Bio20B_Lecture2 - Bio 20B Kidney Form and Function Water...

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Kidney Form and Function Water and Electrolyte Balance in Animals Water balance is critical Key Concepts o Homeostasis-maintaining the cellular environment o Kidney Structure and Function o The Kangaroo Rat-how to live in a desert o Marine Mammals-how to live in a salt water environment Homeostasis – Two main physiological approaches o Conformational Homeostasis: Osmoconformers Solute concentration is same as environment o Regulatory Homeostasis: Osmoregulators Requires a physiological adjustment to maintain proper solute concentrations in tissues o Isotonic: same as environment o Hypotonic: More solutes outside (Freeman Fig. 42.2a) Marine Fish Drink water o Hypertonic: more solutes inside (Freeman Fig. 42.2b) Freshwater Fish Don’t drink water o Terrestrial Animals lose water to the environment by evaporation from body surfaces: respiration Gain metabolic water from food and drink water o Sharks and Cartilaginous Fish are special Fluids are Isotonic with seawater, but salt levels are same as other marine fish Use other components like urea (synthesized in the body) to make fluids isotonic with seawater Still gain electrolytes from seawater (gills) Solution: (Freeman Fig. 42.5) Shark excretion in shark rectal gland Use ATP and push sodium out and a little potassium comes in Na+/K+ ATP pumps NA out, electrochemical gradient Cotransporter powered by gradient Na+ diffusion K+ and Cl- concentration increases, out via channels Net movement of salts out of tissues and into gland Once in gland, salts are excreted to environment o Some marine Vertebrates (Seabirds and Reptiles) have extra – renal Salt Glands in addition to kidney (Campbell Fig. 44.9) o Urine is a filtrate o Main Processes: Diffusion and Osmosis for filtrate Diffusion: When solutes can move across barriers (Freeman Fig. 42.1a)
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Bio20B_Lecture2 - Bio 20B Kidney Form and Function Water...

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