Lecture 25

Question 1

What is hypertension?

Answer 1

High arterial blood pressure

Question 2

What are the values of SAP and DAP when they are elevated?

Answer 2

120-129
and
<80

Question 3

What are the values of SAP and DAP at stage | hypertension?

Answer 3

130-139
or
80-89

Question 4

What are the values of SAP and DAP at stage || hypertension?

Answer 4

> 140
or
90

Question 5

Is the prevalence of cardiovascular disease in NZ likely to be over or underestimated? Why is this?

Answer 5

It is likely to be underestimated because not all people with hypertension are diagnosed and because not all people diagnosed will currently be taking medication

Question 6

What are two physiological factors that determine MAP?

Answer 6

• CO (heart rate and stroke volume)

- peripheral resistance

Question 7

Where is there the largest pressure drop?

Answer 7

In the small arteries and arterioles because they are the resistance vessels

Question 8

What are the physical factors that determine mean arterial blood pressure?

Answer 8

Arterial blood volume and arterial compliance

Question 9

What happens to arterial blood volume and arterial compliance during hypertension?

Answer 9

Arterial blood volume increases and arterial compliance decreases

Question 10

Explain how arterial blood volume is regulated in the long term

Answer 10

Osmoreceptors detect increased osmotic pressure and baroreceptors (in the aortic arch and carotid sinus) detect decreased blood pressure. The hypothalamic neuron stimulates the release of ADH from the posterior pituitary gland which causes vasoconstriction in the blood vessel and increased reabsorption of water in the kidney. This leads to increased blood volume and increased blood pressure

Question 11

What are the three layers of a blood vessel?

Answer 11

Tunica intima, Tunica media, and Tunica externa

Question 12

What is the difference between arteriosclerosis and atherosclerosis?

Answer 12

Ateriosclerosis is a disease of the media which leads to it thickening in large or resistance arteries. This increases the stiffness of the arteries.
Atherosclerosis is a disease of the intima and causes a blockage of the arteries

Question 13

What is arteriosclerosis related to?

Answer 13

hypertension from aging

Question 14

What is atherosclerosis related to?

Answer 14

Coronary and peripheral artery disease

Question 15

What is atherosclerosis related to?

Answer 15

coronary and peripheral artery disease

Question 16

Do arteries become more or less compliant with age? What can this result in?

Answer 16

less compliant

this can lead to hypertension

Question 17

What does reduced compliance mean?

Answer 17

With high compliance, when there is a small increase in the pressure, there is a large increase in the volume. With reduced compliance, the same increase in pressure leads to less increase in volume

Question 18

How does the structure of the arterial wall change with age?

Answer 18

There is less elastin, more collagen and more cross-linking. Because collagen is 1000x stiffer than elastin, this makes the artery much more stiff

Question 19

What causes hypertension?

Answer 19

An increase in the peripheral vascular resistance due to a decrease in arterial compliance

Question 20

By how much do diastolic and systolic blood pressure have to change to be classed as hypertension?

Answer 20

Diastolic blood pressure needs to increase between 10 and 40 mmHg and systolic pressure needs to increase between 50 and 100 mmHg

Question 21

Why is the increase in diastolic pressure less than the increase in systolic pressure during hypertension?

Answer 21

This is because the increase in vascular resistance increases systolic pressure more than the increase in diastolic pressure

Question 22

Arteries become more/less compliant when arterial pressure rises

Answer 22

less

Question 23

What causes the structural changes in the vessel wall of the resistance vessels?

Answer 23

ageing

Question 24

Describe the compliance of the aorta and the flow waves

Answer 24

In systole, there is a flow wave generated by the heart. The aorta is flexible. During diastole, the valves are closed and the aorta recoils to push blood into the capillaries

Question 25

Why is the compliance of the aorta essential?

Answer 25

Because it is needed to damped the pulsatile waves of the heart

Question 26

What is the effect of age/hypertension on the flow waves from the aorta? What is the problem with this?

Answer 26

A rigid/stiff aorta means that there is almost mo storage of stroke volume. During systole, the aorta and capillary flow increases and during diastole, the capillary flow decreases which means that capillary flow is now pulsatile and so there is less O2 and nutrient exchange

Question 27

During systemic hypertension, the compliance of the aorta: A. decreases, which decreases the pulsatility of blood flow through the capillaries. B. decreases, which increases the pulsatility of blood flow through the capillaries. C. increases, which decreases the pulsatility of blood flow through the capillaries. D. increases, which increases the pulsatility of blood flow through the capillaries.

Answer 27

B. decreases, which increases the pulsatility of blood flow through the capillaries.

Question 28

What is a pulse wave?

Answer 28

This is generated by the heart, independent of blood flow (it is not a flow wave)

Question 29

How do the velocities of blood flow and the pulse wave differ?

Answer 29

Blood flow: 20 - 0 cm/s | Pulse wave: 3 - 12 m/s

Question 30

Explain the forward wave, the reflected wave and the observed wave

Answer 30

The forward wave is the first pulse wave that is generated to go over the aorta. This wave hits a bifurcation and reflects a wave in the opposite direction. The observed wave is the forward wave plus the reflected wave

Question 30

Explain the forward wave, the reflected wave and the observed wave

Answer 30

The forward wave is the first pulse wave that is generated to go over the aorta. This wave hits a bifurcation and reflects a wave in the opposite direction. The observed wave is the forward wave plus the reflected wave

Question 31

What do the wave depend on?

Answer 31

The compliance of the vessels

Question 32

How does the speed of the pulse wave change depending on whether the vessels are stiff or compliant? How does this relate to the speed of the pulse wave in proximal versus distal vessels? Give examples

Answer 32

If the vessels are flexible, the speed of the pulse wave is slower and it takes longer for the pulse wave to go over the tube. If the vessels are stiff, the pulse wave travels very fast. Distal vessels are stiffer than proximal vessels which means that the pulse wave travels faster in distal than proximal vessels. For example, Aorta 3-5 m/s Radial artery 5-12 m/s

Question 33

Distal vessels are stiffer which means that they have a faster/slower pulse wave and have smaller/larger contribution of reflections compared to proximal vessels. Explain this

Answer 33

faster larger The blood pressure in the distal arteries is slightly higher than the blood pressure in the aorta. This also means that pressure measured with a blood pressure cuff will be higher than what is happening at the heart. These changes are minor but in this could be contributing to the high blood pressure

Question 34

How is the pulse wave affected by age? How does this affect the blood pressure?

Answer 34

It increases with age because the vessels become less compliant. Stiffer vessels have a higher contribution to the observed wave so the blood pressure increases

Question 35

How do stiffer arteries affect the observed wave and blood pressure?

Answer 35

The stiffer artery (due to remodelling and/or ageing has a large contribution of reflections because the reflected wave starts earlier and therefore the observed wave will be higher so the blood pressure must be higher

Question 36

How does the pulse wave velocity change with age/hypertension and how does this affect the blood pressure and coronary perfusion?

Answer 36

In a young heart, the observed wave is higher in the distal vessels compared to the proximal vessels. The reflected wave reaches the heart after the closure of the aortic valve which contributes to coronary perfusion. In an old heart, the reflected wave reaches the heart before the closure of the aortic valve which increases the afterload so the heart has to contract more forcefully so it generates an even larger pressure (increased systolic blood pressure). The coronary blood flow is also affected

Question 37

The pulse wave velocity of the aorta decreases with older age BECAUSE at older age remodeling of the arterial wall results in a faster reflected pulse wave.

Answer 37

D. Only the second statement is correct and the first statement is incorrect.