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Osmoregulation
| Term | Definition |
|---|---|
| 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
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