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Alevel Biology > 3.2 > Flashcards

3.2 Flashcards

1
Q

Double circulatory system

A

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

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2
Q

Single circulatory system

A

Heart pumps blood into a haemocel and tissue surrounded by blood takes requirements and removes waste

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3
Q

Transport

A

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

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4
Q

Arteries

A

Vessels that carry blood away from heart

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5
Q

Arterioles

A

Small blood vessels that distribute blood from artery to capillaries

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6
Q

Capillaries

A

Very small vessels with very small walls

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7
Q

Closed circulatory system

A

One in which blood is held in vessels

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8
Q

Open circulatory system

A

One in which blood isn’t held in vessels

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9
Q

Veins

A

Vessels that carry blood back to heart

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10
Q

Venules

A

Small blood vessels that collect blood from capillaries and lead into veins

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11
Q

Blood

A

Fluid used to transport materials round body

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12
Q

Hydrostatic pressure

A

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

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13
Q

Lymph

A

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

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14
Q

Oncotic pressure

A

Pressure created by osmotic effects of solutes

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15
Q

Plasma

A

Fluid portion of blood

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16
Q

Tissue fluid

A

Fluid surrounding cells and tissues

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17
Q

Atrio-ventricular values

A

Valves between atria and ventricles which ensure blood flows in correct direction

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18
Q

Cardiac muscle

A

Specialised muscle found in walls of heart chambers

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19
Q

Semilunar valves

A

Valves that prevent blood re-entering heart from arteries

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20
Q

Cardiac cycle

A

The sequence of events in one full beat of the heart

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21
Q

Bradycardia

A

A slow heart rhythm

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22
Q

Ectopic heartbeat

A

An extra beat or an early beat if the ventricles

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23
Q

Electrocardiogram

A

A trace that records electrical activity of heart

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24
Q

Fibrillation

A

Uncoordinated contraction of atria and ventricles

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25
Q

Myogenic muscle

A

Muscle that can imitate it own contractions

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26
Q

Purkyne tissue

A

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

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27
Q

Sino atrial node

A

Hearts pacemaker, it’s small patch of tissue that sends out waves of electrical excitation at regular intervals in order to initiate contractions

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28
Q

Tachycardia

A

A rapid heart rhythm

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29
Q

Affinity

A

A strong attraction

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30
Q

Dissociation

A

Means releasing the oxygen from the Oct haemoglobin

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31
Q

Fetal haemoglobin

A

Type of haemoglobin usually found only in the fetus

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32
Q

Haemoglobin

A

Red pigment used to transport oxygen in the blood

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33
Q

Carbonic anhydrase

A

The enzyme that catalysed the combination of carbon dioxide and water

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34
Q

Chloride shift

A

Movement of chloride ions into erythrocytes to balance the charge as hydrogencarbonate ions leave the cell

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35
Q

Bohr effect

A

Effect that extra carbon dioxide has on haemoglobin, explains release of more oxygen

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36
Q

Haemoglobinic acid

A

Compound formed by the buffering action of haemoglobin as it combines with excess hydrogen ions

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37
Q

Where are open circulatory systems found

A

In Molluscs and arthropods

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38
Q

How does blood move back into circulatory system in open circuit

A

Via cells

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39
Q

How does insects circulatory system work

A

Heart composed of series of pumps towards head, blood drains from vessel wall directly to areas in need like head and legs, blood flows in a posterior direction and returns to dorsal vessel through holes called Ostia

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40
Q

What animals are closed circulatory systems found in

A

Vertebrates, annelips and cephalopods

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41
Q

How does closed circulatory system work

A

Blood stays in vessels and pumped through them by heart, exchange of nutrients and respiratory gases via diffusion between blood vessels and tissue fluid

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42
Q

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

A

Size, sa:v ratio, level of metabolic activity

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43
Q

What is sa:v ratio

A

For each gram of tissue if their body, they have sufficient area of bodies surface through which exchange can occur, so in larger animals each gram of tissue has smaller area of body surface for exchange

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44
Q

Why do animals need food energy and what does it need along as food

A

So they can move, releasing food energy via aerobic respiration requires oxygen

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45
Q

Why do animals need other energy’s as well as food

A

Mammals need to keep warm so they need energy so more active animals also respire faster so need more oxygen

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46
Q

What is the function of valves

A

Keep blood flowing in one direction

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47
Q

Features of good transport system(fluid or medium)

A

Fluid or medium to carry nutrients, oxygen and waste around body, blood in mammals

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48
Q

Feature of good transport system (pump)

A

Pump to create pressure that will push fluid round body (heart)

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49
Q

Feature of good transport system (exchange surface)

A

Exchange surface to allow substances in o enter and leave blood (capillaries)

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50
Q

Feature of good transport system (tubes/vessels)

A

Include tubes and vessels to carry blood by mass flow and 2 circuits, one to pick up oxygen and one to deliver oxygen to tissue

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51
Q

What type of animals have single circulatory system and what does this mean

A

Fish have single circulatory system where blood flows through heart once for each circuit of the body (heart-gills-body-heart)

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52
Q

What animals have double circulatory system

A

Mammals

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53
Q

What does a double circulatory system mean

A

Have 2 separate circuits, one for carrying blood to lungs and one carry’s oxygen and nutrients around the body to tissues known as systemic circulation

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54
Q

How does double circulatory system work

A

Blood flows through heart twice for each circuit of the body (heart-body-heart-lungs-heart)

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55
Q

What are are disadvantages of single circulatory system

A

In single circulatory system blood pressure drops as blood passes through gills capillaries and means it moves slowly as it travels around body, so rate at which oxygen, nutrients delivered to respiring tissue and CO2 and urea are removed is limited

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56
Q

Why does it not matter that fish only have single circulatory system

A

Fish not as metabolically active as mammals as they don’t have to maintain their body temp so less energy is needed as single circulatory system is sufficient

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57
Q

What are advantages of double circulatory system

A

Blood pressure cannot be too high in pulmonary circulation as may damage delicate capillaries in lungs, but after this heart can increase blood pressure so it flows round body faster as system circulation can carry blood at higher pressure than at pulmonary circulation

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58
Q

Why do mammals need double circulatory system

A

As mammals are active and must maintain body temp, they need food energy for this (energy released from food in respiration) to release lots of energy cells need good blood supply of oxygen and nutrients and removal of waste products

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59
Q

Why is a pump needed for transport medium to be effective

A

Blood I closed in vessels and contraction of muscle causes directional flow for blood to circulate which is what happens in insects and similar animals

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60
Q

What happens in open circulatory system

A

Blood circulated in large open spaces and cells are in direct contact with blood so materials are exchanged by direct diffusion, in open system Herat is weak muscle pumping blood around large area

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61
Q

What do insects have instead of blood

A

Haemocel

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62
Q

Evaluate open circulatory system

A

Inefficient and low pressure

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63
Q

Function of open circulatory system

A

Important in removing nitrogenous gases and supplying nutrients but not oxygen as the tracheal system does that

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64
Q

What happens in closed circulatory system

A

Blood entirely closed in tubular vessels and gas exchange happens across capillary walls, in this system heart is strong and blood pressure high

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65
Q

Evaluate closed circulatory system

A

More efficient that open one, and animals with closed system are larger and more active

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66
Q

Disadvantage of closed system but why does this not matter

A

Diffusion must happen to get air and nutrients to cells and waste to blood, but capillaries near so short diffusion distance

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67
Q

How is blood held in open circulatory system

A

Blood is not always held in vessels but blood fluid circulated through body cavity so that tissues and cells are in direct contact with the blood

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68
Q

What do some animals do to help circulate their blood

A

Some animals move their body

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69
Q

What would happen without movement of blood

A

Transport of o2 and nutrients would stop

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70
Q

What is the structure of an insects circulatory system

A

Long muscular tube that lies under dorsal surface of body, blood enters heart through pores called Ostia, then heart pumps blood to Peristalsis, at front end of heart near head blood pours into cavity and continues when insect is resting but body movements may still effect circulation

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71
Q

What is different about larger insects circulatory system compared to smaller ones

A

Locus have open ended tubes attached to their heart which direct a blow towards active part of body

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72
Q

Disadvantage of open circulatory system

A

Blood pressure low and flow is slow, circulation of blood affected by body movements or lack of body movements

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73
Q

What animals blood stays inside vessels separate from tissue fluid and cells

A

Larger animals as they have double circulatory system

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74
Q

What is tissue fluid

A

Fluid which bathes tissue

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75
Q

Advantages of double circulatory system

A

High pressure, blood flow quick, rapid delivery of oxygen and nutrients and rapid removal of CO2 and waste, transport independent from body movements

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76
Q

What does blood travel in

A

Series of vessels each adapted to a role in relation to distance from heart

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77
Q

Structure of blood vessels

A

All have an in layer/lining made of single layer of cells called endothelium which is a smooth thin layer in order to reduce friction with flowing blood

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78
Q

What is arteries function

A

To carry blood away from heart

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79
Q

When is blood like when in the arteries and why does this effect it’s structure

A

At high pressure so walls must be thick to withstand pressure

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80
Q

Structure of lumen of artery

A

Relatively small to maintain high pressure, inner wall folded to allow lumen to expand as blood flow increase

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81
Q

How many layer does artery wall have

A

3

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82
Q

Structure of inner layer of artery

A

Consists of thin layer of elastic tissue which allows wall to stretch and recoil to help maintain blood pressure

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83
Q

Structure of middle layer of artery

A

Consists of thick layer of smooth muscle

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84
Q

Structure of outer layer of artery

A

Relatively thick layer of collagen and elastic tissue to provide strength to withstand high pressure and recoil to maintain pressure

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85
Q

What are arterioles

A

Small blood vessels that distribute blood from arteries to capillaries

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86
Q

Structure of arterioles

A

Contain layer of smooth muscle

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87
Q

Function of smooth muscle and how it works

A

Contraction of muscle constricts arteriole lumen and increase resistance to flow so reducing rate of flow of blood, the contraction of arteriole wall is used to divert blood flow to body regions demanding more oxygen

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88
Q

Structure and function of capillaries

A

Have thin walls and allow gas exchange of materials between blood and tissue fluid

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89
Q

How wide is capillaries lumen

A

Very narrow (same as red blood cell)

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90
Q

What happens in the capillaries

A

Red blood cells squeezed against their walls reducing diffusion distance which increases resistance and reduces rate of flow

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91
Q

Detail structure of capillaries

A

Walls are single layer of flattened endothelial cells which reduce diffusion distance of exchanging materials and walls are leaky to allow blood plasma and dissolved substances to leave blood

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92
Q

What are venules

A

Small vessels that blood from capillaries flows into, they collect blood from capillary bed and lead into veins

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93
Q

Structure of venule

A

Wall consists of thin layer of muscle and elastic tissue outside endothelium and thin outer layer of collagen

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94
Q

Veins function

A

To carry blood back to heart

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95
Q

What is the blood like in the veins

A

At low pressure so walls don’t need to be too thick

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96
Q

Structure and function of veins

A

Relatively large lumen to ease blood flow, walls have thinner layer of smooth muscle, elastic fibres and collagen than arteries as don’t need to stretch and recoil and don’t actively constrict to reduce blood flow

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97
Q

Why do veins have valves

A

To help blood flow back to heart and prevent it flowing in opposite direction

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98
Q

What does veins relatively thin walls mean

A

They can be flattened by action of surrounding skeletal muscle and contraction of surrounding skeletal muscle applies pressure to blood forcing blood to move along in direction determined by valves

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99
Q

What is blood

A

Fluid held in our vessels which contains a liquid called plasma and many blood cells

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100
Q

What does plasma contain

A

Many dissolved substances such as oxygen, CO2, minerals, glucose, amino acids, hormones and plasma proteins

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101
Q

What are the various components in blood plasma

A

Erythrocytes, different types of leukocytes and fragments called platlets

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102
Q

What is the difference between tissue fluid and blood plasma

A

Doesn’t contain most cells that are found in blood plasma and doesn’t contain plasma proteins

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103
Q

How is tissue fluid formed

A

Plasma leaking from capillaries to surrounding cells and tissue and supply them with the oxygen and nutrients they need

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104
Q

What happens as blood plasma leaks from capillaries

A

Carries dissolved substances into tissue fluid called mass flow, not diffusion

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105
Q

What happens to cells waste products from metabolism

A

Carried back into capillaries as some tissue fluid is returned to capillaries

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106
Q

What happens when arteries reach tissue

A

They branch into smaller articles and then into a capillary network to eventually link with venules to carry blood to veins so blood flowing into organ/tissue is contained in capillaries

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107
Q

What is the pressure at the arterial end of the capillaries

A

Quite high known as hydrostatic

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108
Q

What does high pressure at arterial end of capillaries mean

A

High pressure pushed blood fluid out of capillaries through their walls, fluid leaves between tiny gaps between cells in capillary walls

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109
Q

What does fluid that leaves blood at capillaries contain

A

Plasma with dissolved nutrients and oxygen

110
Q

What remains in the blood when plasma leaves the capillaries and why

A

All red blood cells, platelets, most white blood cells and plasma proteins all stay in capillaries as they are too large to be pushed out of gaps in capillary walls

111
Q

Why does tissue fluid surround cells

A

So exchange of gas and nutrients can occur across their plasma membrane

112
Q

How does exchange from tissue fluid to cell occur

A

By diffusion, facilitated diffusion or active uptake

113
Q

What is the blood pressure at venous end of capillaries and what does this mean

A

Low pressure as allows some tissue fluid to return to capillaries carrying CO2 and other waste substances into blood

114
Q

Does all tissue fluid return to the blood

A

No

115
Q

What happens to tissue fluid that doesn’t return to the blood

A

Some directed to another tubular system called lymphatic system which drains excess tissue fluid out of tissues and returns it to blood system in subclavian vein in the chest

116
Q

What is fluid in lymphatic system called

A

Lymph

117
Q

What is lymph

A

Similar composition to tissue fluid but contains more lymphocytes produced at lymph nodes

118
Q

What are lymph nodes

A

Swellings found at intervals along lymphatic system which are important in immune response

119
Q

What is blood plasma hydrostatic and oncotic pressure

A

High hydrostatic pressure and oncotic is more negative than tissue fluid

120
Q

Are there fats in blood plasma

A

Yes transported as lipoproteins

121
Q

What is tissue fluid hydrostatic and oncotic pressure

A

Hs is low and oncotic is less negative than blood plasma

122
Q

What is lymph hydrostatic and oncotic pressure

A

Low hydrostatic pressure and less negative oncotic pressure than blood plasma

123
Q

Is hydrostatic pressure the only influence on movement of fluid in and out of capillary

A

No

124
Q

Tissue fluid has its own hydrostatic pressure of solutes which also has an influence and is called….

A

Oncotic pressure

125
Q

What does hydrostatic pressure of blood tend to do

A

To push fluid out into tissues

126
Q

What does hydrostatic pressure of tissue fluid tend to do

A

Push fluid into capillaries

127
Q

What does oncotic pressure of blood tend to do

A

Pull water back into blood (negative figures)

128
Q

What does oncotic pressure of tissue fluid do

A

Pulls water into tissue fluid

129
Q

What does the net force of hydrostatic and oncotic pressure mean

A

Net result of these forces means fluid pushed out of capillaries at arterial end and drawn back at venule end

130
Q

What is a mammal heart

A

A muscular pump divided into two sections

131
Q

How is the heart divided

A

Right side has deoxygenated blood which goes to the lungs to be oxygenated and left side has oxygenated blood to go around the whole body

132
Q

What muscle is the heart

A

A dark red cardiac muscle

133
Q

What are the two main pumping chambers and what is bigger

A

Ventricle and atrium, ventricles much bigger

134
Q

Where are coronary arteries located

A

Live over the surface of the heart

135
Q

What is the function of coronary artery

A

Supply oxygenated blood to the heart muscle which is important as heart is a hard working muscle

136
Q

Why is it dangerous if coronary arteries restricted

A

Restricts blood flow to the heart muscle reducing oxygen and nutrient such as fatty acids and glucose which may cause angina or myocardial infarction

137
Q

What carries blood into the heart

A

Veins (pulmonary vein and vena cava)

138
Q

What carries blood away from heart

A

Arteries (aorta and pulmonary artery)

139
Q

Where are atria located in the heart

A

2 found at top of the heart

140
Q

What blood flows into each atria

A

Deoxygenated blood from body flows into right atrium through vena cava and oxygenated blood flows in through pulmonary vein to left atrium

141
Q

Where does blood go after the atria

A

It flows down through atrioventricular valve to ventricle

142
Q

Why don’t valves turn inside out when ventricle walls contract

A

Valves are attached to tendinous chords to prevent this

143
Q

What is the septum

A

Separates the ventricles from one and other to ensure oxygenated and deoxygenated blood stays separate

144
Q

What happens when deoxygenated blood leaves right ventricle

A

Flows to pulmonary artery which leads to the lungs where it can be oxygenated

145
Q

Where do blood go once it has left the left ventricle

A

Into aorta to be transported around the body

146
Q

Why are there valves at the base of the two major arteries and what are they called

A

They prevent blood returning to the ventricles as heart relaxes and called semilunar valves

147
Q

How is high pressure created in the heart

A

Cardiac muscle in wall of each chamber will contract to create high pressure in the blood

148
Q

What does high blood pressure mean

A

The blood can travel round the body further at high speed

149
Q

Structure of atria

A

Very thin walls as don’t need to create much pressure

150
Q

Function of atria

A

To receive blood from veins and push it into ventricles

151
Q

Structure of right ventricle and why

A

Thicker walls than atria as must pump blood out of heart to lungs but lungs are near the heart so it doesn’t need to travel very far and alveoli are delicate so they may be damaged if blood is at high pressure

152
Q

Structure of left ventricle and why

A

Wall of left ventricle is 2/3 thicker than right ventricle as blood is pumped through aorta and need sufficient pressure to overcome resistance of systemic circulation and must travel round the whole body

153
Q

What does the cardiac muscle consist of

A

Fibres that branch producing cross-bridges which help to spread stimulus around heart and ensure muscle can produce squeezing action rather than a simple reduction in length

154
Q

Why are there many mitochondria between muscle fibres (myofibrils) in the heart

A

To supply energy for contraction

155
Q

How are muscle cells separated in the heart and what does this do

A

Intercalated discs which facilitate synchronised contraction

156
Q

What does each cell in the heart muscle have and how is each cell divided

A

Each has a nucleus and each cell is divided into contractile units called sarcomeres

157
Q

In single circulation(fish) what blood flows into the heart

A

Only deoxygenated blood flows through heart

158
Q

Is there a left and right side in fish hearts (single circulatory)

A

No

159
Q

What is plasma

A

Mainly water containing variety of dissolved substances which transport around body like glucose, amino acid taken up from small intestines to liver and takes urea form liver to kidneys

160
Q

What does plasma provide a medium for

A

Cells to exchange waste for needed materials

161
Q

What is it called when heart contracts and then called when it relaxes

A

Systole, diastole

162
Q

What happens when pressure in atria is higher than ventricles

A

Atrioventricular valve opens

163
Q

Which side is the tricuspid valve on and which is the bicuspid

A

Tricuspid is on the right and bicuspid is on the left as it only has two flaps

164
Q

What is the cardiac cycle

A

Systole followed by diastole where heart refills with blood again before contracting

165
Q

What happens when blood pumped into aorta due to the semilunar valve

A

Wall of the first section of the artery becomes distended but as heart relaxes so does this section of the aorta

166
Q

Why do capillaries only have a single layer of squamous endothelium

A

To allow rapid diffusion

167
Q

How can the pressure in the capillaries be changed

A

Muscle at arteriole end can contract or relax

168
Q

How are lymphatic vessels different to veins

A

More valves and no red blood cells but otherwise the same

169
Q

What does the lymph system do

A

Return tissue fluid to blood as lymph

170
Q

Role of heart

A

To create pressure that pushes blood round heart

171
Q

What must the wall of all four chambers do and what is this process Called

A

Contract in synchronised sequence to allow heart to fill will blood before pumping it out, known as cardiac cycle

172
Q

What is ventricular systole

A

Left and right ventricle contact to pump blood into aorta/ pulmonary artery

173
Q

What is diastole

A

All muscles in each chamber relaxes, elastic recoil causes chamber volume to increase so blood flows in from veins

174
Q

What is atrial systole

A

Left and right atrium contract, thin wall so only small pressure increase to push blood into ventricle to ensure they’re full of blood

175
Q

What do valves insure

A

Blood flows in correct direction

176
Q

What causes valves to open and close

A

Different pressures in the heart chambers

177
Q

What happens after ventricular systole

A

Ventricular walls relax and recoil causing pressure in ventricles to rapidly drop lower than atria pressure causing blood in atria to push open atrioventricular valve open

178
Q

What happens in diastole when blood enters atria

A

Flows directly through atria into ventricle causing the pressure in atria and ventricle to both slowly rise as they fill with blood

179
Q

At what stage in the cardiac cycle does the atrioventricular valve close

A

Valve is open when atria contracts but closes when atria starts to relax

180
Q

What causes the closing of the atrioventricular valve

A

Swirling action in blood around valves when ventricle is full

181
Q

What happens in cardiac cycle as ventricle begins to contract

A

Ventricular systole, pressure of blood in ventricles rises and when it becomes higher than atria pressure it begins to move upwards

182
Q

What prevents blood flowing back into the atria

A

The rising of the blood in the ventricles fills the valve pockets keeping them shut and tendinous chords stop them turning inside out so blood doesn’t flow back into atria

183
Q

Why are the semi lunar valves closed before ventricular contraction

A

Pressure in arteries is higher than in ventricles

184
Q

What happens in ventricular systole

A

Ventricular systole causes blood pressure to rise quickly in ventricles, and when pressure in ventricles is higher than in arteries the semilunar valves are pushed open, blood under high pressure is forced out of ventricle in powerful spurt

185
Q

What happens once the ventricles Finnish contracting

A

Semilunar valve closes and all heart muscles relax (diastole)

186
Q

What happens in diastole

A

Elastic tissue in wall of ventricles recoiled which stretches muscle so it turns back to its original size causing pressure in ventricles to drop rapidly

187
Q

What happens when ventricular pressure drops below arterial pressure

A

Blood starts to back flow into ventricle but semilunar valves are closed by this blood collecting in the valve pockets to prevent blood returning to ventricles

188
Q

When is a pressure wave created

A

When left semilunar valve closes it is the pulse felt on neck or wrist

189
Q

The graph of pressure change of the heart usually shows what side of the heart and why

A

Left side as it contracts at more pressure than right side so more visible on a graph

190
Q

What is on y axis of graph of pressure change in heat

A

Pressure (kPa)

Revise graph

191
Q

How does blood enter the arteries

A

In a rapid spurt

192
Q

What is the issue with blood being rapidly spurted from heart into arteries and how is it resolved

A

Tissue requires blood delivery in even flow but artery wall has lots of elastic tissue and wall stretches when blood spurted in which helps even flow

193
Q

What happens as blood moves on and out of aorta

A

Pressure in aorta drops so elastic recoil in artery wall helps maintain a higher pressure but the further along the arteries the blood flows the further the pressure drops and fluctuations are less obvious

194
Q

Why is it important to maintain pressure gradient between aorta and arterioles

A

Helps keep blood flowing in the right direction towards the tissue

195
Q

When do you see the largest and then smallest blood pressure fluctuations on a graph

A

Most at aorta as high pressure and least at capillaries, venules and veins as low blood pressure

196
Q

What does it mean when you say the heart is a myogenic muscle

A

Can initiate its own contractions

197
Q

What will the heart muscle do in terms of its rhythm

A

Contract and relax rhythmically even when not connected to the body due to it being myogenic

198
Q

What does the muscle from the atria and ventricle both have

A

Their own natural frequency of contraction

199
Q

Does atria or ventricle contract at higher frequency

A

Atria contracts at higher frequency

200
Q

What happens if heart chambers contractions aren’t in sync and how is this solved

A

Problem known as fibrillation often solved with addition of a pace maker

201
Q

What is found at the top of right atrium where superior vena cava puts blood into atria

A

Sino-atrial node (SAN)

202
Q

What is the sino-atrial node

A

Small patch of tissue that initiates electrical activity, SAN initiates wave of excitation at regular intervals

203
Q

How often does the SAN initiate wave of excitation in human

A

55-80 times a minutes

204
Q

What is the SAN also described as

A

Pacemaker

205
Q

What happens when SAN initiates wave of excitation

A

Wave quickly spreads across walls of both atria travelling across membranes of the muscle tissue and as wave of excitation passes, it causes cardiac (atria) muscles to contract known as atrial systole

206
Q

Why can’t wave of excitation spread directly down to ventricle walls

A

Tissue at base of atria cannot conduct the wave of excitation

207
Q

What is located at the top of the inter ventricular septum

A

Atrioventricular node (AVN)

208
Q

Why is the atrioventricular node necessary

A

As it is the only route to get the wave of excitation through to the ventricles

209
Q

What happens at AVN

A

Wave of excitation is delayed to allow atria to stop contacting and ventricle to fill with blood

210
Q

What happens after wave of excitation is delayed at AVN

A

Wave carried away from AVN down specialised conducting tissue called purkyne fibres

211
Q

What is located just before the purkyne fibres

A

The bundle of His

212
Q

Where does the bundle of his run down to

A

Runs down inter-ventricular septum

213
Q

Where does bundle of His turn into purkyne fibres

A

At apex of heat where tissue rises around the ventricles

214
Q

What happens to wave of excitation at bottom of septum

A

Wave spreads out over ventricle walls, wave spreads from apex upwards and causes the muscle to contract from base upwards which pushes blood up towards major arteries at top of the heart

215
Q

What is an ECG used to measure

A

Hearts electrical activity

216
Q

How do you work an ECG

A

Attach sensors to skin, picked up on ECG as some electrical activity generated by heart spreads through tissue close to the heart and out to the skin, the sensors on the skin pick up this electrical excitation from the heart and convert it into a trace

217
Q

On an ECG what does the P wave show

A

Excitation of atria (atria systole)

218
Q

What does the QRS complex on ECG represent

A

Indicates excitation of ventricle (ventricular systole)

219
Q

What does T wave show in ECG

A

Diastole

220
Q

Why are ECG used

A

To show if heart is healthy or not and can diagnose heart issues

221
Q

What does bundle of his separate into

A

Purkyne fibres

222
Q

How much blood does heart pump into the arteries compared to what it receives from veins

A

Pumps out same amount as it receives

223
Q

When is the greatest systolic contraction

A

The more the heart muscle stretches in diastole the greater the contraction will be

224
Q

How is oxygen transported round body

A

In erythrocytes which contain the protein haemoglobin

225
Q

What is oxygen + haemoglobin

A

Oxyhemoglobin

226
Q

What is haemoglobin structure

A

It is a complex protein with 4 subunits, each subunit has a polypeptide chain and a haem (non-protein group) and each charm has an iron ion Fe2+

227
Q

What can the iron ion on haemoglobin attract and hold and what does this mean

A

One oxygen molecule meaning iron ion has high affinity for oxygen

228
Q

How many oxygen molecules can each haem group hold

A

One oxygen molecule

229
Q

How many haemoglobins are there in a Red blood cell

A

About 280million

230
Q

How many oxygen molecules can an erythrocytes carry

A

Over a billion

231
Q

Where is oxygen absorbed into the blood

A

At alveoli

232
Q

What happens to oxygen molecules diffusing into blood plasma

A

Enter red blood cells and become associated with haemoglobin

233
Q

What does it mean when oxygen molecule associated with haemoglobin

A

Oxygen binds reversibly to the haemoglobin

234
Q

How is a steep contraction gradient maintained between oxygen in blood and alveoli

A

Oxygen associates with haemoglobin to make oxyhemoglobin so oxygen molecule taken out of blood plasma and therefore low concentration of oxygen in blood plasma

235
Q

Where does blood go after lungs

A

Back to the heart before travelling around body to supply tissue with oxygen and nutrients

236
Q

In the tissue what do cells need oxygen for

A

Aerobic respiration

237
Q

What happens at cells to oxyhemoglobin

A

It dissociates so cell just gets the oxygen not the haemoglobin molecule

238
Q

What does haemoglobins ability to associate with and release oxygen depend on

A

Oxygen concentration in surrounding tissue

239
Q

How is concentration of oxygen measured and in what units

A

Relative pressure (which is contributed to by a mixture of gases) called partial pressure of oxygen (pO2) or oxygen tension and measured in units of pressure (kPa)

240
Q

What would you expect concentration of oxygen absorbed by the liquid to be in a normal liquid

A

It would be directly proportional to oxygen tension in surrounding air so a graph showing this would be linear (not the case with haemoglobin)

241
Q

How does haemoglobin associate with oxygen in terms of a graph

A

Associates in a way that produces an s-shaped curve

242
Q

What is haemoglobins s-shaped curve called

A

Haemoglobin dissociation curve

243
Q

What happens to haemoglobin association to oxygen at low oxygen tension

A

Haemoglobin doesn’t readily associate with oxygen molecules as haem groups that attract oxygen are at centre of haemoglobin molecule making it hard for oxygen molecules to reach haem group to associate with it

244
Q

What accounts for low saturation levels of haemoglobin molecule and low oxygen tensions

A

Difficulty in combining haemoglobin with the 1st oxygen molecule which is why starts of with low partial pressure and percentage saturation

245
Q

What happens to haemoglobin as oxygen tension rises

A

Diffusion gradient into haemoglobin molecule increases

246
Q

What is conformational change

A

Eventually one oxygen molecule enter haemoglobin and associates with one of the haem groups causing a slight change in shape of haemoglobin molecule know as conformational change

247
Q

What happen after one oxygen molecule associates

A

Allows more oxygen molecules to enter haemoglobin molecule and associate with other haem groups relatively easily which is why curve gets steeper as oxygen tension increases

248
Q

Why does the curve level of at the end

A

Haemoglobin molecule has reached 100% saturation of oxygen

249
Q

Why is it good that mammalian haemoglobin is well adapted to transport oxygen to tissues of a mammal

A

As oxygen tension found in lungs is sufficiently high to produce close to 100% saturation and oxygen tension in respiring body tissue is sufficiently low to cause oxygen to dissociate from oxyhemoglobin

250
Q

Why is fetal haemoglobin different to adult haemoglobin and how does this affect dissociation curve

A

Has higher affinity for oxygen so haemoglobin dissociation curve for fetal haemoglobin it to the left of adult haemoglobin

251
Q

Why is it necessary that fetal haemoglobin has higher affinity for oxygen

A

As it must be able to associate with oxygen in an environment where the oxygen tension is low enough to make adult haemoglobin release oxygen

252
Q

What happens in placenta where oxygen tension is low

A

Fetal haemoglobin will absorb oxygen from surrounding fluids which reduces oxygen tension in mothers blood which in turn makes maternal haemoglobin release more oxygen (dissociation)

253
Q

What must happen to CO2 released from respiring tissue

A

Must be removed from tissue and transported by blood to lungs for excretion

254
Q

What are the three ways CO2 is transported and what it its percentages

A

5% dissolved directly in blood plasma, 10% combined with haemoglobin to form carbaminohaemoglobin, 85% transported in form of hydrocarbonate ions (HCO3-)

255
Q

What is the first step in formation of hydrocarbonate ions

A

CO2 in blood plasma diffuses into red blood cells where it combines with water to form a weak acid called carbonic acid (CO2 + h2o -> H2CO3)

256
Q

What enzyme catalysed the reaction between CO2 and water to form carbonic acid

A

Carbonic anhydrase

257
Q

What happens after CO2 combined with water into carbonic acid

A

Carbonic acid then dissociates to release hydrogen ions (H+) and hydrocarbonate ions (HCO3-),,,, (H2CO3 -> HCO3- + H+)

258
Q

What happen after formation of hydrocarbonate ions and hydrogen ions in formation of hydrocarbonate ions

A

Hydrocarbonate ions diffuse out of red blood cell into blood plasma which causes pH in red blood cell to change but is maintain by movement of chloride ion (Cl-) from plasma in erythrocyte known as the chloride shift

259
Q

What happens after the chloride shit in red blood cell

A

Hydrogen ions building up in erythrocyte could cause content of red blood cell to become very acidic and to prevent this hydrogen ions are taken out of solution by associating with haemoglobin to produce haemoglobinic acid (HHb)

260
Q

When the haemoglobin and hydrogen associate what is the haemoglobin acting as

A

Haemoglobin acting as a buffer (compound which maintains a constant pH)

261
Q

What does blood entering respiring tissue carry blood as

A

Oxyhaemoglobin

262
Q

Is partial pressure of oxygen at respiring tissue lower or higher than at the lungs and why

A

Lower as used in respiration

263
Q

What does low partial pressure of oxygen at respiring tissues cause

A

Oxyhaemoglobin to dissociate so oxygen is released into the tissue meaning that haemoglobin is available to take up a hydrogen ion forming haemoglobinic acid

264
Q

What happens where tissue is more active

A

More CO2 released causing dramatic effect on the haemoglobin

265
Q

What does the Bohr effect describe

A

Describes effect than an increasing concentration of CO2 has on haemoglobin

266
Q

What is Bohr effect

A

CO2 entering erythrocyte forms carbonic acid which dissociates to release hydrogen ions which have affect on pH of RBC cytoplasm, change in pH can affect tertiary structure of haemoglobin, for example more acidic alters haemoglobin structure and reduces its affinity for oxygen, so haemoglobin is unable to hold as much oxygen and o2 released from oxyhaemoglobin to the respiring tissue

267
Q

Is there more or less CO2 at respiring tissues

A

More

268
Q

What does more CO2 at respiring tissues result in

A

There will be more hydrogen ions produced in the red blood cells causing oxyhaemoglobin to release more oxygen as it has a higher affinity for hydrogen than oxygen

269
Q

What happen to oxygen saturation in haemoglobin when more CO2 is present

A

Haemoglobin becomes less saturated with o2

270
Q

What happens to dissociation curve when there is more CO2

A

Shifts down and to the right known as the Bohr shift

271
Q

What does Bohr effect mean overall and why is this good

A

Bohr effect results in more Oxygen being released when more CO2 is produced in respiration and this is exactly what muscles need in order for aerobic respiration to continue

Alevel Biology (25 decks)

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