Biochemistry Flashcards
What is hypertension a major risk factor for?
- Stroke
- IHD
- HF
- CKD
- Cognitive decline
- Premature death
- CAD
- Myocardial ischaemia
What is a hypertensive urgency?
- 180mmHg systolic or 110mmHg diastolic
- Symptoms include headache, SOB, nosebleed, severe anxiety
- Management: oral medication, outpatient
What is a hypertensive emergency (malignant)?
- Target organ damage - brain, heart, kidneys
- Systolic 180mmHg or diastolic 120mmHg
- Encephalopathy can occur - cerebral arteries lose ability to regulate blood flow in cerebral capillaries and so leaking of fluid into interstitial space > cerebral oedema > increased pressure > brain dysfunction
What is the function of beta receptors in the heart and blood vessels?
- Heart: increased contractility (adenylate cyclase > ATP>cAMP > protein kinase A > Ca)
- Blood vessels: release of cAMP causes relaxation of the artery
Where are baroreceptors found?
Nerve endings in all thoracic and neck arteries. 2 major populations: carotid sinus and arch of aorta. They are activated on stretch e.g. high BP.
- They are important in maintaining postural BP
Describe chemoreceptors
- Sensitive to low O2, high CO2 and acidosis
- Chemoreceptor organs: 2 carotid bodies (in each bifurcation), 1-3 aortic bodies
- Reduction in blood flow (<80mmHg) causes metabolic stimulation
What is the atrial volume reflex?
Atrial stretch to pressure causes:
- Reflex dilation of renal afferent arteriole causing increased glomerular capillary pressure > increased filtration of fluid to renal tubule so fluid loss by kidneys
- Reduced secretion of anti-diuretic hormone from hypothalamus causing reduction in water resorption from renal tubule > fluid loss by kidneys
What is the role of angiotensin II?
Increased sympathetic activity, tubular NaCl reabsorption and K excretion with H2O retention, aldosterone secretion and is a potent vasoconstrictor. Causes the release of ADH secretion from the posterior pituitary which causes resorption of water from the collecting ducts.
What is hyperaldosteronism?
Increased aldosterone > decreased K and decreased H = hypokalaemic alkalosis
What are the causes of hyperaldosteronism?
- Unilateral aldosterone producing adenoma or Conn’s syndrome (50-60%)
- Bilateral adrenal hyperplasia (40-50%)
What are the pathologies caused from type 2 diabetes and hypertension?
- Increase in wall thickness
- No change in lumen diameter
- Impairment of endothelial function
What are the pathologies caused from essential hypertension?
- Increase in wall thickness
- Reduction in lumen diameter
- Increase in wall to lumen ratio
- Preservation or mild impairment of endothelial function
What are the renovascular causes of secondary hypertension?
- Acute elevation in serum creatinine (at least 30%) after ACEi or ARB
- Diffuse atherosclerosis, unilateral small kidney or asymmetry in renal size of more than 1.5cm that cannot be explained by another reason
- Recurrent flash pulmonary oedema
- Abnormal urinalysis
What drugs cause a temporary rise in BP related to use?
- Oral contraceptive pill
- NSAIDs
- Stimulants e.g. cocaine, methylphenidate
- Calcineurin inhibitors
- Antidepressants
What conditions cause elevated BP?
- Pheochromocytoma (tumour of adrenal gland) - triad of headache, palpitations and sweating
- Primary aldosteronism - unexplained hypokalaemia with urinary K wasting
- Cushing’s syndrome - central obesity, proximal muscle weakness and ecchymoses
- Sleep apnea syndrome - daytime somnolence, fatigue and morning confusion
- Coarctation of aorta - diminished or delayed femoral pulses, low or unobtainable BPs in legs
- Hypothyroidism
- Primary hyperparathyroidism - elevated serum calcium
