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Biology A Level > Transport in Animals > Flashcards

Transport in Animals Flashcards

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1
Q

What are the main factors affecting an organisms need for a transport system?

A
  • Size
  • SA:V ration
  • Metabolic activity
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2
Q

Why do organisms with a small surface area to volume ratio need a transport system?

A

Larger animals have a smaller surface area to volume ratio, this means that each gram of tissue doesn’t have a sufficient area of body surface for exchange meaning that cells won’t be supplied with sufficient oxygen for respiration

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3
Q

What are the features of an effective transport system?

A
  • A fluid or medium to carry nutrients, oxygen and waste products around the body (the blood)
  • A pump to create pressure to push the fluid around the body (the heart)
  • Exchange surfaces that enable substances to leave and enter the blood when needed (capillaries)
  • Tubes or vessels to carry blood by mass flow
  • A double circuit, one to pick up oxygen and another to deliver oxygen to the tissues
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4
Q

What is a single circulatory system?

A

A circulatory system where blood flows through the heart once for each circuit of the body

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5
Q

Describe the route of blood in a fish’s body

A

Heart → Gills (where the blood is oxygenated) → Body (where oxygen is delivered to the tissues)→ Heart

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6
Q

What is a double circulatory system?

A

A circulatory system that has two circuits, one circuit carries blood to the lungs to pick up oxygen, the other circuit transports this oxygen to the tissues. Blood flows through the heart twice for each circuit of the body

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7
Q

Describe the route of blood in a mammal’s body?

A

Heart → Lungs → Heart → Tissues → Heart

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8
Q

What are the disadvantages of a single circulatory system?

A
  • Blood pressure drops as the blood passes through the capillaries of the gills
  • Blood has a low pressure as it flows towards the tissues meaning it will be flowing slowly
  • The rate at which oxygen and nutrients are delivered to tissues and CO2 and urea are removed is limited
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9
Q

What are the advantages of a double circulatory system?

A
  • The heart can pump blood to the lungs at lower pressures than it pumps blood to the tissues, this maximises the rate of blood flow without damaging the capillaries in the lungs
  • This ensures that cells have a good supply of oxygen to release energy from food in the process of respiration and therefore mammals are able to maintain their body temperature and also be active
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10
Q

What si an open circulatory system?

A

A circulatory system that blood isn’t held within vessels, blood fluid circulates the body cavity and bathes the tissues and cells

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11
Q

How does blood enter an insect’s blood?

A

Through pores in the heart called ostia

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12
Q

What are the disadvantages of an open circulatory system?

A
  • Blood pressure is low so blood flow is slow

- Circulation of blood may be affected by body movements or lack of body movements

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13
Q

What is a closed circulatory system?

A

A circulatory system where blood stays entirely in vessels, a separate fluid called tissue fluid bathes the cells and tissues, the tissue fluid allows nutrients and oxygen to diffuse into the cells

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14
Q

What are the advantages of a closed circulatory system?

A
  • Higher pressure so blood flow is faster
  • More rapid delivery of oxygen and nutrients
  • More rapid removal of waste products such as CO2 and urea
  • Transport is independent of body movement
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15
Q

Describe the structure and function of arteries

A

Arteries carry blood away from the heart, the blood arteries carry is at high pressure as it has just been pumped by the heart. Arteries have thick walls to withstand the high pressure and a small lumen to maintain this high pressure. The inner wall of the artery is folded to allow the lumen to expand when blood flow is increased

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16
Q

What are the three layers of the arterial wall?

A
  • Inner layer (tunica intima) that consists of a layer of elastic fibres that allows the wall to stretch and recoil to help maintain blood pressure
  • The middle layer (tunica media) that consist of a thick layer of smooth muscle
  • The outer layer (tunica adventitia) that consist of a relatively thick layer of collagen fibres and elastic tissue, this provides strength to withstand the high pressure and stretch and recoil to maintain pressure
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17
Q

What is the function of arterioles?

A

Arterioles are small blood vessels that distribute blood from arteries into the capillaries, arteriole walls contain a layer of smooth muscle. Smooth muscle can be used to reduce blood flow by contracting and constricting the diameter of the arterioles. Constriction of the arteriole walls also can be used to divert flow of blood to the active tissues

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18
Q

Describe the structure and function of capillaries

A
  • Capillaries allow exchange between blood and tissue fluid
  • They have very thin walls (just the endothelium which is one cell thick)
  • They have a very narrow lumen, its diameter is the same as the diameter of a red blood cell, this squeezes the RBCs against the wall of the capillary maximising diffusion of oxygen as it reduces the diffusion distance for the oxygen, the narrow lumen also reduces rate of flow
  • Their walls consist of a single layer of endothelial cells which reduces the diffusion distance for the material being exchanged
  • Their walls are leaky, they allow blood plasma and dissolved substances to leave the blood, this is the formation of tissue fluid
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19
Q

What is the inner layer of all blood vessels made up of?

A

A single layer of cells called endothelium

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20
Q

How is tissue fluid formed?

A

Blood plasma leaks out of the capillaries, the plasma contains dissolved substances such as O2, CO2, amino acids. This forms tissue fluid that

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21
Q

How do waste products enter the blood?

A

Waste products from metabolism diffuse from the cell into the tissue fluid. The waste products will then be carried into the blood as some of the tissue fluid returns to the capillaries at the venule end

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22
Q

Which blood vessel carries blood to organs and tissues?

A

When arteries reach tissues they branch into arterioles and then a network capillaries so capillaries carry blood to organs and tissues

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23
Q

Why can’t proteins enter the tissue fluid?

A

They are too large

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24
Q

What happens to tissue fluid that doesn’t re-enter the capillaries?

A

The tissue fluid is directed to another tubular system called the lymphatic system, the fluid in the lymphatic system is called lymph and is very similar to the tissue fluid except it contains lymphocytes as these are produced in the lymph nodes

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25
Q

What is hydrostatic pressure?

A

Pressure that a fluid exerts when pushing against the sides of a vessel or container

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26
Q

What is oncotic pressure?

A

Pressure created by the osmotic effects of solutes (oncotic pressure is basically just another word for water potential

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27
Q

Where is hydrostatic pressure highest?

A

Arteriole end of the capillary

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28
Q

Where is hydrostatic pressure lowest?

A

Anywhere in the tissue fluid

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29
Q

Where is oncotic pressure highest?

A

Anywhere in the tissue fluid

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30
Q

Where is oncotic pressure lowest?

A

Anywhere in the capillary

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31
Q

What is the net direction of flow of tissue fluid at the arteriole end?

A

Outwards

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32
Q

What is the net direction of flow of tissue fluid at the venule end?

A

Inwards

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33
Q

What is the overall flow of tissue fluid?

A

Out of the capillary at the arteriole end and into the capillary at the venule end. This enables oxygen and other nutrients to diffuse into the cell from the tissue fluid and CO2 to diffuse into the tissue fluid from the cell and be carried into the blood by the tissue fluid flowing back into the blood at the venule end

34
Q

How does blood plasma leave the capillary to form tissue fluid?

A

Mass flow

35
Q

Does the left side of the heart pump deoxygenated or oxygenated blood?

A

Oxygenated blood to the tissues

36
Q

Does the right side of the heart pump deoxygenated or oxygenated blood?

A

Deoxygenated blood to the lungs

37
Q

What does the heart mainly consist of?

A

Dark-red muscle called cardiac muscle

38
Q

What are the coronary arteries?

A

Arteries that supply the heart with oxygenated blood, they lie on the surface of the heart

39
Q

Describe the flow of deoxygenated blood around the body

A
  • Deoxygenated blood from the tissues flows into the right atrium through the vena cava
  • Through the atrio-ventricular valve and into the right ventricle
  • Blood flows out of the heart through the semi-lunar valves into the pulmonary artery then to the lungs where the blood is oxygenated
40
Q

Describe the flow of oxygenated blood around the body

A
  • Oxygenated blood from the lungs flows into the left atrium through the pulmonary vein
  • Through the atrio-ventricular valve into the left ventricle
  • Blood flow out of the heart through the semi-lunar valves into the aorta where blood flows to the tissues and is deoxygenated
41
Q

What does pulmonary mean?

A

Related to the lungs

42
Q

Are the walls of the atria thin or thick?

A

The atrial walls are very thin as they don’t need to create much pressure, they only need to receive blood from the veins and push it into the ventricles

43
Q

Are the walls of the right ventricle thick or thin?

A

Thicker than the walls of the atria, this enables the ventricles to pump the blood out of the heart and to the lungs. The pressure that the right ventricles pump blood at mustn’t be too high or the alveoli may be damaged. The lungs being in the chest cavity beside the heart means that the blood doesn’t need to travel very far so high pressure isn’t necessary

44
Q

Are the walls of the left ventricle thick or thin?

A

Very thick, the walls of the left ventricle can be two or three times thicker than that of the right ventricle. This is because the blood from the from the left ventricle needs sufficient pressure to overcome the resistance of the systemic circulation

45
Q

What separates the ventricles from each other?

A

A wall of muscle called the septum

46
Q

Describe the process of diastole

A

Muscular walls of all four chambers relax, elastic recoil causes the chambers to increase in volume and blood flows in from the veins

47
Q

Describe the process of atrial systole

A

Both left and right atria contract together, the walls of the atria are only thin so a small increase in pressure is create by this contraction, this helps to push blood into the ventricles, this stretches their walls and ensures they are full of blood

48
Q

Describe the process of ventricular systole

A

Both right and left ventricles pump together, contraction starts at the apex (base of the heart) so that blood is pushed upwards towards the arteries

49
Q

Describe the action of the atrio-ventricular valves

A
  • After ventricular systole, the ventricular walls relax and recoil
  • This causes pressure in the ventricles to drop rapidly below the pressure in the atria
  • Blood in the atria pushes the atrio-ventricular valves open
  • Blood entering the heart flows straight through the atria and into the ventricles
  • The pressure in the atria and ventricles rise slowly as they fill with blood
  • As the atria is contracting during atrial systole, the atrio-ventricular valves remain open, but as the atria relax, they close
  • The closure is caused by a swirling action of the blood around the valves when the ventricle is fill
  • The ventricles begin to contract (ventricular systole) and the pressure in the ventricles rises above that in the atria
  • The blood starts to move upwards back towards the atria but the blood fills the valve pockets and prevents the valve from opening and the blood from flowing back into the atria
  • The tendinous chords attached to the valves prevent them from turning inside out
50
Q

Describe the action of the semi-lunar valves

A
  • Before ventricular contraction, the pressure in the major arteries is higher than that in the ventricles
  • This means that the semi-lunar valves are closed
  • Ventricular systole raises the pressure in the ventricles very quickly and the pressure rises above that in the major arteries
  • Once it has risen above that in the major arteries, the semi-lunar valves open
  • Blood is under very high pressure when it leaves the ventricles in a very powerful spurt
  • Once the ventricle walls have stopped contracting, the heart relaxes (diastole)
  • Elastic tissue in the walls of the ventricles recoil and the pressure in the ventricle drops quickly below that in the major arteries as the ventricle returns to its original size
  • As the pressure drops below that in the major arteries, the blood starts to flow back towards the ventricle, the blood collects in the pockets of the semi-lunar valves and pushes the semi-lunar valves closed
  • This prevents blood from returning to the ventricles
51
Q

What is our pulse created by?

A

The pressure wave created by the left semi-lunar valve

52
Q

When the pressure in the ventricles rises above the pressure in the atria, which valve opens or closes and which stage of the cardiac cycle is occurring?

A

Atrio-ventricular valve closes to prevent blood flowing back into the atra from the ventricles, atrial systole has just occurred and ventricular systole has just started. The contraction of the atria, which helps to pump blood into the ventricles, and the contraction of the ventricles both raise the pressure in the ventricles above that in the atria

53
Q

When the pressure in the ventricles rises above that of the major arteries, which valve opens or closes and which stage of the cardiac cycle is occurring?

A

The semi-lunar valve opens to allow blood to flow out of the heart. Ventricular systole is occurring as the contraction of the ventricles raises the pressure in the ventricles above that in the major arteries

54
Q

When the pressure in the ventricles drops below that in the major arteries, which valve opens or closes and which stage of the cardiac cycle is occurring?

A

The semi-lunar valve closes to prevent blood flowing back into the ventricles. Diastole has just started and ventricular systole has just stopped, this causes pressure to drop in the ventricles below that in the major arteries

55
Q

When the pressure in the ventricles drops below that in the atria which valve opens or closes and which stage of the cardiac cycle is occurring?

A

The atrio-ventricular valve opens to allow blood to flow into the ventricles from the atria, diastole has just occurred, this rapidly decreases the pressure in the ventricles as the elastic walls recoil and the ventricles return to their original size. The atria aren’t affected as much as their walls are thin and they can’t create much of a pressure difference.

56
Q

How is blood pressure maintained in the arteries?

A

The artery walls close to the heart have a lot of elastic tissue that can stretch and recoil to maintain the blood pressure in the arteries. The further the blood flows along the arteries the more the pressure drops as the cross sectional area of the arteries increases(lumen increases in size), this is essential to have blood pressure lower in the arterioles than the aorta so that blood flows towards the tissues

57
Q

What is the sino-atrial node (SAN)?

A

A small patch of tissue located at the top of the right atrium near to where the vena cava empties blood into the atria that generates electrical activity, the SAN initiates a wave of excitation that occurs 55-80 times a minute

58
Q

How does the wave of excitation cause atrial systole?

A
  • The wave of excitation spreads quickly over the walls of both atria
  • It travels along the walls of the membranes of the muscle tissue
  • As the wave of excitation passes, it causes the cardiac muscle in the atria to contract
  • This is an atrial systole
59
Q

What is the atrio-ventricular node (AVN)?

A

The tissue of the atria can’t conduct the wave of excitation meaning the wave can’t pass through to the ventricles. The AVN is located at the top of the ventricular septum and is the only route that can conduct the wave of excitation

60
Q

How are are atrial systole and ventricular systole coordinated?

A

The wave of excitation is delayed at the AVN to allow the atria to finish contracting and the blood to flow down into the ventricles before they begin to contract

61
Q

How does the wave of excitation cause ventricular systole?

A
  • After the delay caused by the AVN, the wave of excitation is carried away from the AVN down specialised conducting tissue called purkyne tissue
  • This runs down the ventricular septum
  • At the base of the septum, the wave of excitation spreads upwards from the base of the ventricles it causes the cardiac muscle in the ventricles to contract
  • This means ventricles contract from the base upwards, pushing blood from the ventricles into the major arteries
62
Q

What is purkyne tissue?

A

Specialised conducting tissue in the ventricles

63
Q

What does a P wave show in an ECG?

A

Excitation of the atria (atrial systole)

64
Q

What does the QRS complex show in an ECG?

A

Excitation of the ventricles (ventricular systole)

65
Q

What does the T wave in an ECG show?

A

Diastole

66
Q

What is a sinus rhythm of the heart?

A

A normal heart rate

67
Q

What is bradycardia?

A

A slow heart rate

68
Q

What is tachycardia?

A

Fast heart rate

69
Q

What is atrial fibrilation?

A

Where the atria beat more frequently than the ventricles

70
Q

What is an ectopic heart rate?

A

The third beat is an early ventricular beat (the patient often feels as though a heart beat has been missed)

71
Q

Does oxygen associate or dissociate from haemoglobin when partial pressure of oxygen is low?

A

Dissociates

72
Q

Does oxygen associate or dissociate from haemoglobin when partial pressure of oxygen is low?

A

Associates

73
Q

How does oxygen associate with haemoglobin?

A

Oxygen from the air in the alveoli diffuses into the tissue fluid, the tissue fluid then moves back into the capillary at the venule end. This means that the O2 that is now in the blood plasma can associate with the haemoglobin by binding to the Fe2+ ion in the haem group. This keeps the concentration gradient from the alveoli to the blood plasma high as all oxygen is associated with haemoglobin and not dissolved in the blood plasma. This allows more oxygen to diffuse into the blood from the lungs and be transported to the tissues

74
Q

Why is the haemoglobin dissociation curve non-linear?

A

The haem groups that the oxygen molecules have to bind to are in the centre of the haem group, this makes it hard for the oxygen molecules to associate with the haemoglobin molecules. As the partial pressure of oxygen increases, there is a greater diffusion gradient of oxygen into the blood plasma meaning that more oxygen is trying to associate with haemoglobin. Eventually one oxygen molecule associates with the haemoglobin molecule, this causes a conformational change of the haemoglobin molecule which makes it easier for the other oxygen molecules to bind to the haemoglobin molecule

75
Q

What is the difference between fetal haemoglobin and adult haemoglobin?

A

Fetal haemoglobin has a slightly higher affinity for oxygen than adult haemoglobin, this is because fetal haemoglobin needs to be able to associate with oxygen at partial pressures low enough for adult haemoglobin to dissociate from oxygen

76
Q

How does the baby absorb oxygen from the mothers blood?

A

The fetal haemoglobin absorbs oxygen in the placenta from the surrounding fluid where the oxygen tension (partial pressure) is low, this reduces the oxygen tension in the placenta even further, this causes more oxygen from the mothers blood plasma to diffuse into the placenta. This reduces the oxygen tension in the mothers blood which makes more oxygen dissociate from the mother’s haemoglobin

77
Q

How is carbon dioxide transported to the lungs for excretion?

A
  • 5% dissolved directly in plasma
  • 10% combined with haemoglobin to from carbaminohaemoglobin
  • 85% in the form of HCO3- ions
78
Q

What does carbon dioxide that has dissolved in water produce?

A

Carbonic acid which dissociates to produce H+ and HCO3- ions, the formation of carbonic acid is catalysed by carbonic anhydrase

79
Q

What happens to H+ ions produced when H2CO3 dissociates?

A

They combine with haemoglobin to form HHb (haemoglobinic acid) this helps maintain pH of the cytoplsm

80
Q

What happens to the HCO3- ions produced when H2CO3 dissociates?

A

They diffuse out of the red blood cell into the blood plasma, Cl- ions move in to maintain the charge of the cytoplasm

81
Q

Describe the Bohr effect

A

As tissues are respiring, more CO2 is released, CO2 enter red blood cells and forms carbonic acid. This dissociates to form H+ ions which decrease the pH of the cytoplasm and alter the tertiary structure of haemoglobin reducing haemoglobin’s affinity for oxygen, this causes oxygen to dissociate and enter the tissues. The haemoglobin that has dissociated from oxygen combines with H+ ions to maintain the pH in the cytoplasm

82
Q

What is the effect of the Bohr shift on the haemoglobin dissociation curve?

A

It shifts right as oxygen is less associated with haemoglobin at the same partial pressures of oxygen when partial pressures of CO2 are higher

Biology A Level (21 decks)

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