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184 Cards in this Set
- Front
- Back
What organs comprise the urinary system?
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-Urine forming organs: Kidneys
-Urine storing and transport organs: ureters, bladder and urethra. |
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What are the urine forming organs?
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The kidneys
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What are the three regions of the internal Kidney?
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-Renal Cortex: outer layer
-Renal Medulla: Inner layer: darker in color -Renal Pelvis |
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What is the smallest functional unit of the Kidney?
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The nephron
|
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How many neprhons are present in each kidney?
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1 million
|
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What tissues make up the vascular component of the nephron?
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-Afferent arteriole (branch of the renal artery)
-Glomerulus (tuft of capillaries) -Efferent Arteriole -Peritubular capillaries: drain blood back to the renal vein |
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In general, what makes up the tubular component of the Nephron?
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-Bowman's capsule
-Proximal convoluted tubule -Descending and Ascending Loop of Henle -Distal convoluted tubule -Collecting Duct |
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How many nephrons drain into a common collecting duct?
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About 6-8
|
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What is the Juxtaglomerular Apparatus?
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Area where distal tubule comes in very close to the glomerulus and regulates the formation of urine by the nephron
|
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What are the 3 regional differences in the 2 types of nephrons?
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1. How superficial or deep the glomerulus sits in the cortex
2. The length of the loop of henle 3. A portion of their vasculature |
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What are the 2 types of nephrons?
What percentage of each is present in the kidneys? |
1. Superficial Cortical Nephrons (80%)
2 Juxtamedullary nephron (20% |
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Describe the (Superficial) Cortical Nephrons.
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- In the outer cortex
-Short loops of henle that dip shallowly into the renal medulla -Have peritubular capillaries that surround the entire nephron |
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Describe Juxtamedullary Nephrons.
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-Have very long loops of henle that extend deep into the renal medulla (tips are close to renal pelvis)
-Instead of peritubular capillaries they have VASA RECTA |
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What is the vasa recta?
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The vasculature that specifically travels alongside the loop of henle in the juxtamedullary nephrons.
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Why does the Vasa Recta only run alongside the loop of henle in the juxtamedullary nephrons?
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-To not disturb the osmolarity inside the medulla.
-Prevents excess fluid exchange |
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What key role do the juxtamedullary nephrons play in the body?
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-They allow us to create urine of varying concentrations
-Allow for our body's ability to conserve or excrete water |
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What type of nephrons predominate the kidneys of camels?
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Juxtamedullary nephrons (allow for more water conservation)
|
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What are the 3 basic renal processes?
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1. Glomerular filtration
2. Tubular Reabsorption 3. Tubular Secretion |
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What percentage of the CO is received by the kidneys?
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About 20%
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What is the perenchyme?
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They actual tissue of the kidney
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What is the movement called if substances are filtered from the tubule into the periuibular capillaries?
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Tubular reabsorption
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What is tubular secretion?
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Substances from the peritubular capillaries move into the renal tubule to become part of urine
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Where does blood go first after being filtered by the glomerulus?
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Proximal Convoluted Tubule
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What section of the tubular system do we make the most adjustments?
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Proximal Tubule
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What is the renal corpuscle?
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Glomerulus + Bowman's Capsule
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What are the 3 layers of the glomerular membrane from capillary side --> out?
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1. Innermost: Endothelial wall of glomercular caps
2. Basement membrane: acellular layer, small sheet of CT covering glomerular caps 3. Inner layer of bowman's capsule: composed of podocytes |
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What are podocytes?
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Comprise the inner layer of bowman's capsule
-have long foot processes that wrap around the glomerular membranes and interdigitate |
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What are the 3 layers of the glomerular membrane designed to do?
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Ensure NO plasma proteins and no cells can get filtered and end up in the urine
|
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What is the fluid that is filtered in the capsule called?
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Protein-free plasma (plasma free filtrate)
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What can the presence of protein in the urine be an indicator for?
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Hypertension
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What are the forces involved in GLOMERULAR FILTRATION?
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Like the Starling forces
1. Capillary blood pressure 2. Plasma Oncotic Pressure 3. Hydrostatic pressure (in bowman's capsule **No oncotic pressure for bowman's capsule because proteins don't get through glomerular membrane |
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What kind of force is Capillary blood pressure in glomerular filtration?
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-Pushing pressure that promotes glomerular FILTRATION
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What kind of pressure is exerted by plasma oncotic pressure in glomerular filtration?
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-osmotic pressure from the proteins in the plasma
-pulling pressure that opposes glomerular filtration |
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What does hydrostatic pressure do to glomerular filtration?
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-Is the fluid in Bowman's capsule causes a pushing pressure fromt the capsule.
**opposes glomerular filtration** |
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Glomerular filtration is highly dependent on what force?
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Capillary blood pressure
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What value must the net filtration pressure be to have urine formation?
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Must have a + number!
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What does the Net filtration pressure depend on?
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Capillary blood pressure
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What is the glomerular filtration rate (GFR)?
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mLs/min the kidneys are filtering and is an important measure of renal function
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What does the GFR depend on?
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1. Status of Net Filtration Pressure (determined by Capillary Blood Pressure)
2. SA available for filtration 3. Permeability of the glomerular membrane |
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What is glomerulonephritis? What can it lead to?
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-active inflammation of the glomerular membrane
-can lead to glomerulosclerosis (scarring) -Scar tissue reduces permeability, so GFR suffers |
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What 2 types of control are used in GFR regulation?
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1. Autoregulation
2. Extrinsic control of the GFR |
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What is the overall purpose of autoregulation of the kidneys?
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-Since our BP is fluctuating often, the kidneys use this method to prevent the normal BP fluctuations from affecting GFR
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What response occur through autoregulation of the glomerulus if there is a drop in BP?
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Drop in BP --> more blood flow through afferent arteriole --> rise in glomerulus BP --> rise in NFP--> rise in GRF
**Here, autoregulation kicks in and causes constriction of the afferent arteriole** |
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What happens in the glomerulus if the afferent arteriole is constricted?
What is this a response to? |
-Get less blood in the glomerulus --> CBP drops down
*This would occur if the bodies BP were to rise** |
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Why would autoregulation kick in to dilate the afferent arteriole?
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To prevent a drastic change in GFR in a response to a drop in systemic BP
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How does autregulation sense and correct for a change in GFR?
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-Through the JGA
|
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What two types of cells are located in the JGA?
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1. granular cells
2. Macula densa cells |
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What 2 functions do the cells of the JGA have?
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1. sensory function
2. secretory function |
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What do the cells of the JGA sense?
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Can sense pressure within their lumen
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What is the job of the granular cells of the JGA?
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Sense pressure within the afferent arteriole
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The macula densa cells are responsible for what?
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Sensing the rate of fluid flow through the distal tubule
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Which cells are responsible for regulating the diameter of the afferent arteriole?
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-Granular cells
-If there is a rise in GFR, they secrete a vasoconstricor -A drop in GFR will result in a vasodilator |
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What is the tubuloglomerular feedback system?
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The macula densa cells reinforce the message sent by the granualr cells.
-Is the mechanism behind GFR autoregulation! -Constant monitoring of arteriole BP -consequent adjustment of the afferent arteriole |
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Does the GFR stay stable during changes in BP?
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Yes because of tubuloglomerular feedback system!
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What entails extrinsic control of the GFR?
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When the sympathetic NS intervenes and effects GFR
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What is the goal of extrinsic control of GFR?
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to OVERRIDE AUTOREGULATION!!!
-Alters GR in an attempt to control BLOOD VOLUME and therefore BP |
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Is there any parasympathetic innervation to the kidneys?
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NO, the vagus nerve does not innervate the kidneys
-sympathetic input is either high or low |
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If sympathetic NS causes you to INCREASE GFR, what reaction will you feel in the body?
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-Increase in urine output
-Peeing off volume |
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What affect does sympathetic STIMULATION have on the afferent arteriole?
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constrict it!
-NE and E bind to alpha 1 adrenergic receptors on the afferent arteriole --> decreasing GFR |
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Where does the 80% of plasma, not filtered into the glomerulus, go?
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-Into the peritubular capillaries and is subject to tubular secretion and tubular reabsorption
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What process of tubular filtration is ALWAYS SELECTIVE?
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Tubular REABSORPTION!
-can happen through passive or active transport |
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What 2 layers must substances cross in order to get reabsorbed into the peritubular capillaries?
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1. Luminal membrane: faces the lumen of the tubule
2. Basolateral membrane: faces the interstitial space |
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What percentage of H2O, glucose, Na+ and K/Cl- that was filtered get reabsorbed?
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Water: 99%
Glucose: 100% Na+: 99.5% K/Cl-: 50% |
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What does Na+ need to be reabsorbed?
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Energy (actively reabsorbed)
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Why is Na+ so draining and yet important in the kidney?
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-89% of the energy requirements of the kidney is used in the transport of Na+
-But we COUPLE the transport of many substance to the movement of Na+ |
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Na+ requires energy to get across what membrane?
Which membrane does it move passively over? |
-Energy: basolateral membrane
-Passive: luminal membrane |
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Where is the largest portion of Na+ reabsorbed?
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Proximal Tubule
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What role does the reabsorption of Na play in the ASCENDING loop of Henle?
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-Role in the kidney's ability to concentrate urine and conserve water
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What controls the Na reabsorption in the distal tubule and the collecting duct?
What role does it play? |
Hormonal control
-Plays a role in regulating the ECF volume, blood volume and BP |
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What is the only tubule that does not have Na Reabsorption?
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The descending limb of the Loop of HENLE
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What pump is used to get Na+ back to the bloodstream and where is it located?
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Na/K ATPase pump
-clustered along the basolaterl membrane of the renal epithelial cells |
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What is Na+ job in the proximal convoluted tubule?
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In the PCT, Na+ is DIRECTLY couple to the reabsorption of glucose, AA and water soluble vitamins
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What type of transporters are along the luminal membrane of the PCT?
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COTRANSPORTERS for glucose, AAs and water soluble vitamins.
-Couple with Na+ |
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How do glucose, AAs and water soluble vitamins get across the basolateral membrane once Na has transported them into the tubule cell?
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-They cross the membrane usually through facilitated diffusion by a protein carrier.
-Diffuse into the pertitubular capillaries |
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Why is there a LIMIT to how fast substances can be transported across the tubules?
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Because it requires carriers
-at some point we could potetially saturate all the transporters |
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What is the Tubular Maximum?
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-the maximal RATE of transport of a substance
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What is the RENAL THRESHOLD? how is it different from the tubular maximum?
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-Renal threshold: max plasma concentration (plasma concentration that pushes you to your tubular maximum)
-Tubular maximum: max RATE of reabsorption. |
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How much higher than the normal plasma concentration for glucose is needed for it to be seen in the urine?
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3x
|
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What happens to the renal threshold if the GFR decreases?
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It increases: it takes a higher plasma concentration to get you to the tubular max
-Can occur in elderly due to age related decline in GFR |
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What does the degree to which Na is reabsorbed in the distal and collecting duct depend on?
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-Varies on the body's contol of overall blood volume
-Under hormonal control |
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What does Na transport in the distal tubule and how?
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Transports chloride
-uses cotransporter! |
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How does Na get into the collecting duct?
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Crosses through a leak channel
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What tubule is the only place where WATER is not reabsorbed?
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the ascending loop of henle
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What is the most important substance to be coupled with Na?
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WATER!
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How much water is reabsorbed in the proximal tubule and the descending loop of henle?
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80%
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What are the 2 mechanisms that water is reabsorbed?
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1. Paracellular Route
2. Transcellular Route |
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What is the paracellular route of water reabsorption?
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-Occurs between epithelial cells through leaky tight junctions (majority in the PCT)
-After Na is pumped across basolateral, it accumulates and creates a strong OSMOTIC gradient that allows for movement of water in between these epithelial cells |
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What is the transcellular route of water reabsorption?
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-water moves THROUGH epithelial cells
-Requires aquaporins (always on the BASOLATERAL membranes on tubular epithelium cells) |
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What are luminal aquaporins?
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-Present in the PCT and descending LofH
-Under hormonal (ADH) control in the DT and CD |
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What hormone controls the luminal aquaporins in the DT and CD?
What is its function? |
ADH!!!
-Regulates the extend of water reabsorption in these parts of the nephron |
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How and where does chloride reabsorption occur?
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-in the -PCT
-After water leaves the tubule it concentrates everything left behind and creates a gradient for Cl, urea and Potassium to exit through tight junctions -Cl is secondary to K |
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Where does the electrical gradient occur in the PCT?
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In the lateral spaces where there is a high density of Na.
-Cl's movement through leaky tight junctions is promoted! |
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What substance in the PCT is both a byproduct and also used to create urine?
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Urea
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What % of urea do we reabsorb and what is its reabsorption connected to?
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50%
-connected to the extent of Na-water reabsorption (urea reabsorbed secondary to water) |
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What does it mean if a person has high BUN levels?
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They may be dehydrated
-urea reabsorption follows H2O reabsorption |
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What dictates the reabsorption of K and where does it occur?
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-in the PCT
-reabsorbed secondary to Na/water |
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Do the kidneys help control blood glucose levels?
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NO, there is no homeostatic feedback loop that allow for an error of 300%
|
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Do the kidneys help regulate the blood levels of Ca++ and Phosphate?
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Yes!
-Renal threshold for Ca++ and phosphate reasorption is set to = the normal plasma concentration of these 2 substances |
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What does not get reabsorbed in the nephron?
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Waste (endogenous or unanticipated *drugs)
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What is tubular secretion?
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The sending of substances to the tubules from the peritubular capillaries to be excreted in the urine
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What type of transport is used in tubular secretion?
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Almost always active and selective
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Where does H+ secretion occur?
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-PCT
-CD -LofH |
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How does H+ get secreted?
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-Comes from the blood first crosses the basolateral membrane through a proton pump
-Crosses luminal membrane (mechanism depends on the tubule) --PCT: uses Na+/H+ antiporter (exchanger) --DC and LofH: facilitated diffusion |
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What substance is both reabsorbed and secreted?
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Potassium
|
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Is potassium secretion regulated by the body?
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Yes
-when potassium levels are low, secretion will drop. |
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What is the mechanism for K secretion?
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The SAME as NA REABSORPTION!
-occur simultaneously |
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Where does K secretion occur?
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DT and CD
|
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What happens to K secretion if you enhance Na reabsorption?
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K secretion is enhanced
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Do we have K secretion everywhere Na is reabsorbed? Why or Why not?
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No
-becuase the opportunity for K to cross the luminal memrane is ONLY at the DT and CD -in the PCT and ascending, the K channels are on the basolateral membrane |
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What controls the coupling of Na and K?
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Aldosterone
|
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What is the function of Aldosterone?
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It promotes the reabsorption of Na and the Loss of K!
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What tubules does aldosterone act on?
What does it do there? |
DT and CD
-Acts to reabsorb Na and secrete K |
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What 2 effects does aldosterone have?
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1. immediate: Na reabsorption and K secretion
2. Long-term: stimulates DT and CD cells to increase production of ATPase pumps in basolateral membrane!! |
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What is Addison's Disease?
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Adrenal cortical dysfunction
-Vulnerable to orthostatic hypotension b/c their Na levels are so low and they can't control their BP and blood volume |
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What are the 2 categories of organic compounds secreted in the nephron?
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1. Organic Anions
2. Organic Cations |
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What are endogenous and exogenous compounds secreted from the nephron?
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-metabolites of hormones or drugs
-food additives -environmental pollutants -recreational drugs -organic compounds of WASTE |
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Where are Organic compound secreted?
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in the PCT!!
|
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What can be said about the transport mechanisms of organic compound secretion?
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There are different mechanisms for cation and anions, but both are COUPLED to Na transport
|
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What is the purpose of the secretory pathway?
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-Allows for another opportunity for organic compounds (maybe ones bound to proteins) to be excreted as urine
-Increases the rate of substances' elimination. |
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What is the range of urine concentration that the kidney can possibly produce?
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100mOsm - 1200mOsm
|
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What is the isotonic concentration of urine?
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300mOsm
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What is the most dilute urine?
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100mOsm
|
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What is the smallest volume of urine produced by the kidneys?
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0.3ml/mins
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Do the kidneys ever stop producing urine?
Why or why not? |
No
-called obligatory water loss to remove waste |
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Can dehydration become more and more severe?
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Yes, due to obligatory water loss
|
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What system allow us to produce variable concentrations of urine?
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Medullary countercurrent system
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Where is the greatest concentration of intersitital fluid located in the Renal Medulla?
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Nearest to the renal pelvis
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Name the 2 structures of the Medullary Countercurrent System
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Superficial cortical nephrons and the Juxtamedullary Nephrons
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In the MCCS, what is the function of the juxtamedullary nephrons?
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Responsible for establishing for establishing and maintaining the medullary osmotic gradient
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Which tubules use the gradient to create different concentrations of urine?
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The DT and the CD
|
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What is countercurrent multiplication?
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The process by which the vertical osmotic gradient is established
|
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What is permeable across the descending loop?
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Permeable to water, NOT Na
|
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What limb is permeable to Na?
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Ascending ONLY, IT IS ACTIVELY PUMPED OUT!
|
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What is the osmolarity of the urine as it enters the DT?
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100mOsm
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The presence of this hormone determines how much water is reabsorbed in the DT and CD.
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ADH
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What is the function of ADH?
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Increases permeability of the DT and CD to water, but in a concentration dependent way
|
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What is occuring in the CD and DT when ADH is nearly 0?
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There is no water reabsorption in the DT and CD
|
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What is the interstitial fluid concentration in the CORTEX?
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Isotonic
|
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What is the function of the Vasa Recta?
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It prevents the medulla interstitial fluid from becoming isotonic.
|
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What happens to the blood in the vasa recta as it moves along the limbs?
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It actually gets concentrated and then diluted
|
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What mechanism does ADH use to reabsorb water in the DT and CD?
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Binds to receptors on basolateral side of DT and CO
-Stimulates the insertion of LUMINAL AQUAPORINS -Once the water passes through the luminal aquaporins it then passes through basolateral aquaporins that are ALWAYS PRESENT! |
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Why do we want a system to control our plasma volume (2)?
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1. For long term regulation of BP
2. To ensure that our cells don't swell or shrink because of an unfriendly ECF environment |
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What would happen to the cells if our ECF is hypertonic?
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Pull water out of the cell: Shrinking
|
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What are the first cells to be adversely effected by ECF concentration changes?
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The cells of the CNS
|
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What is the MAIN osmostic constituent in regulating ECF volume?
|
Na!
-Water follows Na |
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What is the main mechanism of Na gain?
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Through ingestion
|
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What are the two mechanisms of Na loss?
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Renal and non-renal loss
|
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What is the point of control for Na loss?
|
Renal loss
|
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What are the 3 sensors for Na concentrations in the body?
|
Baroreceptors!
1. Aortic Arch 2. Carotid Sinus 3. RENAL BARORECEPTORS |
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Do our renal baroreceptors adapt?
|
NO
|
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Where do the renal baroreceptors occur?
|
In the granualr cells of the Juxtaglomerular apparatus
|
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What are the granular cells designed to monitor?
|
Stretch as a result of changes in BP
|
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What type of regulation do the renal barorecptors use in the kidney?
|
Autoregulation of pressures
|
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What action do the renal baroreceptors do when a decrease in plasma volume occurs?
|
Corresponds to a decrease in BP
-RBs will increase the release of Renin |
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What is the funciton of Renin?
|
Enzyme that converts Angiotensinogen to Angiotensin I.
|
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What is the limiting reagent in the production of Angiotensin II?
|
Renin
|
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What is the purpose of Angiotensin II?
|
It is our biologically active hormone that corrects for a drop in plasma volume
|
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Why is Renin the limiting reagent for the production of Angtiotensin II?
|
Because its levels are under regulation and control by renal baroreceptors
|
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What is Angiotensin II's action on the adrenal cortex?
|
Stimulates the release of Aldosterone
|
|
Describe the function of aldosterone
|
Acts on the DT and CD to enhave Na reabsorption and conserves water
|
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What is an adverse effect of aldosterone?
|
It promotes the LOSS OF POTASSIUM
|
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What ways does angiotensin II decrease GFR?
|
1. Vasoconstrict the renal and system blood vessels
2. Enhances the Tubuloglomerular feedback system |
|
How does constriciton of the renal and system blood vessels increase BP?
|
They reduce GFR and prevent the loss of further plasma by reducing filtration rate
|
|
What is the Tubuloglomerular Feedback system?
|
A way to constrict the afferent arteriole
-Does it indirectly by enhancing autoregulation -Makes the macula densa cells trigger at a lower threshold |
|
Other than aldosterone release, how does A-II increase Na reabsorption?
|
Stimulate the Na-H exchangers in the PT, which increases Na reabsorption DIRECTLY!! Also enhaces H+ secretion at the same time!!
|
|
How does A-II act to increase water consumption?
|
Acts on the hypotalamus to increase the sensation of thirst
|
|
What 2 functions does the hypothalamus use to increase plasma volume?
|
1. Stimulates the sensation of thirst
2. Stimulates the release of ADH |
|
What action do the aortic and carotid baroreceptors instantly take to a drop in BP?
|
They increase sympathetic activity
|
|
What are the 2 major effects of increased sympathetic response by the carotid and aortic baroreceptors?
|
1. Increases renal nerve activity to innervate the vasculature
2. Innervates the juxtaglomerular apparatus (incrases ganular cells to increase release of Renin) |
|
How does ADH effect water and NA?
|
It increases water reabsorption but does not have an effect on Na
|
|
What are the ways that water is gained?
|
1. Consumed
2. liberated through metabolic processes |
|
What are tehe 3 ways water is lost?
|
1. Urine (primary)
2. Feces (diarrhea) 3. Profuse sweatig |
|
How does the brain detect plasma osmolarity?
|
Through Central Osmorespectors
|
|
What type of organs are central osmoreceptors?
|
Circumventricular organs
|
|
What are the 2 circumventricular organs that serve as the central osmoreceptors?
|
1. OVLT
2. SFO |
|
When a rise in plasma omolarity occurs, what action in taken by OVLT and SFO?
|
they fire action potentials that project to the hypothalamus to tell it to relese ADH from Post Pit
|
|
What type of relationship is there between a change in plasma osmolarity and a change in ADH?
|
Linear relationship! 1% increase in plasma = 1% increase in ADH
|
|
What 2 areas of the hypothalamus do the axons of the OVLT and SFO project to?
|
Paraventricular Nucleus and the Supraoptic Nucleus
|
|
Describe the function of PVN and SON?
|
Continuously synthesize ADH and packages It into secretory vescicles that are stored in Post Pituitary
|
|
Once the sensation of the thirst is quenched, have we met our hydration needs?
|
No, barely half the amount is actually met
|
|
A person with liver disease has what [ADH]?
|
Increased, because the liver decreases the breakdown of ADH
|
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What effect does pain, fear or trauma have on ADH?
|
Stimulation of release due to increased sympathetic activation
|
|
What effect does alcohol have on ADH?
|
decreases plasma [ADH] concentrations causing more dehydration
|
|
What is voluntary dehydration?
|
The cessation of the thirst before water needs are met by the body.
|