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What is the kidney's role in regulating BP? (p.20)
What mechanisms are involved?
- Renin-angiotensin system
- Sodium homeostasis
- Renal vasodepressor substances (dilators)
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Humoral factors - constrictors
(BP regulation)
- Increase BP
- Include:
- - Angiotensin II - most powerful vasoconstrictor
- - Catecholamines
- - Thromboxanes
- - Leukotrienes
- - Endothelin
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Humoral factors - Dilators
(BP Regulation)
- Decrease vascular resistance = decrease BP
- Include: relaxing factors
- - Prostaglandins (PG)
- - Kinins
- - Nitric oxide/EDRF
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Volume factors
(BP Regulation)
- Sodium = eat a lot of salt --> drink a lot of water --> retain volume
- Mineralcorticoids = steroids encourage Na+ retention --> retain volume
- Atrial natriuretic peptide (ANP) = encourages volume retention
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What are determinants of arterial blood pressure? (p.19)
- BP = cardiac output (CO) x peripheral resistance (PR)
- Influenced by:
- - blood volume
- - humoral factors
- - cardiac factors
- - neural factors
- - local factors
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What effect do humoral factors have on renal vasculature? (e.g., PGE2) (p.20)
- PGE2 (prostaglandin E2) - relaxing factors
- - cause vasodilation, primarily of afferent arterioles
- - improves glomerular blood flow
- - decreases ischemia
- - counterbalance effects of vasoactive agents like renin, endothelin, and angiotensin
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Essential hypertension (p.19)
- 90% of people with elevated BP
- Idiopathic
- Precise cause not known or clearly understood
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Secondary hypertension
- 10% of people with elevated BP
- Most usually due to renal disease
- Sometimes narrowing of renal artery from atheromatous plaque
- Rarely caused by adrenal disorders:
- o Aldosteronism (excess aldosterone)
- o Cushing’s
- o Pheochromocytoma
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What physiologic factors contribute to essential hypertension?
Combination of lifestyle factors and genetic defects that interact to increase BP
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Established risk factors for hypertension: (p.21-22)
- Genetic factors
- Racial factors – more prevalent in black
- Age/sex
- - 35-45 years
- - Sex – more common in females (better prognosis for females; males 1.5-2 times mortality)
- Environmental: Stress – living in urban areas
- Diet – obesity and salt
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Treatment and management of hypertension
- Rule out secondary causes
- Do serum Na+/K+, Mg2+, Ca2+ (maybe RBC Mg2+)
- Decrease weight if obese
- Decrease ratio of NaCl to K+
- - Increase food low in NaCl
- - Increase food high in K+ (like tubers, roots, cereal grains, seeds, nuts, and fruits – apples) – also high in Mg2+
- Program of regular exercise
- - Maintain ideal weight
- - Improve insulin resistance
- Avoid alcohol if heavy drinker
- Smoking cessation
- Oral contraceptives –
- - Possible estrogen and progestin facilitation of Na+ and H2O retention secondary to increased plasma renin activity
- Drug therapy if necessary
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What effect will cytosolic Ca2+ and Mg2+ have on arterial smooth muscle cells? (p.23)
Calcium stimulates contraction of smooth muscle cells
Magnesium causes dilation
- Calcium stimulates contraction of smooth muscle cells
- Magnesium causes dilation
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