Hypertension Flashcards
What are the types of hypertension?
-primary/essential
-secondary
-whitecoat
-malignant
-masked
define hypertension
The chronic elevation of arterial blood pressure and can exist in either the pulmonary or systemic vascular system
What two mechanisms is BP usually regulated by?
-nervous system with afferent and efferent pathways
-humoral using the kidneys and adrenal glands
What 4 systems are directly responsible for influencing BP?
-cardiac-generates pressure
-blood vessels-systemic resistance
-kidneys-intravascular volume
-nervous and humoral -regulating the function s of the other three systems
What does RAAS mean?
renin-angiotension-aldosterone-system
Describe the role of Renin in blood pressure regulation
-produced near the renal blood vessels that enter the glomerulus- the juxta glomerular apparatus
-main stimulus to renin production is a reduced blood flow or volume- sensed as a lowered renal perfusion pressure
-renin converts angiotensinogen (produced by liver) to a physiologically inactive polypeptide- angiotensin1 changed in the lungs to angiotensin2
Describe the role of angiotensin II in the control of BP
-its a powerful vasoconstrictor
-stimulates brain to activate the thirst sensation, enhances contractility of the heart
-promotes supranenal glands to produce more aldosterone
-this substance causes sodium and water retention, increasing circulating plasma volume and raising BP
-increase in aldosterone reduces renin production
What’s the standard hypertension figure?
140/90 mmHg
Describe primary/essential hypertension
-no known cause
-multifactorial and could be linked to genetics, environment, nutrition
-foetal factors, low birth weight caused by the environment e.g in the placenta or mothers nutrition
-no known therapy has been identified to treat or cure essential hypertension
Describe secondary hypertension
-high BP directly attributed to a cause.
-can be caused by, renal diseases,cushing disease, aldosteronism, phaeochromocytoma, catecholamine secreting tumours usually in the adrenal medulla, pregnancy, hyper or hypo thyroidism
What are some indications of secondary hypertension?
-age- before 20 or after 50
-severity- more severe than essential hypertension
-onset- more sudden
-signs/symptoms
-family history
What is white coat hypertension?
-anxiety can easily influence BP by greater than 30mmHg SBP
-cant be influenced by reassurance or familiarisation
-can occur in normotensive and hypertensive patients
-fight or flight reaction increases BP by 50-60mmHg
What is malignant hypertension?
DBP>120mmHg
-leads to kidney damage, retinal haemorrhage, optic nerve swelling
-patients can present with renal or heart failure
-considered a medical emergency, without effective treatment <20% patients survive a year
What is masked hypertension?
normal BP on presenting in clinic but elevated measurements out of the clinic
Whats the equation for BP?
BP= CO x Peripheral resistance
What are the four main factors effecting BP?
-blood volume
-peripheral resistance
-elasticity
-viscosity
how does blood volume influence BP?
if circulating volume increases, more pressure is exerted against arterial walls.
How does peripheral resistance influence BP?
arteries and arterioles are surrounded by smooth muscle hat contracts and relaxes to change the diameter of the lumen , hence resistance and poisselles law.
How does elasticity influence BP?
as the pressure within arteries increases, the diameter of vessels increases to accommodate the pressure change
How does viscosity influence BP?
-effects the ease with which blood flows through small vessels, the percentage of haematocrit in the blood determines its viscosity
Name some local regulators that lower BP
nitric oxide
-hydrogen ions
-adenosine
Name some local regulators that increase BP
oxygen
endothelin
What major organs does hypertension effect?
-heart
-blood vessels
-kidney
-retina
How does hypertensive retinopathy occur?
existing high BP causes changes to the microvasculature e.g rupture of the small retina vessels
-can cause visual impairment
