Controlling BP Flashcards
Outline short term physiological BP control systems
Baroreceptor reflex alters sympathetic and parasympathetic stimulation of the heart. Sympathetic effects vasoconstriction levels as well.
List long term BP controllers.
Neurohumeral responses control extracellular Na+. These include: RAAS Sympathetic innervation ADH Naturetic peptides Prostaglandins Dopamine
What is hypertension?
Sustained increase in BP
How do we classify hypertension?
Stage 1 >140/90
Stage 2 >160/100
Stage 3 >180/110
Limits are lower if measured at home to account for white coat effect.
What causes hypertension?
95% is primary and unknown
5% is secondary to renal disease, renovascular disease, hyperaldosteronims or Cushings.
What can we target in HTN treatment?
In secondary- treat the cause
In primary- lifestyle advice, diuretics, L type Ca channel blockers, alpha antagonist, beta blockers, ACE inhibitors, AngII receptor blockers
What effect does angiotensin II have on the hypothalamus?
Increase thirst by increasing ADH secretion
How does aldosterone work?
Acts on principle cells of the kidney to stimulate Na+ and water reabsorption by activating Epithelial Na Channels or ENaCs. Increases extrusion through the basolateral membrane by Na/K-ATPase.
What is bradykinin and how does it interact with ACE?
ACE breaks down bradykinin which is itself a vasodilator.
What suffix to ACE inhibitor drugs have?
-pril
How does sympathetic innervation control BP
Increase HR and force of contraction
Increase TPR
Vasoconstriction means reduced renal perfusion stimulating JGA
Directly stimulates Renin release from JGA- activate RAAS
Activates apical Na/H exchangers and the K/NA pump in PCT.
How does ADH control BP.
Stimulates thirst which increases blood volume and increases SV which increases CO so BP increases
How does ADH control BP.
Stimulates thirst and helps retain water. Sodium is retained in the thick ascending limb due to stimulation of the NA/K/Cl co-transporter. Has direct vasoconstriction effects. All of which increases blood volume and increases SV which increases CO so BP increases
What stimulates ADH production?
Increase plasma osmolarity
Hypovolaemia
What effect so naturetic peptides have on BP?
Decrease BP
Which natural systems increase BP?
baroreceptor reflex- acutely
ADH
RAAS
Sympathetic stimulation
ANP is released in response to….
atrial stretch
What does ANP do?
Vasodilates afferent arteriole of kidney.
GFR thus gets more blood so less renin release.
Inhibit sodium reabsorption
Lose sodium in urine
How do prostaglandins affect BP?
Vasodilate
Reduce sodium reabsorption
So increase BP
Buffer excessive constriction in RAAS or sympathetic systems.
Dopamine is given to Parkinsons patients but how does it effect BP?
Vasodilator which increases renal blood flow and reduces NaCl reabsorption. Inhibits NHX and NA/K ATPase in PCT and TAL of kidney.
Lowers BP
What proportion of people get high BP?
1/3
What factors increase risk of primary HTN
Genetics
Enviromental
What happens in renal disease to cause HTN?
Vasodilators lost in early stages but in the late stages the glomerular filtration fails and sodium is retained.
What is Conn’s syndrome?
Aldosterone secreting adenoma
What are the signs of Conn’s?
Hypertension
Hyperkalaemia
What is Cushings?
Excess cortisol
Why does bushings give HTN?
at high conc glucocorticoids like cortisone may act on aldosterone receptors in the kidney and cause Na+ retention .
What tumour of the adrenal medulla secretes catecholamines?
Phaeochomocytoma
Why treat HTN?
Damages heart and vessels so if left untreated potential for: MI Stroke Renal failure Retinopathy
High systolic BP associated with increased…. rate
mortality
How does HTN lead to left ventricular hypertrophy and increased oxygen demand from heart tissue?
Increases after load so heart has to work harder to push against it
What is a side effect of left ventricular hypertrophy?
Heart failure
How can MI or ischaemia of myocardium occur in hypertensives?
Hypertension increases after load.
Heart has to work harder and so needs more O2.
Higher O2 demand is harder to meet so risk hypoxia.
How can MI or ischaemia of myocardium occur in hypertensives?
Hypertension increases after load.
Heart has to work harder and so needs more O2.
Higher O2 demand is harder to meet so risk hypoxia.
The high BP damages arteries and increases risk of atherosclerosis.
Atherosclerosis increases risk of MI.
Why do you get micro vascular haemorrhages in hypertension?
Artery walls damaged and become leaky or become anerysmic
List non pharmacological HTN treatments
Diet
Exercise
Reduce Na+ intake
Reduce alcohol intake
Lifestyle changes should always be advised even in conjunction with pharmaceuticals because lifestyle limits the therapeutic effects of drugs.
List non pharmacological HTN treatments
Diet
Exercise
Reduce Na+ intake
Reduce alcohol intake
If you are treating HTN with tablets why do you always give life style advice with drug therapy for hyper tension and not just drugs?
Lifestyle changes should always be advised even in conjunction with pharmaceuticals because lifestyle limits the therapeutic effects of drugs.
How do you treat HTN targeting the RAAS?
ACE inhibitors
AngII receptor antagonists
L type calcium channel blockers may be used in hypertension, what is the mechanism of action?
Reduce Ca2+ entering vascular smooth muscle- vasodilate
What is the side effect of vasodilating using alpha 1 blockers?
postural hypotension
What is bendroflumethazide and how does it work?
thiazide diuretic reduces circulating volume to reduce BP.
Give an example of an aldosterone antagonist and indicate if its a first line treatment for HTN?
Spirinolactone
Not first line
What circumstance would you give a beta blocker for HTN?
If they have other indications like history of MI
