Hypertension Flashcards
What is hypertension and what is the normal adult BP range
Sustained increase in blood pressure
Between 90/60 and 120/80mmHg
What are the three classifications of hypertension and what are the BPs associated with them
Stage 1 = >140/90
Stage 2 = >160/100
Severe = >180 systolic or >110 diastolic
How are the causes of hypertension classified
Primary - cause is unkown
Secondary - cause can be defined
Name some diseaes attributable to hypertension
Heart failure
Stroke
Cerebral haemorrhage
Chronic kidney failure
Coronary heart disease
Myocardial infarction
Left ventricular hypertrophy
Aortic aneurysm
Peripheral vascular disease
Myocardial ischaemia
What controls an acute change in BP
The baroreceptor reflex
How is BP controlled in the medium and long term
Through interaction of neurohumoral responses directed at controlling sodium balance and extracellular fluid volume
What are the four neurohumoral pathways that control circulating volume and BP
Renin-angiotensin-aldosterone system
Sympathetic nervous system
Antidiuretic hormone (ADH)
Atrial natriuretic peptide (ANP)
What causes renin release
Reduced NaCl delivery to distal tube
Reduced perfusion pressure in kidney
Sympathetic stimulation to JGA
Where is renin released from
Granular cells of juxtaglomerular apparatus
How does the renin-angiotensin-aldosterone system work
Angiotensinogen found in blood is converted to angiotensin I by renin
Angiotensin converting enzyme in lungs converts Ang I into Ang II
Ang II acts at AT1 receptor causing vasoconstriction, stimulates Na+ reabsorption in kidney, stimulates aldosterone, causes increased release of NA, increases thirst sensation (ADH release)
What are the actions of aldosterone
Acts on principal cells of collecting ducts
Stimulates Na+ and water reabsorption
Activates apical Na+ channel [epithelial Na channels (ENaC)] and apical K+ channel
What is one of the side effects of using an ACE inhibitor and why
Causes a dry cough
Inhibiting ACE means bradykinin is not broked down by ACE into peptide fragments, so its levels rise causing the dry cough
How does the SNS control BP
High levels of SNS stimulation reduces renal blood flow by vasoconstriction of arterioles and decreased GFR, both of which raise BP
Actives apical Na/H-exchanger and basolateral Na/K-ATPase in PCT
Stimulates renin release
How is ADH involved in control of BP
Involved in formation of concentrated urine by retaining water to control plasma osmolarity - increases water reabsorption in distal nephron
Stimulates Na+ reabsorption - thick ascending limb, stimulates apical Na/K/H co-transporter
Causes vasoconstriction
How is ADH release stimulated
Increased plasma osmolarity
Severe hypovolaemia
How do natriuretic peptides control BP
ANP promotes Na+ secretion reducing the circulating volume
They are released by atria cells in response to strech with more released at higher BP
What are the actions of ANP
Vasodilation of afferent arteriole of kidney
Increased blood flow increaes GFR
Inhibits Na+ reabsorption
What are prostaglandins and what are their functions
Are vasodilators - buffer to excessive vasoconstriction
Enhance glomerular filtration
Reduce Na+ reabsorption
Where is dopamine produced and what are its affects
Formed in kidney from L-DOPA
Receptors are present on renal BV and cells of PCT and TAL
Cause vasodilation and increase renal flow
Reduce reabsorption of NaCl by inhibiting NHX and N-K-ATPase
Name some diseases/syndromes which cause hypertension
Renovascular disease
Renal parenchymal disease
Conn’s syndrome
Cushing’s syndrome
Tumour of adrenal medulla
What happens in renovascular disease to cause hypertension
There is renal artery stenosis causing a fall in perfusion pressure to that kidney
This causes an increased renin production - activation of renin-angiotensin-aldosterone system
Results in vasoconstriction and Na+ retention at other kidney
How does renal parenchymal disease cause hypertension
Na+ and water retention dje to inadequate glomerular filtration
What are some non-pharmacological approaches to treating hypertension
Exercise
Diet
Reduced Na+ intake
Reduced alcohol
What can you use to target the RAA system
ACE inhibitors
Ang II receptor antagonists
Name some vasodilators
L-type Ca2+ channel blockers - reduce Ca2+ entry to vascular SM causing relaxtion of them
Alpha-1 receptor blockers - reduce sympathetic tone
Name some diuretics
Thiazide diuretics - reduce circulating volume, inhibit Na/Cl transporter on apical membrane of cells in DT
Aldosterone antagonists
What do beta blockers do
Block B1 receptors in heart to reduce effects of sympathetic output - reduce rate and contractility
