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LU 4 : OSMOREGULATION ((OSMOLARITY (Moles of osmotically active particles…
LU 4 : OSMOREGULATION
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OSMOSIS
2 solutions separated by membrane differ in osmotic pressure or osmolarity :
- water flows from hypo- to hyperosmotic solution
OSMOREGULATION
- Controlled movement of solutes between internal fluids and the external environment
- Regulates solute concentrations
- Balances the gain and loss water
- Water and solutes must be maintained within narrow limits
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COUNTERCULTURE MECHANISM
- Descending thin loop of Henle permeable to water. water diffuses from the lumen (high water concentration) to the peritubular fluid (low water concentration)
- Ascending thin loop of Henle permeable to solute but not water. Na+ and Cl- undergo passive diffusion from tubular fluid to peritubular fluid
- Ascending thick limb loop of Henle is permeable to water. Active reabsorption of Na+ occur
-Countercurrent multiplication - utilization of energy to generate osmotic gradient
RENAL CLEARANCE
- Renal Clearance - Measurement of kidney is ability to remove substance from the plasma
- Used to measure:
- GFR - Glomerular filtration rate
- RPF - Renal plasma flow
- RBF - renal blood flow
to understand how substances are reabsorbed / secreted
to compare kidney function for diagnostic purposes
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GLUCOSE REGULATION
Transport max - Tm
- The maximum rate for reabsorption of substances depends on the carrier.
- When amount of filtration approaching limit of reabsorption, substance will start to appear in urine
Tm glucose - when re absorption reaches tubular capacity, glucose starts appearing in urine
