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Major Danger of HTN II
Strokes especially those prone to aneurysms
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BP Regulating Mechanisms
-Short Term Mechs
-Long Term Mechs
- -Sympathetic nervous system, baroreceptors, Vascular endothelium
- -Renal and Hormonal Processes
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Norepinephrine
-Effects on α-1, α-2, ß-1, ß-2, dopamine receptors
- A short term BP regulating mechanism part of the Sympathetic Nervous system.
- α-1 Vasoconstrict, ↑contractility
- α-2 Vasoconstrict
- ß-1 ↑ contractility, HR, conduction, renin secretion
- ß-2 Vasodilation
- Dopamine Vasodilation
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Baroreceptors
-Location
-↑ BP effects
-↓ BP effects
-Long term HTN effects
- Short term BP regulatory mechanism
- -Carotid aorta and aortic arch
- - Inhibitory impulses sent to sympathetic vasomotor complex in the brain-- causes decreased HR and Contractility and peripheral vasodilation
- - Stimulates kidneys to release renin which cause peripheral arteries to contract, increased HR and contractility.
- -Desensitizes receptors will not respond to increased BP so inhibitory impulses will not be sent to brain and BP will not be lowered by this mechanism.
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Vascular Endothelium
Releases vasoactive substances and growth hormones in response to changes in the arteries including Nitric Oxide, Endothelin, Prostacyclin
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Nitric Oxide
- Released by vascular endothelium
- Keeps arterial muscle wall relaxed at rest, inhibits smooth muscle growth, inhibits platelet aggregation
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Prostacyclin
- Released by vascular endothelium
- Vasodilates
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Endothelin
- Released by vascular endothelium
- Vasodilates
- -ET-1 is most potent vasodilator, also stimulates smooth muscle growth and neutrophil aggregation.
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RAAS
- Long term BP regulatory mechanism.
- Baroreceptors in the Kidneys release renin in response to hight BP.
- Renin converts Ang 1 to Ang 2
- Angiotensin II vasoconstricts which increases SVR and BP
- Angiotensin II also stimulates the release of aldosterone from the adrenals which tells the kidneys to retain Na and H2O which increases ECF, Blood Volume and BP
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Epinephrine
Increases HR and Contractility--> CO
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Isolated Systolic Hypertension
- Systolic > 140 while Diastolic <90
- Common in the elderly as SBP rises with age
- DBP increases until ~ 55yo then declines due to decreased elasticity and arteriosclerosis
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Pseudohypertension
- When the blood pressure cuff isn't able to occlude sclerotic arteries resulting in higher readings.
- An intraarterial catheter may be used to measure BP in these pts.
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Why Age increases BP
- Arteriosclerosis/atherosclerosis increasing with age
- – After age 50, SBP>140 is more important than DBP
- – ↓ elasticity in large arteries due to atherosclerosis
- – ↑ collagen and stiffness of myocardium
- – ↑ PVR
- – ↓ adrenergic receptor sensitivity, baroreceptor reflexes
- – ↓ renal function = ↓ renin response to Na/H20 depletion,excretion of meds prolonged
- – ↓ blood flow to gut = ↓ med absorption
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