood pressure

Question 55

how does type 2 diabetes increase the risk of atherosclerosis

Answer 55

can damage endotherlium

Question 56

how does stress increase the risk of atherosclerosis

Answer 56

-stress causes the release of cytokines -which trigger an inflammotory response in blood vessels -leading to plaque formation -stress can also raise blood pressure

Question 57

what are the functions of blood clots

Answer 57

-prevents the loss of blood which can be fatal -prevents pathogens entering the body and causing disease

Question 58

what is the function of serotonin

Answer 58

-a hormone -causes the smooth muscle of blood vessels to contract, which narrows blood vessels, cutting off blood flow to damages areas

Question 59

what is the function of thromboplastin

Answer 59

-an enzyme -initiates the blood clotting cascade

Question 60

explain the blood clotting cascade

Answer 60

-damaged tissue exposes collagen fibres -the contact between platelets and collagen fibres causes platelets to break open to release thromboplastin -thromboplastin catalyses the conversion of prothrombin (soluble enzyme) into thrombin (soluble enzyme), this happens in the presence of calcium ions -thrombin catalyses the conversion of fibrinogen (soluble protein) into fibrin (insoluble protein) -fibrin forms a mesh of fibres to cover the wound -platelets and blood cells get trapped in the fibrin mesh to form the blood clot -proteins in the platelets contract, making the clot tighter and tougher to form a scab

Question 61

what is tissue fluid

Answer 61

-cells which make up the capillary walls aren't directly touching each other, there is space between each cell -making the capillary walls very permeable -this space isn't large enough for erythrocytes or plasma proteins to pass through -a fluid that is plasma containing leukocytes and other components of the blood moves out of the capillaries and bathes the individual cells of the body

Question 62

what is the definition of oncotic pressure

Answer 62

the tendency for water to move into the capillaries by osmosis

Question 63

explain oncotic pressure in terms of tissue fluid

Answer 63

-the blood in capillaries has a low water potential -because plasma proteins in the blood exert an osmotic effect -the tissue fluid surrounding the capillaries has a higher water potential -because water moves from an area of high to low water potential, the tendency is for water to move into the capillaries by osmosis -the pressure behind this movement is oncotic pressure

Question 64

what is hydrostatic pressure in terms of tissue fluid

Answer 64

-it is the left over pressure from the heartbeat that remains as the blood enters the arterial end of the capillary bed -this hydrostatic pressure forces tissue fluid out through the capillary walls

Question 65

explain the movement of tissue fluid as blood flows from the arteriole end of the capillary bed into the capillaries

Answer 65

-as blood flows from the arterioles into the capillary bed -the hydrostatic pressure foring fluid out is relatively high -the oncotic pressure tending to force water into the capillaries is fairly constant -the hydrostatic pressure is higher than the oncotic pressure -so fluid is squeezed out of the capillaries and fills the space around all body cells -diffusion between cells and the tissue fluid take place

Question 66

explain the movement of tissue fluid as blood flows from the capillaries into the venule end of the capillary bed

Answer 66

-as blood flows from the arterioles into the capillary bed -hydrostatic pressure falls to be relatively low -because the pressure from the heartbeat is completely gone -and some fluid moves out of the capillaries to form tissue fluid, so volume of blood in the capillaries is lowered -oncotic pressure of the blood is still constant due to the constant presence of large plasma proteins -the oncotic pressure exerted by water moving into the capillaries is greater than the hydrostatic pressure -water returns to the capillaries by osmosis -once blood enters the venules most of the tissue fluid has returned to the blood vessels

Question 67

what happens to tissue fluid when hydrostatic pressure is greater than oncotic pressure

Answer 67

fluid moves out of the capillaries forming tissue fluid

Question 68

what happens to tissue fluid when oncotic pressure is greater than hydrostatic pressure

Answer 68

water moves into the capillaries and tissue fluid is lost

Question 69

explain how lymph is formed

Answer 69

-90% of tissue fluid returns to blood vessels but 10% doesn't -this 10% of tissue fluid drains into lymph capillaries and becomes lymph -lymph has fewer nutrients and less oxygen than tissue fluid as these have been taken up by cells -lymph may have a high level of fatty acids because they can be absorbed directly into the lymphatic system in the villi of the small intestine -lymph capillaries join up to make bigger lymph vessels -lymph vessels are similar to veins because they have valves which prevent the backflow of lymph -and contractions of body muscles as we move, move the lymph -lymph is returned to the blood in the neck where it joins the left and right subclavian veins

Question 70

explain the role of lymph glands in the immune system

Answer 70

-lymphocytes accumilate in the lymph glands to produce antibodies -produced antibodies are carried by the lymph and empties into the blood at the subclavian veins -lymph glands remove bacteria and other pathogens to be destroyed by phagocytes -if a patient has enlarged lymph glands they are fighting an infection

Question 71

explain what is meant by haemoglobin has positive cooperativity

Answer 71

-the 1st oxygen molecule that binds to haemoglobin alters the arrangement of molecules making it easier and easier for the following O2 molecules to bind -after the 1st oxygen molecule dissociates with heamoglobin it is harder and harder for the rest of the O2 molecules to dissociate

Question 72

explain how a concentration gradient in maintained even though oxygen is binding to erythrocytes

Answer 72

-the oxygen concentration of erythrocytes entering the lungs is relatively low -oxygen is picked up and bound to heamoglobin so the free O2 concentration of the cytoplasm of erythrocytes stays low -the steep concentration gradient between air in the lungs to erythrocytes allows more and more O2 to diffuse

Question 73

explain how oxygen travels from erythrocytes into respiring body cells

Answer 73

-O2 concentration in body tissue is relatively low -O2 concentration in the cytoplasm of erythrocytes is higher than that of the surrounding tissue because oxyhaemoglobin has dissociated to release some O2 molecules -so O2 diffuses into body cells -some oxyhaemoglobin molecules dissociate to release some O2 molecules which diffuse into body tissue -when resting only 25% of oxygen carried by oxyhaemoglobin is released into body cells

Question 74

what are the 3 ways carbon dioxide is transported in the body

Answer 74

-some CO2 dissolves into the plasma -some CO2 combines with haemoglobin to form carbaminohaemoglobin -most CO2 is converted into hydrogencarbonate ions

Question 75

explain how CO2 is transported by being converted into carbaminohaemoglobin where does this happen

Answer 75

-haemoglobin contains 4 polypeptide chains -on one end of each polypeptide chain there is a free amino group -in the respiring tissue there is a high concentration of CO2 -each amino group reacts with 1 CO2 molecule to form carbaminohaemoglobin -this is a reversible reaction -in the lungs there is a low concentration of CO2 -carbaminohaemoglobin breaks down releasing CO2

Question 76

Describe the similarities and differences between the circulatory systems in mammals and insects

Answer 76

Similarities: both have hearts and valves Differences: insects have an open system, mammals have a closed system with blood vessels Gas exchange in insects occurs in the tracheal system, in mammals it’s in the pulmonary circulatory system

Question 77

what is the oxygen dissociation curve for myoglobin not s shaped

Answer 77

-myoglobin's affinity for oxygen doesn't change -because myoglobin doesn't have cooperative bonding to oxygen

Question 78

explain how tissue fluid is formed (1 mark)

Answer 78

high hydrostatic pressure forces plasma (and other components of the blood) out of the arteriole end of the capillaries

Question 79

explain how tissue fluid is returned to the capillaries

Answer 79

-there is are more proteins than tissue fluid in the blood in the capillaries -because plasma proteins cannot pass through the capillary wall -oncotic pressure generated by the plasma proteins is greater than hydrostatic pressure -so the water potential outside the capillary is greater than inside -fluid moves into the capillaries

Question 80

Explain how thrombosis develops

Answer 80

Thrombosis is a clot that forms in the coronary arteries The presence of an atheroma on the endothelium means the endothelium is hardened So the endothelium is more likely to suffer cracks or damage When platelets come into contact with collagen fibres exposed by a damaged blood vessel the blood clotting cascade is triggered Or the endothelium may become damaged due to high blood pressure or smoking

Question 81

compare and contrast the structures and roles of haemoglobin and myoglobin

Answer 81

similarities: -both have prosthetic haem groups which bind to oxygen -the secondary structure of myoglobin and a single polypeptide chain of haemoglobin have similar structures because they are both alpha helices -globular proteins differences: -myoglobin has a single alpha helix with a single haem group whereas haemoglobin has 2 alpha helices, 2 beta-pleated sheets and 4 haem groups -myoglobin has a higher affinity to oxygen so becomes saturated at a lower partial pressure of oxygen than haemoglobin does -myoglobin is found in muscles whereas haemoglobin is found in red blood cells in the blood

Question 82

describe how the structure of the aorta is different to the structure of the pulmonary valve

Answer 82

-the aorta has thicker walls -the aorta has more smooth muscle and elastic fibers -the aorta has a narrower lumen -the aorta contain semi-lunar valves

Question 83

compare and contrast the structure of the circulation system of an insect with the structure of the circulatory system of a mammal

Answer 83

-both have a heart -both have valves -mammals have blood contained in blood vessels, insects have an open circulatory system -mammals have a separate pulmonary circulation system where O2 diffuses into the blood at the alveoli, whereas O2 diffuses directly into cells in the tracheal system -mammals have a double circulatory system, insects have a single circulatory system

Question 84

explain how electrical events during the cardiac cycle can lead to an increase in stroke volume (3 marks)

Answer 84

-more frequent waves of depolarisation -from SA node to AV node to bundle of His to Purkyne fibres -therefore stronger contractions of the ventricles

Question 85

explain why the dissociation curve for mouse haemoglobin is to the right-hand side of the dissociation curve for elephant haemoglobin (3 marks)

Answer 85

-mice haemoglobin has a lower affinity to oxygen than elephant haemoglobin at the same partial pressure of oxygen, therefore mice release more oxygen at the same partial pressure of oxygen -because mice have a large SA:vol than elephants -therefore lose more heat -so have a higher respiration rate and their cells require more oxygen