Chapter 29: Renal Regulation Of K, Ca, PO, Mg Flashcards
Ions controlled by an overflow mechanism
Potassium
Phosphate
ECF Potassium concentration
4.2mEq/L
Hormones that increase potassium uptake into cells
Insulin
Aldosterone
Epinephrine
Acid-base abnormality causing a decrease potassium concentration in the ECF or Hypokalemia
Alkalosis
Effect of increased H ion concentration on K
Reduces activity of Na-K ATPase pump –> Increases K on ECF
Potassium abnormality caused by Cellular lysis, strenuous exercise and intake of B-adrenergic blockers
Hyperkalemia
How does increased ECF osmolarity increase K in the ECF
Osmosis out of cells –> cellular dehydration –> increased K concentration in cells –> K diffusion out of the cells
Most important sites for regulating K excretion
Principal cells of the late distal tubules and cortical collecting tubules
Intercalated cells of the late distal tubules and cortical collecting tubules contain what transporter which aids in potassium reabsorption
H-K ATPase in the luminal membrane
3 mechanisms that raises K secretion during increased ECF K concentration
- stimulation of Na-K ATPase pump
- diffusion of K from increased gradient
- stimulation of aldosterone secretion
Effect of Addison’s disease in K concentration in the blood
Hyperkalemia
Addison’s dse –> dec aldosterone –> dec K secretion –> hyperkalemia
Chronic Acidosis leads to what potassium abnormality
Hypokalemia
Chronic acidosis decreases NaCl and Water reabsorption in the proximal tubules –> increasing distal volume delivery –> overrides inhibitory effect oh inc H on Na-K ATPase pump –> K secretion
ECF Ca ion concentration
2.4 mEq/L
50% of Ca is in what form, which has biologic activity at cell membranes
Ionized form
Effect of alkalosis in the binding of Ca and plasma proteins
More Ca is bound to plasma proteins in alkalosis –> prone to hypocalcemic tetany
Large share of Ca excretion occurs in
Feces
Percentage of Ca deposition in the bone
99%
Effect of PTH
Increases Bone resorption –> increase Ca levels in ECF
Calcium is filtered, reabsorbed and secreted in the kidneys. True or False
False. Only filtered and reabsorbed; not secreted
Most of calcium reabsorption occurs through which transport pathway in the proximal tubule
Paracellular pathway
Transport mechanism for Ca as it exits the cell across the basolateral membrane from the proximal tubule
Primary active transport (Ca-ATPase)
Secondary active transport (Na-Ca counter transport)
50% of Ca reabsorption in the thick ascending limb occurs through the paracellular route by passive diffusion and 50% through the transcellular pathway which is stimulated by what hormone?
PTH
PTH, Vitamin D and Calcitonin stimulates ca reabsorption in which tubular segments?
Thick ascending limb
Distal tubule
Reabsorption of Ca in which segment parallels Na and water reabsorption and is independent of PTH
Proximal tubule
Effect of acidosis on Ca reabsorption
Increased
Threshold of phosphate in the ECF
0.8 mM/L
Proximal tubule reabsorbs 75-80% of filtered Phosphate occurring through which pathway and transporter in luminal membrane?
Transcellular pathway through the Na-PO4 con-transporter
Effect of PTH on Phosphate and Ca reabsorption
Decreased PO4 reabsorption
Increased Ca reabsorption
Ions stored in the bones
Ca
PO4
Mg
Total plasma Mg concentration
1.8 mEq/L
Free ionized concentration of Mg
0.8 meq/L
In disturbances of kidney function which are not too severe, Na balance may be achieved mainly by systemic adjustments. True / False
False. Mainly by intrarenal adjustments with minimal changes in ECF volume
Severe perturbations of the kidney exhausts intrarenal compensations so that systemic adjustments must be invoked. True / False
True
If kidneys become greatly vasodilated and GFR increases, NaCl delivery to the tubules leads to two intrarenal compensations. What are these?
- glomerulotubular balance
- macula densa feedback
Refers to the effect of increased BP to raise urinary volume excretion
Pressure diuresis
Effect of increased Na excretion that occurs with increased BP
Pressure natriuresis
Chronic increases in BP suppresses the release of which hormone, which enhances the effectiveness of pressure natriuresis
Renin
Trace the basic renal-body fluid feedback mechanism
Increase fluid intake ➡️ fluid accumulation in ECF ➡️ inc blood volume ➡️ inc mean circulatory filling pressure ➡️ inc venous return ➡️ inc cardiac output ➡️ inc arterial pressure ➡️ pressure diuresis to inc urine output
Blood volume and ECF volume are controlled simultaneously. True / False
True. Ingested fluid initially goes into the blood but rapidly becomes distributed between interstitial spaces and plasma
Neither a decrease nor an increase in circulating angiotensin II has a large effect on ECF volume or blood volume as long as HF or KF does not occur. True or False
True
Excess ADH secretion causes only small increases in ECF volume and large increases in Na concentration. True or False
False. Only small increases in ECF due to pressure diuresis and large decreases in Na concentration because of ECF dilution
Action of ANP
Increased salt and water excretion d/t increase GFR and decrease Na reabsorption by the collecting ducts
Conditions that cause large increases in blood volume and ECF volume
- heart diseases
- increased capacity for circulation (pregnancy, varicosities)
Conditions that cause large increases in ECF volume but with normal blood volume
Nephrotic syndrome
Liver cirrhosis
