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Physiology (Test 3)

What are the 8 homeostatic functions of kidneys? 1)excretion of metabolic waste products&foreign chem, 2)reg of H2O& e- balances, 3)reg of fluid osmolality and e- cntn, 4)reg of art press, 5)reg of acid-base balance, 6)secretion, metabolism&excretion of hormones, 7)gluconeogenesis, 8)control dev. of RBC
Waste products excreted by the kidneys are primarily ___________ products. nitrogenous
How is urea/ammonia created? proteins are made up of amino acids; metabolism takes off the amine/ammonia group
What 2 things can happen with the amine group metabolized out of proteins? 1)released free as ammonia (deamination), 2)transferring it onto a ketoacid (transamination)
Define deamination. amine group released free as ammonia after metabolized off of protein
Define transamination. amine group transferred onto a ketoacid (to make an amino acid) after metabolized off of a protein
What makes up an amino acid? ketoacid + amine group
True or False: In order to transfer an amine group into a ketoacid to make an amino acid, you need the help of enzymes. True
What are the enzymes called that transfer an amine group onto a ketoacid to form an amino acid? transaminases/ aminotransferases
What are 2 examples of transaminases/ aminotransferases? 1)ALA-transferases, 2)AST-transferases
What amino acid uses ALA-transferases? alanine
What amino acid uses AST-transferase? aspartate
If you have a high level of transaminases/ aminotransferases, suspect... liver damage
True or False: Ammonia is toxic. True
The liver takes ammonia and makes a less-toxic compound called ______________. urea
Define BUN. blood urea nitrogen: we look at levels of ammonia and urea simultaneously
What is the name of the compound in the muscles that makes ATP from ADP? creatine
What is the breakdown product of creatine? creatinine
We have a scavenger pathway that reconverts uric acid back into _______________. Why? nucleic acid; we want to minimize levels of uric acid b/c higher levels of uric acid in blood are likely to crystallize and end up in joints, causing gout or kidney stones
What are 4 causes of gout? 1)genetically deficient in scavenger pathway that coverts uric acid into nucleic acid, 2)diets rich in nucleic acids/purine-rich foods, 3)excess alcohol intake, 4)side effect of certain medication (statins)
Heme from hemoglobin is broken down into __________ and ___________. iron and porphyrin
Porphyrin (breakdown of heme) is broken down further into ______________ and ______________. biliverdin and bilirubin
What color is biliverdin? green
What color is bilirubin? red/yellow
How does the liver get rid of biliverdin and bilirubin? made into bile
What are some examples of metabolic wastes that the kidney excretes? urea/ammonia, creatinine, uric acid, hemoglobin breakdown units, hormones and their metabolites
Define gluconeogenesis. amino acids/ketoacids/glycerol/fatty acids (noncarbohydrates) are put back into the citric acid cycle (backwards) to make glucose
Where are RBC formed? bone marrow
What is the formation of RBC called? hematopoesis
What governs the development of RBC? erythropoietin from kidneys
Where in the body are the kidneys located? retroperitoneal in the abdominal cavity
What surrounds the kidneys? a capsule of connective tissue
What is the inside of the kidney called? renal medulla
What is the outside of the kidney called? renal cortex
Describe the flow of urine from the kidneys to the ureter. renal pyramids --> minor calyces --> major calyces --> renal pelvis --> ureter
What is the purpose of the kidney? filter the blood
What is the apex of the renal pyramid called? papilla
Describe the flow of blood through the kidney. afferent arteriole --> glomerulus (capillary bed) --> efferent arteriole --> peritubular capillary bed --> arcuate vein (exit)
True or False: Each nephron has a common collecting duct. False: The collecting duct may supply multiple nephrons.
Describe cortical nephrons. located in the renal cortex; have short loops of Henle
Describe juxtamedullary nephrons. plunge down into the renal medulla; have long loops of Henle
What are the 4 process of a nephron? 1)glomerular filtration, 2)tubular reabsorption, 3)tubular secretion, 4)excretion
Describe a nephron's glomerular filtration? water, small molecular weight molecules are filtered out of capillaries into the tubule
Glomerular filtration is a (selective or nonselective?) process. nonselective
What is the limitation on molecules that can be filtered by glomerular filtration. molecular size
What is GFR? ____mL/min; ____L/hr; _____L/day glomerular filtration rate:total filtration rate of all nephrons, cumulatively (125mL/min=7.5L/hr=180L/day)
Describe tubular reabsorption. reabsorbed from lumen of tubules back into peritubular capillaries via carrier molecules, cotransport, active pumps, etc
What are some examples of molecules that go through tubular reabsorption? glucose (cotransport), amino acids (cotransport), sodium (active transport), water (passive transport)
Describe the renal plasma threshold. tubular reabsorption transport maximum; (ex. if there is too much glucose in circulation, the cotransport molecules cannot reabsorb it all, so there will be some glucose in urine)
_______% of what we filter is reabsorbed. 99%
_______% of reabsorption takes place in the proximal convoluted tubule (PCT). 65%
What part of the nephron is referred to as the "workhorse" of the nephron? proximal convoluted tubule (PCT)
What type of cells make up the walls of the PCT? simple cuboidal cells
Define tubular secretion. reverse of tubular reabsorption; pull things out of circulation/capillary back into the tubule
What type of cells make up the outer wall of the Bowman's capsule? simple squamous epithelium
What type of cells make up the inner wall of the Bowman's capsule? podocytes w/ pedicels hanging off
The capillaries of the glomerulus have gaping holes called __________________. fenestrations
Define endothelium. simple squamous cells that line the lumen of any capillary (including the glomerulus)
Polyanionic (negatively charged) dextrans are (easier or harder?) to get filtered through the glomerular capillaries. harder
Polycationic (positively charged) dextrans are (easier or harder?) to get filtered through the glomerular capillaries. easier
The basement membrane of the glomerular capillaries must be poly (anionic or cationic?). Why? polyanionic (b/c it attracts polycationic particles)
Define glomerular hydrostatic pressure. the driving pressure of glomerular filtration; the BP inside the glomerulus that drives filtration out and into the Bowman's capsule (60mmHg)
Define Bowman's capsule pressure. an opposing pressure of glomerular hydrostatic pressure; pressure that pushes back from the capsular space; hydrostatic pressure of filtrate (18mmHg)
Define glomerular colloid osmotic pressure. pressure inside glomerulus; plasma proteins trapped in capillary pull the filtrate back in (32mmHg)
What are the 3 pressures that drive glomerular filtration. 1)glomerular hydrostatic pressure; 2)hydrostatic pressure of filtrate; 3)glomerular colloid osmotic pressure
What ends up being the total glomerular filtration pressure? 60-18-32=10 (which is enough to produce adequate, but not excessive urine)
True or False: Each nephron self regulates its own filtration so that the total filtration = 125mL/min. True
Where is the juxtaglomerular apparatus located? where the distal tubule comes right between afferent and efferent tubule
True or False: Macula densa cells are part of the bowman's capsule. False
True or False: Macula densa cells are part of the distal tubule. True (way downstream from where filtration takes place)
What is the function of the macula densa cells? they sense how much Na is in the filtrate passing by them and adjust filtration accordingly
If the macula densa cells sense too little Na,they assume inadequate filtration and secrete ____________ back into the afferent arteriole, which are detected by the juxtaglomerular cells which __________ the afferent and ___________ the efferent tubules. prostaglandins; vasodilate the afferent tubule; vasoconstrict the efferent tubule
How does the juxtaglomerular apparatus vasoconstrict the efferent tubule? renin-angiotensin system --> raises hydrostatic pressure to increase GFR
Define renal clearance. the volume of plasma that is completely cleared of the substance by the kidneys per unit of time
What is the renal clearance equation? Cs X Ps = Us X V (C=clearance rate, P=plasma cntn, U=urine cntn, V=urine flow rate)
True or False: GFR=Cs True
The clearance of what 2 substances can be used to estimate GFR? inulin and creatinine
What is a normal GFR, and therefore a normal clearance rate? 125mL/min
What is taking place if a drug's clearance is greater than 125mL/min? the kidneys are handling the drug by filtration AND secretion
Define the estimation of GFR using inulin. If inulin is freely filtered and is not reabsorbed or secreted, then the rate at which it is excreted in the urine (Us X V) is equal to the filtration rate by the kidneys. (GFR X Ps)
What is an advantage to using creatinine to estimate GFR? doesn't have to be injected
A normal creatinine levels tells us what 2 things? 1)muscles are OK, 2)kidneys are working well
What can be used to estimate renal plasma flow? PAH (para-amino hippuric acid)
How is para-amino hippuric acid helpful in estimating renal plasma flow? if a substance is completely cleared from the plasma, the clearance rate of that substance is equal to the total renal plasma flow (RPF); the amount that appears in the urine is totally dependent on the amount brought to the kidneys via the plasma
What is the purpose of the renal countercurrent mechanism? to establish and maintain hyperosmolarity in the renal interstitium
What is the general osmolarity of the interstitial fluid/blood in the body? ~300 milliosmoles
True or False: The osmolarity of the filtrate at the beginning of filtration is also ~300 milliosmoles. True
The (ascending or descending?) loop of Henle is equalosmotic with the interstitium? descending
The (ascending or descending?) loop of Henle contains Na/K pumps which pump Na from the filtrate back into the interstitial space. ascending
Due to the Na/K pumps on the ascending loop of Henle, the osmolarity in the interstitial space is (greater or less?) than the filtrate. greater than
True or False: With each pass, more Na is pulled from the filtrate into the interstitial space at the ascending loop of Henle. True
How does the descending loop of Henle react to the increasing osmolarity of the interstitial space? the descending loop of Henle is freely permeable, so it equilibrates after each pass
After several passes, the interstitial osmolarity is (higher or lower?) at the bottom of the loop of Henle than at the top. higher
How does the renal countercurrent mechanism serve an important function of the kidney? Na gradient makes a suction effect to bring water back into the body
What does a dilute urine look like? high volume, clear
What causes a dilute urine? overhydration
What does a concentrated urine look like? less volume, dark color
What causes a concentrated urine? dehydration
What is the first symptom of dehydration? thirst
True or False: Thirst causes us to drink enough to rehydrate ourselves. False: We don't drink enough to rehydrate ourselves; we only drink enough to satisfy our thirst.
How do our kidneys conserve water for us? osmole receptors sense a need for hydration and send a signal to the posterior pituitary gland, causing the release of hormones
What are 2 examples of hormones that are released by the posterior pituitary glands? 1)oxytocin, 2)antidiuretic hormone (ADH)
What part of the posterior pituitary gland releases oxytocin? paraventricular nucleus
What are 3 functions of oxytocin? 1)induces labor, 2)moves milk from mammary glands into ducts to be available for infant, 3)induces a nurturing/mothering instinct in lower animals
What part of the posterior pituitary gland releases ADH? supraoptic nucleus
What is the function of ADH? causes kidneys to retain water in the late distal tubules and collecting ducts
How does ADH cause kidneys to retain water? ADH binds to receptors in the late DT and CD to form proteins called aquaporins which act as pores for water to leave the lumen of the tubules and flow out of the interstitium and into the peritubular capillaries
What are aquaporins? proteins formed when ADH binds to receptors in the late DT and CD which act as pores for water to leave the lumen of the tubules and flow into the interstitium and into the peritubular capillaries
What is the driving force of the retention of water by ADH? the NaCl gradient of the interstitial will suck the water in
How does water reabsorption affect the NaCl gradient? it dilutes the NaCl gradient; but don't worry... it will be reestablished by the countercurrent mechanism for the next time