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109 Cards in this Set
- Front
- Back
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Osmoregulation |
-Maintains internal environment -Cells need appropriate amount of water and solutes to function -Animals need to get rid of waste products (Nitrogen) from metabolism |
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Renal System |
-Kidney |
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Water in |
-Drinking -Feeding -Metabolic H20 -C6H1206 + 602 --> 6H2O + 6CO2 |
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Water out |
-Breathing -Urine -Feces -Sweating (evaporative water loss) |
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Osmoregulatory Organs |
Depends on properties of transport epithelium --> gills, skin, kidneys, gut |
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Apical Surface (View figure in notes) |
Like the mucosal, luminal --- of epithelium faces the space that is continuous with the outside world e.g. lumen of gut, lumen of renal tubule |
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Basal Surface (View figure in notes) |
Like the serosal (i.e. blood/serum) -Has deep basal clefts -Faces internal environment (extracellular fluid) |
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ATP |
-Used to move ions against concentration gradients |
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3 classes of ion-motive ATPases (pumps) (View figure in notes) |
1) H+F-ATPsynthase 2) H+V-ATPase 3) P-ATPases |
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H+F-ATPsynthase (View figure in notes) |
-Mitochondria, chloroplasts -Used to make ATP with movement of H+ |
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H+V-ATPase (View figure in notes) |
-Vacuole type -Used to move H+ against a gradient with ATP hydrolysis |
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P-ATPases (View figure in notes) |
-Phosphorylated intermediates --Na+/K+ ATPase --Ca2+ P-ATPase --H+/K+ P-ATPase -----H+ into gastric juice |
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Mammals (View figure in notes) |
Kidney - makes up 1% of body --get 25% of cardiac output |
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Cortex |
Outer |
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Medulla |
Inner |
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Path of urine |
Renal pelvis --> Ureter --> Bladder --> Urethra --> Outside (penis/vulva) |
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Humans |
-Produce about 1 liter urine/day -pH ~ 6 -Kidneys - maintain volume and composition of body |
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Kidneys |
Maintain volume and composition of body |
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Urine |
Reflect H20 ingested & H20 of metabolism -Food intake affects urine -Normally yellow ----methylene blue (a dye) --> blue ----asparagus --> odor |
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Micturition
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-Urination |
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Micturition - Urination |
-Contract bladder wall (smooth muscle) -Relax skeletal sphincter muscle around the urethral opening |
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Nephron (View figure in notes) |
-Functional unit of the kidney -Epithelial tube closed at one end and opened at the distal end -Empties into the Collecting Duct (CD) -CDs combine to form papillary ducts that lead to renal pelvis |
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Blood supply to the nephron |
Comes from renal artery via an afferent arteriole which forms a tuft of capillaries called the glomerulus |
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The nephron has many segments, each with an epithelium with specialized transport |
Segments include: -Bowman's capsule -Proximal Convoluted Tubule (PCT) -Loop of Henle which is divided into the descending limb, and ascending limb -Distal Convoluted Tubule (DCT) |
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The Distal Convoluted Tubule (DCT) connects to |
the Collecting Duct (CD) |
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Ultrafiltration occurs between the |
-Glomerulus & Bowman's Capsule -So an ultra filtrate from the blood enters the nephron |
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Pre-urine will be processed |
-in the nephron to produce the urine that collets in the bladder |
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2 types of nephrons |
1) Juxtamedullary nephron 2) Cortical nephrons |
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Juxtamedullary nephron |
-Glomerulus in inner part of the kidney cortex with long loops in the medulla, they make concentrated urine |
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Cortical Nephrons |
Glomerulus in upper cortex with short loops in the cortex |
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Circulation |
Juxtamedullary nephrons are surrounded by a structure called the vasa recta |
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Vasa recta |
-Is composed of afferent and efferent arterioles connected by a capillary bed which surrounds the loop of Henle -Takes up material the exits the nephron |
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Urine Production (3 processes)
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1) Filtration of blood plasma 2) Tubular Reabsorption 3) Tubular Secretion |
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Filtration of blood plasma |
Creates ultra filtrate at Bowman's Capsule |
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Tubular Reabsorption |
99% of water and most salts, but leaves the waste products (urea) |
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Tubular Secretion |
of substances via active transport into pre-urine |
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Glomerular Filtration (3 Factors Involved) |
1) Net Hydrostatic Pressure 2) Colloid Osmotic Pressure 3) Hydraulic Permeability |
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Net Hydrostatic Pressure |
Difference between lumen of the glomerular capillaries and lumen of Bowman's Capsule |
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Colloid Osmotic Pressure |
of blood plasma |
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Hydraulic Permeability |
(Sieve like properties of 3 layers of tissue between the compartments, blood vessel, and nephron lumen) |
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Humans and pressure |
Glomerular Capillary Pressure --> 55 torr (Minus) Bowman's Capsule Intracapsular Pressure --> 15 torr (Minus) Colloid Osmotic Pressure --> 30 torr Net Filtration Pressure --> 10 torr |
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Net Filtration Pressure (10 torr) |
This pressure determines the glomerular filtration rate alone with the permeability of Bowman's capsule. |
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Filtrate includes: |
-water -salts -urea -glucose -sucrose -but not large molecules like proteins (serum albumen, Hb, etc.) |
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Intrinsic Regulation of Filtration |
1) Increase blood pressure in afferent arteriole 2) Juxtamedullary apparatus (JGA) 3) Sympathetic neurons in afferent arterioles |
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Increase blood pressure in afferent arteriole |
Increase blood pressure in afferent arterioles --> increase stretch in vessel --> increase blood flow to Glomerulus stretch leads to vasoconstriction & decrease in flow since macula densa release ATP & adenosine --> increase vasoconstriction |
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Juxtamedullary Apparatus (JGA) |
-at Bowman's Capsule -between afferent and efferent arterioles and Distal Convoluted Tubule (DCT) |
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2 Types of cells present in the Juxtamedullary Apparatus (JGA) |
1) Macula Densa 2) Granular cells or Juxtaglomerular cells |
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Macula Densa |
-monitors filtrate flow in Distal Convoluted Tubule (DCT) and osmolarity --> causes vasoconstriction or vasodilation via ATP and adenosine release or vasodilation via nitric oxide (NO) |
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Granular or Juxtaglomerular cells |
-in wall of afferent arterioles -release renin (an enzyme) which activates a hormone that regulates blood flow |
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Sympathetic neurons |
-in afferent arterioles --> cause vasoconstriction, which will decrease the Glomerular Filtration Rate (GFR) |
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Tubular Reabsorption |
-99% of water filtered is reabsorbed -1800 g of NaCl filtered and only 10 g in urine/day |
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Filtration-filtered |
-reabsorption -secretion |
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Renal Clearance |
Measure of whether a substance is secreted or reabsorbed |
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Formula for clearance |
C = UV/P C = clearance (mL/min) V = Urine volume / unit time U - concentration of substance in urine P = concentration of substance in plasma |
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If substance is neither secreted nor reabsorbed, then |
C = GFR GFR = Glomerular Filtration Rate |
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Example of a substance that is neither secreted nor reabsorbed |
Inulin |
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If C < GFR |
the substance is reabsorbed |
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If C > GFR |
the substance is secreted |
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If C = GFR |
the substance is neither secreted nor reabsorbed |
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Glucose C = 0 mL/min |
-It is filtered at the glomerulus and reabsorbed in the tubule via a glucose cotransport with sodium ions (SGLT 2) |
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Only at high plasma glucose concentration does one find glucose in urine |
-Called glycosuria -since the concentration surpasses the carrying capacity of the glucose transporter |
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Diabetes mellitus |
uncontrolled can lead to high plasma glucose and glycosuria so now there is an SGLT 2 inhibitor called Invocana allows for loss of glucose in urine when plasma level is high, but not above the carrying capacity of SGLT 2 so you lower blood glucose via urine |
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Proximal Convoluted Tubule |
-70% of Na+ removed from lumen via active transport along with a proportional amount of water --> Cl- follows -75% of filtrate is reabsorbed before it reaches the loop -fluid here is isosmotic with interstitial, about 300 mOsmol/L -glucose, amino acids are reabsorbed with Na+ dependent cotransporter -phosphate, Ca2+ are reabsorbed up to the body requirements -parathyroid hormone modulates the Ca2+/phosphate reabsorption via calcitrol, the active form of Vitamin D |
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Descending limb of Loop of Henle and the thin ascending limb of the Loop of Henle |
Cells have few mitochondria and no brush border (less surface area) |
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Descending limb of Loop |
-has no active transport of salts (NaCl) -low permeability to NaCl and urea -water exits to make the filtrate more concentrated (aquaporins present) |
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Thin Ascending Limb of Loop of Henle |
-has no active transport -highly permeable to NaCl -low permeability to water (no aquaporins present) and urea |
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Thick Ascending Limb of Loop of Henle |
-active transport of NaCl out of lumen into interstitium -low water permeability, solutes leave, water does not -fluid in lumen becomes hypo-osmotic relative to the extracellular fluid |
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Distal Convoluted Tubule and Collecting Duct |
-transport of K+, H+, NH3 into lumen -transport of Na+, Cl-, HCO3- out of interstitial into lumen -water passively follows -salt transport is under hormonal control to adjust osmolarity |
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Collecting Duct water permeability is controlled by |
Antidiuretic Hormone (ADH) aka vasopressin |
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Since water follows NaCl this changes the volume of extracellular fluid (ECF) |
-increase ECF --> increase blood volume --> increase blood pressure -decrease ECF --> decrease blood volume --> decrease blood pressure |
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Blood pressure indicates: |
blood volume |
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RAAS |
Renin - Angiotensin - Aldosterone System |
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Macula Densa & JGA |
-able to sense blood pressure -decrease BP or decrease solute reaching DCT --> release of RENIN (an enzyme) |
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Renin then acts on: |
-Angiotensinogen, an alpha globulin, which is produced by the liver and is constitutively present in the plasma |
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Angiotensinogen |
-NOT released due to low blood pressure or a drop in solute delivery to DCT -it is always present in plasma |
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Angiotensin I |
Renin cleaves off Angiotensin I from Angiotensiongen
(Angiotensin I is not biologically active) |
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Angiotensin Converting Enzyme (ACE)
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-acts on Angiotensin I to cleave off a few amino acids to make Angiotensin II
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Angiotensin II
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-vasoconstriction --> increase BP
-increases GFR by acting on arterioles -releases aldosterone (a hormone) from adrenal glands --> increase Na+ reabsorption in DCT, water follows -----increase BV --> increase BP -water retention by stimulating release of ADH -causes thirst which leads to increase in water uptake |
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ACE (Angiotensin Converting Enzyme) inhibitors
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-captopril
-cause a decrease in BP in patients with moderate hypertension -inhibits production of Angiotensin II from Angiotensin I which prevents the RAAS |
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Negative feedback
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These effects of RAAS cause a negative feedback which inhibits the release of renin by JGA
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Atrial Natiuretic Peptide (ANP) |
-from the atria and an analog from the brain ---BNP oppose the RAAS -oppose RAAS --> Na+ excretion --> decrease urine volume --> decrease BP They inhibit Na+ reabsorption in kidneys and inhibit release of aldosterone from adrenal glands and secretion of ADH from pituitary |
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Tubular Secretion |
-K+ -H+ -ammonia -organic acids -organic bases |
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Secretion of organic ions removes: |
potentially harmful substances from blood |
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K+ is filtered at: |
glomerulus and actively reabsorbed in PCT via Na+/2 Cl-/ K+ cotransport in the apical membrane (luminal side) and Na+ / K+ ATPase in basolateral membrane (serosal side) |
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K+ is actively secreted in: |
DCT and CD |
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Aldosterone controls |
-Na+ reabsorption -K+ excretion |
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Increase in K+ in blood causes: |
-release of Aldosterone from adrenal glands causing an increase in tubular K+ secretion |
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A decrease in plasma Na+ acts via: |
RAAS to cause release of Aldosterone |
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Regulation of pH by kidney |
-secrete H+ (protons) all along tubule -Na+/H+ antiporters in PCT and Loop of Henle -DCT and CD have specialized cells that deal with pH |
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The 2 types of specialized cells DCT and CD have that deal with pH |
1) Type A cells 2) Type B cells |
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Type A cells |
-secrete H+ -reabsorb HCO3- and K+ |
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Type B cells |
-secrete HCO3- - |
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In the filtrate the H+ can react with various molecules to trap them in urine |
1) NH3 + H+ produces NH4+ --ion not permeable, cannot leave lumen 2) HCO3- + H+ produces CO2 and H20 3) HPO42- + H+ makes H2PO4 |
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The osmolarity increases in: |
the interstitium the deeper you go in the medulla of kidney |
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At the cortex it is 300 mOsmolar (View figure in notes) |
moves to 1200 mOsmolar at the end of loop of Henle (up to 3000 mOsmolar in some animals) |
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As the filtrate moves down the nephron from cortex |
water is lost to the blood passively via osmosis |
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In ascending limb of loop |
NaCl is lost, but not water (NaCl active transport) |
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Thick/thin ascending limb is |
impermeable to water |
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Interstitial osmolarity due to active transport of NaCl from ascending loop and selective permeabilities of: |
-Water, salt, urea in other segments of nephron |
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Filtrate in CD has:
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high urea concentration |
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From PCT up to CD |
urea is impermeable in most segments, except the thin ascending limb of the loop |
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Urea exits CD as: |
filtrate moves down into medulla which makes osmolarity of insterstitium higher |
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Urea enters the nephron from: |
interstititum at the thin ascending limb of the loop to regulate the urea concentration |
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Vasa recta moves blood: |
in opposite direction of the ultra filtrate in the nephron -- counter current flow |
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Blood takes up: |
salts/urea and gives up water to the interstitium |
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There is an increase in blood osmolarity as it: |
descends into the medulla and decrease in osmolarity as it ascends |
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Control of water reabsorption |
-either low BP or high blood osmolarity will cause the hypothalamic neuroscretory cells which have secretory terminals in the pituitary release ADH (vasopressin) into blood stream |
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ADH cause: |
an increase in water permeability by increasing aquaporins in CD and water is reabsorbed into ECF and then blood which increases BP and decreases blood osmolarity, which in turn stops secretion of ADH |
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Alcohol inhibits: |
release of ADH so lose water to urine and lower blood osmolarity which may lead to hangover |
