Cardiovascular strand: Lecture 10 - blood pressure control Flashcards
What is blood pressure?
- driving force propelling blood to tissues
- delicate balance between organ perfusion ad vascular damage (if BP is too high)
- closely autoregulated
How do we calculate total resistamce to blood flow?
R = 8nL/ πr^4
where r = restistance
N = viscosity of blood
L = length of blood flow
r = radius of blood vessel
Whats the relationship between radius of blood vessel and total peripheral resistance?
slightly reducing the radius will largely increase the total peripheral resistance
What factors can alter blood pressure?
- heart rate
- stroke volume
- cardiac output
- total peripheral resistance
- mean systemic arterial pressure
We must balance any changes to maintain consistent organ perfusion pressure
What test can you do to check for heart failure and how does it work?
BMP - Brain natruitic peptide
Levels of BMP are high during heart failure
How do naturituretic peptides work?
- induce excreton of Na+ in the urine
- they reduce the central venous pressure
this means you pee out more water which reduces pressure in the system therefore reducing blood pressure
What are the two types of natriuretic peptides?
ANP -Atrial natriuretic peptide
BNP - Brain natriuretic peptide
When are the natriuretic peptides released?
Released when myocytes are mechanically stretched by increased plasma volume
Why does hypertension occur?
When BP control mechanisms are dysfucntional or are unable to compensate for stressors on body
At what value of BP is hypertension confirmed?
when SB > 140 mmHg and/or DBP > 90mmHg
What is the prevelance of hypertension in the populatuon and what are the most common reversible risk factors?
- 30-45%
- Most common reversible risk factors: IHD, CVA, CCF, AF, PVD
Explain the two types of hypertension classification?
Primary and secodnary
Give 5 features of primary hypertension
- 90% of cases
- over-activaton of physiological mechanisms
- age related decrease in barorecetor sensitivity
- age-related vascular calcification
- vessels get more stiff
- no identifiable cause
Give 5 features of secondary hypertension
- 10% of cases
- secondary is related to someting else that is causing high BP
for example:
- renal e.g renovascular disease
- endocrine e.g cusings syndrome, coarctation of the aorta
- tumour
- pregnancy
How do we classify the severity of hypertension?
Grade I (least severe) - Grade III (most serve)
What problems on the heart can arise from having high blood pressure?
- LVH (left ventricular hypertrophy) - heart muscle can get thicker to try to pump blood at such high pressures
- diastolic dysfunction - if the ventricle is stiff and thick it won’t be able to relax well enough
- hypertensive heart failure
What is Laplace’s Law?
ask about this
for any given LV cavity pressure (P), the wall stress will be directly proportional to the LV cavity size or radius (R) and inversely proportional to the LV thickness (T)
so…
LVH increases LV thickness, reduces LV cavity radius and therefore reduces wall stress
wall stress = surface tension
What problems can high blood pressure have on vessels?
prolonged hypertension causes vascular remodelling
blood vessels get thicker and bigger to reduce stress
In small arteries - eutropic remoddeling: media to lumen ratio goes up
In large arteries - hypertrophic remoddeling: muscles in the wall get hypertrophy and you have narrowing of blood vessels so the systemic resistance goes up
What is hypertension?
Cells get bigger, they don’t increase in number
If you have high blood pressure, what vascular conditions are you more likely to get?
Atherosclerosis (hardening of arteries) and large vessel strucural damage
What other conditions can atherosclerotic disease manifest into ?
What problems can high blood pressure have on the kidney?
hypertensive nephropathy:
-renal arterial thickening - luminal narrowing
resulting ischaemia (redcued blood supply to kidneys) - tubular atrophy (wasting away) & interstitial fibrosis
damage to glomeruli - haemoproteinuria
How can high blood pressure cause eye problems?
Papilloedema - optic disc swelling due to increased intracranial pressure
Exudates - fats of blood on retina
Flamed haemorrhages - bleeding
Cottom wool spot - caused by damage to nerve fibres
