Renal 5 & 6 Flashcards
In the first half of the proximal tubule, Na+ uptake into the cell is couple with _____
H+ or organic solutes
Na+ - H+ antiporter couples
entry of Na+ with extrusion of H+ (H+ secretion leads to reabsorption of NaHCO3-
SGLT2
Na+-glucose symporter in the apical membrane
In the second half of the proximal tubule, How much of Na+ reabsorption follows transcellular and how much follows paracellular?
- 67% transcellular
- 33% paracellular
- Na+ is primarily reabsorbed with Cl-
What is your urine/plasma osmolality ratio & ADH concentration if your urine is dilute and pale?
- x < 1.0
- low ADH
What is your urine/plasma osmolality ratio & ADH concentration if your urine is concentrated and dark?
- x > 1.0
- high ADH
Describe the thick ascending limb of the loop
- actively reabsorbs 25% Na+
- H2O impermeable
Describe thin descending limb.
- passive H2O reabsorption
- Na+ & Cl- impermeable
Describe thin ascending limb
- passive Na+ & Cl- impermeable
- H2O impermeable
What does Angiotensin II (AT-II) do?
Increases reabsorption of Na+, Cl-, and H2O in proximal tubule
What does aldosterone do? Its stimulus?
- Increases reabsorption of Na+, Cl-, and H2O in thick ascending loop, distal tubule, and collecting duct
- high AT-II or plasma K+
What does Atrial Natriuretic Peptide and Urodilatin do? Stimulus?
- increases excretion of Na+
- decreases reabsorption of Na+ & Cl- and ADH
- stimulus is higher blood pressure or extracellular volume
What do the sympathetic nerves do? Stimulus?
- increase catecholamines
- increases reabsorption of Na+ & Cl- in proximal and distal nephron
- lowered Extracellular fluid
What does Dopamine do? Stimulus?
- lowers reabsorption of Na+ & Cl- in proximal tubule
- high Extracellular fluid
What does ADH do? Stimulus?
- reabsorption of H2O in collecting duct
- lowered Extracellular fluid
Insensible water loss
water loss from cells of the skin and respiration
Routes of water output
- insensible
- sweat
- feces
- urine (main route)
Total Body Water
- 50% - 70% of total body mass
- 42L
ICF
- 30% - 40% of total body mass
- 28L
ECF
- 20% - 30% of total body mass
- 14L
- (ISF + P)
ISF
-Fluid that bathes all cells
Plasma (P)
- Dynamically circulating volume, regulates composition of interstitial and transcellular water
- 3.5L
Transcellular water
2L
Positive water balance
-when intake exceeds loss
Major determinant of plasma osmolality
Na+
ADH (Negative) Feed back system
- PHYSIOLOGICAL REGULATORS (osmolality & volume and pressure)
- SENSORS (hypothalamic osmoreceptors stimulates ADH
- EFFECTOR (exocytosis of ADH from terminal axons and paraventricular neurons into blood of the post pituitary)
- TARGET cellular ADH receptors in distal tubules and collecting ducts)
- RESPONSE (change in cytoarchitecture and cellular matrix remodeling)
ADH Stimulus
- ADH release - near 280 osmalality
- thirst threshold - near 298
- 10% below normal threshold
ADH affects urea permeability where?
Lower collecting duct
