Heart and Haemoglobin Flashcards
1
Q
What are the main constituents of blood?
A
- liquid plasma
- cells
2
Q
How are the arteries adapted to withstand the pumping action of the heart’s ventricles?
A
They have thick but flexible walls
3
Q
How many layers does an artery wall have?
A
3
4
Q
What is the outer most layer of an artery?
A
A layer of tough protein fibres
5
Q
What is the middle layer of an artery like?
A
A thick mixture of muscle cells and elastic fibres
6
Q
What is the innermost layer of an artery like?
A
Flattened cells with an extremely smooth surface
7
Q
What’s the inner most layer of an artery called?
A
Endothelium
8
Q
What happens if the innermost layer of an artery gets damaged?
A
Blood clots are liable to form and may block the artery
9
Q
What is the purpose of the middle layer of the heart?
A
To allow the artery to expand each time the heart beats.
10
Q
How can the arteries maintain a constant blood flow?
A
By the fibres recoiling to their original length between heartbeats. This smooths out the changes in pressure.
11
Q
What is different in veins compared to arteries?
A
Veins have thinner walls. Also the blood pressure is lower and it moves more slowly.
12
Q
How is blood drawn to the heart from the veins?
A
When the chambers expand and there is a period of lower pressure.
13
Q
How is blood adapted to carry oxygen?
A
Red blood cells…
- are small in size
- it’s shaped like a flattened disc
- ir has a thin central part of the disc
- no organelles such as nucleus or mitochondria
- filled with haemoglobin.
14
Q
How does the absence of organelles benefit red blood cells?
A
Because this provides maximum space for haemoglobin
15
Q
How does a thin central part of the red blood cell disc benefit blood?
A
Because the thin centre allows the cell to be flexible so that it can bend through any narrow capillaries.
16
Q
What does the flattened disc shape of a red blood cell do?
A
It increases the surface area to volume ratio and greatly increased the area through which oxygen can diffuse.
It also means that haemoglobin can be close to the surface giving a short diffusion pathway.
17
Q
Benefit of the small size of red blood cells?
A
It allows red blood cells to pass through narrow capillaries.
18
Q
Benefit of having haemoglobin in red blood cells?
A
It greatly increases the oxygen carrying capacity of the blood.
19
Q
What is haemoglobin?
A
A quarternary protein that consists of 4 polypeptides called glowing and a haemoglobin group in the centre of each.
20
Q
How is oxygen carried round the body?
A
By haemoglobin
21
Q
How is oxyhaemoglobin formed?
A
In the lungs, oxygen forms to haemoglobin in red blood cells
22
Q
What type of reaction is haemoglobin to oxyhaemoglobin?
A
Reversible
23
Q
Why is haemoglobin to oxyhaemoglobin a reversible reaction?
A
Because when oxygen leaves oxyhaemoglobin near the body cells, it turns back to normal haemoglobin
24
Q
Haemoglobin saturation depends on…
A
The partial pressure of oxygen
25
What carries haemoglobin?
Red blood cells
26
What does the haem group contain?
An iron ion
27
Why is haemoglobin red?
It contains iron which makes it red
28
What is partial pressure a measure of?
Oxygen concentration
29
What does a high partial pressure mean?
A great concentration of oxygen in the lungs
30
Haemoglobin's affinity for oxygen depends on...
The partial pressure of oxygen
31
When does haemoglobin load onto oxygen?
When there is a high partial pressure
32
When does haemoglobin unload its oxygen?
When there's a low partial pressure of oxygen.
33
What does a disassociation curve show?
How saturated the haemoglobin is with oxygen at any given partial pressure
34
On a disassociation curve, what does it mean when haemoglobin is 100% saturated?
Every haemoglobin molecule is carrying a maximum of 4 oxygen molecules.
35
On a disassociation curve, what does 0% saturation mean?
None of the haemoglobin molecules are carrying any oxygen.
36
Example of where partial pressure is high
In the lungs
37
Example of where partial pressure is low
In respiring tissues
38
Why does a disassociation curve have shallow bits st the start and end but is steep in the middle?
Because when haemoglobin combines with its first oxygen molecule, its shape changes which makes it easier for other oxygen molecules to combine. (So it's steep in the middle). However once the haemoglobin starts to become saturated, it gets harder for oxygen molecules to attach.
39
Why might there be a low partial pressure?
In respiring cells when they unload oxygen.
40
Why would a disassociation curve shift to the right?
Because there is a high partial pressure of oxygen, so an increased rate of oxygen unloading (the rate at which oxyhaemoglobin disassociates to form oxygen and haemoglobin)
41
Organisms that are very active and have a high oxygen demand have haemoglobin with a ___ affinity for oxygen.
Lower
42
Why do mammals need a specialised transport system?
Because they have a low surface area to volume ratio.
43
What is the circulatory system made up of?
The heart and blood vessels
44
What supplies blood to the heart?
The coronary arteries
45
Why are capillaries found very near cells in exchange tissues?
So that there is a short diffusion pathway
46
How thick are the walls of a capillary?
They are one cell thick
47
Why are capillary walls so thin?
To shorten the diffusion pathway
48
Why is there a large number of cappileries?
To increase surface area for exchange
49
What's a capillary bed?
Networks of capillaries in tissue
50
Why doesn't tissue fluid contain large proteins or red blood cells?
Because they are too large to be pushed out of the capillary walls.
51
What type of organisms have open circulatory systems?
Smaller organisms (e.g. insects)
52
What does the open circulatory system include?
A pump (the heart) and open ended vessels
53
What type of organisms have a closed circulatory system?
Larger multicellular organisms
54
Why do larger multicellular organisms have a closed circulatory system?
Because it would take too long for an open system to serve cells deep within the body.
55
How do active insects maintain a high metabolic rate with an open circulatory system?
They have a system of air tubes (tracheae) that respiratory gases diffuse through to reach every cell in the body.
56
Problem with open circulatory system?
It limits the maximum body size of insects
57
What kind of circulatory system do fish have?
Single circulatory system.
58
What does single circulatory system mean?
Blood flows through the heart once in a complete system around the body
59
What type of circulatory system do mammals have?
Closed double circulatory system.
60
What does closed double circulatory system mean?
Blood travels twice through the heart in one complete circuit around the body.
61
What does the mammalian circulatory system consist of?
Pulmonary circulation and systemic circulation
62
How do arteries maintain their pressure?
They have narrow lumen
63
What is blood? (and what does it consist of?)
A specialised tissue composed of:
Cells including erythrocytes (RBC), leucocytes (WBC) and platelets.
Suspended in plasma.
64
What does plasma consist of?
Many dissolved substances. For example:
- salts
- nutrients (eg glucose, amino acids)
- CO2
- waste products (eg urea)
- hormones (eg insulin)
65
How is the efficiency of exchange between plasma and tissue fluid increased?
- thin capillary walls composed of squamous epithelium give a short diffusion distance.
- capillary bed has large surface area.
- steep concentration gradient
66
How is tissue fluid formed?
Due to high hydrostatic pressure at the artery end of the capillary bed, plasma is forced out of the capillary through gaps in the capillary wall by ultrafiltration.
67
Where does escess tissue fluid drain to?
Lymph vessels. This is then returned to the blood in the subclavian veins.
68
How does an atheroma occur?
When damage occurs to the endothelium (inner lining of artery) eg by high blood pressure, white blood cells and lipids from the blood clump together under the lining to form fatty streaks.
Over time more WBC, lipids and connective tissue build up and harden to form an atheroma.
69
What is an atheroma?
A fibrous plaque.
70
How does coronary heart disease occur?
When the coronary arteries have lots of atheromas, which restricts blood flow to the heart muscle.
71
What are the risk factors for cardiovascular disease?
- high blood cholesterol and poor diet
- cigarette smoking
- high blood pressure
72
Explain high blood cholesterol and poor diet as a risk factor for cardiovascular disease.
Cholesterol is one of the main constituents of the fatty deposits that form atheromas. These can then lead to increased blood pressure and blood clots. This can block the flow of blood to the coronary arteries which could cause a myocardial infarction.
73
Why is cigarette smoking a risk factor for cardiovascular disease?
- nicotine increases the risk of high blood pressure.
- carbon monoxide combines with haemoglobin and reduces the amount of oxygen transported in the blood, and so reduces the amount of oxygen available for tissues. If the heart muscles don't revise enough oxygen it can lead to a heart attack.
- smoking decreases the amount of antioxidants in the blood. This means cell damage in the coronary artery walls is more likely, which can lead to atheroma formation.
74
Why is high blood pressure a risk factor for cardiovascular disease?
- high blood pressure increases the risk of damage to artery walls.
- damaged walls have an increased risk of atheroma formation, causing a further increase in blood pressure.
- atheromas can also cause blood clots to form.
- the blood clot could block the flow of the heart muscle, resulting in myocardial infarction.
75
What does affinity mean?
Attraction for
76
What does the binding of the first oxygen to haemoglobin induce?
A conformational change in haemoglobin - so that the Hb more readily binds to the second and third oxygen.
77
Allosteric mechanism
When the binding of a molecule at one site influences the binding of another molecule at a different site.
78
In the placenta of a pregnant woman, why is the partial pressure low?
So that that adult haemoglobin disassociates and releases oxygen.
The fetal haemoglobin can the bind to this oxygen due to its high affinity for oxygen than the adult Hb.
79
Myoglobin?
It acts as an oxygen store in muscle cells for when the partial pressure is very low due to high levels of aerobic respiration in contracting muscles. When this occurs, it will release oxygen.
80
In haemoglobin, what are the polypeptide chains?
2 identical alpha chains and 2 identical beta chains.
81
Why do red blood cells have a flattened disc shape?
- to increase the surface area to volume ratio which increases the area through which oxygen can diffuse.
- the haemoglobin is close to the surface, giving it a short diffusion pathway.
82
Why do red blood cells have a thin central part of the disc?
It allows the cell to be flexible so that it can bend and squeeze through narrow capillaries.
83
Why is there an absence of organelles in red blood cells?
To allow maximum space for haemoglobin.
84
What happens if the heart stops beating?
The body will be deprived of oxygen. Cells do not have reserves of oxygen, and the brain is sensitive to a shortage of oxygen. Thus, if the oxygen supply is stopped, brain cells will die.
85
What component of haemoglobin determines its precise properties (meaning varieties exist)?
The globin component
86
Advantage of the Bohr effect?
When a muscle is respiring more, it receives an increased oxygen supply.
87
Why are the proportions of plasma and cells important in blood?
Because efficient oxygen supply requires a large proportion of red blood cells.
On the other hand, a decrease in the proportion of plasma makes the blood more viscous (sticky), and the heart has to pump harder to pump it round the body. This increases blood pressure and places additional strain on the heart.
88
Difference between veins and arteries?
Veins have thinner walls than arteries.
Veins have a lower blood pressure.
The blood moves more slowly in veins.
Veins have a wider lumen.
89
What are the four valves of the heart?
Two semilunar valves and two atrioventricular valves
90
Why does oxyhaemoglobin keep its oxygen until it reaches the capillaries in tissues?
Because the walls in veins, arteries and arterioles are too thick to allow oxygen to escape rapidly.
See textbook pg 163
91
What does a high partial pressure mean?
A greater concentration of dissolved oxygen in cells.
92
What does the partial pressure of CO2 mean?
A measure of the concentraron of CO2 in a cell.
93
When does oxygen load onto haemoglobin to form oxyhaemoglobin?
Whine there's a high partial pressure.
94
When does oxyhaemoglobin unload its oxygen?
When there's a low partial pressure.
95
Where partial pressure is high, haemoglobin will will have a _____ affinity for oxygen.
High.
(ie it will readily combine). So it has a low saturaioknof oxygen.
96
Where partial pressure is low, haemoglobin has a ____ affinity for oxygen.
Low.
Which means it will release oxygen rather than combine with it. So it has a low saturation of oxygen.
97
What is tissue fluid?
Fluid that surrounds cells in tissues. It's made from small molecules that leave blood plasma (eg oxygen, water, nutrients).
However unlike blood, it doesn't contain any RBC or large proteins as they're too large to be pushed out of the capillary wall.
98
What causes an accumulation of tissue fluid in the capillaries?
High blood pressure means high hydrostatic pressure in the capillaries, which can cause an accumulation of tissue fluid in the tissues.
99
Why do multicellular organisms eg mammals need a specialised transport system (circulatory system)?
Because they have a low SA:V ratio.
100
The circulatory system is made of...
The wart and blood vessels.
101
What is the function of arteries?
Carry blood away from the heart to the rest of body.
102
How are arteries adapted for their function?
They have thick, muscular walls.
Have elastic tissue to stretch and recoil as the heart beats, which helps to maintain high pressure.
The inner lining (endothelium) is folded, allowing the artery to stretch - also helping to maintain high pressure.
103
Arteries divide into...
Arterioles.
104
What is the function of veins?
To take blood back to the heart under low pressure.
105
Outline the structure of veins.
- wider lumen
- very little elastic or muscle tissue.
- contain valves to stop blood flowing backwards.
106
All veins carry _____________ blood.
Deoxygenated
107
Why do all veins carry deoxygenated blood?
Because they're taking blood back to the heart - and the oxygen has been used up by body cells.
108
In what way are pulmonary veins different to normal veins?
Pulmonary veins carry oxygenated blood from the heart to the lungs.
109
Arteries divide into arterioles, which then divide into...
Capillaries.
110
In what ways are capillaries adapted for efficient diffusion?
- they're found very near cells in exchange tissues; short diffusion pathway.
- walls are only one cell thick, shortening diffusion pathway.
- large number of capillaries, to increase SA for exchange.
111
What is tissue fluid?
The fluid that surrounds cells in tissues, made from small molecules that leave the blood plasma (e.g. oxygen, water).
112
Tissue fluid is different to blood as it doesn't contain red blood cells and certain proteins. Why?
Because they're too large to be pushed out through the capillary walls.
113
What happens to any excess tissue fluid?
It's drained back into the lymphatic system, which can then transport this excess tissue fluid back into the circulatory system.
114
Outline how substances move out of the capillaries into the tissue fluid.
1. Start of capillary bed, hydrostatic pressure inside the capillaries is greater than that in tissue fluid.
2. This difference in pressure forces fluid out of the capillaries, into the spaces around cells, forming tissue fluid.
3. As fluid leaves, hydrostatic pressure reduces in capillaries (so is lower at venue end of capillary bed).
4. Due to fluid loss and increasing conc of plasma proteins, the WP at the venue end is lower than WP of tissue fluid.
5. Therefore some water renters the capillaries from tissue fluid at the venule end by osmosis.
115
Why is the left ventricle thicker than the right?
It's more muscular because it needs to contract powerfully to pump blood all around the body. Whereas the right ventricle only needs to get blood to the lungs, which are nearby.
116
Why do the ventricles have thicker walls than the atria?
Because they have to push blood out of the heart,
| but atria just need to push blood over a short distance into the ventricles.
117
What are the atrioventricular valves?
They link the atria to the ventricles and atop blood flowing back into the atria when ventricles contract.
118
What do the semilunar valves do?
SL valves link the ventricles to the pulmonary artery and aorta.
They stop blood flowing back into the heart after the ventricles contract.
119
Difference between AV and SL valves?
AV valves link atria to ventricles, whereas SL valves link ventricles to pulmonary artery.
AV valves stop blood flowing back into the ATRIA after ventricles contract, but SL valves stop blood flowing back into the HEART after ventricles contract.
120
How does blood only flow in one direction through the heart?
Because the SL and AV valves only open one way.
121
Outline how the AV and SL valves work.
If there's a higher relative pressure behind a valve, it's forced open.
But if pressure is higher in front of the valve, it's forced shut.
122
How are atheromas formed?
1. Damage occurs to endothelium of artery.
2. WBC and lipids from blood climb together under the lining to form fatty streaks.
3. Over time, more WBC, lipids and connective tissue build up and harden to form fibrous plaque - atheroma.
123
In what way are atheromas formed?
The fibrous plaque (atheroma) partially blocks the lumen of artery and restricts blood flow - causing blood pressure to increase.
124
Artheromas increase the risk of two types of disease...:
Aneurism and thrombosis.
125
Outline how an atheroma can lead to the development of thrombosis.
1. An atheroma can rupture (burst through) the epithelium of artery.
2. This damages the artery wall, leaving a rough surface.
3. Proteins and fibrin (a protein) accumulate at the sire of damage and form a blood clot (a thrombus).
4. This blood clot can. Aide the complete blockage of an artery.
5. Debris from the rupture can cause a blood clot further down the artery.
126
Outline how interrupted blood flow can cause a myocardial infarction (heart attack).
If the coronary artery becomes completely blocked (eg by a blood clot), an area of the heart will be totally cut off from its blood supplement receiving no oxygen (from blood) - needed to carry out respiration.
This causes myocardial infarction (heart attack).
This can cause damage and death if the heart muscle.
127
Name 3 risk factors to cardiovascular disease.
- smoking
- high blood cholesterol and poor diet
- high blood pressure
- age
- gender (men mor likely)
128
Which cells carries haemoglobin?
Red blood cells
129
Outline the structure of haemoglobin.
A large protein with a quaternary structure - with a polypeptide chain (4 polypeptide chains).
Each chain has a haem group, containing an iron ion
130
Where is the iron ion found in haemoglobin?
In the haem group on each polypeptide chain.
