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Renin Angiotensin Aldosterone System
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1
Question
What is the primary function of the Renin-Angiotensin-Aldosterone System (RAAS)?
Answer
The RAAS is central in the regulation of blood pressure, electrolyte balance, and blood vessel and heart remodeling.
2
Question
Describe the basic structure of the nephron from start to finish.
Answer
The basic structure of the nephron is the glomerulus, proximal tubule, loop of Henle, distal tubule, and collecting duct.
3
Question
What is the glomerulus and how does blood flow through it?
Answer
The glomerulus is at the start of the nephron where afferent arterioles bring blood in and efferent arterioles drain blood out; fluid filters from the blood into Bowman's capsule, forming filtrate.
4
Question
What happens to the filtrate as it travels along the nephron?
Answer
The filtrate travels along the nephron where various chemicals are secreted and reabsorbed before draining through the collecting ducts as urine.
5
Question
Where are juxtaglomerular cells located and what do they sense?
Answer
Juxtaglomerular cells are found at the afferent arterioles and sense the blood pressure in the afferent arterioles.
6
Question
What enzyme do juxtaglomerular cells secrete and under what condition?
Answer
Juxtaglomerular cells secrete renin when blood pressure is low; they secrete less renin when blood pressure is high.
7
Question
What protein does the liver produce that renin acts on?
Answer
The liver produces angiotensinogen, which renin converts to angiotensin I.
8
Question
How is angiotensin I converted to angiotensin II?
Answer
Angiotensin I is converted to angiotensin II in the lungs with the help of angiotensin-converting enzyme (ACE).
9
Question
What are the three main effects of angiotensin II?
Answer
Angiotensin II causes vasoconstriction, hypertrophy and remodeling of the heart and blood vessels, and stimulates the adrenal glands to release aldosterone.
10
Question
How does angiotensin II cause vasoconstriction?
Answer
Angiotensin II acts directly on blood vessels to cause them to constrict by contracting the smooth muscle in vessel walls, narrowing the lumen, increasing resistance, and raising blood pressure.
11
Question
What long-term effect does angiotensin II have on the heart and blood vessels?
Answer
Angiotensin II stimulates hypertrophy (thickening) of the myocardium and vascular smooth muscle, leading to cardiac remodeling and thickening of blood vessel walls.
12
Question
What does angiotensin II stimulate in the adrenal glands?
Answer
Angiotensin II stimulates the adrenal glands to release aldosterone.
13
Question
What type of hormone is aldosterone and where does it act?
Answer
Aldosterone is a mineralocorticoid steroid hormone that acts on the nephrons of the kidneys.
14
Question
What are the effects of aldosterone on sodium, potassium, and hydrogen in the nephron?
Answer
Aldosterone increases sodium reabsorption from the filtrate into the blood in the distal tubule, increases potassium secretion from the blood into the filtrate in the distal tubule, and increases hydrogen secretion from the blood into the filtrate in the collecting ducts.
15
Question
How does sodium reabsorption by aldosterone affect water and blood pressure?
Answer
Sodium reabsorption draws water by osmosis, increasing fluid retention, intravascular volume, and blood pressure.
16
Question
What is fludrocortisone used for?
Answer
Fludrocortisone is a mineralocorticoid medication used to replace aldosterone in adrenal insufficiency and to treat postural hypotension by increasing and maintaining blood pressure.
17
Question
What is hyperaldosteronism?
Answer
Hyperaldosteronism refers to raised aldosterone levels.
18
Question
What is the prevalence and main feature of hyperaldosteronism?
Answer
Hyperaldosteronism may be present in 5-10% of patients with hypertension; hypertension is the crucial presenting feature, and many patients are asymptomatic.
19
Question
What non-specific symptoms can hyperaldosteronism cause?
Answer
Hyperaldosteronism may cause headaches, muscle weakness, and fatigue.
20
Question
What is primary hyperaldosteronism?
Answer
Primary hyperaldosteronism is when the adrenal glands directly produce too much aldosterone.
21
Question
In primary hyperaldosteronism, what happens to renin levels and why?
Answer
In primary hyperaldosteronism, serum renin is low because high blood pressure suppresses renin production by juxtaglomerular cells.
22
Question
What are possible causes of primary hyperaldosteronism?
Answer
Causes include adrenal adenoma (Conn's syndrome), bilateral adrenal hyperplasia, and familial hyperaldosteronism.
23
Question
What is an adrenal adenoma in the context of hyperaldosteronism?
Answer
An adrenal adenoma is a hormone-secreting tumor that secretes aldosterone, originally called Conn's syndrome.
24
Question
What is bilateral adrenal hyperplasia?
Answer
Bilateral adrenal hyperplasia is enlargement and overfunctioning of both adrenal glands.
25
Question
What is familial hyperaldosteronism?
Answer
Familial hyperaldosteronism is a rare genetic condition causing excess aldosterone.
26
Question
What causes secondary hyperaldosteronism?
Answer
Secondary hyperaldosteronism is caused by excessive renin stimulating excess aldosterone release.
27
Question
Why is renin excessive in secondary hyperaldosteronism?
Answer
Excessive renin is released due to disproportionately low blood pressure reaching the juxtaglomerular cells in the kidneys, despite normal or high systemic blood pressure.
28
Question
What conditions can cause secondary hyperaldosteronism?
Answer
Conditions include renal artery stenosis, heart failure, or liver cirrhosis.
29
Question
What is renal artery stenosis and how does it relate to RAAS?
Answer
Renal artery stenosis is narrowing of the renal arteries supplying the kidneys, usually due to atherosclerosis, leading to lower intrarenal blood pressure, excessive renin release, and increased aldosterone.
30
Question
How does renal artery stenosis affect juxtaglomerular cells?
Answer
In renal artery stenosis, the narrow renal artery results in lower blood pressure inside the kidney, causing juxtaglomerular cells to sense low pressure and excrete more renin.