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BIOM20002 - HSF > Lecture 56 - Blood Pressure and its Regulation > Flashcards

Lecture 56 - Blood Pressure and its Regulation Flashcards

(75 cards)

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1
Q

What questions do we ask when we see a patient with low BP?

A
  • Is it genuine hypertension?
  • is the heart rate appropriate for BP?
  • What is the cardiac filling?
  • does the heart contract normally?
  • is the patient abnormally vasodilated?
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2
Q

What are the factors that effect BP?

A

TPR
CO
Blood volume
Elasticity

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3
Q

Describe the generalised tissue structure of veins and arteries

A

Tunica intima
Tunica media
Tunica externa

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4
Q

What is special about the structure of arteries?

A

Elastic tissue

For elastic recoil to move blood along the artery

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5
Q

Describe the structure of arterioles, and how this relates to the function

A

Smooth muscle
Endothelium

Smooth muscle for resistance

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6
Q

Describe the pressure changes from the heart to veins

A 
Heart: Fluctuates from 5-120 mmHg with beating
Arteries: pulse: 120/80 mmHg
Arterioles: drops, pulse present
Capillaries: around 40 mmHg
Veunles: around 20
Veins: 20 down to 0
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7
Q

What is pulse pressure?

A

Strength of the pressure wave

Sys. - Dys.

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8
Q

What is MAP?

A

Average pressure responsible for driving blood forward

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9
Q

What unit is used to measure BP?

A

mmHg

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10
Q

What is driving pressure?

A

Pressure that pushes blood forward

Generated by the heart

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11
Q

What is transmural pressure?

A

Pressure difference between inside of vessels and outside of vessels

eg. Brain in skull: skull means that there is high transmural pressure

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12
Q

What is hydrostatic pressure?

A

Pressure in a column of water due to the height of the liquid

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13
Q

What are the origins of pressure in circulation?

A

Gravity
Compliance
Viscous resistance
Inertia

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14
Q

When does gravity affect pressure?

A

Gravity affects hydrostatic pressure when there is a height difference

ie when standing

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15
Q

Does gravity affect driving pressure?

A

No

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16
Q

What is the difference in pressure of the arteries and veins when standing and lying at any given point on the body?

A

85 mmHg

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17
Q

What is compliance?

A

The ‘expandability’ of the walls of the vessel

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18
Q

What sort of container has zero compliance?

What happens when we keep adding liquid to this container?

A

eg. A steel tube

Pressure increases
Volume does not increase

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19
Q

What happens when we add liquid to a container with infinite compliance?

A

Increase in volume

Pressure remains at zero

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20
Q

What happens when we add liquid to a container with finite compliance?

A

Increase in volume
Increase in pressure

(walls can expand)

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21
Q

Change in pressure with a given change in volume is greater if the compliance of the vessel is…

A

Lower

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22
Q

What is viscous resistance?

A

Sticky fluid stick to the side of the vessel and thus exert resistance.

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23
Q

What does blood viscosity depend on?

A 
Fibrinogen concentration
Hematocrit
Vessel radius
Linear velocity
Temperature
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24
Q

How does vessel radius affect blood viscosity?

A

Lesser radius, greater viscosity

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25
How does temperature affect blood viscosity?
Greater temperature, lower viscosity
26
What does the law of conservation of energy say about fluid pressure and velocity?
When blood velocity increases, fluid pressure must decrease
27
What causes the decrease in pressure of the blood when blood velocity increases?
Inertia
28
What is 'Z'?
Impedance
29
What does vascular impedance depend on?
Flow resistance Compliance Inertiance
30
According to Poiseuille's law, what is resistance affected by?
Length of tube Viscocity Radius of tube
31
What is conductance?
Inversely proportional to resistance Bloop flow through a vessel at a given pressure difference
32
Where is total resistance highest? | Why?
Arterioles
33
Why is it important for the walls of the arteries to be elastic?
When blood flow in, the wall stretches out. The elastic recoil then pushes the blood forward. The elastin stretching is stored potential energy that is converted into kinetic energy
34
What happens when MAP is too high or low?
Low: dizziness, organ failure High: stroke, aneurysm
35
What things determine MAP?
MAP = CO x TPR (Cardiac output TPR) Also: - total blood volume - HR - SV
36
Why must flow into a segment equal flow out?
If this is not maintained, BP will either be too high or too low.
37
How is MAP calculated?
1/3(sys - dys) + dys
38
What is DP?
Pressure gradient | ie P1 - P2
39
What functions does the movement of blood fulfill?
Heat transport Gas Nutrient Wastes
40
What things help the movement of blood?
``` Heat (energy source) Elastic tissue Gravity Skeletal muscle Diaphragm ``` Of course, heart contraction
41
What is normal CO?
5 L/min
42
What is normal SV?
Stroke volume 70 mL
43
How is SV calculated?
EDV - ESV End diastolic volume - End systolic volume
44
What factors affect stoke volume?
- preload - contractility = inotropy - afterload
45
What is preload?
EDV: end diastolic volume What is there before systole
46
What is afterload?
ESV: end systolic volume What is left after systole
47
Explain the Frank-Starling Law
As EDV increases, SV increases. The greater the stretch of the cardiac muscle, ie the more blood coming into the heart, the heart will eject more blood in the next stroke.
48
At any one time, what percentage of blood is in the veins? | How about arteries?
Veins: 64% Arteries: 13%
49
What determines preload?
Venous return determines EDV
50
What factors affect venous return?
``` Muscle pumps Respiratory pump Neural control (sympathetic tone vasoconstriction) ```
51
How does noradrenaline affect EDV?
NA increases EDV and thus SV
52
What does increased afterload mean?
decreased SV | Increased ESV
53
What does increased inotropy mean?
Increased SV | Decrease ESV
54
What does increased proload mean?
Increased SV | Increased EDV
55
What things control the heart rate?
Neural: - Intrinsic: autorhythmic cells - Extrinsic: ANS
56
Describe the sympathetic effect on HR
Increases contraction of the heart by: - changing ion permeability - so that the cells reach threshold potential sooner - depolarisation
57
Describe the parasymathetic effect on HR
Decreased contraction rate of the heart by: - changing ion permeability - so that the cells take longer to reach threshold (hyperpolarisation)
58
Which cells does the sympathetic and parasympathetic act on?
B-adrenoceptors and mAChR Conduction through the internodal pathways
59
What happens to MAP when there is a decrease in TPR?
Decrease in MAP
60
What does an organ do to achieve greater blood supply?
Decreased arterial resistance | Relaxation of arterial smooth muscle
61
What compensatory mechanisms are effected to compensate for low MAP?
Increase CO Increased TPR Increased HR Increase SV
62
What happens when CO decreases?
Pooling of blood in the legs
63
How does the body monitor CO?
pH CO2 O2 BP
64
How is BP regulated over the short term?
Neural (ANS) | Baroreceptor reflex
65
Describe the baroreceptor reflex when standing up
1. Decreased stretch detected by baroreceptors 2. Central integration 3. Activation of Sym. and deactivation of Parasym. 4. Increased: - HR - Force of contraction - TPR 4b. Decreased: - atrioventricular conduction time
66
Where are the baroreceptors located?
Carotid sinus | Aortic arch
67
What are the normal effects of the parasympathetic division on the heart
Decreased HR | Increased antrioventricular conduction time
68
Describe the baroreceptor reflex when lying down
1. Excess stretch detected by baroreceptors 2. Central integration 3. Activation of Parasym. and deactivation of Sym. 4. Increased: - AV conduction time 4b. Decreased: - TPR - HR - Force of contraction
69
What do chemoreceptors detect?
Low pH | Low O2
70
What does low O2 and high pH stimulate?
Increased respiration rate | Increased BP
71
How is BP regulated over the long-term?
1. Cardiac Output - hormonal - renal 2. TPR - hormonal - vascular structure
72
How do we increase CO over the long-term?
Increased ECF | Decreased renal salt excretion
73
How do we increase TPR over the long-term?
Hypertrophy of arterial wall | Vasoconstrictive hormones
74
Which receptors detect low BP?
Atrial baroreceptors
75
Describe the function of atrial baroreceptors
Monitor changes in central blood volume --> Thirst stimulated

BIOM20002 - HSF (60 decks)

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