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CCEA AS Biology Unit 2 > U2T3 - Circulatory Systems In Mammals > Flashcards

U2T3 - Circulatory Systems In Mammals Flashcards

1
Q

What is the structure + BP of an artery?

A

Thick wall (thin outer fibrous tissue which withstands high pressure, thick middle muscle + elastic tissue, inner endothelial of squamous endothelium) + narrow lumen, rounded. High BP in pulses.

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2
Q

What is the structure + BP of a vein?

A

Thin wall (thin outer fibrous tissue, thin middle muscle + elastic tissue, inner endothelial of squamous endothelium), large lumen + valves. Less regular shape. Low BP. Distance from heart increases friction. Squeezed by contraction of surrounding muscles so flexible.

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3
Q

What is the structure + BP of a capillary?

A

Tiny vessel, one cell thick of squamous endothelium. Very low BP.

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4
Q

What is the purpose of elastic tissue?

A

Allows arteries to stretch as blood pulses out of heart,. As it recoils between heartbeats, helps to push blood along artery.

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5
Q

What is the purpose of smooth muscle in the middle layer?

A

Provides support and can constrict or dilate to control blood flow to organs depending on metabolic needs. Can be contracted and lumen narrowed to maintain BP.

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6
Q

What is the purpose of a large lumen in veins?

A

Offers little resistance to low pressure blood flow.

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7
Q

What is the purpose of valves in veins?

A

Prevent blood backflow. Ensure unidirectional flow.

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8
Q

What is the purpose of fibrous tissue?

A

Offers protection.

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9
Q

What is the purpose of the squamous endothelial layer in veins + arteries?

A

Creates smooth surface, reducing friction to allow blood to flow. Collagen inside offers support.

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10
Q

What are the adaptations of capillaries?

A

Small size allows large network so large SA. Thin walls for gas exchange, permeable to water + solutes, short diffusion distance. RBCs squeeze through, reducing distance.

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11
Q

In the aorta + arteries, describe the blood pressure, velocity, and cross sectional area of blood vessel.

A

Blood at high pressure as close to heart, no significant increase in CSA. Pulse effect in BP not matched by pulse in blood velocity due to smoothing effect of elastic + muscle tissue in artery wall.

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12
Q

From the arteries to the arterioles, describe the blood pressure, velocity, and cross sectional area of blood vessel.

A

Increase in number means increase in CSA + lower pressure + velocity allows exchange of materials between capillaries + surrounding tissues.

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13
Q

From the capillaries to venules to veins, describe the blood pressure, velocity, and cross sectional area of blood vessel.

A

CSA decreases but large lumen in veins means less friction between walls + blood so velocity increases although pressure still low. Valves prevent low pressure backflow.

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14
Q

How does an atheroma develop?

A

Squamous endothelium cells lining artery become damaged due to toxins (smoke, high BP), atheroma builds up in wall under SECs, macrophages move into wall + build up cholesterol, dead muscle cells, salts + fibrous tissues. Atheroma hardens into plaque. Larger, bulges more, narrows lumen + restricts flow. Fibrous tissue in atheroma damaged artery elasticity so can’t regulate blood flow so well. Narrowing raises BP, worsening condition.

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15
Q

Describe the pathway of blood through the heart.

A

Deoxygenated blood arrives at heart from vena cava and moves into right atrium, then through tricuspid atrioventricular valve, into right ventricle, through semilunar valve into pulmonary artery to lungs and back via pulmonary vein into left atrium, through bicuspid atrioventricular valve, into left ventricle, out through semilunar valve into the aorta, around the body and back again.

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16
Q

Which side of the heart has thicker muscle?

A

Left ventricle, it has to pump blood around the body.

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17
Q

Describe the heart.

A

Fist sizes, lies in thorax between lungs + beneath breastbone (sternum). Hollow organ with muscular wall situated within pericardium. Made up of cardiac muscle + is myogenic.

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18
Q

How many times does the heart tend to beat per minute?

A

Around 75 times.

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19
Q

What are the 3 stages of the cardiac cycle?

A

Atrial systole, ventricular systole + diastole.

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20
Q

What are the 2 stages of a heartbeat? Describe.

A

Systole (Heart contracts) + Diastole (Heart relaxes)

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21
Q

Describe the pressure changes in the heart during atrial systole in terms of atrial pressure, ventricular pressure + aortic pressure.

A

Atrial walls contract, increasing atrial pressure. AV valves are open as atrial pressure is more than ventricular pressure + SL valves are closed as aortic pressure is more than ventricular pressure. When contraction complete (atria empty of blood) + ventricles begin to contract (V pressure < A pressure) AV valves closing creating ‘lub’ sound.

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22
Q

Describe the pressure changes in the heart during ventricular systole in terms of atrial pressure, ventricular pressure + arterial pressure.

A

Closed AV valves bulge, increasing atrial pressure then decrease as little present so walls relax so blood flows slowly back in. Continued ventricular contraction so as V pressure > arterial pressure SL valves open. As arterial pressure > v pressure, SL valves close due to blood loss from ventricular causing ‘dub’.

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23
Q

Describe the pressure changes in the heart during diastole in terms of atrial pressure, ventricular pressure + arterial pressure.

A

Ventricular pressure falls as little blood + walls relax so Atrial pressure > v pressure so AV valves open. Blood passively flows into ventricles from atria.

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24
Q

Describe how the heart beat occurs, up until the AV septum.

A

Muscle fibres radiating out from SAN conduct wave of excitation to atria muscles. Triggers atrial systole. Atrioventricular septum at base of atria stops wave moving further. This slows the wave to ensure atrial systole is completed + blood has filled ventricles before ventricular systole occurs.

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25
Q

Describe how the heart beat occurs, from the AV septum to the end.

A

Atrioventricular node picks up wave and passes it to walls of ventricles through purkinje fibres into the bundle of His. This triggers ventricular systole so blood is squeezed out of heart through arteries. Wave passes upwards from apex through ventricular walls.

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26
Q

What happens after each heartbeat + why?

A

Refractory period. Relatively long. Allows heart to beat throughout life.

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27
Q

How is the SAN controlled?

A

Under nervous system control even though heartbeat is myogenic. This means the rate can be altered as needed.

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28
Q

How is the heart supplied with O2 + glucose.

A

Needs to respire to have energy for contraction. Wall of heart has own vessels as nutrients couldn’t diffuse from chambers throughout all layers. Coronary Circulation.

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29
Q

What is P in an ECG?

A

Represents spread of electrical activity from SAN over atrial surface.

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30
Q

What do QRS represent in an ECG?

A

Passage of electrical activity over the ventricles.

31
Q

What does T represent in an ECG?

A

Electrical charges occurring during filling of heart (relaxation)

32
Q

Why is R bigger than P in an ECG?

A

Larger ventricles with thicker muscles so need more electrical activity to make them contract.

33
Q

What does the short flat section between P + Q in an ECG represent?

A

Delay caused by AV septum, allowing ventricles to fill with blood.

34
Q

What are the main 4 parts of the blood?

A

Plasma, white blood cells, erythrocytes + platelets.

35
Q

What are 3 types of leucocytes?

A

Polymorphs, monocytes + lymphocytes.

36
Q

Give examples of what substances are transported in plasma.

A

CO2, nutrients, waste products, ions, hormones, proteins, blooding clotting factors, antigens + antibodies, water, bacteria + viruses + heat.

37
Q

Where are these substances transported + why:

Nutrients, waste products, ions, hormones, proteins.

A

Transported from small intestine to liver to all cells.
Transported from cells to liver to kidneys for excretion.
Transported from small intestine to cells, help buffer pH.
Transported from glands to targets organs.
Amino acid reserve.

38
Q

Where are these substances transported + why:

Blood clotting factors, antigens + antibodies, water + heat.

A

13 diff substances required to make blood clot.
Part of immune system.
Transported from large intestine + cells to kidneys for excretion.
Transported from muscles to skin for heat exchange.

39
Q

Where are substances transported in plasma exchanged?

A

Between blood + cells in capillary cells. Don’t move directly between blood and cell, first diffuse into tissue fluid around cells then to cells/

40
Q

How is tissue fluid formed?

A

Ultrafiltration occurs. Fluid now forms tissue fluid surrounding cells, materials exchanged between it and cells across cell membranes. At venous end of capillary bed, blood at low pressure since it has lost so much plasma. Water returns to blood by osmosis since blood has low WP. Solutes (CO2, urea, salts) enter blood by diffusion, down conc gradients.

41
Q

What is the difference between tissue fluid + lymph?

A

Both consist of plasma minus large proteins. Tissue fluid surrounds tissues but lymph only found in lymph vessels.

42
Q

Describe how lymph makes it’s way back into the blood.

A

Lymph capillaries join to form lymph vessels. Slow flow, relies on nearby muscle pressure, valve action, negative pressure created in chest when we inhale. Only drawn from tissues towards heart. Empty into subclavian veins under collar bones where it mixes with blood + joins vena cava. At intervals in system, there are lymph nodes whic play part in defence. Fats modified in lymph to make them more soluble in blood.

43
Q

Describe how blood clotting occurs.

A

Damage to tissues/blood vessel, exposing collagen, platelets activated (release clotting factors) i.e. thromboplastin. Form plug to seal minor damage. Thromboplastin catalyses calcium ions, vitamin K, factors 8 + 9 convert prothrombin to thrombin (enzyme), then catalyses conversion of fibrinogen to fibrin which forms mesh that traps RBCs to form clot.

44
Q

Why is blood clotting important?

A

Reduce blood loss as it’s necessary for O2 transport + fighting infection.

45
Q

Describe the process of oxygen transport.

A

RBCs pick up O2 in capillaries covering alveoli. Here, pO2 is high + haem saturated with O2. (1st O2 molecules attaches with difficulty but produces conformational change) Second easier + so on until all 4 attach + saturated with O2. RBCs then carry oxyhaemoglobin to respiring tissue where pO2 lower as O2 constantly used in respiration. Oxyhaemoglobin gives up O2 to respiring cells.

46
Q

At what stage is blood fully saturated with O2.

A

100% saturation is at pO2 14kPa. 50% means half of all haemoglobins are carrying O2.

47
Q

At what stage will oxyhaemoglobin dissociate?

A

At pO2 of 2 - 5 kPa. Reversible, just as when it saturates with O2.

48
Q

What do the properties of haemoglobin ensure? How is this illustrated?

A

At high pO2, it combines with large amounts of O2 whilst at low pO2, it combines with very little O2. Sigmoidal curve of oxygen dissociation graph, means relatively rapid dissociation between 2 - 5 kPa so O2 made available in large amounts to respiring tissues even though small range of partial pressures.

49
Q

What are the 2 things which haemoglobin depends on in terms of its O2 carrying ability.

A

Partial pressure of oxygen + carbon dioxide.

50
Q

What causes the oxygen dissociation curve to move further right?

A

Increased CO2 (haemoglobin readier to give up O2), CO2 acidic so increased pH, increased temp (increased O2 supply to tissues where increased resp). Haemoglobin affinity for O2 decreases as partial pressure/conc of CO2 is increased.

51
Q

The further an oxygen dissociation curve moves to the left, the most readily it ____?

A

Picks up O2.

52
Q

As level of activity increases, as does the rate of respiration of muscles, increasing the amount of CO2, so haemoglobin will ____?

A

Give up a greater amount of O2 it’s carrying.

53
Q

How is CO2 transported?

A

In blood (plasma + RBCs) as hydrogencarbonate ions.

54
Q

What is the equation for CO2 being transported as hydrogencarbonate ion?

A

CO2 + H2O —(Carbonic Amylase)—> HCO3- + H+

55
Q

What does carbonic amylase do?

A

Catalyses CO2 -> hydrogencarbonate ions. Hydrogen ions are also a product, these become associated with haemoglobin which acts as buffer for H+, preventing blood becoming acidic.

56
Q

When will myoglobin give up it’s O2 store?

A

At low pO2, when muscle active for long time, O2 conc in muscle may fall below 1kPa so oxymyoglobin will dissociate to supply O2 for aerobic resp. Finally, if muscle contraction continues + myoglobin yielded all O2, switches to anaerobic resp by lactic acid fermentation so muscle can continue to contract.

57
Q

Myoglobin oxygen dissociation curve is to left of haemoglobin, what does this signify?

A

At each pO2, myoglobin has higher percentage O2 saturation than haemoglobin.

58
Q

Describe pO2 at higher altitudes.

A

Lower (less O2 in air, thinner). More difficult to breathe if not used to this. Haemoglobin of those who live at high altitudes saturates with O2 at lower pO2 than those at lower, increases O2 demand by individual at lower. After time at high altitude, acclimatisation occurs so higher breathing rate + more RBCs produced to transport less oxygen more efficiently.

59
Q

Why might athletes have increased RBC production during high altitude training?

A

Rate of production controlled by erythropoietin which is released from kidneys. Normally rate produced = rate destroyed but when O2 shortage at high altitude, number increases to meet new demands. This is because decrease in amount of O2 reaching kidneys results in increase in erythropoietin, stimulating production.

60
Q

How is total pressure of mixture of gases calculated?

A

Add up all partial pressures.

61
Q

What is atmospheric air made up of?

A

O2, CO2, nitrogen, water vapour + several other gases in small quantities.

62
Q

How is the partial pressure of O2 in the atmosphere calculated?

A

Multiply percentage of atmospheric air composed of O2 (21%) by total atmospheric pressure (760 mm Hg) = 160 mm Hg. At high altitudes, this is lower i.e. 0.21 x 500 mm Hg = 105 mm Hg. This means less O2 available for haemoglobin at higher altitudes so not saturated so kidneys release more E to stimulate RBC production so haem has lower O2 affinity.

63
Q

Talk about training at higher altitudes.

A

Lower O2 levels at altitude means less O2 delivered to muscles so RBCs released from store in spleen, within 12 hours faster RBC production rate thanks to E. This leads to haemoglobin increase by 50-90% + capacity for blood to carry O2 increases. Phosphate substances inside RBCs increases. These combine with haem to reduce O2 affinity so it dissociates with O2 easier when it reaches muscles. At 2000-2500m, takes 2 weeks for body to acclimatise.

64
Q

What are the differences between tissue fluid + lymph?

A

Tissue fluid contains no cells whilst blood does. Tissue fluid surrounds tissues, not in vessels, unlike blood which travels in vessels. Tissue fluid is at lower pressure than blood.

65
Q

Suggest what could happen in tissues if tissue fluid isn’t draining properly.

A

Build up of waste products and fluid, leading to swelling and low blood volume creating odema and possibly lysis of cells.

66
Q

Why does foetal haemoglobin have a higher oxygen affinity than adult haemoglobin?

A

So O2 dissociates from mother’s haemoglobin + is donated to baby so baby can breathe.

67
Q

What are some symptoms of a lack of O2?

A

Mountain sickness - Breathlessness, nausea + fatigue.

68
Q

What are some risk factors of atherosclerosis?

A

Smoking, inactivity, stress, obesity, excess salt, high cholesterol, excess alcohol, diabetes, age + genetic predisposition.

69
Q

Why is it beneficial for athletes to train at high altitudes?

A

More RBCs for more O2 so can carry more O2 + perform better.

70
Q

Why do diving mammals have more myoglobin?

A

Live in O2 stressed environments so need it to store O2 for diving and to avoid anaerobic respiration.

71
Q

What causes the delay in transmission of impulse to the ventricles?

A

AV septum, layer of non conducting material passes transmission to AV node where it moves on causing delay.,

72
Q

What is the advantage of having a higher RBC count at high altitude?

A

More haemoglobin to carry O2. More O2 uptake overall compensates for lower ppO2.

73
Q

What are the possible dangers of injecting artificial erythropoietin?

A

Thicker blood, clogged capillaries, higher risk of heart attack/stroke from blood clot.

CCEA AS Biology Unit 2 (10 decks)

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