Human Anatomy and Physiology : Help with RAAS Physiology
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Example Questions
Example Question #14 : Excretory Physiology
The release of renin ultimately results in the stimulation of which gland?
Anterior pituitary gland
Thyroid gland
Adrenal cortex
Adrenal medulla
Adrenal cortex
Renin is a hormone released by granular cells in the juxtaglomerular apparatus, near the nephron glomerulus. These cells monitor the pressure of the filtrate in the distal convoluted tubule. The release of renin will stimulate a cascade of angiotensin I and II. Angiotensin II will ultimately stimulate the adrenal cortex to release aldosterone and increase sodium reabsorption and potassium excretion from the filtrate, leading to water retention.
Example Question #1 : Help With Raas Physiology
Which of the following directly stimulates the release of aldosterone?
Renin
Angiotensinogen
Angiotensin II
Vasopressin
Adrenocorticotropic hormone
Angiotensin II
Aldosterone is a steroid hormone that is released from the adrenal cortex. The function of aldosterone is to increase reabsorption of sodium ions from the distal tubule. Increased sodium ion concentration in the blood then causes the diffusion of water from the nephron into the circulatory system, preventing water loss due to excretion and increasing blood pressure and volume)
Release of aldosterone is mediated by the renin-angiotensin system (RAS). When juxtaglomerular cells detect low blood pressure, they release renin. Renin travels to the liver, where there angiotensinogen is produced, and cleaves angiotensinogen to produce angiotensin I. Angiotensin I then travels to the lungs, where angiotensin converting enzyme (ACE) cleaves it to produce angiotensin II. Angiotensin II then travels to the adrenal cortex to stimulate release of aldosterone into the blood.
Adrenocorticotropic hormone is secreted by the anterior pituitary and acts on the adrenal cortex to stimulate release of cortisol and cortisone, but does not affect aldosterone release. Vasopressin is released by the posterior pituitary and helps the body to retain water; it is not related to aldosterone release.
Example Question #2 : Help With Raas Physiology
Which of the following is not an effect of angiotensin II?
Stimiulates 
Dilutes the urine in order to rid the body of excess fluid
Indirectly increases blood volume via the action of antidiuretic hormone
Promotes the effects of aldosterone to further increase reabsorption
Vasoconstricts the afferent and efferent arterioles to maintain glomerular filtration rate
Dilutes the urine in order to rid the body of excess fluid
Angiotensin II is a major influence on the kidney's function when the body needs to retain fluid - it works in tandem with antidiuretic hormone and aldosterone to accomplish this. Angiotensin II will also act upon the afferent and efferent arterioles in order to control the glomerular filtration rate and stimulates reabsorption to ensure that the body is keeping necessary solutes/molecules. Diluting the filtrate in the nephron is the opposite effect that angiotensin has on the kidney.
Example Question #3 : Help With Raas Physiology
Too much of which of the following substances would cause chronic hypertension (high blood pressure)?
Nitric oxide
Prostacyclin
Angiotensin II
Atrial natriuretic peptide
Brain natriuretic peptide
Angiotensin II
Angiotensin II (part of the RAAS) works in the body to cause vasoconstriction in an effort to raise blood pressure. Too much of this substance will cause hypertension, another name for elevated blood pressure. Nitric oxide and prostacyclin work to vasodilate and lower blood pressure. Atrial natriuretic peptide and brain natriuretic peptide are released by the body to lower blood pressure in volume overloaded states.
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