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21 Cards in this Set
- Front
- Back
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What does ANP do and where does it act?
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Atrial Natriuretic Peptide makes you pee more.
--> interferes with Na reabsorption by inhibiting channels in medullary portion of tubule AND by suppressing renin and aldosterone release. --> vasodialates the afferent arteriole (also constricts the efferent arteriole) ANP is released in response to volume overload in the right atrium (stretch receptors). |
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What are the major intracellular electrolytes?
What percent of body water is in the ICF? |
K, Phos, CL
2/3 total body water |
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What are the major extracellular electrolytes?
What percent of body water is in the ECF? |
NaCl
1/3 total body water |
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what are the clinical features of hypovolemia?
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– Tachycardia
– Hypotension – Orthostatic hypotension – Dry mucous membranes – - - - Reduced skin turgor |
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What are the mechanisms for volume retention in hypovolemia?
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• Decreased loss of sodium from reduced renal perfusion (reduced GFR) --> minor!
• Increased sympathetic tone to kidneys enhances sodium retention • Increasedactivityofrenin-angiotensin-aldosterone system enhances sodium retention • Increased ADH activity leads to more reabsorption of water, reduced urine output • Decrease in Atrial Natriuretic Peptide activity |
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What are the causes of hypervolemia?
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1. Decreased renal Na excretion
a) Heart failure b) Renal failure c) Hyperaldosteronism (adrenal adenoma) 2. Massive Na intake 3. Increased production of red blood cells (polycythemia) – much less common than 1 +2 |
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Calculate the blood volume
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plasma volume/(1-hematocrit)
Plasma volume is 1/12 of total body water. |
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Calculate the single nephron GFR (SNGFR)?
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K(deltaP - pigc)
Kf (deltaP – piGC) |
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Calculate the filtration fraction
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GFR/RPF
glomerular filtration rate/renal plasma flow calculate in ml/min. Usually around 20% |
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What are filtered ("cleared") more easily, cations or anions?
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Cations!
Regarding electrostatic charge, the glomerular capillary basement membrane is rich in sialoproteins that confer on it a negative electrostatic charge. Hence, albumin (molecular weight approximately 69,000, negatively charged) is largely withheld from crossing the glomerular capillary, with less than 60 mg normally excreted in 24 hours. |
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Calculate the clearance of a substance
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UV/P
expressed in ml/min or L/day. |
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What substance can you use to calculate the Renal Plasma Flow? How do you do it?
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PAH, but true RPF is about 10% higher
SInce PAH delivered = PAH excreted RPF = UrinePAH X Flow (V)/PlasmaPAH = ClearancePAH |
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Calculate the Renal Blood Flow
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RBF = RPF/(1-Hct)
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Calculate the reabsorption rate.
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GFR x Plasma Glucose - glucose excretion = Reabsorption rate
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Filtration Fraction
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GFR/RPF
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Calculate the Renal Plasma Flow
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RPF = clearance of PAH x 1.1
(10% more than PAH clearance, which is UV/P). |
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Where does Angiotensin II act?
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Constricts the afferent and efferent arterioles (efferent more than afferent). This mechanism helps preserve GFR.
**Angiotensin II acts directly on the proximal tubule to increase reabsorption of Na+ by increasing activity of the Na+H+ exchangers. |
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Aldosterone
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Aldosterone acts on the cortical collecting duct to enhance sodium reclamation by increasing epithelial Na+channels (ENaC’s) in the luminal membrane of principal cells.
Aldosterone also increases Na+K+-ATPase activity in the basolateral membrane . This means that it also makes you pee out more potassium! Angiotensin II stimulates the release of aldosterone from the zona glomerulosa cells of the adrenal cortex. |
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What happens to potassium in Anion gap acidosis?
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K is not redistributed! examples: DKA or Renal failure
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What happens to potassium in Non-anion gap acidosis?
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Bad! Because cells are less permeable to Cl- than to H+, as H+ enters the cell K+ must leave in order to maintain electroneutrality. With a non-anion gap metabolic acidosis (such as an acidosis created by diarrhea or renal failure) hyperkalemia can occur as H+ is buffered inside cells and K+ moves to the ECF.
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What is the renal response to K+ depletion?
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PRINCIPAL CELL
Decrease in K+ secretion bc Low Aldosterone means less Na/K pump activity. Less K leaving in urine. INTERCALATED CELL Increase in K+ reabsorption. Intercalated cells increase K+ reabsorbtion via H+K+ATPase pumps. K+ excretion can be as low as 1% |
