Term
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Definition
Kidneys function to regulate water and electrolyte balance, arterial BP, RBC and Vit D production and the excretion of metabolic waste, hormones and xenobiotics |
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Term
| 2 sections of the kidneys |
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Definition
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Term
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Definition
•The nephron is the functional unit of the kidney
•~1 million nephrons in the kidney
•Nephron consists of the renal corpuscle and the tubules
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Term
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Definition
•Filtration : Water and solutes move from the blood through the filtration barrier into Bowman’s space
•Reabsorption : Moving substances from the lumen to the surrounding interstitium and generally back into the blood
•Secretion : Moving substances into the tubular lumen
•Excretion : Substances are removed in the urine
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Term
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Definition
•Renal Corpuscle consists of the glomerulus, Bowman’s space and Bowman’s capsule
•Glomerulus: capillary tuft where filtrate comes from
•Bowman’s Space: where the filtrate goes
•Bowman’s Capsule: surrounds glomerulus and Bowman’s space
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Term
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Definition
•Filtrate contains mostly water, inorganic ions (Na, K, Cl, HCO3-), low MW organic solutes and virtually no proteins
•Blood from afferent arteriole enters glomerulus where it gets filtered and then leaves through the efferent arteriole
• Endothelial cells of the glomerular capillaries have fenestrations (holes ~70nm wide) that allows the movement of small solutes but blocks the movement of solutes > 7kDa (No RBCs or large proteins)
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Term
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Definition
•Clearance volume of plasma that is completely cleared of a substance (vol/time)
•Cx = (Ux x Vurine) / Px
–Ux : [x] in urine
–Vurine : urine flow rate
–Px : [x] in plasma
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•If a substance is readily filtered, but not reabsorbed, secreted, or metabolized by the tubule, then its clearance is equal to GFR
–In this case, clearance would be equal to the volume of plasma originally filtered
–There is no substance normally present in the plasma that meet this criteria so creatinine clearance is often used in the clinical setting to approximate GFR
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Term
| glomerular filtration rate |
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Definition
•We can estimate GFR using substances that are freely filtered but not reabsorbed or secreted
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•Creatinine : formed from the metabolism of creatine phosphate in skeletal muscle
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•CCr = (UCr x Vurine) / PCr ≈ GFR
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•Creatinine is freely filtered and not reabsorbed, but there is a small amount that is secreted by the proximal tubules so this overestimates GFR slightly (10-20%)
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Term
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Definition
•Glomerulus filters ~180L per day, but most of this fluid is reabsorbed to conserve essential substances (water, ions, glucose….)
–99% water reabsorbed
–100% sugar reabsorbed
–99.5% of NaCl reabsorbed
–At normal body pH, almost all of the filtered bicarbonate is reabsorbed
•Reabsorption can occur by:
•Passive Reabsorption: flux using electrochemical or osmotic gradient
•Active Reabsorption: flux through the addition of an energy source to move a substance against its electrochemical gradient
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Term
| renin angiotensin aldosterone |
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Definition
•Juxtaglomerular Apparatus – area where the distal tubule comes between the afferent and efferenet arteriole
–Consists of the extraglomerular matrix cells, macula densa cells and granular cells
•Macula densa cells sense [NaCl]. A decrease in [NaCl] will cause the release of a chemical signal to the granular cells to release renin
•Granular cells produce, store and regulate the release of renin (protease)
Angiotensin II promotes the release of
Aldosterone from the adrenal gland
•Aldosterone is a mineralcortacoid hormone
• Aldosterone will act on the cells of the distal tubule and collecting ducts to increase sodium reabsorption (and therefore also water reabsorption) and decrease potassium reabsorption
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Term
Atrial Natriuretic Peptide (ANP) |
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Definition
•Synthesized and secreted by cells in the cardiac atria
•Released when pressure (or stretch) in the atrium gets too high, ie. high BP.
•Causes relaxation of afferent arteriole into the renal corpuscle
•Inhibits release of renin
–Which will cause an increase or decease in Na+ reabsorption? Water reabsorption?
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Term
| arginine vasopressin (ADH) |
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Definition
•AVP (aka Antidiuretic hormone) – hormone made in the hypothalamus and stored in the posterior pituitary
•AVP release is controlled by blood pressure, plasma osmolality and ANG II
•AVP acts to increase water permeability of distal tubules and collecting ducts -> increase water reabsorption
•Note: Ethanol (alcohol) inhibits the release of ADH, so you will excrete dilute urine -> dehydration -> contribute to symptoms of hangover
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Term
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Definition
•Body naturally produces acid from metabolism, respiration and food
•Acid-base balance is maintained by the reabsorption of virtually all filtered HCO3 and the secretion of H+
•Most of the bicarbonate is reabsorbed in the proximal tubule (80%) and loop of henle (10-20%) and the rest is absorbed in the distal tubules and collecting ducts
•Acid (H+) is secreted using buffers:
–HPO42- + H+ --> H2PO4-
–Kidney hydrolyzes glutamine to produce NH3 and HCO3-
–The HCO3- is reabsorbed and the NH3/NH4+ buffers the H+ in the lumen
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Term
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Definition
•Specific gravity is a ratio of the density of a material to the density of water
•Specific gravity = pmaterial/ pwater
• This will be used as an index of the total solute within the urine (osmolarity)
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Term
| What is the role of the renal system? Draw a diagram of a nephron and explain the movement of Na+, urea, glucose, Cl- and water across the luminal walls of the nephron. How does this promote urine formation and water reabsorption? |
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Definition
-Cl and water move passivley using concentration gradients
- Na uses na/k pumpsto create a graidnet that is used to transport glucose and creates some of the osmotic pressure
- Na reabosprtions drives the passive and equal movement of water
urine excretion is the amount that is not reabsorbed and remain in the tublules. they are excreted |
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Term
| Define clearance. What are inulin and creatinine? Why are clearance rates for inulin or creatinine good estimators of the GFR? |
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Definition
-The volume of plasma that is completely cleared of a specific compound in a given unit of time. Renal clearance is a measure that is used as a test for kidney function.
inulin- polysaccaride that is neither absorbed or secrected so it porportional the amount of water and solutes that are filtered by the GFR.
-Creatinine- product of phosphate creatine muscle breakdown
-GFR- the flow rate of filtered fluid trhoguh the kidney
- creatinine clearance- it is not reabsorbed so is measured the volume od blood plasma that is cleared of creatinine per unit time and is useful measure for GFR. |
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Term
What are the forces that influence GFR and what are their effects upon filtration? |
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Definition
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thehydrostatic pressurewithin the glomerular capillaries.
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the hydrostatic pressure within the Bowman's capsule.
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thecolloid osmotic pressurewithin the glomerular capillaries.
and the colloid osmotic pressure within the Bowman's capsule.
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Term
| Juxtaglomerular apparatus macula densa |
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Definition
The juxtaglomerular apparatus is a microscopic structure in the kidney, which regulates the function of each nephron.It secretes renin when blood pressure in the arteriole falls. Renin increases blood pressure via the renin-angiotensin-aldosterone system.
Macula densa cells are columnar epithelium thickening of the distal tubule. The macula densa senses any increase in the sodium chloride concentration in the distal tubule of the kidney and secretes a locally active (paracrine) vasopressor which acts on the adjacent afferent arteriole to decrease glomerular filtration rate (GFR), as part of the tubuloglomerular feedback loop.
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Term
| creatnine clearance and what should happen to GFR in hypotonic/ isotonic/alkalyytic drinks and why |
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Definition
- creatinine clearance should increase for the hypotonic and isotonic because it is niether excretEd nor absorbed...the alkaline had such a little volume it won't increase it will stay the same, control will decrease
... This will show the same as GFR. |
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Term
| Present the Na+ clearance for your test subjects. What changes in Na+ clearance would you expect to see for each of these subjects? How can you determine whether Na+ was secreted or absorbed? How does the body compensate for reduced body Na+? How does the body compensate for elevated Na+? |
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Definition
clearance of NA= (flow rate x urine concentration of NA)/ plasma contration od NA
you can determine if it was secrteted or absorbed by the amount in urine.
- the kidney reabsorb NA if it has a reduced sodium concentration. excretes it if it elevated.
isotonic- increase
hypotonic- decrease
bicarbonate- no changes
no fluid- no changes |
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Term
| Present the data for urine specific gravity for the test subjects. Where are the osmoreceptors located? Describe their role in water balance and ADH release. Did these osmoreceptors affect urine production in any of the subjects? |
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Definition
Isontonic- No change
hyptonic- decrease
bicarbonate- increase
no fluid- NC
They are located in the hypothalamus and are used to detect changes in osmotic pressure/osmolarity in surrounding fluid. They help with water balance by either increasing ADH release or suppressing it. If there is excess water in the body the receptors will decrease ADH so that it will increase urination. If there is too little water then ADH is increased as to conserve water.
- yes, osmorecptors affect urine production... large amounts of water should of decreased ADH to increase urine production same with saline. osmolarity should have increased that increased ADH so water is retained for control.
-The alkalosis subject drank a sodium bicarbonate solution which should have increased the pH because of a reduction in H+ in the blood |
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| If a subject were to exercise in a hot environment, describe the disturbance in water balance and the compensatory responses that restore normal levels of body water. |
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Definition
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Exercising in the heat is a stressor that prompts the body to dissipate heat through sweating
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The loss of NaCl and H2O represents a loss of fluid volume and solute
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This triggers at least three responses:
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Osmoreceptor spiking/vasopressin release
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Baroreceptor firing constricts afferent arterioles of kidney, reducing GFR to save NaCl-
- Granular cells release renin, leading to the production of aldosterone
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Term
| renin-aldosterone response |
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Definition
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Term
| Flow rate: which subjects exhibited the greatest change in flow rate? compared to GFR? |
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Definition
hyptonic the greatest over 400%
- isotonic 100 increase
alkalosis- 83.84 NC/decrease
control 61.53 NC/decrease
GFR: control: No change
hypo - increase
iso- increase most?
alkalosis- decrease/ NC
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Term
water diuresis
what pathologic/ state induces it ? |
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Definition
ingestion and excetion of an excess of water, without a corresponding amount of sodium
involed: expansion of plasma volume, increased left atrial pressure, inhibition of ADH
- alcoholism- reduces Antidiuretic hormone- so less water is reabosorbed
- urethal obstruction- unblocked can cause increase urine and electrolyte output
-Diabetes- blood sugar is exceeding normal limits and causes osmotic diureses- draws in excess water |
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Term
| how does diabetes insipidus affect diuresis |
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Definition
- excess thrist and urination - dilute urine
- causes by lack of or no response to AVP which control water balance
- AVP helps increase reabosrption of water by increasing the permability for water in the distal tubules and collecting ducts
-lack or no response to avp doesn't reabsorb water therefore increased unrination |
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Term
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Definition
iso- nc/increase
hyp- nc/increase
bicarb- increase the most
no fluid- decrease/nc |
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