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Biology A Level Eduqas > Transport in animals > Flashcards

Transport in animals Flashcards

1
Q

Explain why counter current flow is more efficient than parallel flow?

A

water and blood flow in opposite directions so the blood is always in contact with water that has a higher O2 concentration maintaining the conc gradient and allowing for more efficient diffusion

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2
Q

What 3 features do all transport systems in animals have?

A

1) A suitable medium in which to carry materials
2) A pump, such as the heart, for moving blood
3) valves to maintain the flow in one direction

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3
Q

What 2 features do some transport systems have?

A

1) A respiratory pigments, such as in vertebrates and some invertebrates, which increases the volume of oxygen which can be carried
2) A system of vessels with a branching network to distribute the transport medium to all parts of the body

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4
Q

What is an open circulatory system?

A

The blood does not move around the body in blood vessels but it bathes the tissue directly while held in a cavity called the haemocoel.

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5
Q

Describe the circulatory system in an insect

A

They have an open blood system.

They have a long, dorsal tube-shaped heart. It pumps blood out at low pressure into the haemocoel where materials are exchanged between the body and blood cells.

There is no respiratory pigment and therefore lack of respiratory gases in blood.

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6
Q

What is a closed circulatory system?

A

The blood moves in blood vessels

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7
Q

Describe the circulation in an earth worm

A

1) It has a single, closed circulation system
2) Respiratory gases carried in blood by haemoglobin
3) Blood moves forward in the dorsal vessel and is pumped into the ventral vessel by pseudohearts which are muscular blood vessels (vascularisation)

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8
Q

Describe the circulation in a fish

A

It has a closed, single circulatory system

The ventricle of the heart pumps deoxygenated blood to the gills. Oxygenated blood is carried to the tissues and then deoxygenated blood returns to the atrium of the heart

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9
Q

Why do mammals need a double circulation system?

A

The blood passes through the heart twice - blood pressure is reduced in the lungs and would be too low to provide the body’s tissues with nutrients quickly enough. Instead the blood is returned to the heart which raises its pressure again, to make sure circulation is efficient.

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10
Q

Why is double circulation in a mammal more efficient than single circulation in a fish?

A

Because oxygenated blood can be pumped around the body at higher pressure

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11
Q

What is the innermost layer of a blood vessel and what is its function?

A

Endothelium - it is one cell thick and is surrounded by the tunica intima.

It is a smooth lining, reducing friction with a minimum resistance to blood flow

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12
Q

What is the middle layer of the blood vessel and what is it made up of?

A

The tunica media - contains elastic fibres and smooth muscle

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13
Q

Why is the tunica media thicker in arteries than in veins?

A

Elastic fibres stretch and recoil, pushing blood through the artery. This maintains blood pressure as the blood is transported further from the heart.

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14
Q

What is the outer layer of the blood vessel called? What is it made of?

A

Tunica externa - it contains collagen fibres, which resist overstretching

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15
Q

What is the function of arteries?

A

Carry blood away from the heart. Their thick muscular walls withstand the pressure of the blood derived from the heart.

Arteries -> Arterioles -> Capillaries

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16
Q

How do capillaries help return blood to the heart?

A

Blood from the capillaries collects into venules, which take blood into veins.

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17
Q

How are veins different to arteries?

A

1) They have valves
2) They have a larger diameter lumen
3) Thinner walls with less muscle than arteries - blood pressure and flow rate are lower

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18
Q

How does blood return to the heart from veins?

A

For veins above the heart, blood returns to the heart by gravity and for other veins it moves by the pressure from surrounding muscles.

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19
Q

Describe the structure of capillaries

A

They have thin walls, which are only one layer of endothelium on a basement membrane.

There are pores between the cells making the walls permeable. So exchange of substances such as glucose and water can take place between blood and tissues.

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20
Q

How do capillaries function?

A

Capillaries reduce the rate of blood flow due to friction against their wall and this means that there is plenty of time for the exchange of materials.

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21
Q

Why can the heart be thought of as two separate pumps?

A

One deals with oxygenated blood - pumping blood to the rest of the body.

One deals with deoxygenated blood - pumping blood to the lungs.

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22
Q

What is the heart made of and why is this suitable?

A

It consists largely of cardiac muscle, a specialised tissue which can relax and contract rhythmically of its own accord.

It is involuntary muscle and unlike voluntary muscles it never tires.

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23
Q

How can heart rate be modified?

A

By nervous and hormonal stimulation

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24
Q

What is cardiac output?

A

The volume of blood expelled by the heart in one minute

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25
Q

How do you calculate cardiac output?

A

Stroke volume x number of heart beats per minute

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26
Q

What is the atrial systole?

A

The atrium walls contract and the blood pressure in the atria increases. This pushes the blood through the tricuspid/bicuspid valves, down into the ventricles which are relaxed.

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27
Q

What is ventricular systole?

A

The ventricle walls contract and increased blood pressure in the ventricles. This forces blood up through the semi-lunar valves, out of the heart into the pulmonary artery and aorta

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28
Q

Why do the bicuspid and tricuspid valves close? And what does this prevent?

A

They close when pressure in ventricles exceeds pressure in atria which prevents the back flow of blood

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29
Q

What is diastole? And why does this cause the semi-lunar valves to close?

A

The ventricles relax, the volume in the ventricles increases and so pressure in the ventricles falls.

This risks the blood in the pulmonary artery and aorta flowing backwards, this tendency causes the semi-lunar valves to shut.

30
Q

Describe the flow of blood through the left side of the heart

A

1) The left atrium relaxes and receives oxygenated blood from the pulmonary vein
2) When full, the pressure forces open the bicuspid valves (between atrium and ventricle)
3) Relaxation of the ventricle draws blood from the left atrium
4) The left atrium contracts, pushing the remaining blood into the left ventricle
5) With The left atrium relaxed and with the bicuspid valve closed, the left ventricle contracts.
6) The high pressure from the ventricle pushes blood up out the heart, through semi-lunar valves into the aorta and closes the bicuspid valves.

31
Q

Why do atria walls have little muscle compared to ventricle walls?

A

Because in the atria the blood only has to go to the ventricles, whereas ventricle walls need to generate more pressure, as they have to send the blood to the lungs or the rest of the body.

32
Q

Why does the left ventricle have a thicker, more muscular wall than the right ventricle?

A

Because it has to pump blood all round the body, whereas the right ventricle has to pump the blood a shorter distance to the lungs.

33
Q

What does the SAN do?

A

It causes a wave of electrical simulation to arise which spreads over both atria causing them to contract together. Acts as pacemaker

34
Q

Where is the SAN found?

A

In the wall of the right atrium

35
Q

What does the AVN do?

A

The AVN introduces a delay in the transmission of the electrical impulse. This ensures that the ventricles do not contract before the atria have finished contracting (are empty).

36
Q

What does the P-wave on an electrocardiogram show?

A

The depolarisation of the atria during atrial systole

37
Q

What does the PR interval on an electrocardiogram show?

A

It is the time taken for the excitation to spread from the atria to the ventricles, through the atria-ventricular node.

38
Q

What does the QRS complex on an electrocardiogram show?

A

It shows the spread of depolarisation through the ventricles, resulting in ventricular systole

39
Q

What does the T wave on an electrocardiogram show?

A

Shows the repolarisation of the ventricle muscles during ventricular diastole

40
Q

How does pressure change in the aorta and large arteries?

A

It rises and falls rhythmically with ventricular contraction

41
Q

How does pressure change in the arterioles?

A

Friction between the blood and vessel walls and the large total surface area causes a progressive drop in pressure.

42
Q

How do the extensive capillary beds reduce blood pressure?

A

Fluid leaks from the capillaries into the tissues, lowering hydrostatic pressure.

43
Q

Why do veins have a lower blood pressure?

A

Because they are not subject to pressure changes derived from the contraction of the ventricles.

44
Q

Does blood flow faster in capillaries or in veins?

A

In veins because they have a larger diameter lumen.

45
Q

Why does the aortic pressure never equal 0?

A

Because the semi-lunar/aortic valves close

46
Q

Function of Purkinje fibres

A

They transmit an impulse to the apex of the ventricles which causes the ventricles to contract from the bottom upwards

47
Q

What is the function of tendons in the heart?

A

Tendons prevent valves inverting

48
Q

How are red blood cells adapted to their function?

A

Thin centre - reduces the diffusion distance making gas exchange faster

Biconcave shape - larger surface area, so more oxygen diffuses across membrane

No nucleus - there is more room for haemoglobin so more oxygen can be carried

Contain haemoglobin - pigment which reacts with oxygen

49
Q

What is contained in plasma and what is its function?

A

It is about 90% water

Transports nutrients, hormones, excretory products and also distributes heat

50
Q

Describe the structure of haemoglobin

A

Each haemoglobin molecule contains 4 haem groups, each haem contains an ion of Fe2+.

51
Q

How does oxygen bind to haemoglobin?

A

Each iron ion can bind to one oxygen molecule, so four oxygen molecules can bind to each haemoglobin molecule, carrying it as oxyhaemoglobin

52
Q

Describe cooperative binding and how it is useful

A

The first oxygen molecule is hard to bind and changed the shape of the haemoglobin molecule, making it easier for the second molecule to attach - this changes the shape again making it easier for the third oxygen molecule to attach. This allows haemoglobin to pick up oxygen very rapidly in the lungs.

53
Q

How does haemoglobin associate readily with oxygen at the alveoli but dissociate with oxygen at the muscles?

A

It changes its affinity for the oxygen by changing its shape.

54
Q

Describe a normal oxygen dissociation graph

A

The oxygen affinity of haemoglobin at high partial pressures of oxygen is high and oxyhaemoglobin does not release oxygen, but binds to it.

At low oxygen partial pressures the oxygen affinity of haemoglobin decreases and it dissociates from oxygen for aerobic respiration

55
Q

Where does haemoglobin load oxygen and where does it unload oxygen?

A

(Loads ) In the lungs where the oxygen partial pressure is high and the haemoglobin has a high affinity for oxygen, so it becomes saturated.

(Unloads) At tissues where the oxygen partial pressure is low due to it being used up by respiration and haemoglobin has a low affinity for oxygen.

56
Q

Describe the oxygen dissociation curve of fetal haemoglobin

A

The haemoglobin of a fetus must absorb oxygen from the maternal haemoglobin at the placenta.

Fetal haemoglobin has a higher affinity for oxygen than the mothers haemoglobin at all partial pressures meaning it can get full saturation at a lower partial pressure (living in lower oxygen environment)

This causes the percentage saturation of the fetus’s blood to be higher than its mothers (oxygen moves into blood of fetus)

Oxygen dissociation curve moves to the left

57
Q

Describe the oxygen dissociation curve of an animal in a low-oxygen partial pressure environment e.g Lugworm

A

The oxygen dissociation curve will be to the left of a humans.

This means it’s haemoglobin has a higher affinity for oxygen at all partial pressures

Haemoglobin can become saturated at lower oxygen partial pressure

Higher percentage saturation at all partial pressures

58
Q

What is a disadvantage of having an oxygen dissociation curve further to the left?

A

Haemoglobin cannot release oxygen as quickly.

59
Q

Describe how carbon dioxide concentration effects the oxygen dissociation curve

A

If carbon dioxide concentration increases (e.g during exercise) haemoglobin releases oxygen more readily at any oxygen partial pressure.

Haemoglobin is less saturated with oxygen

Curve moves to the right - The Bohr effect

60
Q

What is a solution to the problem of low oxygen availability which occurs in people who live at high altitudes?

A

They make more red blood cells, allowing more oxygen to be carried around the body to respiring muscles.

61
Q

Describe the oxygen dissociation curve of an animal with a higher metabolic rate e.g a mouse

A

Their haemoglobin will have a lower affinity for oxygen at reduced partial pressures, lower percentage saturation with oxygen because more carbon dioxide is being produced

Haemoglobin can unload oxygen more quickly at higher oxygen partial pressures

62
Q

What is a disadvantage of having a dissociation curve to the left?

A

Harder to unload O2

63
Q

How is CO2 transported in the blood?

A

As the hydrogen carbonate ion and carbaminohaemoglobin

64
Q

Describe the process of how HCO3- ions are produced from carbon dioxide

A

1) Carbon dioxide in the blood diffuses into the red blood cell
2) Carbonic anhydrase catalysed the combination of carbon dioxide with water, making carbonic acid
3) Carbonic acid dissociates into H+ and HCO3- ions
4) HCO3- ions diffuse out of the red blood cell into the plasma

65
Q

How does the red blood cell remain at a neutral PH after HCO3 ions diffuse out?

A

1) To balance the outflow of negative ions and maintain electrochemical neutrality, chloride ions (chloride shift) diffuse into the red blood cell from the plasma
2) H+ ions cause oxyhaemoglobin to dissociate into oxygen and haemoglobin. The H+ ions combined with haemoglobin to make haemoglobinic acid. This removes hydrogen ions and so the PH of the red blood cell does not fall
3) Oxygen diffuses out of the red blood cell into the plasma

66
Q

How does haemoglobin help keep PH constant?

A

It buffers the blood by removing hydrogen ions which prevents the PH from falling

67
Q

How is tissue fluid useful?

A

It is forced out of the capillary walls and it bathed the cells, supplying them with solutes they need to survive and removing any waste made by the cells.

68
Q

What happens at the arterial end of a capillary bed?

A

1) Hydrostatic pressure is greater than osmotic pressure, so water and small soluble substances are forced out through capillary walls forming tissue fluid
2) Osmotic pressure - plasma has a low solute potential, due to plasma proteins being too large to be forced out so they pull water back into the capillary by osmosis
3) Solutes such as glucose, oxygen and ions are used during metabolism - concentration is higher in blood than around cells so diffuses from blood into tissue fluid.

69
Q

What happens at the venous end of the capillary bed?

A

1) The blood hydrostatic pressure is lower than at the arterial end because much fluid has been lost and at venous end osmotic pressure of the blood is higher than hydrostatic pressure
2) Most Water from tissue fluid moves back into blood capillaries by osmosis down water potential gradient

70
Q

What happens to remainder of tissue fluid

A

Some is returned to blood via the lymph vessels

Biology A Level Eduqas (25 decks)

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