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89 Cards in this Set
- Front
- Back
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What do factors do the kidneys control that help maintain homeostasis?
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- Volume and composition
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What are some of the main functions of the kidneys?
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- Filtering blood plasma
- blood volume, pressure, and osmotic concentration regulation - secreting renin - secreting erythropoietin - synthesizing calcitrol |
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What are some examples of metabolic waste materials?
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- metabolic wastes
- nitrogenous wastes - urea - uric acid - creatinine |
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What is excretion and how is it carried out?
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-separation and elimination of wastes
- respiratory system - integumentary system - digestive system - urinary system |
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What are some of the principle parts of the nephron?
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- Renal corpsucle
- glomerulus - glomerular capsule - renal tubule - PCT - nephron loop - DCT - collecting duct |
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What are the two different types of nephrons?
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- cortical
- juxtamedullary |
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What are the 4 main steps of urine formation?
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- glomerular filtration
- tubular reabsorption - tubular secretion - water conservation |
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What is glomerular filtration?
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- filtration of blood
- makes "filtrate" |
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What is tubular reabsorption?
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- Returning water and solutes to blood
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What is tubular secretion?
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- Addition of substances to "filtrate"
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What is water conservation?
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- conserving water
- concentrating urine |
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Can you describe the role of capsular space in glomular filtration?
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- passive and non-selective process
- hydrostatic pressure |
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Can you describe the role of the filtration membrane during globular filtration?
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- capillary endothelium
- fenestrated - basement membrane - negatively charged gel |
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Can you describe the function for filtration slits for globular filtration?
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- podocytes
- foot processes - negatively charged |
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Can you list the permeable materials?
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- water
- electrolytes - glucose - amino acids - nitrogenous wastes - vitamins |
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Can you list the non permeable materials?
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- calcium
- iron - fatty acids - thyroid hormones - proteins |
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What are the different filtration pressures?
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- glomerular hydrostatic pressure
- capsular hydrostatic pressure - calloid osmotic pressure - capsular osmotic pressure |
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What is globular hydrostatics pressure?
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- Higher (60mmHg) than other capillaries (15mmHg)
- Efferent arteriole smaller diameter than afferent arteriole |
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What is colloid osmotic pressure measuring?
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- Pressure of proteins, etc within blood
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What is special about capsular osmotic pressure?
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It is essentially 0 mmHg unless kidney disease
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What is globular filtration rate (GFR)?
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- Amount of filtrate per minute by kidneys
- males = 125 mL/minute or 180 L/day - females = 105mL/ minute or 151 L/days - 50 - 60 times more than blood plasma - only 1-2 Liters per day of urine output |
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What happens if GFR is too high? Too low?
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Too high
- fluid too high - urine output rises - dehydration - electrolyte depletion Too low - Fluid too slow - reabsorb wastes |
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How are homeostasis mechanisms maintained?
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- changes in glomerular BP
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What are the homeostatic mechanisms?
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Renal autoregulation
- kidneys alter GFR despite high arterial BP Sympathetic control - SNS Renin angiotensin mechanism |
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What is renin auto regulation?
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- Regulation of afferent/efferent arterioles
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What are the steps of the myogenic mechanism?
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- Pressure change in renal blood vessels
- Smooth muscle contracts when stretched - high BP = stretches AA = constricts AA = lower blood flow |
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What is tubuloglomerular feedback?
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- Juxtaglomerular apparatus (JGA)
- juxtaglomerular cells (JG) - macula dense cells - mesangia cells |
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What is the job of the macula densa?
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- Flow or fluis composition
- Secrete messenger to stimulate JGC |
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What do JG cells do?
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- constrict or dilate afferent arteriole
- secrete renin |
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What do masangiali cells do?
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- chemo/mechanoreceptor
- communication between MD and JGC |
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How does the sympathetic nervous system affect the kidneys?
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- Constrict afferent arterioles
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How doe adrenal epinephrine stimulate sympathetic control?
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- constrict afferent arterioles
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How does strenuous exercise or circulatory shock affect sympathetic control?
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- shunts blood away from kidneys
- indirectly triggers renin-angiostensin mechanism stimulating the macula dense cells - SNS directly stimulates JG cells to release renin |
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How is renin released in the renin-angiotensin mechanism?
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- Angiotensin I made
- converted to angiotensin II - Angiotensin converting enzyme (ACE) |
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What happens when angiotensin II vasoconstricts?
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- Increases MAP (mean arteiole pressure)
- Constrics AA and EA - Stimulates aldosterone - Stimulates ADH |
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What is happening during reabsorption
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- reclaims materials
- from nephron to blood pertibular capillaries |
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What is happening during secretion?
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- Removes materials
- From blood to nephron - pertibular capillaries |
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Why are reabsorption and secretion so important?
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Maintain homeostasis
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What is the difference between the transcellular route and paracellular route of reabsorption?
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Transcellular
- through cytoplasm Paracellular - move between cells |
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What are the 3 methods of reabsorption?
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- primary active transport route
- secondary active transport - solvent drag |
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What is primary active transport?
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- sodium potassium pump
- antiport |
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What is secondary active transport?
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- indirectly by ion gradients
- SGLT - symport |
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What is solvent drag?
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- Solutes follow solvent
- Gradients must be present |
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What is the distribution of reabsorption for a proximal convoluted tubule?
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- Reabsorbs most tubular fluid
- All glucose, lactate, and amino acids - 65 - 70% of sodium - 65 - 70% of water - 90% of bicarbonate - 50 % of chloride - 90% of potassium - Most other electrolytes |
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What does sodium reabsorption do?
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- Creates osmotic and electrical gradient to drive reabsorption of water and others
- out of tubule and into tubule cell - into ECF - Into particular capillary |
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How is sodium reabsorption achieved out of the tubule and into the tubule cell?
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- Facilitated diffusion
- Symport with glucose, AA, phosphate, lactate - Antiport with H+ |
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How is sodium reabsorption achieved into the ECF?
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- Antiport with Na-K pump
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How is sodium reabsorption achieved into the peritublar capillary?
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- Solvent drag with water
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What are the factors for chloride reabsorption?
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- chloride follows sodium
- water reabsorption |
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How is chloride reabsorption into tubule cells achieved?
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- Antiport exchange (sodium)
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How is chloride reabsorption into ESF achieved?
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- Symport (K+ - Cl-)
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How is chloride reabsorption into peritubular capillary achieved?
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- Solvent drag
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Why is there no concentration gradient for glucose reabsorption?
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- More glucose in cell than tubule
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How is glucose reabsorption from the lumen to the tubule cell achieved?
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- Use SGLT
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How is glucose reabsorption from the tubule cell into the ECF achieved?
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- Facilitated diffusion
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How is glucose reabsorption into the peritubular capillaries achieved?
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- Solvent drag
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What is transport maximum?
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- Reflects limited number of protein carriers in renal tubules available
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How is the transport maximum determined?
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Number specific to material carried
- example glucose - Tm = 320 mg/min. - Normal = 125 mg/min |
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What happens if no carrier is available?
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- The solute remains and appears as part of urine
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Where does bicarbonate reabsorption occur?
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Bicarbonate reaction occurs within a tubule cell
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How do electrolytes undergo reabsoprtion?
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- K, Mg, P04 diffuse with water
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How do nitrogenous wastes undergo reabsoprtion?
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- Urea diffuses with water
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How do organic solutes undergo reabsorption?
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- Lactates, amino acids, peptide hormones
- symport with sodium - leave via facilitated diffusion |
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Why does water reabsorption occur?
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- Tubular fluid is hypotonic compared to other
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How does water reabsorption into the tubule cell occur?
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- Osmosis
- Diffusion through aquaporin |
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How does water reabsorption occur into the ECF?
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- Osmosis
- Through aquaporin |
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How does water reabsorption into peritubular capillaries occur?
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- solvent drag
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What is happening during tubular secretion in PCT?
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- waste removal from blood
- urea, uric acid, bile acids, ammonia, catecholamines, creatine - pencillin, pollutants, morphine, aspirin |
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What maintains the acid-base balance in tubular secretion in PCT?
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Hydrogen
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What is the primary purpose of the loop of henle?
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- Enable collecting duct to concentrate urine and conserve water
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What are the thin segment permeability characteristics of the loop of hence?
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- mostly descending limb
- water cannot leave tubule |
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What are the thick segment characteristics of the loop of hence?
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- mostly ascending limb
- impermeable to water - Na transport not cpupled to water movement - Contransport of Na, K, and Cl |
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What are the loop of Henle reabsorption rates?
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- 20 - 25% water
- 20 - 25% Na+ - 35% Cl- - 40% K+ - in ascending limb |
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What keeps the tubular fluid secretion under control?
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DCT and CD reabsorption under hormonal control?
- Principle cells - receptors for hormones - involved in salt and water balance - Intercalated cells - reabsorb K, secrete H - Mainly acid-base balance |
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What is a nickname for alosterone and DCT/CD?
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"salt-retaining hormone"
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What is aldosterone released in response to?
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- Decreased blood volume and BP
- low Na concentration or high K conccentration - stimulating renin - angiotensis mechanism |
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What actions does aldosterone promote?
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- Principle cells of DCT and portable part of collecting duct
- Increase Na reabsoprtion - Stimulates synthesis of more Na transporters and K channels - Movement of Sodium is followed by Cl and water - Reduces urine volume - more K in urine but less Nacl |
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What are the results of no aldosterone?
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- No sodium reabsorbed from DCT and CD?
- Catastrophic loss of sodium via excretion in urine |
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What is ANP and how is it stimulated?
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- Atrial Natiuretic Peptide (or Factor)
- secreted by cells in atrial myocardium - Stimulated by high blood pressure or high blood volume |
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What are the actions of ANP?
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- Dilation of AA and constriction of EA
- Increases GFR - Inhibits aldosterone and renin secretion - Inhibits ADH - Inhibits Na+ and water reabsorption in CD - reduced blood volume |
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What is ADH and what does it do?
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- Antidiurtic hormone
- increases permeability of CD - water reabsoprbed into blood |
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What is parathyroid hormone and what does it do?
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- Promotes Ca reabsoprtion in loop and DCT
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How is water conversation absorbed?
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- Collecting Duct
- Reabsorbs water - Creates hypertonic (concentrated) urine |
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Why is water reabsorption favored?
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- ECF osmolarity is higher than medulla
- Medullary (lower) portion of CD more permeable to water than NaCl |
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What does the concentration of urine depend upon?
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- hydration state
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What do water diuresis depend upon?
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- Large water intake = hypertonic urine
- Cortical CD reabsorbs more NaCl |
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What happens during dehydration?
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- ADH released at a fairly constant rate
- If reduction in blood solute concentration, ADH declines - # of aquaporins in in principal cells of CD increases - more water into ECF - concentrated tubular fluid |
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Describe the countercurrent multiplier
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- Flow of tubular fluid through nephron loop
- Juxtamedullary nephrons - Maintains osmotic gradient - Salinity of renal medulla is 4X the cortex - would attempt to equilibrate salt content |
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What is the counter current exchange?
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- Relationship of nephron group, CD and vasa recta
- maintains hypertonic envrionment of renal medulla - movement of NaCl, water, and urea in each structure |
