Water Balance, Acid/Base Balance, Calcium, Mg, and Phosphate Homeostasis
Where is most water reabsorbed?
thin descending limb
Which part of the Loop of Henle is permeable to water?
the sharp turn
Which part of the Loop of Henle is permeable to urea?
thick ascending limb
Which part of the Loop of Henle has the Na/K/Cl cotransporter?
helps create concentrated urine
What is the role of the counter current mechanism?
~water flows out into the interstitial fluid creating a more concentrated filtrate in the loop and helping the body retain water ~Because the descending limb is highly permeable to water, water moves by osmosis here. As described above, it moves out of the tubule and into the medullary interstitial fluid for reabsorption
What is the role of the descending limb in the loop of henle?
pumps solutes out of the filtrate and into the medullary interstitial fluid for reabsorption; helps maintain the concentration gradient
What is the role in the ascending limb of the loop of henle?
the vasa recta are a group of peritubular capillaries that run along the loop of henle in the kidney. The blood in the vasa recta flows the opposite direct of the filtrate in the loop of henle creating the counter current exchange mechanism.
What is the vasa recta?
helps maintain hypertonicity in the renal medulla and helps return electrolytes and fluids to the blood supply ~salt reabsorbed from the Loop of Henle is trapped and recycled within the medulla by the countercurrent flow of blood in the vasa recta
What is the role of the vasa recta?
-loop diuretic -affects the thick ascending limb -blocks Na/K/Cl symport -results in : decreased NaCl reabsorption, decreased K+ reabsorption, decreased potential in lumen, decreased paracellular mechanism for cation reabsorption
What are the effects of furosemide?
1. ADH 2. aldosterone (RAAS)
What are the two hormonal ways that the body increases blood volume?
What is the hormonal way that the body decreases blood volume?
cardiac muscle cells when atrial blood pressure increases
Where is ANP released from?
ADH and aldosterone
What two hormones does ANP inhibit the release of?
Does ANP causes vasoconstriction or vasodilation?
Does ANP increase or decrease blood pressure?
Does ANP increase or decrease blood volume?
Does ANP increase or decrease urine output?
1. angiotensinogen is produced in the liver 2. cells of the juxtaglomerular apparatus in the kidney sense a drop in blood pressure and secrete renin 3. renin converts angiotensinogen to angiotensin I 4. ACE then converts angiotensin I to angiotensin II 5. angiotensin II causes vasoconstriction which helps return blood pressure back to normal 6. angiotensin II tells the adrenal cortex to secrete aldosterone 7. aldosterone causes the kidney to increase sodium and water reabsorption and decrease urine volume which also helps return blood pressure to normal
Describe the mechanism of action of the RAAS.
stretching of the osmoreceptors in the atria and ventricles occurs as a result of an increase in blood pressure; then signals are sent to the brain which cause ANP to be released from the heart muscle cells to normalize the BP
What causes the release of ANP?
a proteolytic enzyme that converts angiotensinogen to angiotensin I and is released by the juxtaglomerular cells of the kidney in response to a decrease in blood pressure;
What is the role of renin?
causes vasoconstriction and the release of aldosterone and ADH to increase blood pressure
What is the role of angiotensin II?
B. angiotensin II E. high serum K+
Which are the two main factors that stimulate the production of aldosterone? A. high serum Na+ B. angiotensin II C. ANP D. ADH E. high serum K+
C. adrenal cortex
Where is aldosterone produced? A. renal cortex B. renal medulla C. adrenal cortex D. adrenal medulla E. myocardium
~produced by the adrenal cortex ~increases reabsorption of Na+ in the distal tubule and collecting ducts of the kidney ~as a result water and chloride follow the sodium thus water retention ~promotes excretion of K+ and H+
What is the role of aldosterone?
in the distal tubule and collecting ducts of the kidney
Where does aldosterone act?
1. ANP 2. dopamine
Which two hormones decrease aldosterone release?
1. angiotensin II 2. increase in blood potassium levels 3. ACTH 4. decrease in blood sodium levels
What stimulates the release of aldosterone?
What drug inhibits the action of renin?
What is the effect of aldosterone on sodium excretion by the kidney?
What is the effect of aldosterone on potassium excretion by the kidney?
1. decreased neuromuscular excitability 2. decreased neurotransmission 3. muscle weakness 4. decreased GI motility 5. arrhythmias 6. hypertension 7. hypercalciuria 8. increased bone mass
What are the symptoms of hypercalcemia?
voltage sensitve sodium channels
What channels are sensitive to extracellular calcium concentration?
Where is most calcium reabsorbed?
~found in the PCT, DCT, collecting duct, and Loop of Henle ~sense extracellular fluid levels of calcium and make adjustments to keep levels normal in the blood
What is the kidney calcium receptor?
What hormone regulates the reabsorption of calcium in the thick ascending limb in the Loop of Henle?
It enhances active reabsorption of calcium and magnesium from distal tubules and the thick ascending limb. It also decreases the reabsorption of phosphate, with a net loss in plasma phosphate concentration. When the calcium:phosphate ratio increases, more calcium is free in the circulation.
What is the role of parathyroid hormone in the kidney?
Calcitriol increases blood calcium levels by increasing renal tubular reabsorption of calcium thus reducing the loss of calcium in the urine. It also increases absorption of calcium in the GI tract.
What is the role of calcitriol in the kidney?
PTH reduces the reabsorption of phosphate from the proximal tubule of the kidney, which means more phosphate is excreted through the urine.
What role does parathyroid hormone play on phosphate reabsorption?
1. Inhibits renal tubular cell reabsorption of Ca2+ allowing it to be excreted in the urine. 2. Inhibits phosphate reabsorption by the kidney tubules
What are the effects of calcitonin on the kidney?
in response to low blood calcium levels
When is PTH released?
What produces calcitriol?
1. decreases the expression of phosphate transporters in kidneys and the intestines 2. decreases calcitriol synthesis 3. decreases serum phosphate levels
What is the role of fibroblast growth factor 23?
1. increases calcium, magnesium, and phosphate absorption in the gut and reabsorption in the kidney 2. stimulates calcium transport into the cells 3. enhances bone formation
What are the roles of calcitriol?
in response to high levels of calcium in the blood
When is calcitonin secreted?
by parafollicular cells of the thyroid gland
Where is calcitonin produced?
Where is most phosphate reabsorbed?
How is phosphate transported across the apical membrane?
Where is most of the magnesium in the body?
in the thick ascending limb of the Loop of Henle
Where is most of magnesium reabsorbed?
expressed in the human thick ascending limb tight junctions and seems to play a role in the control of magnesium and calcium reabsorption
What is paracellin 1?
A. increased calcium reabsorption
What is the effect of PTH on the kidney? A. increased calcium reabsorption B. increased phosphate reabsorption C. increased GFR D. decreased GFR E. decreased calcitriol synthesis
C. g protein receptor
The PTH receptor is a ____________. A. transcription factor B. tyrosine kinase C. g protein receptor D. ion channel E. guanylate cyclase
A. increase cAMP
PHT act at the PTH receptors on the kidney cells to ________, which produces an increase in calcitriol synthesis. A. increase cAMP B. decrease cAMP C. activate phospholipase C D. increase FGF23
B. a steroid
Calcitriol is best described as __________. A. an amine B. a steroid C. a protein D. an ecosanoid E. a cannabinoid
A. transcription factor
The vitamin D receptor is a ___________. A. transcription factor B. tyrosine kinase C. g protein receptor D. ion channel E. guanylate cyclase
Loop of Henle
100 mOsm/L with no ADH
1200 mOsm/L with ADH
1. 0% if the kidney is healthy and sugar intake is normal
5. 100 %
5. 100 All creatinine should be cleared if the kidney is functioning properly because it is not reabsorbed.
4. 40% since more urea is reabsorbed than secreted
5. 100% I believe this is the answer because PAH is not reabsorbed. I'm not positive though.