drugs for hypertension. a. introduction hypertension (ht) is defined as a sustained elevation of...
Post on 30-Dec-2015
Embed Size (px)
Drugs for hypertension
Drugs for hypertensionA. IntroductionHypertension (HT) is defined as a sustained elevation of systemic arterial blood pressure.
There are 2 components of blood pressure: systolic and diastolic:Systolic pressure: ventricles contract and eject blood, creating pressure in the arteriesDiastolic pressure: ventricles relax, heart temporarily stops ejecting blood, pressure in arteries falls
One in three adults in the U.S. have been diagnosed with HT, making this the most common of the cardiovascular diseases.
HT is usually found incidentally by healthcare professionals, and it is estimated that up to 30% of people with HT do not know they have it.
B. Factors affecting blood pressureThere are 3 major factors which affect blood pressure1. directions from vasomotor center, based on input from baroreceptors 2. emotions3. hormonal/enzyme factors
1. Vasomotor centerVasomotor center: this is a cluster of neurons in the medulla oblongata which regulates blood pressure on a minute to minute basis
Nerves travel from the medulla oblongata to the arteries and direct smooth muscle to constrict ( blood pressure) or relax ( blood pressure)
Baroreceptors are clusters of neurons in the aorta and carotid artery that have the ability to sense blood pressure within these vessels and then provide the vasomotor center with this information
2. EmotionsEmotions can affect an individuals blood pressureMental depression and lethargy may cause B.P. to decrease.
Anger and stress may cause an increase in blood pressure, and if present for a long time may contribute to chronic hypertension.
3. Hormonal/Enzyme factorsa. Renin-angiotensin-aldosterone (RAA) pathwayThis is the primary homeostatic mechanism controlling blood pressure and fluid balance
When there is a in blood pressure or blood volume (due to hemorrhage, dehydration, etc) the enzyme renin is released by the kidneysRenin acts on angiotensinogen (produced by liver) converting it to angiotensin I (inactive)
In the lung capillaries, angiotensin converting enzyme (ACE) modifies angiotensin I to angiotensin II (active)
Angiotensin II then:a. stimulates secretion of aldosterone which causes Na1+ retention and H2O reabsorption at kidneys
b. stimulates the secretion of ADH (vasopressin) which is synthesized in the hypothalamus and stored in the posterior pituitary, leading to H2O reabsorption
c. stimulates hypothalamus to activate the thirst reflex
b. atrial natriuretic peptide(ANP)
An in blood pressure or blood volume leads to a stretching of the cardiac muscle fibers in the walls of the atria They release ANP, whose 3 effects are the opposite of angiotensin II:
a. ANP enhances the secretion of Na1+ and H2O at kidneys
b. ANP inhibits the secretion of aldosterone and ADH
c. ANP suppresses thirst
C. Diagnosis of hypertensionA new classification scheme was introduced in 2003:CategorySystolic DiastolicNormal< 120