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OCR AS/A Level Biology Context > module 3.2: transport in animals > Flashcards

module 3.2: transport in animals Flashcards

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1
Q

what is a double circulatory system

A

one in which the blood flows through the heart twice for each
circuit of the body

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2
Q

what is the single circulatory system

A

one in which the blood flows through the heart once for each circuit of the body

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3
Q

what is transport

A

the movement of substances such as oxygen, nutrients, hormones, waste and heat around the body

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4
Q

what is the reason for a transport system

A
  • they also need to remove waste products so that these do not build up and become toxic
  • larger animal with a complex anatomy will have more than two layers of cells. the diffusion distance becomes too long, and diffusion alone will be too slow to supply all the requirements
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5
Q

what are the 3 main factors that influence the need for a transport system

A

size
sa:v ratio
level of metabolic activity

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6
Q

how does size influence the need for a transport system

A
  • the cells inside a large organism are further from its surface — the diffusion pathway is increased
  • the diffusion rate is reduced, and diffusion is too slow to supply all the requirements
  • also, the outer layers of cells use up the supplies, so that less will reach the cells deep inside the body
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7
Q

how does sa:vol ratio influence the need for a transport system

A
  • small animals have a large surface area to volume ratio meaning that for each gram of tissue in their body they have a sufficient area of the body surface through which exchange can occur
  • however, larger animals have a smaller surface area to volume ratio meaning that each gram of tissue has a smaller area of the body surface for exchange
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8
Q

how does the level of metabolic activity influence the need for transport system

A
  • animals need energy from food, so that they can move around - releasing energy from food by aerobic respiration requires oxygen
  • if an animal is very active, its cells need good supplies of nutrients and oxygen to supply the energy for movement
  • animals that keep themselves warm, such as mammals, need even more energy
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9
Q

what features are included in an effective transport system

A
  • a fluid or medium to carry nutrients, oxygen and wastes around the body — this is the blood
  • a pump to create pressure that will push the fluid around the body — this is the heart
  • exchange surfaces that enable substances to enter the blood and leave it again where they are needed — these are the capillaries
  • tubes or vessels to carry the blood by mass flow
  • two circuits — one to pick up oxygen and another to deliver oxygen to the tissues
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10
Q

what type of circulatory system does a fish have

A

single

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11
Q

what route does the blood flow in a fish

A
  • the blood flows through the heart once for each circuit of the body
  • the blood takes the following route: heart->gills-> body->heart
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12
Q

what circulatory system does a mammal have

A

double

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13
Q

explain the blood route in a mammal

A
  • one circuit carries blood to the lungs to pick up oxygen. this is pulmonary circulation
  • the other circuit carries the oxygen and nutrients around the body to the tissues. this is systemic circulation
  • blood flows through the heart twice for each circuit of the body. the blood takes the following route: heart-> body-> heart -> lungs-> heart
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14
Q

what happens in the single circulatory system of fish

A
  • the blood pressure drops as blood passes through the tiny capillaries of the gills
  • blood has a low pressure as it flows towards the body, and will not flow very quickly
  • the rate at which oxygen and nutrients are delivered to respiring tissues, and carbon dioxide and urea are removed, is limited. fish are not as metabolically active as mammals, as they do not maintain their body temperature. therefore, they need less energy. their single circulatory system delivers sufficient oxygen and nutrients for their needs
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15
Q

what happens in the double circulatory system of mammals

A
  • the blood pressure must not be too high in the pulmonary circulation, otherwise it may damage the delicate capillaries in the lungs
  • the heart can increase the pressure of the blood after it has passed through the lungs, so the blood is under higher pressure as it flows to the body and flows more quickly
  • the systemic circulation can carry blood at a higher pressure than the pulmonary circulation
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16
Q

what are arteries

A

vessels that carry blood away from the heart

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17
Q

what are arterioles

A

small blood vessels that distribute blood from an artery to the capillaries

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18
Q

what are capillaries

A

very small vessels with very thin walls

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19
Q

what is a closed circulatory system

A

one in which blood is held in vessels

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20
Q

what is a open circulatory system

A

one in which blood is not held in vessels

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21
Q

what are veins

A

vessels that carry blood back to the heart

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22
Q

what are venules

A

small blood vessels that collect blood from capillaries and lead into the veins

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23
Q

explain what happens in an open circulatory systems

A
  • many animals, including insects, have an open circulatory system, meaning that the blood is not always held within blood vessels. Instead, the blood fluid circulates through the body cavity, so that the tissues and cells are bathed directly in blood
  • in some animals, movements of the body help to circulate the blood — and without movement the blood stops moving, so that transport of oxygen and nutrients stops
  • in other animals, such as insects, there is a muscular pumping organ much like a heart. this is a long, muscular tube that lies just under the dorsal (upper) surface of the body
  • blood from the body enters the heart through pores called ostia. the heart then pumps the blood towards the head by peristalsis. at the forward end of the heart (nearest the head), the blood simply pours out into the body cavity
  • this circulation can continue when the insect is at rest, but body movements may still affect circulation
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24
Q

what are disadvantages of open circulatory systems

A
  • blood pressure is low and blood flow is slow
  • circulation of blood may be affected by body movements or lack of body movements
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25
Q

what are advantages of closed circulatory system over open circulatory system

A
  • higher pressure, so that blood flows more quickly
  • more rapid delivery of oxygen and nutrients
  • more rapid removal of carbon dioxide and other wastes
  • transport is independent of body movements
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26
Q

what are the structures and functions of arteries

A
  • the blood is at high pressure, so the artery wall must be thick in order to withstand that pressure
  • the lumen is relatively small in order to maintain high pressure, and the inner wall is folded to allow the lumen to expand as blood flow increases. the wall consists of three layers:
  • inner layer (tunica intima) consists of a thin layer of elastic tissue which allows the wall to stretch and then recoil to help maintain blood pressure
  • middle layer (tunica media) consists of a thick layer of smooth muscle
  • outer layer (tunica adventitia) is a relatively thick layer of collagen and elastic tissue. this provides strength to withstand the high pressure, and recoil to maintain the pressure
  • arteries near the heart have more elastic tissue in the wall, in order to allow stretch and recoil, which helps to even out the fluctuations in blood pressure created by the heart. further from the heart, the walls contain more muscle tissue
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27
Q

what are the structure and function of arterioles

A
  • walls contain a layer of smooth muscle. contraction of this muscle will constrict the diameter of the arteriole. this increases resistance to flow and reduces the rate of flow of blood. constriction of the arteriole walls can be used to divert the flow of blood to regions of the body that are demanding more oxygen
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28
Q

what are the structures and functions of capillaries

A
  • have very thin walls. they allow exchange of materials between the blood and tissue fluid
  • the lumen is very narrow — its diameter is about the same as that of a red blood cell. the red blood cells may be squeezed against the walls of the capillary as they pass along the capillary; this helps transfer of oxygen, as it reduces the diffusion path to the tissues. it also increases resistance and reduces rate of flow
  • the walls consist of a single layer of flattened endothelial cells. this reduces the diffusion distance for the materials being exchanged
  • the walls are leaky. they allow blood plasma and dissolved substances to leave the blood
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29
Q

what are the structures and functions of venules

A
  • these collect the blood from the capillary bed and lead into the veins
  • the venule wall consists of thin layers of muscle and elastic tissue outside the endothelium, and a thin outer layer of collagen
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30
Q

what is the structures and functions of veins

A
  • at low pressure and the walls do not need to be thick
  • the lumen is relatively large, in order to ease the flow of blood
  • the walls have thinner layers of collagen, smooth muscle and elastic tissue than in artery walls. they do not need to stretch and recoil, and are not actively constricted in order to reduce blood flow
  • the main feature of veins is that they contain valves to help the blood flow back to the heart and to prevent it flowing in the opposite direction
  • as the walls are thin, the vein can be flattened by the action of the surrounding skeletal muscle
  • contraction of the surrounding skeletal muscle applies pressure to the blood, forcing the blood to move along in a direction determined by the valves
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31
Q

what is blood

A

the fluid used to transport materials around the body

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32
Q

what is the hydrostatic pressure

A

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

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33
Q

what is lymph

A

the fluid held in the lymphatic system, which is a system of tubes that returns excess tissue fluid to the blood system

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34
Q

what is oncotic pressure

A

the pressure created by the osmotic effects of the solutes

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35
Q

what is plasma

A

the fluid portion of the blood

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36
Q

what is tissue fluid

A

the fluid surrounding the cells and tissues

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37
Q

what does the blood consist of

A
  • consists of a liquid called plasma, containing many blood cells
  • the plasma contains many dissolved substances, including oxygen, carbon dioxide, minerals, glucose, amino acids, hormones and plasma proteins
  • the cells include the red blood cells (erythrocytes), various white blood cells (leucocytes) and fragments called platelets
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38
Q

what is tissue fluid formed by

A

by plasma leaking from the capillaries

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39
Q

what is the tissue fluid surrounded by

A
  • it surrounds the cells in the tissue, and supplies them with the oxygen and nutrients they require
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40
Q

what happens when blood plasma leaks from the capillaries

A

it carries all the dissolved substances into the tissue fluid. This movement is mass flow rather than diffusion

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41
Q

what happens to the waste products from cell metabolism

A

it will be carried back into the capillary as some of the tissue fluid returns to the capillary

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42
Q

what happens in the formation of tissue fluids

A
  • when an artery reaches the tissues, it branches into smaller arterioles, and then into a network of capillaries. these eventually link up with venules to carry blood back to the veins. therefore blood flowing into an organ or tissue is contained in the capillaries
  • at the arterial end of a capillary, the blood is at relatively high (hydrostatic) pressure. this pressure tends to push the blood fluid out of the capillaries through the capillary wall. the fluid can leave through the tiny gaps between the cells in the capillary wall
  • the fluid that leaves the blood consists of plasma with dissolved nutrients and oxygen. all the red blood cells, platelets and most of the white blood cells remain in the blood, as do the plasma proteins. these are too large to be pushed out through the gaps in the capillary wall. this tissue fluid surrounds the body cells, so exchange of gases and nutrients can occur across the plasma membranes. the exchange occurs by diffusion, facilitated diffusion and active uptake
  • oxygen and nutrients enter the cells; carbon dioxide and other wastes leave the cells
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43
Q

is the blood pressure at the venous end of the capillary lower or higher and what does this allow

A

lower and this allows some of the tissue fluid to return to the capillary carrying carbon dioxide and other waste substances into the blood
- not all of all the tissue fluid re-enters the blood. some tissue fluid is directed into another tubular system called the lymph system or lymphatic system
- this drains excess tissue fluid out of the tissues and returns it to the blood system in the subclavian vein in the chest

44
Q

what is the fluid in the lymphatic system called

A

lymph

45
Q

what does lymph contain more of and where does it produce

A

contain more lymphocytes and are produced in the lymph nodes

46
Q

where are lymph nodes found

A

at intervals along the lymphatic system

47
Q

what happens if the tissue is infected

A

the capillaries become more leaky and more fluid is directed into the lymph system — this helps direct bacteria towards the Lymph nodes

48
Q

does blood plasma have a high or low hydrostatic and oncotic pressure and what does it contain

A
  • has high hydrostatic pressure, more negative oncotic pressure than tissue fluid
  • contains red blood cells, neutrophils, and lymphocytes
  • it also contains plasma proteins and fats transported in lipoproteins
49
Q

does tissue fluid have a high or low hydrostatic and oncotic pressure and what does it contain

A
  • has a low hydrostatic pressure and a less negative oncotic pressure than blood plasma
  • it contains some neutrophils, especially in infected areas. it contains few proteins and few fats
50
Q

does lymph have a high or low hydrostatic and oncotic pressure and what does it contain

A

has a low hydrostatic pressure. It has a less negative oncotic pressure than blood plasma and contains lymphocytes, few proteins, and more fats than in tissue fluid, especially near the digestive system

51
Q

what is the effect of hydrostatic and oncotic pressure of the blood

A
  • the hydrostatic pressure of the blood tends to push fluid out into the tissues
  • the hydrostatic pressure of the tissue fluid tends to push fluid into the capillaries
  • the oncotic pressure of the blood tends to pull water back into the blood (it has a negative figure)
  • the oncotic pressure of the tissue fluid pulls water into the tissue fluid
52
Q

what are atrioventricular valves

A

valves between the atria and the ventricles, which ensure that blood flows in the correct direction

53
Q

what are cardiac muscles

A

specialised muscle found in the walls of the heart chambers

54
Q

what are semilunar valves

A

valves that prevent blood re-entering the heart from the arteries

55
Q

generally explain the structure of a mammalian heart

A
  • it is divided into two sides
  • the right side pumps the deoxygenated blood to the lungs to be oxygenated the left side pumps oxygenated blood to the rest of the body
  • on both sides, the heart squeezes the blood, putting it under pressure. this pressure forces the blood along the arteries and through the circulatory system
56
Q

describe the external features of the heart

A
  • in humans, the heart lies just off-centre towards the left of the chest cavity
  • the main part of the heart consists of firm, dark-red muscle called cardiac muscle
    here are two main pumping chambers — the ventricles
  • above the ventricles are two thin-walled chambers — the atria. these are much smaller than the ventricles and are easy to overlook
  • lying over the surface of the heart are coronary arteries that supply oxygenated blood to the heart muscle. as the heart is a hard-working organ, these arteries are very important
  • if they become constricted, it can have severe consequences for the health of the heart. restricted blood flow to the heart muscle reduces the delivery of oxygen and nutrients such as fatty acids and glucose. this may cause angina or a heart attack (myocardial infarction)
  • at the top of the heart are a number of tubular blood vessels. these are the veins that carry blood into the atria and the arteries that carry blood away from the heart
57
Q

explain the internal features of the mammalian heart

A
  • the heart is divided into four chambers. the two upper chambers are atria. these receive blood from the major veins
  • deoxygenated blood from the body flows through the vena cava into the right atrium. oxygenated blood from the lungs flows through the pulmonary vein into the left atrium
  • from the atria, blood flows down through the atrioventricular valves into the ventricles. attached to the valves are tendinous cords, which prevent the valves from turning inside out when the ventricle walls contract
  • a wall of muscle called the septum separates the ventricles from each other. this ensures that the oxygenated blood in the left side of the heart and the deoxygenated blood in the right side are kept separate
  • deoxygenated blood leaving the right ventricle flows into the pulmonary artery leading to the lungs, where it is oxygenated
  • oxygenated blood leaving the left ventricle flows into the aorta. this carries blood to a number of arteries that supply all parts of the body
  • at the base of the major arteries, where they exit the heart, are the semilunar valves. these prevent blood returning to the heart as the ventricles relax
58
Q

explain the structure of atria

A

the muscle of the atrial walls is very thin because these chambers do not need to create much pressure
- their function is to receive blood from the veins and push it into the ventricles

59
Q

explain the structure of right ventricle

A
  • the walls of the right ventricle are thicker than the walls of the atria which enables the right ventricle to pump blood out of the heart
  • the right ventricle pumps deoxygenated blood to the lungs. the lungs are in the chest cavity beside the heart, so that the blood does not need to travel very far
  • also, the alveoli in the lungs are very delicate and could be damaged by very high blood pressure
60
Q

explain the structure of the left ventricle

A
  • the walls of the left ventricle can be two or three times thicker than those of the right ventricle
  • the blood from the left ventricle is pumped out through the aorta and needs sufficient pressure to overcome the resistance of the systemic circulation
61
Q

what do cardiac muscles consists of and what does it help with

A

fibres that branch, producing cross-bridges. these help to spread the stimulus around the heart, and also ensure that the muscle can produce a squeezing action rather than a simple reduction in length

62
Q

what does cardiac muscles having numerous mitochondria help with

A

supplies energy for contraction between the muscle fibres (myofibrils)

63
Q

what are the cardiac muscle cells are separated by and what does it do

A

intercalated discs which facilitate synchronised contraction

64
Q

what does each cardiac cell have and what is divided into

A

nucleus
sarcomeres

65
Q

what is a cardiac cycle

A

the sequence of events in one full beat of the heart

66
Q

what happens in atrial systole

A
  • both the right and left atria contract together
  • the muscle in the walls is thin so only a small increase in pressure is created by this contraction which helps to push blood into the ventricles stretching their walls and ensuring that they are full of blood
67
Q

what happens in ventricular systole

A

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

68
Q

what happens in diastole

A

the muscular walls of all four chambers relax. elastic recoil causes the chambers to increase in volume allowing blood to flow in from the veins

69
Q

what happens during the cardiac cycle to the atrioventricular valves

A

after systole, the ventricular walls relax and recoil
* the pressure in the ventricles rapidly drops below the pressure in the atria
* blood in the atria pushes the atrioventricular valves open
* blood entering the heart flows straight through the atria and into the ventricles
* the pressure in the atria and the ventricles rises slowly as they fill with blood
* the valves remain open while the atria contract, but close when the atria begin to relax
* this closure is caused by a swirling action in the blood around the valves when the ventricle is full
* as the ventricles begin to contract (systole), the pressure of the blood in the ventricles rises
* when the pressure rises above that in the atria, the blood starts to move upwards
* this movement fills the valve pockets and keeps them closed
* the tendinous cords attached to the valves prevent them from turning inside out
* this prevents the blood flowing back into the atria

70
Q

what happens to the semilunar valves during cardiac cycle

A
  • before ventricular contraction, the pressure in the major arteries is higher than the pressure in the ventricles, meaning that the semilunar valves are closed
  • ventricular systole raises the blood pressure in the ventricles very quickly. once the pressure in the ventricles rises above the pressure in the major arteries, the semilunar valves are pushed open
  • the blood is under very high pressure, so it is forced out of the ventricles in a powerful spurt. Once the ventricle walls have finished contracting, the heart muscle starts to relax (diastole). elastic tissue in the walls of the ventricles recoils, which stretches the muscle out again and returns the ventricle to its original size
  • this causes the pressure in the ventricles to drop quickly. as it drops below the pressure in the major arteries, the blood starts to flow back towards the ventricles.
  • the semilunar valves are pushed closed by the blood collecting in the pockets of the valves which prevents blood returning to the ventricles
  • the pressure wave created when the left semilunar valve closes is the ‘pulse’ that we can easily feel at the wrist or neck
71
Q

what does the structure of the artery walls aid with

A
  • the artery walls close to the heart have a lot of elastic tissue
  • when blood leaves the heart, these walls stretch
  • as blood moves on and out of the aorta, the pressure in the aorta starts to drop
  • the elastic recoil of the walls helps to maintain the blood pressure in the aorta
  • the further the blood flows along the arteries, the more the pressure drops and the fluctuations become less obvious
  • it is important to maintain the pressure gradient between the aorta and the arterioles, as this is what keeps the blood flowing towards the tissues
72
Q

what is badycardia

A

a slow heart rhythm

73
Q

what is ectopic heartbeat

A

an extra beat or an early beat of the ventricles

74
Q

what is an electrocardiogram

A

a trace that records the electrical activity of the heart

75
Q

what is fibrillation

A

uncoordinated contraction of the atria and ventricles

76
Q

what is myogenic muscle

A

muscle that can initiate its own contraction

77
Q

what is Purkyne tissue

A

consists of specially adapted muscle fibres that conduct the wave of excitation from the AVN down the septum to the ventricles

78
Q

what is sinoatrial nodes (SAN)

A
  • the heart’s pacemaker
  • it is a small patch of tissue that sends out waves of electrical excitation at regular intervals in order to initiate contractions
79
Q

what is tachycardia

A

a rapid heart rhythm

80
Q

what type of muscle is the heart

A

myogenic. the muscle will contract and relax rhythmically even if it is not connected to the body

81
Q

describe muscle contraction and relaxation

A

the muscles from the atria and the muscles from the ventricles each have their own natural frequency of contraction. the atrial muscle tends to contract at a higher frequency than the ventricular muscle. this property of the muscle could cause inefficient pumping if the contractions of the chambers are not synchronised — a condition known as fibrillation. so the heart needs a mechanism that can coordinate the contractions of all four chambers

82
Q

what happens in the initiation and control of the heartbeat

A

at the top of the right atrium, near the point where the vena cava empties blood into the atrium, is SAN. this is a small patch of tissue that generates electrical activity. the SAN initiates a wave of excitation at regular intervals. in a human, this occurs 55-80 times a minute. the SAN is also known as the pacemaker

83
Q

describe the contraction of the atria

A
  • the wave of excitation quickly spreads over the walls of both atria.
  • it travels along the membranes of the muscle tissue
  • as the wave of excitation passes, it causes the cardiac muscle cells to contract
  • this is an atrial systole
84
Q

what is the role of the AVN

A

at the top of the interventricular septum (the septum separating the two ventricles) is another node
This is the only route that can conduct the wave of excitation through to the ventricles. the wave of excitation is delayed in the node. this allows time for the atria to finish contracting and for the blood to flow down into the ventricles before they begin to contract

85
Q

describe the contraction of the ventricle

A
  • after this short delay the wave of excitation is carried away from the AVN and down specialised conducting tissue called the Purkyne tissue
  • this runs down the interventricular septum
  • at the base of the septum, the wave of excitation spreads out over the walls of the ventricles
  • as the excitation spreads upwards from the base (apex) of the ventricles, it causes the muscles to contract. this means that the ventricles contract from the base upwards
  • this pushes the blood up towards the major arteries at the top of the heart
86
Q

what is an electrocardiogram (ECG)

A

monitor the electrical activity of the heart

87
Q

how is an ECG used

A

this involves attaching a number of sensors to the skin. some of the electrical activity generated by the heart spreads through the tissues next to the heart and outwards to the skin. the sensors on the skin pick up the electrical excitation created by the heart and convert this into a trace

88
Q

what does P mean on the ECG

A

shows the excitation of the atria

89
Q

what does QRS represent

A

indicates the excitation of the ventricles

90
Q

what does T represent

A

diastole

91
Q

what can the shape of the ECG trace indicate

A

when part of the heart muscle is not healthy. such traces can be used by medical professionals to diagnose heart problems

92
Q

what is affinity

A

a strong attraction

93
Q

what is dissociation

A

releasing the oxygen from the oxyhaemoglobin

94
Q

what is fetal haemoglobin

A

the type of haemoglobin usually found only in the fetus

95
Q

what is haemoglobin

A

the red pigment used to transport oxygen in the blood

96
Q

what does haemoglobin do

A

oxygen is transported in the red blood cells (erythrocytes). these cells contain the protein haemoglobin. when haemoglobin takes up oxygen, it becomes oxyhaemoglobin
haemoglobin + oxygen-> oxyhaemoglobin

97
Q

describe the structure of haemoglobin

A

a complex protein with four subunits. each subunit consists of a polypeptide chain and a haem (non-protein) group. the haem group contains a single iron ion in the form of Fe. this iron ion can attract and hold an oxygen molecule. the haem group is said to have a high affinity (attraction) for oxygen. as each haem group can hold one oxygen molecule, each haemoglobin molecule can carry four oxygen molecules

98
Q

when does association of oxygen and haemoglobin occur

A

in the lungs where pO2 is high

99
Q

when does dissociation of oxygen and haemoglobin occurs

A

in the tissues where pO2 is low

100
Q

describe the transport of oxygen

A

oxygen is absorbed into the blood as it passes the alveoli in the lungs. oxygen molecules diffusing into the blood plasma enter the red blood cells. here they become associated with the haemoglobin. this means that the oxygen binds reversibly to the haemoglobin. this takes the oxygen molecules out of solution and so maintains a steep concentration gradient, allowing more oxygen to enter the blood from the lungs and diffuse into the cells. the blood carries the oxygen from the lungs back to the heart, before travelling around the body to supply the tissues. in the body tissues, cells need oxygen for aerobic respiration. therefore the oxyhaemoglobin must be able to release the oxygen. this is called dissociation

101
Q

what is the partial pressure of oxygen (pO2)

A

the concentration of oxygen is measured by the relative pressure that it contributes to a mixture of gases

102
Q

what is the unit used for the partial pressure of oxygen

A

kPa

103
Q

haemoglobin can associate with oxygen in a way that produces an S-shaped curve. what is this called

A

haemoglobin dissociation curve

104
Q

as the oxygen tension rises, what happens to the diffusion distance into the haemoglobin molecules

A

increases

105
Q

when one oxygen molecule enters the haemoglobin molecule how many of the haem group does it associate with

A

one

106
Q

what is conformation change

A

this causes a slight change in the shape of the haemoglobin molecule

107
Q
A

OCR AS/A Level Biology Context (24 decks)

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