3. Hormonal Control of Tubular Reabsorption

4. HORMONES THAT REGULATE ABSORPTION
EFFECTS
Aldosterone
↑ NaCl,H2 O reabsorption, ↑ K+ secretion
Angiotensin -II
↑ NaCl,H2 O reabsorption, ↑H+ secretion
Antidiuretic Hormone
↑H2 O reabsorption
Atrial Natriuretic Peptide
↓ NaCl reabsorption
Parathyroid Hormone
↓ Phosphate Reabsorption ,
↑ Ca++ Reabsorption

5. Extracellular Fluid Osmolarity Sodium Ion Concentration
Dr Farzana Salman

6. P osm=2.1x Plasma sodium concentration
= 298 mOsm/L
= 300 mOsm/L

7. Osmoreceptor-ADH Feedback System
Thirst mechanism
Salt appetite mechanism.

10. Cardio Vascular Reflexes
Decreased blood pressure
Decreased blood volume.
Arterial Baroreceptor reflexes
Cardiopulmonary reflexes.

11. Other Stimuli For ADH Release
INCREASE
Nausea
Nicotine
Morphine
DECREASE
Alcohol

12. Thirst Mechanism
THIRST
The conscious desire for drinking water.

13. Thirst Centers AV3V region Anterolaterally in the preoptic nucleus.
Increased osmolarity of CSF

14. Stimuli For Thirst Increase ECF osmolarity
Decrease in ECF volume and arterial pressure.
Angiotensin II
Dryness of mouth and mucous membrane of the esophagus.
GIT and Pharyngeal stimuli .

15. Threshold For Drinking
When the sodium concentration increases only 2meq/L above normal the thirst mechanism is activated causing a desire to drink water .

16. Integrated Responses of Osmoreceptor-ADH Thirst mechanism in controlling ECF osmolarity and Sodium ion concentration

17. Salt Appetite Mechanism
Increase salt appetite
Decreased ECF sodium concentration
Decreased blood volume or BP

18. Obligatory Urine Volume
Normal 70 Kg human must excrete 600 milliosmoles of solute each day.
Maximum urine concentrating ability= milliosmoles/L.

19. The minimum volume of urine that must be excreted is obligatory urine volume.
600mOsm/day divided by 1200m Osm/day
=0.5L/day
Severe dehydration occurs if one attempts to drink sea water.

20. kidney