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Water Balance, Acid/Base Balance, Calcium, Mg, and Phosphate Homeostasis

Patho/Physio 2 Schreier NSU Pharmacy Packets 6-8
STUDY
PLAY
PCT
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?
ANP
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?
causes vasodilation
Does ANP causes vasoconstriction or vasodilation?
decrease
Does ANP increase or decrease blood pressure?
decrease
Does ANP increase or decrease blood volume?
increase
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?
Tekturna (aliskiren)
What drug inhibits the action of renin?
decrease
What is the effect of aldosterone on sodium excretion by the kidney?
increase
What is the effect of aldosterone on potassium excretion by the kidney?
aldosterone secreting adrenal adenoma causing primary hyperaldosteronism
What is conn's syndrome?
aldosterone antagonist used to treat hyperaldosteronism
What is spironolactone?
ACE inhibitor
What is Lisinopril?
angiotensin II antagonist
~treats hypertension
What is losartan?
the hypothalamus
What part of the brain regulates water balance?
~increases blood volume and blood pressure
~causes insertion of aquaporins into the apical membrane for water reabsorption
~causes smooth muscle contraction leading to vasoconstriction
What is the role of ADH?
posterior pituitary
Where is ADH secreted?
1. increase in extracellular fluid osmolarity
2. angiotensin II
3. decrease in BP
4. decrease in extracellular fluid volume
What causes secretion of ADH?
1. ANP
2. ethanol
What inhibits secretion of ADH?
hypothalamus
Where is ADH produced?
the collecting duct of the kidney
Where does ADH act?
B. increase urine osmolarity
What does ADH do?
A. increase urine volume
B. increase urine osmolarity
C. increase urea excretion
D. increase sodium excretion
competitive ADH receptor antagonist
What is Tolvaptan?
1. secretes H+
2. reabsorbs and produces HCO3-
3. produces NH3, and excretes NH4+
What are 3 ways the kidney adjusts to maintain pH?
act to stabilize the pH of a liquid
What is the role of a buffer?
the bicarbonate buffer system
What is the primary buffer system for extracellular fluid?
the protein buffer system
What is the primary buffer system for intracellular fluid?
phosphate buffer system
What is the primary buffer of the urine?
bicarbonate
What is the major ion that influences the pH of the blood?
carbonic anhydrase converts CO2 + H20 to carbonic acid which can move across the membrane then converts to bicarbonate and H+
How is CO2 transported from the tissue to the lungs?
CO2 levels
What is the primary cause of respiratory acid/base imbalances?
False
It causes acidosis
True or False
Hypoventilation causes alkalosis.
true
True or False
Hyperventilation causes alkalosis.
PCT
Where is the majority of HCO3- reabsorbed?
its reabsorbed at CO2 and H20 from the filtrate and then converted back to HCO3-
How is bicarbonate reabsorbed?
carbonic anhydrase
What enzyme plays a major role in the reabsorption of bicarbonate?
the PCT and DCT
Where in the kidney does carbonic anhydrase act?
1. Glutamine is deaminated to produce NH3. NH3 takes H+ to form NH4+ and is excreted via the kidney
2. H+ combines with H2PO4-- to make H2PO4- and is excreted by the kidneys
How is excess H+ excreted?
a carbonic anhydrase inhibitor
~used to treat glaucoma and metabolic alkalosis
What is acetazolamide?
when the blood pH is below 7.35
What is acidemia?
when the blood pH is above 7.45
What is alkalemia?
less than 22 mEq/L
At what plasma level of bicarbonate classifies as metabolic acidosis?
greater than 28 mEq/L
At what plasma level of bicarbonate classifies as metabolic alkalosis?
1. rapid breathing
2. confusion or lethargy
3. shock
What are the symptoms of metabolic acidosis?
the difference in the measured cations and the measured anions in serum, plasma, or urine
~helpful when trying to determine the cause of metabolic acidosis
What is the anion gap?
1. lactic acidosis
2. ketoacidosis
3. renal failure
4. toxins
When the anion gap is increased what could be a possible cause of metabolic acidosis?
1. diarrhea
2. renal acidosis
3. ammonium chloride
4. acetazolamide
When the anion gap is normal what could be a possible cause of metabolic acidosis?
increase in pulmonary ventilation
What is the initial response to metabolic acidosis?
increased production of NH3 from glutamate
What is the primary adaptive response of the kidney to metabolic acidosis?
decrease in pulmonary ventilation
What is the initial response to metabolic alkalosis?
excrete excess HCO3-
What is the adaptive response of the kidney to metabolic alkalosis?
1. shallow breathing
2. hand tremor
3. light headedness
4. muscle twitching
5. nausea, vomiting
6. numbness or tingling in hands/feet
7. prolonged muscle spasms
What are the symptoms of metabolic alkalosis?
~hypercalcemia, renal insufficiency, and metabolic alkalosis that occurs in patients who ingest large amounts of milk or calcium carbonate antacids
What is milk alkali syndrome?
False
True or False
Metabolic acid/base imbalances are related to CO2 levels.
1. in the bone
2. as hydroxyapatite
Where is most of the body's calcium stored and what molecule is it stored as?
causes an increase in free Ca++ plasma concentration
What does acidosis do to calcium levels?
causes a decrease in free Ca++ plasma concentration
What does alkalosis do to calcium levels?
leads to respiratory alkalosis and decreases plasma levels of free calcium
What does hyperventilation do to calcium levels?
leads to respiratory acidosis and increases plasma levels of free calcium
What does hypoventilation do to calcium levels?
1. numbness
2. arrhythmias
3. osteoporosis
4. epilepsy
5. tetanic muscle contractions
6. paresthesias
7. neuromuscular irritability
What are the symptoms of hypocalcemia?
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?
PCT
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?
parathyroid hormone
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?
the kidney
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?
PCT
Where is most phosphate reabsorbed?
Na+/PO4 exchangers
How is phosphate transported across the apical membrane?
in bones
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
300 mOsm/L
Bowman's Capsule
100 mOsm/L
Distal Tubule
1200 mOsm/L
Loop of Henle
100 mOsm/L with no ADH
Collecting Duct
1200 mOsm/L with ADH
Collecting Duct
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.