The Excretory System COPY Flashcards
Distal convoluted tubule
Distal convoluted tubule additional tweaking of* aldosterone acts right here causing* the H+ and K+ when adding last chance things to filtrate** called secretion
Secreting some more H+ and K+ into filtrate there that is helpful if blood is getting too acidic* just to connect it with someone with untreated diabetes making all kinds of ketone bodies going into ketoacidosis, their kidney is going insane trying to get rid of H+ may be not enough ppl with ketoacidosis still land in emergency room but distal tubule still pumping as hard as they can to get H+ out of filtrate
Only tiny part of NaCl being pumped out main thing is water
If there is ADH present then even more water would be reabsorbed, filtrate usally more concentrated then blood helps us conserve water which is adaptive** have a million of these nephrons in these kidneys, filtrate each nephron making is all pooling together, then filtrate really called urine at that point goes through tube left kidney and right kidney leading to bladder, uretehers then bladder then ureathra* if ADH is there all you need to know more aquaporins
Q. 14 A drug tht acts as an agonist of the aquaporin protein channel would likely result in which of the following?
a. a dec in blood volume
b. an increase in urine volume
c. an increase in blood pressure
d. increased secretion of ADH
e. all of the above
c. an increase in blood pressure
aquaporin channels allows water to be reabsorbed, more channels in means more reabsorption means more blood volume, so more blood pressure why C is the answer!
Tease apart MCAT logic- D is not a correct answer, if have a drug stimulating aquaporin channel, lots of aquaporin channels, your body wouldn’t also then secrete more adh, drug doing job of ADH, so not secrete more adh, if tell some exogenous agent like a drug doing that don’t simulatenously get upregulation of natural pathway, D says increased secretion of ADH, this drug raises people’s blood pressure which is great but suppresses natural pathway, natural pathway will nto do its thing, giving person drug because natural pathway isn’t working in the first place, bypassing what ADH would normally do
- a wrong becuase would inc blood volme, agonist means stimulate!
- nonsense mutations in the genes encoding V2 receptors would most likely:
a. increase blood pressure
b. lead to decreased aldoesterone secretion
c. promote more frequent urination
d. mimic the effects of adding aquaporins to the renal collecting duct
Answer is C- would promote frequency urination
Nonsense mutaitons- make nonfunctional proteins, introduce a premature stop codon
So nonfiunctional proteins are V2 receptors, right in there in pathway leads to more reabsorption, triggering G protein cacade, downstream effect more aquaporin channels more reabsorption!
If mutation in that pathway which leads to more reabsorption, so if suppress enzyme, mutate protein will get less reabsorption! If less reabsorption, water not going back to blood going out in urine, so answer choice C says more frequent urination or higher volume of urine, more peeing less reabsorption!
b wrong becuase wouldnt impace aldoserone secretion acts on V2 receptors, aldosterone already secreted and pathway is normal*
- According to the info in the passage, one can conclude that the aquaporin receptor is most likely synthesized:
a. on ribosomes bound to the rough ER
b. on free cytoplasmic ribosomes
c. in a carboxy to amino direction
d. a and c
I was wrong answer is only a, not a and c
PROTEINS ALWAYS MADE N to C direction!!!!! not C to N
made on rough ER because a transmembrane
Rough ER contiguous with nuclear envelope
Part of endomembrane system
Site of synthesis for secreted proteins, transmembrane proteins, lysosomal proteins
- Highly elevated phosphodiesterase activity in the cells of the renal collecting duct will most likely lead ot which of the following?
a. a dec in the concentration of the blood solute
b. an increase in aldosterone secretion
c. a dec in urine vlume
d. an increase in blood pressure
b. an increase in aldosterone secretion
phosphodiesterase, on G protein coupled receptor pathway notes, the thing to know about this is that it is the enzyme that deactivates cyclic AMP, if crank off phosphodiesterase turn off pathway faster!
So if go back to the paragraphs on previous page this is cyclicamp pathway, even just skiming through this G protein cascade, elevated cyclic amp and downstream how get more aquaporins in walls of collecting duct, highly elevated phosphodiesterase means shut that down, less reabsorption of water at the collecting duct.
Inc makes ADH less effective, shutting down that pathway, causing there ot be less reabosprtion at collecting duct, because overlapping redundant ystems to absorb more water, something broken over there not allowing for enough reabsorption so secretes more aldosterone other trick it has up its sleeve for raising blood volume, reasoning is think water not being reabsorbed properly, body will try to do it a totally different way with this different hormone acting on distal tubule
- An increase in Co2 in the blood would most likely lead to:
a. reduced secretion of protons in the distal tubule
b. a drop in urine pH
c. a drop in filtration rate
d. an increase in blood pressure
answer: b. a drop in urine pH
Co2 is acidic in water is acidic, make blood acidic body really sentitive to blood pH has to keep it in tight range, if have to keep it acidic where does it put H+ to get rid of excess H+ by secreting it into distal tubule.
D. probably wouldn’t have huge impact on blood pressure, maybe change ion balance a little bit, but if anything getting ions out of blood into filtrate, H+ isn’t the most important blood pressure regulator more about pH
- the filtrate is iostonic to blood at the beginning of:
a. the collecting duct
b. the distal tubule
c. the ascending limb of the loop of Henle
d. the ureter
anser is a- nothing in the loop of henle is isotonic to blood but may be isotonic to interstal area in loop of henle TRICKY not blood the interstitial fluid!
a. collecting duct-stuff in collecting duct at beginning is iostonic to blood, but as go down lower and lower it is more salty isotonic to intestial fluid of medulla but not blood*
nephron and collecting duct
- everything that gets filtered in filtrate in blue box, little salts ions, glucose and amino acids not too big and pass into the filtrate. Blood cells and big proteins like albumin big blood protein thoes things stay behind in blood
filtrate is the rough draft of what urine is going to be a lot of things in there that we don;t actually want to get rid of through excretion, do not want to get rid of gluocse and too much water
- proxmial tubule reabsorb important stuff, so arrows start at light blue tube and go up the purples are passive transport and nutrients like glucose adn amino acids have to be ctively transported*
salt actively transported and water follows salt* so big mechanism that pump a solute like ion and water follows along, very very important mechanism for rebsorbing water. A lot of water is being conserved by being sent back to blood at this stage of hte process. at this end of proximal tubule no longer any more nutrients and a lot of things that we do not want to get rid of have been returned to the blood through reabsorption* some passive some active but overall lots of reabsorption*
THROUGHOUT THIS TIME THE FILTRATE IS ISOTONIC TO BLOOD, same concentration of blood and same concentration of immediate surroundings* the filtrate remains isotonic to its immediate surroundings but not in loop
Isotonic concentrations
- environment nephron passing through gets more and more concentrated and salty
- solute concentration inc outer to inner medulla
as filtrate goes down the tube it stays isotonic to its surroundings whatever is right outside it does that by passively losing water, how walls of decending loopof henle permeable to water not salt, so water leaving and fitlrate is isotonic to surroundings fitlrate gets more and more concentraed as surrounding gets more salty so filtrate and kidney stay isotonic
- area outside of nephron gets more concentrated, kidney has to expend energy to keep it tht way part of mehcanism to make concentrated urine necessary to the mechanism*
- at the bottom of loop of henle VERY SALT 4x as salty as it was at the top* then going back up ascending limb go into reverse filter gets more diulte again and now it gets more dilute by giving away salt. flows upward and its environment becomes less adn less salty filtrate wants ot keep pace with surroudnings os first will passively release nacl* so it stays isotonic, but then in upper part of ascending limb the red NaCl active transport of NaCl so by top of ascending limb filtrate is less concentrated by its surroundings*** only spot where filtrate is out of stop with its immediate environment in terms of concentration very very dilute right at hte top there as entering hte distal tubule*
as the filtrate moves up the environment outside of the loop of henle is more dilute, and filtrate still very salty so as it moves up and environment is mroe waterly some salt will go out so it matches environment interms of concentration moving into less salty region to keep pace with that gets rid of some of own salt as it moves its surroundings are changing in terms of saltiness
Concentrations 2
- salt leaving ascending so moving down gradient, so salt following its own gradient to leave the loop of henle in the ascending limb
- process where filtrate keeps getting refined but more water needs to be reabsorbed so not done so another round at distal tubule, secretion of K+ and H+ active transport of ions put INTO filtrate last chance thigns that didn’t make it into filtrate in beginnign another opportunity to pop things in there so they are also secreted*
- filtrate specifically dilute at begining of distal tubule, at end of distabl tubule filtrate now isotonic to blood
goes down collecting duct and gets more cocentraed as it goes* important moment for filtrate about to become urine to be very concentrated* because on tis way out at this point and you do nto want to lose too much water in that process*
- Consider filtration of glucose at the glomerulus and its reabsorption in the proximal convoluted tubule. Which of the following statements is correct?
a. an increase in blood presure would dec the glomerular filtration rate of glucose
b. a decrease in the tubular reabsorption of glucose could cause the appearance of glucose in te eurine
c. glucose not absorbed in the proximal tubule will be reabsorbed in the collecting duct
d. all of the above are correct
Answer is b a dec in the tubular reabsorption of glucose could cause the apperance of glucose in the urine! Glomerular filtration of everything is dependent on blood pressure
inc blood pressure higher glomgerula filtration rate, bigger push causes all this stuff to
a. wrong becuase it says an inc in bp would decrease the glomerula filtration rate, it would be the opposite an inc in blood pressure would inc the glomerula filtration rate of glucose and eveyrhting because glomerula filtraiton rate can think of blood pressure as providing this big push so it would push a higher glomerula filtration**
b. if do not get full reabsorption in proximal tubile cannot get it anywhere else
c. glucose CANNOT be absorbed anywhere else! answer b.
- Which of the following would most likely NOT occur in a patietn who has lost a lot of blood as a result for instace of a gunshot wound?
a. the patien’ts kdineys will release renin
b. production of angiotensin II will be inhibited
c. Reabsorption of sodium from the distal tubule will be stimulated
d. the patients’s collecting duct will become more permeable to water
- aldosterone works on distal tubule causing sodium to be pumped back to the blood and then water follows the sodium so that is how you get higher vlood volume and higher blood pressure* how they get water into blood***
B. NO would be stimulated!!!! low bp inc aldosterone*
aldosterone promotes Na+ reabsorption and then WATER FOLLOWS**** how it works
ADH does not promote Na+ reabsorption right? has nothing to do with Na+
Aquaporin
adh tells body to put aquaporins into membranea nd allows water ot move through membrane and be reabsorbed*
(like insulin tells cell to put more transporters into membrane and allows glucose to move)
- Highly elevated phosphodiesterase activity in teh cells of the renal collecting duct will most likely lead to which of the following?
a. a decrease in the concentration of blood solute
b. on free cytoplasmic ribosomes
c. in a carboxy to amino direction
d. a and c
e. none of the above
an increase in aldosterone secretion
phosphidesterase
cAMP is part of pathway that puts aquaproins in membrane, so phosphdieseraste braks down cAMP and makes it 5’AMP
- so lots of phosphodiesterase, less cyclic AMP less aquaporins put in membrane, so less reabsorption of water which means blood pressure would stay low and teh whole ADH mechanism is not doing the trick bp is still too low. so the other pathway that deals with this the aldoesterone pathway can kick in as Plan B
- An increase of CO2 in the blood would most likely lead to:
a. redcued secretion of protons in the distal tubule
b. a drop in urine pH
c. a drop in filtration rate
d. an increase in blood pressure
b. a drop in urine pH
- cannot change amount of H20
- would push to product side of Le Chatlier’s principle and increase H+ therefore decrease urine pH
- CO2 is not relevant at all to water balance* in real contrasts to what we were sayig with sodium hwere water follows the sodium that was a big mechanis, CO2 is not like that at all!
excretory system=
rid body of metabolic waste, big thing talked about before amino groups clipped off of amino acids, other soruces of nitrogen based waste, how do we deal with nitrogenous waste?!
answer is we send ammonia to kidney and convert to urea less toxic form but still have to get rid of it!
Kidney has big effect on blood volume which has a big effect on blood pressure –kidney is majorly important in regulating blood pressure, one of its top functions
excretory system 2
Rids body of metabolic wastes
Regulates osmolarity, blood volume and pressure
Main metabolic wastes are H2O, CO2, and urea
H2O and CO2 from respiration
Urea from nitrogen waste (amino acid deamination → ammonia → less toxic urea)
Skin, lungs, liver, and kidney are part of excretory system
Skin excretes sweat (H2O, salt, and urea)
Lungs give off CO2 and H2O vapor
Liver converts ammonia → urea
Kidney excretes urine (H2O, salt, urea)
Excretion contrasts with elimination (feces are undigested material)
Urea
Urea from nitrogen waste (amino acid deamination → ammonia → less toxic urea)
Liver converts ammonia → urea
Kidney excretes urine (H2O, salt, urea)
excretion contrasts with….
contrasts with elimination (feces are undigested material)
All of that is elimination/ waste products that come through the GI tract.
Elimination is different than excretion, excretion is urine! We are focusing on production of urine and excretion
=we really excrete urea, what we are focusing on! ex of excretion sweat, but here we are focusing on kidney
Kidney 1
major excretory organ
responsible for maintaining blood volume and pressure, governing concentrations of all different solutes in our blood
the main blood vessel bringing blood to kidney is renal artery
- it brings oxygenated blood to kidney
main vein bringing blood away from kidney, anything RENAL THINK OF KIDNEY
does all your blood go through kidney? = components of blood dont enter filtrate, but all blood needs ot be filtered**
Inner region of kidney
= medulla
Outer region of kidney
= cortex
Kidney 2
Maintains volume and osmolarity of blood and interstitial fluid
Maintains pH of blood and interstitial fluid
Filters blood plasma and removes metabolic wastes
Renal artery brings blood to kidney
Renal vein moves blood away from kidney
Collecting ducts empty into renal pelvis
Renal pelvis funnels urine into ureter
One ureter from each kidney flows to bladder
Bladder
Bladder is a pouch that stores urine
Surrounded by smooth muscle, can expand significantly
Urine enters via two ureters
Urine exits through urethra
Urination controlled by a sphincter
In males, urethra also carries semen
Nephron
Nephron is the functional unit in the kidney
Charged with/ responsible for filtration and collection
Situated in two parts of the kidney first part is outside area like the shell of the kidney, as a shell we call it the renal cortex a term heard of before like adrenal crotex, just means hte shell! ligther tan part
Situated between cortex and medulla (meaning middle)
~1 million nephrons in each kidney
Nephron has four regions:
- Bowman’s capsule surrounding glomerulus
- Proximal convoluted tubule
- Loop of Henle
- Distal convoluted tubule
Filtration 1
This means bulk movement of fluid with lots of dissolved ions and nutrients from blood into Bowman’s capsule which is the blue lines!
Through process of filtration, a lot of material moves through blood stream through glomerulus into nephron which forms the filtrate! blue box filtrate lists what forms filtrate to have it in front of us, ton of water goes into filtrate, salts including NACl, biocarbonates, urea, (part of point to get urea into filtrate) glucose, amino acid, some drugs, ton of stuff
The criterion that allows material to pass into bowman’s capsule is really size! Big things stay behind and smaller things go to bowman’s capsule, one example BLOOD CELLS never have blood in urine or something is wrong! Also some really big proteins in blood that are too big to enter the nephron through this process of fitlration, will talk about a bunch called albumin big solid, protein that sits in blood to make sure there is always some SOLUTE IN THE BLOOD!
Other function it has is to help transport lipid soluble hormones like last time, aldosterone, esterogen, testosterone can hitch a ride on albumin, big solute doesn’t go into filtrate
Blood flow details
- filtrate needs to exchange material with the blood so much interplay with the blood capillaries wound all over the place
- useful to trace the flow here afferent arteriol from renal artery= arteries branch into smaller vessels called arterioles labeled at top of image is afferent material
- then goes into capillary netowk calld glomerulus, hidden inside of ohter structure called bowman’s capsule
- in terms of the blood–> blood goes from afferent arteriole to glomerulus which is capillary then into efferent arteriole then more capillaries called vasa recta!
- then back out through renal vein
- so know how to recite the order of vessels
- capillary beds are what connects artery to veins in kidney* wheich connects the artery adn vein can have O2 flow out and nutrients flow in!
peritubular capillaries= collect nutrients that our kidneys will filter
vasa recta (O2)
efferent arteriole than vasa racta then renal vein* why it is unusual you have afferent arterial, then clomeruls which is capillary but then have another arterial efferent, then another vasa recta another capillary bed and then goes into vein** goes arteriole capillary arteriole capillary then vein, so that is why it is werid*
Blood flow 2
Renal artery>>>Afferent arteriole>>>>Efferent arteriole>>> Vasa recta>>> Renal vein
Glomerulus and Vasa recta are capillaries*
GFR
- high blood pressure, higher GFR
- low blood pressure, decrease GFR top page 111
B/c this depends on blood pressure, if somone is hemroagging the kidneys can fail becuase bp crashes when bleed out many systems in trouble but kdiney is one of them specifically that needs a certain minimum blood pressure to keep this system going
Filtration 2
- we do not want to lose these nutrients so process of refinign what is actually in the filtrate is very important stuff moving from blood into bowman’s capsule, driven by blood pressure***
- people talk about glomerulra filteration rate, or GFR*
Reabsorption in proximal tubule 1
- glucose reabsorbed bykidney here, still means when see word always means THIGN IS GOING INTO BLOOD so it is going back to the blood ALWAYS*
- can see in figure Hco3-, NaCl, H20, nutrients espeically glucose, K+ all beign reabsorbed
- what is red in this image is active transport, purple passive
- under normal circumstances, a lot of important things we do not want to get rid of are supposed ot be going back to the blood in the proximal tubule.
- Concentration of filtrate is VERY similar to concentration of blood, close connection capillaries not really shown in these images, similar to concentration in proximal tubule
- There is an easy exchange between those two compartments*
Diabetes connection to filtrate
- if blood sugar is really high, the rate at which glucose goes into filtrate is very very high
- all of that glucose can overwhelm transporter proteins supposed to bring glucose back to the blood
- filtrate can flow all the way through proximal tubular and still some glucose will not be absorbed properly becuase there is just so much of it
- tha tis why sign someone has diabetes they have glucose in their urine** real explanation blood glucose high and the filtrate glucose will be very high, concentration of glucose in filtrate exceeds capacity of glucose transporters tha are supposed to reabsorb the glucose to the blood
Loop of Henle 1
- the area surrounding the nephron becomes MUCH MORE COCNENTRATED with solute, including salt and urea, environmen taround nephron is changing
- also walls of descending limb are permeable to water, which means as fitlrate flows down and there is all this saltiness right outside in medulla, water naturally flows out of nephron into interstitial area (word for area not inside cell/ not inside blood stream just like an open area in body with fluid
- purple arrow passive flow of water out of loop of henle out of nephron into surrounding for descending loop, filtrate gets darker blue at bottom meant to represent filtrate getting much mroe concentrated because a lot of water is being lost on the way down
- on the way up, ascending limb is permeable to salt BUT NOT TO WATER***
- as go up up toward cortex area around nephron becomes less salty, less concentrated so in order for the nephron to stay isotonic same concentration with its surroundings, now it is salt that moves, as filtrate flows up salt is lost makes filtrate less concentrated on the way up!
- toward distal convoluted tubule have to use energy to pump some out, the rest will take care of it on its own, stuff remains salty
- once ascending limb, sodium left due to passive transport water will follow it, then when water left even saltier solution there in filtrate more sodium going to leave, so how we can get inc and inc saltier the deeper we go down
- whole thing is that once sodium leaves water follows it, since salt cannot leave until enters into ascending limb how we pull all water/salt out if tube! -also bed of capillaries surrounding loop of henle, water will be picked up and go right to blood
