L25 (pathophysiology) Flashcards
does the heart spend more time in diastole or systole
at rest?
during exercise?
what effect does this have on MAP
at rest diastole however during exercise it is systole
this means that MAP is closer to the diastolic pressure than the systolic pressure
what is the equation for MAP
DAP + 1/3(SAP-DAP)
define hypertension
high arterial blood pressure at rest
what is the range for prehypertension/elevated blood pressure
SAP = 120-129mmHg
DAP < 80
therefore it is when only SAP has increased
what is the range for stage 1 and stage 2 hypertension
stage 1
- SAP = 130-139
- DAP = 80-89
stage 2
- SAP >140
- DAP > 90
for both stage 1 and 2 you only need to have in increase in diastolic or systolic pressures
what is the prevalence of hypertension in NZ
and why could this be underestimated
21.4% of NZders or 1:5
this means 1 million people in NZ have hypertension
this could be underestimated because it is only including people that are taking medication to reduce their blood pressure and not everyone knows that they have it and if they have it it doesn’t mean that they ae on medication for it
what is hypertensions relationship with age and gender
the prevalence increases with age
there is no difference between gender
what is the main cause of hypertension
TPR
what determins TPR
Vessels in series and parallel determine TPR
resistance cant cause resistance
where is the largest pressure drop
Largest pressure drop
in small arteries and arterioles
(resistance vessels)
what are the physical factors that cause hypertension
Arterial blood volume increase
Arterial compliance decrease
how is arterial blood volume regulated
by the kidney in the long term
osmoreceptors detect increased osmotic pressure causing the release of ADH from posterior pituitary which acts on the blood vessels causing vasoconstriction-> increased BP
baroreceptors in the aortic arch and carotid sinus detect blood pressure, this causes ADH to be released from the posterior petuitory which acts on the kidney to increase water reabsorption which leads to increased blood volume and pressure
what is the difference between Arteriosclerosis and Atherosclerosis
aRterIosclerosis = disease of the media and alters the stiffness of the vessels (media thickening)
atherOsclerosis = disease of the intam which alters the conduct (blockage)
define aRterIosclerosis
disease of the media and alters the stiffness of the vessels
Media thickening in large or resistance arteries
Increasing stiffness of the arteries
happens because of hypertension (ageing)
define atherOsclerosis
disease of the intam which alters the conduct
Changes of the intima causing blockage of the arteries (plaque formation)
caused by Coronary and peripheral artery disease
describe the relationship between arterial compliance and age
older people have less arterial compliance
when pressure increases in the vessels that do not expand as much
Less compliant vessels with age - reduced arterial compliance = hypertension
whoops
whoops
why does hypertension increase with age
as you age the vessel wall has less and less elastin and more collagen
the collagen that you get with ageing is different to the normal collagen in the wall as this collagen is stiffer as it makes more crosslinks
collagen is 1000x stiffer than elestin therefore with the increase in collagen and the decrease in elestin you REALLY increase the stiffness of the arterial wall increasing peripheral resistance therefore causing hypertension
describe collagen as we age
the collagen that you get with ageing is different to the normal collagen in the wall as this collagen is stiffer as it makes more crosslinks
collagen is 1000x stiffer than elestin therefore with the increase in collagen and the decrease in elestin you REALLY increase the stiffness of the arterial wall causing increase in resistance
normal blood pressure is 120/80
Elevation in peripheral vascular resistance
(due to decrease in arterial compliance) can increase the systolic and diastolic pressures by how much
DAP + 10-40 mmHg
SAP + 50-100 mmHg
what are flow waves
they are generated by the heart in systole when it pumps out blood
flow waves are the flow of blood
In systole, flow waves are generated by the heart
what is their relationship with the compliance of the aorta
Storage of stroke volume in conduit vessels – distensibility of aorta
In diastole, recoil of aorta maintains capillary flow
describe flow waves in the aorta vs the capillaries
why is this
Pulsatile flow into the aorta, but continuous/constant flow through the capillaries
Compliance of the aorta is essential to dampen the pulsatile flow wave of the heart
in hypertension the systolic pressure increases more than the diastolic pressure, why is this
The aorta is the major contributor for dampening the pulsatility of the heart
With hypertension the aorta becomes stiffer therefore there is not storage of SV during systole. once the valve closes then there is no flow through the aorta as there is little elastic recoil
Therefore the aorta becomes less flexible with age which increases and decrease the pressure therefore creating pulsatile flow
what is hypertensions effect on gas exchange in the capillaries
it causes the capillary flow to become pulsatile which is bad for exchange (decreases it)
this is because the aorta is not acting as an elastic reservoir
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.
B
what is a pulse wave
they are generated by the heart, independent of blood flow (not a flow wave)
this is the contraction moving through the wall of the vessel
what are the velocity values of a flow wave compared to a pulse wave
flow wave = 0-20cm/s
pulse wave 2-12m/s
note PW is in m/s and flow is cm/s
in the aorta how many x faster is the pulse wave compared to the flow
100x
what happens when a pulse wave hits a bifurcation
a reflection wave is formed
describe the forward and reflected wave
these are both pulse waves
when the forward wave his a bifurcation it forms a reflected wave which moves in the opposite direction
the reflected wave is always slightly behind the forward wave
what is the observed wave
it is the combonation of the forward and the reflected wave
this is what you measure when you are taking blood pressure
Proximal vessels compliant whereas the Distal vessels are stiffer
what does this mean in terms of the pulse waves
Pulse wave travels faster in distal than proximal vessels
Aorta 3-5 m/s
Radial artery 5-12 m/s
this is because the stiffer the vessel the faster the wave
what does the diffeent stiffness of the vessels mean fo the observed blood pressure
Distal vessels are stiffer (faster pulse wave) they have larger contribution of reflections compared to proximal vessels meaning that the pressure in the distal arteries will be slightly higher
this is a minor difference (5-10mmHg) compared to the classification of hypertension which has ranges of 20mmHg (therefore you don’t have to worry about it that much)
describe pulse wave velocity as we age
Reduced compliance of conduit arteries increases pulse wave velocity
higher contribution of reflected wave
The observed wave will be higher because of stiff arteries which they will contribute more to reflection
who does the reflected wave being faster increase the observed wave (and therefore BP)
the more the waves overlap the more they add together
when the wave is faster it adds together with the forward wave more
in compliant vessels what happens when the reflected wave is reflected back to the heart
normally when the reflected wave reaches the heart the valves are closed therefore it contributes to
when the reflected wave comes back in increases the BP slightly and enters the coronary circulation
in hypertension what happens when the reflected wave is reflected back to the heart
As the arteries become more stiff there is a greater observed wave and pulsatility of the capillaries. This means that the reflected wave will be reflected back before the valves close which will increase afterload.
the coronary blood supply is affected in this as well
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
the first statement should say increases
therefore the first statment is incorrect and the second statment is correct
