L26 Flashcards
what are they 2 types of hypertension and what % of people with hypertension have each type
primary hypertension = 95% of people
secondary = 5%
what causes primary hypertension
the cause is unknown = idiopathic essential
it happens with stiffer arteries with ageing
what causes secondary hypertension
this has specific causes
the 2 main causes of primary hypertension are an increase in arterial blood volume and a decrease in arterial compliance
which is the most important factor
we don’t know between these 2
Salt retention in kidney = increase in blood volume
autoregulation result in arteriolar vasoconstriction
arterial compliance decrease = increase in total peripheral resistance (TPR)
how do these processes relate to each other
Sympathetic activation of the arterioles (hypothalamus-medulla oblongata) = arteriolar vasoconstriction -> arterial compliance decrease -> increase TPR
this causes less blood flow to kidney = release of vasoactive substances and salt retention which increase blood volume
These are not mutual inclusive or inclusive
This indicates the important of the kidney and arterial compliance and sympathetic activation pathway in hypertension. therefore they are both as important as each other
Sympathetic is being activated during moderate exercise
what does this cause
In the vessels we have vasodilation is some vascular beds to that the tissues get more O2 but constriction in other vascular beds
As a consequences of sympathetic activation and excerise means that TPR decreases. This means that during moderate exercise arterial pressure is kept constant. It increases slightly during intense exercise
The increase in overall sympathetic activity then HR goes up SV goes up and MAP goes up
BP is very similar in all mammals
what is an example where this is not the case
a giraffe
their MAP is 172-200mmHg
giraffes are not born hypertensive (they are born normotensive)
why do they develop high blood pressures
because of their neck
As giraffe grows, blood flow to cardiovascular brainstem reduces, due to effects of gravity
Sympathetic nerve outflow increases to cause nerve-mediated hypertrophy of vessel wall (G-suit)
Increase in TPR, and thereby MAP, to preserve cerebrovascular flow
tibbia artery will have massive wall and small luman
carotid artery will have huge luman
giraffes have to put thei heads down to drink
how do they overcome this problem
Minimise blood flowing back into head:
Upper neck - rete mirabile
Jugular veins - seven valves
Lower legs - great pressures
Very tight sheath of thick skin over lower limbs
maintain high extravascular pressure
what are some consequences of hypertension
- Kidney disease
- Development of Atherosclerosis – Stroke
- Atrial Fibrillation
- Myocardial Infarction / Coronary artery disease
- Cardiac Remodelling (Hypertrophy - Heart Failure)
why do you get cardiac remodelling of the heart in hypertrophy
Increases workload (afterload) of the heart because of the stiffer tube (aorta) to eject blood into causing a faster returning reflected pulse wave
it is also because of higher resistance to the output
what ae the 2 ways of cardiac remodelling
there is remodelling at the cellular level
OR
remodelling at the organ level
what is cellular remodelling of the heat
hypertrophy of the cardiac myocytes
or hypertrophy because of fibrosis (this passably could be organ remodelling)
describe hypertrophy of the cardiac myocytes
Increase in number of sarcomeres in the cardiomyocytes (size)
NOT in number of cardiomyocytes or the size of the sarcomeres (might even be less cardio myocytes because of apoptosis)
what causes fibrosis in the heart
If the hearts is under increased load there are tiggers to make more fibrosis
This is because you are the making the cells bigger but you also need to make the scaffolding bigger to support them
hypertrophy cased by fibrosis causes an increase in the extracellular matrix
what does this contain
Collagen type I + III Elastin Proteoglycans Laminin Fibronectin
what collagen type increases first in fibrosis
type 3 and then type 1
i think type 3 is the stiff one
what is the difference between concentric and eccentric remodelling
concentric = wall thicker
eccentric = luman bigger
does pressure overload cause concentric or eccentric remodelling
concentric
does volume overload cause concentric or eccentric remodelling
eccentric
what does pressure overload cause
thickening of the LV and no dealation in early stages of disease
what does volume overload cause
thinning of the LV and significant dilation
this is usually because there is something wrong with the valve
what is hypertrophic cardiomyopathy caused by
predominantly genetic mutations
what does hypertrophic cardiomyopathy cause
gross thickening of the LV walls with no dilation/decrease in LV chamber size
