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Osmoregulation

TermDefinition
Homeostasis Steady state does not equal equilibrium with environment --- Solute concentration --- Volume of water
Hyperosmotic Dilute medium
Hypoosmotic Concentrated medium
Regulator Steady blood solute concentration ( horizontal line parallel with x-axis)
Conformer Variable blood solute concentration and external medium solute concentration. (Isoosmotic Line)
Sites of H2O exchange Gills/lungs, Digestive tract, Kidneys
Sites of solute exchange Gills (not lungs), Digestive tract, Kidneys, Special glands---> Nasal glands ( desert, marine: birds, reptiles , sharks) Sharks- Digitiform gland)
Renal organs (Kidneys) Tubular, communicate with outside, regulate composition and volume of body fluids by excretion of solutes and water.
Why not selectively dump wastes? Energetically expensive, toxins, set up to filter blood, plasma into tubule.
Kidney positioning Paired, Retroperitoneal ( lining of cavity, sequestered behind lining from rest of organs), Adipose capsule
Sagittal Divides body into left and right
Transverse Divides body into top and bottom
Frontal Divides body front to back
Kidneys Function: 1% of body mass, receive 25% of cardiac output Two major functions: Filtration of blood: Removes wastes, esp. nitrogenous Regulation: blood volume and composition, electrolytes, blood pH, Blood pressure
Nephron Functional unit of the kidney 1.) Filtration 2.) reabsorption 3.)secretion 4.)concentration
Urine formation Primary Urine- blood filtrate, aqeuous solution introduced into renal tubules Definitive urine- passed from renal tubules
Ultrafiltration Forms primary urine. Bowmans capsule (Nephron): podocytes interdigitate= filtration slits Glomerulus (blood supply): endothelial pores in capillary (extra leaky)
Afferent vessels Into organ ( thicker)
Efferent Vessels Out of organ ( thin)
Forces that influence filtration Glomerular blood pressure ( high BP) Opposing forces: plasma colloid osmotic pressure ( due to large proteins still in blood), Capsular hydrostatic pressure.
Filtrate Resembles blood plasma, Lacks high-molceular wt. solutes (proteins) no Platelets, RBC, WBC.
Glomerular Filtration Rate (GFR) Volume of plasma filtered/unit time by all renal tubules collectively=GFR In humans GFR= 125ml/min 180L/day Urine Output is about 1-2L a day *about 99% of filtrate is reasbsorbed*
Clearance Volume of blood you would have to completely clear of a substance to yield the excreted quantity. C= [U]xV/P U= Urine [ } V= volume of urine per time (ml/min) P= Plasma [ ]
GFR=Clearance assumptions 1.) enters nephrons only via glomerulus 2.) freely filtered 3.) not secreted or reabsorbed
Substances used for GFR Inulin (not insulin). Long chain polymer of fructose
If clearance = 125 ml/min Inulin is involved, free flow, no secretion or reabsoprtion
If clearance = 65 ml/min reabsorption of substances is taking place
if clearance = 145 ml/min Secretion is occurring.
Bowman's Capsule (cortex) receives filtrate
proximal convoluted tubule reabsorption of water and solutes
Nephron loop/ Loop of Henle (Medulla) Descending limb, ascending limb. Regulates concentration of urine
Distal convoluted tubule Secretion (into tubule)
Collecting Duct Concentration
Proximal Tubule function: Reabsorption, 67% of Na+ diffuses into epithelial cells, Active transport out to interstitial fluids, Cl- follows passively to balance charges, water follows, Other items reabsorbed: Glucose, amino acids, K+, HCO3- secondary active transport.
Descending limb of LH Function: No active Transport of solutes, Passive diffusion of water out of lumen and reabsorbed into body. ( high concentration of urea in medulla drives this)
Thick segment of ascending lim of LH function: Active transport of NaCl into interstitial fluids, low permeability to water, stays in lumen. Countercurrent multiplier (ATP)
Distal tubule Function: Secretion= active transport (K+, H+, HCO3-) Reabsorption (Na+, Cl, HCO3-) Some water follows
Collecting duct Function: Permeable to water, water flows out of lumen(reabsorbed), into interstitial space, Urea diffuse too.
Mechanism of kidney Salt gradient in interstitial fluid of medulla Differential permeability of Loop of Henle High osmolarity of medulla due to urea this pulls water osmotically out of collecting duct Final urine= Hyperosmotic (high solute [ ] )
Loop variations Desert animals= longer loop, deeper in medulla Cortical nephrons= shallow juxtamedullary nephrons= deep in medulla
Regulation 1.) GFR 2.) Salt absorption 3.) water absorption
Regulation of GFR(low) If blood pressure is low, or sodium low or filtration low then mechanisms to regulate GFR start.
Juxtaglomerular apparatus (senses/regulates) Juxtaglomerular cells in wall of afferent arteriole . Macula densa cells in distal tubule: monitor Na+ and Cl- conc. and water, control blood flow into the glomerulus, thus controls filtration.
Mechanism: Renin/Angiotensin system ( if BP is low) Renin is released ( enzyme from arteriole), renin cleaves angiotensin (from liver), Into angiotensin 1, converted in lungs to angiotensin 2.
Angiotensin 2 is responsible for vasoconstriction of peripheral and efferent arterioles, raises blood pressure, increase renal blood flow in afferent arterioles, increase glomerular filtration.
Regulation of GFR(high) if blood pressure high or sodium high , then renin/angiotensin inhibited, ANF (Atrialnatriuretic factor) secreted, urinate more, secrete salt
Regulation of Sodium If low sodium or high potassium. 1.) aldosterone (hormone) Mineral-corticoid from adrenal cortex saves sodium secrete potassium, stimulate by angiotensin 2( helps retain water.
Regulation of Water Hormone ADH( anti diuretic hormone) or vasopressin is released by posterior pituitary, increased permeability of collecting duct, osmotically sensitive neurons detect
Created by: Neiller4