1. SF Biology II1 Kidney Function and Regulation

2. SF Biology II2 Renal Filtration Total body water ~40 litres; Plasma Vol. ~3 litres). Filter ~180 litres/day Daily urine vol. ~ l.5 litres. Hence conclude that ~95% is re-absorbed, i.e. conserved.

3. SF Biology II3 Functional unit of the kidney

4. SF Biology II4 Filtration mechanism

5. SF Biology II5 Functions of the nephron

6. SF Biology II6 Osmotic gradients

7. SF Biology II7 Countercurrent multiplier (1/2)

8. SF Biology II8 Countercurrent multiplier (2/2)

9. SF Biology II9 Renal Concentration Mechanism — Summary Loop of Henle as countercurrent multiplier Ascending limb actively extrudes Na +, K + Hence gradient between limbs (200 mosm) AND vertical gradient in medulla – 300 mosm outside - 1200 mosm inside

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12. SF Biology II12 Renin-Angiotensin — Summary Fall in NaCl, ECF, ABP … JGA release of renin… …catalyses angiotensinogen — AGTI In lungs AGTI — AGTII –…release of vasopressin — H 2 O reabsorption –…arteriolar constriction — reduced renal blood flow –…stimulates thirst — H 2 O intake

13. SF Biology II13 Renin-Angiotensin — Summary AGTII stimulates adrenal release of aldosterone… –…increased reabsorption of Na + @ renal tubules –… hence H 2 O retained (osmotically) in ECF

14. SF Biology II14 ADH/vasopressin

15. SF Biology II15 ?Possible Examination Topics Pattern/regulation of gut motility Pancreatic secretion of bicarbonate/enzymes Digestion/absorption of CHO (vs?) fat Forces involved in glomerular filtration –autoregulation Role of urea in hypertonicity of medulla Basic renin-AGT-aldosterone mechanism –effects on tubular reabsorption

16. SF Biology II16 Urea Recycling — Summary Distal tubule and early collecting tubule NOT permeable to urea or water* *Vasopressin allow water to move passively …hence urea is concentrated. Distal collecting tubule IS permeable to urea …hence urea diffuses into interstitium…

17. SF Biology II17 Urea Recycling — Summary …raising osmotic pressure above tonicity …hence water leaves thin ascending limb (passively) …hence urea is concentrated in ascending limb

18. SF Biology II18 Urea Recycling — Advantages Increase in medullary tonicity – allows production of hypertonic urine Less water per unit wt of urea excreted Both aid water conservation

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24. SF Biology II24 Equilibrium