REVIEW SHEET OSMOREGULATION< KIDNEY FUNCTION


These review sheets are presented as outlines of the material covered in class.  They do not provide details, but try to highlight the important areas and concepts covered.  You should use these as a general guide to be sure that you fully understand all the major topics covered during these lectures.  This is NOT an exhaustive list, but an OVERVIEW.  You are responsible for the material covered in class, whether or not it appears on this general outline.

1.  Osmoregulation
    A.  regulation of body fluids - water and ions
    B.  Marine Invertebrates
        i.  isomostic to environment
        ii.  regulate solutes by protein/amino acid balance
    C.  Elasmobranches
        i. isosmotic
        ii.  use urea and TMAO to maintian solutes
    D.  Marine Teleosts
        i.  hyposmotic to environment
        ii.  maintain balance at gills - active transport of salts
    E.  Marine Mammals
        i.  hyposmostic to environment
        ii.  kidneys concentrate urine
    F.  Freshwater Teleosts
        i.  hyperosmotic to environment
        ii.  maintain balance at gils - active transport of salts into bloodstream
    G.  Terrestrial Animals
        i.  danger of dehydration
        ii.  balance of water loss vs water gain
            a.  kangaroo rat
                1.  relies on metabolic water
    H.  Nitrogen Wastes
        i.  NH3
        ii. urea
        iii. uric acid

2.  Mammalian Kidneys
    A.  Anatomy
        i.  medulla, cortex, pelvis
        ii.  glomerulus, Bowman's Capsule
        iii.  afferent and efferent arterioles
        iv.  proximal and distal convoluted tubules
        v.  Loop of Henle (descending and ascending limb)
        vii.  collecting duct
        viii.  vasa recta
    B.  nephrons
        i..  juxtamedullary vs cortical
        ii.  filtration of blood
            a.  capillary endothelium
            b.  basement membrane
            c.  podocytes
        iii.  forces for filtration
            a.  BP, COP, press in Bowman's capsule
            b.  regulation of BP by afferent and efferent arterioles

3.  Regulation of Urine Composition
    A.  Reabsorption
        i.  transport from urine into bloodstream
            (ex.  glucose, amino acids)
        ii.  co-transport with Na+, indirect dependence on ATP
    B.  Secretion
        i.  transport from bloodstream into urine
             ( ex.  penicillin)
        ii.  normally co-transport or active transport
    C.  Saturation of carrier proteins
    D.  Clearance
        i.. inulin
            a.  filtered only, Cin = GFR
        ii.  glucose
            a.  filtered and reabsorbed, Cglucose = 0
        iii.  penicillin
            a.  filtered and secreted, Cpen > Cin
    E.  Passive Reabsorption
        i. ex.  water, urea
    F.  Loop of Henle
        i.  descending limb impermeable to ions, permeable to water
        ii.  ascending limb impermeable to water, active transport of ions out of urine
        iii.  counter current mulitplier, creates osmotic gradient
    G.  Distal convoluted tubule
        i.  final regulation of ion composition (Na and K)
     H.  Collecting Duct
        i.  water reabsorption depends on aquaporin channels
        ii.  channels regulated by ADH
        iii.  ADH regulation by baroreceptors and osmoreceptors
    I.  Na regulation
        i. nonspecific regulation, dependent on BP and GFR
        ii. specific regulation
            a.  aldosterone
                1.  increases Na/K ATPase synthesis, more Na reabsorption
                2.  release regulated by renin/angiotensin pathway
                3.  juxtaglomerular apparatus
                        A.  macula densa cells in distal convoluted tubule
                        B.  juxtaglomerular cells in afferent arteriole -release renin
                        C.  conversion of angiotensinogen to angiontensin I to angiotensin II
                        D.  importance in BP regulation as well
            b. ANF
                1.  inhibits Na/K ATPase, less Na reabsorption
    J.  K regulation
        i.  can only alter K secretion
        ii.  aldosterone - increases K secretion
        iii. release regulated by blood K levels
    K.  Acid/base balance
        i.. secretion of H+
        ii.  combination with NH3 or HPO4 to keep in urine

3.  Excretory systems in other animals
    A. Insects
        i. malpighian tubules
            a.  no filtration, only secretion
            b.  active transport of K, passive flow of water
       ii.  hormonal regulation
            a.  Rhodnius
                1.  ADH-like hormone regulates water in urine
    B.  Unique adaptations
        i.  amphibians
            a.  Sci Amer article
 
 

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Last udpated November 2004