Flashcards in Introduction to the Cardiovascular System Deck (107)
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1
What is true of all living cells?
They are metabolically active
2
What is the result of living cells being metabolically active?
They use oxygen and nutrients, and produce carbon dioxide and other waste
3
How can single celled or tiny organisms get oxygen and nutrients?
Directly by diffusion from the environment
4
What is diffusion?
Random movement that results in an overall movement from high concentration to a low concentration
5
What is the result in small organisms being able to get oxygen and nutrients directly by diffusion?
They don’t require a cardiovascular system
6
How many cells are in the human body?
10^14 (100 million)
7
What is the problem with the human body having so many cells?
Most are far away from a source of oxygen and nutrients, and therefore can’t obtain them from diffusion
8
Why does the body cells being far away from a source of oxygen and nutrients mean that it can’t get them by diffusion?
Because diffusion is proportional to distance squared, so it works well over short distances, but not larger distances as it takes far longer to travel across
9
What is the result of large cells being unable to get oxygen and nutrients by direct diffusion?
They need a gas exchange and circulatory system to carry oxygen and nutrients to cells, and carry waste produces away
10
What does the right heart do?
Pumps blood to the lungs
11
What happens to blood at the lungs?
Gas exchange takes place and blood becomes oxygenated
12
What happens to blood once it has become oxygenated?
It passes from the lungs to the left heart
13
What does the left heart do?
Pumps blood to the body cells
14
What happens to blood at the body cells?
Oxygen is released
15
What does deoxygenated blood return to the right heart via?
The kidneys and the gut
16
Why does blood return via the kidneys?
Filtering
17
Why does blood return via the gut?
Nutrient acquisition
18
What is the pulmonary circulation?
The circulation of blood form right heart to lungs, to left heart
19
Where is blood pumped in the pulmonary circulation?
Alveoli
20
Why is blood pumped to the alveoli?
So gas exchange can take place by diffusion
21
What is the systemic circulation?
The circulation of blood form left heart, to body, to right heart
22
How does blood in circulation travel?
By convective transport (flow)
23
What is the advantage of convective transport?
It works quickly over long distances
24
What is essential to allow diffusion to take place?
The mechanism for transporting substances close to cells
25
What is the distribution system?
Vessels and blood
26
What is the heart?
Effectively, two pumps
27
What is the exchange mechanism?
The capillaries
28
What does blood transport around the body?
Oxygen
Metabolic substrates
Carbon dioxide
Waste product
29
How does exchange of substances between the blood and body cells occur?
By diffusion
30
What does the cardiovascular system provide?
The correct conditions for diffusion to take place at the tissues and lungs
31
Where does diffusion between blood and tissues take place?
Capillaries
32
What are capillaries composed of?
A single layer of endothelial cells, surrounded by a basal lamina
33
What is the advantage of capillaries being one cell thick?
There is a short distance for diffusion to take place
34
What molecules can directly diffuse through the lipid bilayer?
Those that are lipid soluble, e.g. oxygen and carbon dioxide
35
How do molecules that can’t diffuse through the lipid bilayer get through?
Small aqueous pores between endothelial cells in capillaries
36
What molecules can’t diffuse through the lipid bilayer?
Those that are hydrophilic and not lipid soluble, e.g. glucose, amino acids and lactate
37
In what direction do all molecules move?
Down their concentration gradient
38
What does how easily molecules diffuse through pores depend on?
Size and charge of molecule
39
Why are special transport molecules sometimes needed to get through pores?
In some places, e.g. the brain, the pores are tighter
40
What do leaky pores allow?
More molecules to move in and out of the capillary lumen
41
What does rate of diffusion depend on?
Area, diffusion ‘resistance’, and concentration gradient
42
What does a larger area available for exchange result in?
A faster rate of diffusion
43
What does the area of exchange between capillaries and tissues depend on?
Capillary density
44
What will be true of a tissue that is more metabolically active?
It will have more capillaries (a higher capillary density)
45
What does diffusion resistance pertain to?
The nature of the molecule, the nature of the barrier, and the path length
46
Give an example of what is meant by the nature of the molecule?
Is it hydrophilic or lipophilic
47
Give an example of what is meant by the nature of the barrier
Larger pores mean hydrophilic molecules and larger molecules can diffuse more readily
48
What does a greater path length lead to?
A slower rate of diffusion
49
What is the rate of diffusion proportional to?
The square of the distance it needs to travel
50
What does the path length depend on?
Capillary density
51
Where is path length shortest?
The most active tissues
52
What is normally the rate limiting factor of diffusion?
Concentration gradient
53
What does a greater concentration gradient lead to?
Greater rate of diffusion
54
What is the concentration gradient that matters in the human body?
Between the capillary blood and the tissues
55
What must happen to the concentration gradients for exchange to continue
The gradient between capillary blood and tissues must be maintained
56
What will happen to concentrations when a substance is used by tissues?
It will have a lower concentration in capillary blood that arterial blood
57
What happens to the concentration of oxygen as it’s used by tissues?
It falls in the blood
58
What does the extent of oxygen concentration decrease depend on?
Rate of use by tissue
Rate of blood flow through capillary bed
59
What does a higher rate of flow through the capillary bed mean?
The more the concentration gradient can be maintained to match the rate of use in tissues
60
What is the result of a lower blood flow at any rate of use?
The lower the capillary concentration
61
What must the rate of blood flow do?
Be high enough to maintain a sufficient concentration gradient for diffusion
62
What does the rate of blood flow determine?
The concentration gradient driving oxygen or nutrient diffusion into cells
63
What must blood flow match?
The tissues metabolic needs
64
What is the result of a higher rate of metabolism?
The greater the demand for oxygen and nutrients, and so an increase in blood flow
65
What is the rate of blood flow known as?
Perfusion rate
66
What is the perfusion rate of the brain?
Needs constant high flow
0.5ml per min per gram
67
What is the perfusion rate of heart muscle?
0.9ml per min per gram at rest
3.6ml per min per gram during exercise
68
What is the perfusion rate of kidneys?
Need high, constant flow
3.5ml per min per gram
69
Give two places where blood flow varies?
Skeletal muscle
Gut
70
When is skeletal muscle blood flow high?
During exercise
71
When is gut blood flow high?
After a meal
72
What is the cardiac minimum flow in for a 70kg man?
5 litres per min
73
What is the cardiac maximum flow in for a 70kg man?
24.5 litres per min
74
What must the cardiovascular system do?
Supply between 5 and 25 litres per minute of blood to the tissue, whilst at all times maintaining perfusion to vital organs such as the brain, heart and kidneys
75
How long would the heart have to stop beating for you to go unconscious?
2 to 4 secs
76
What happens once the heart stops beating for a minute?
Neurones start to die
77
What are the components of the cardiovascular system?
Pump- the heart
Distribution system- vessels and blood
Exchange mechanisms- capillaries
Flow control
78
What acts as the flow control in the cardiovascular system?
Arterioles
Pre-capillary sphincters
79
What do pre-capillary sphincters and specialised arterioles have?
Lots of smooth muscle cells
80
How do pre-capillary sphincters and arterioles control flow?
The smooth muscle cells tense to restrict blood flow, or relax to increase blood flow to the area
81
What would happen if there was no flow control?
Blood would only flow to the parts that are easier to perfuse
82
What is the problem with blood flowing only to the easiest to perfuse areas?
The brain is harder to perfuse, due to gravity
83
What needs to be added to the system to regulate blood flow?
Resistance
84
What is meant by adding resistance to the system?
Reducing the ease with which some reasons are perfused, in order to direct blood flow to the more difficult to perfuse regions
85
What are the resistance vessels?
Arterioles
86
Why are the arterioles the resistance vessels?
As they narrow flow to one area, and therefore allow it to go to other areas
87
What is the heart made up of?
Two pumps in series
88
What does the left heart do?
Pumps blood around the systemic circulation
89
What does the right heart do?
Pumps blood around the pulmonary circulation
90
What does the heart pump to in the systemic circulation?
Arteries via the aorta
91
What do the arteries supply?
Arterioles
92
What do arterioles supply?
Capillaries
93
What do capillaries produce?
A branching network
94
What does the capillaries branching network provide?
A large surface area for diffusion
95
What do capillaries drain into?
Venules
96
What do venules drain into?
Veins
97
What must the total flow in the system be able to do?
Change
98
What does the ability to change the total flow in the system require?
A temporary store of blood, which can be returned to the heart at a different rate
99
Why does a change in total flow in the system require a temporary store of blood?
The heart can only pump more blood through if it has more blood going into it
100
What provides the temporary store of blood?
The capacitance of veins
101
Why are veins able to provide a temporary store of blood?
Because they have thin walls with smooth muscle in them, so they can easily distend of collapse, enabling them to act as a variable reservoir
102
In what direction does blood flow?
From high to low pressure
103
How does the pressure of blood change as it goes through the system?
The heart increases the pressure of the blood to push it into the high pressure arterial system
Blood goes to resistance vessels, to exchange vessels, to capacitance vessels, resulting in blood being in the low pressure venous system
104
What causes the highest drop in blood pressure?
Arterioles
105
What is the result in drop in blood pressure caused by arterioles?
By the time that blood reaches capillaries, its at low pressure
106
What is the distribution of blood in the body?
It varies, but it is approximately-
11% in arteries and arterioles
5% in capillaries
17% in heart and lungs
67% in veins
107
