kidney Flashcards
what substances are about 100% reabsorbed by the kidney
Gluc,Na,Chloride,bicarbonate
which is not excreted at all by the kidney secondary to being 100% absorbed
Glucose
which substance is 100% excreted and not reabsorbed
Creatinine
between Filtration,reabsorption and secretion which of these are regulated and which ones are not
Filtration is not Regulated, reabsorption and secretion are by their receptors being regulated
whats the average % of reabsorption that happens in the prox tubule
about 60%
what location is majority of the rest of reabsorption done
Distal tubule does the rest of reabsorption
Only for small number of ions .
Na/cl/k/ca/mg
2 pathways exist for reabsorption namely
Transcellular and paracellular pathways
PAracellular pathways are used these 2 electrolytes
potassium and Chloride
Tight junctions are present in transcellular or paracellular pathway
Paracellular.this goes in between the cells through tight junctions
which pathway is used most by the kidney
transcellular pathway,
transcellular pathways, crossing the 2 cells membrane(kidney uses this more)
what are the characteristics of Facilitated Diffusion
carrier proteins or channel used to move a substance down its conc gradient without the use of energy, meaning they are inactive.
Characteristics of primary active transport
Primary active: Actively using Atp or energy to move up
a solute against conc gradient.
characteristics of secondary active transport
Sodium moves down its conc gradient producing energy to move something else against its conc gradient
What transport medium does the kidney use
Secondary active transport.
what is Cotransport(symport) and do we use this in excretion or secretion or reabsorption
move sodium into the cell along with something else, reabsorption uses this medium
what is Counter transport(Antiport)
will move sodium into the cell but move something else outside the cell…
Secretion uses this.
During reabsorption in the kidney, What channels do we have on the Apical and Basolateral Membrane
Sodium/Gluc on the Apical membrane and
NA/K on the Basolateral membrane
What membrane does reabsorption begin on
Basolateral membrane
What it the track for reabsorption starting for the Tubular fluid
Tubular Fluid-Apical Membrane-Epithelial cells-Basolateral membrane-peritubular fluid-capillary Endothelial cells-plasma
what reaction happen son the Basolateral membrane
na moves out through the na/k pump into the plasma and will pump potassium into the cell
what reaction happens on the Apical membrane during sodium reabsorption
sodium moves into the cell pulling gluc with it(symporter),since the conc of sodium in the cell has dropped…moving down its conc gradient.After that sodium is pumped out into the blood using the sodium/k pump on the Baso membrane
How does glucose move into the blood from the Epithelial cells
Glucose will use Glut 2 transporter as a facilitated transporter to go past the peritubular fluid and into the blood down its conc gradient.
Since we reabsorb all the Glucose, does this happen before transport max or after transport max
This reabsorption happens before transport max
is reached.
what happens when we reach the transport max per reabsorption. for glucose
Reabsorption will stop and excretion begins after transport max is reached and the curve flattens out.
In Nondiabetics how does transport max, excretion and absorption relate to each other
DM…non diabetic shud not have gluc in their urine,,,gluc level in the plasma shud be below transport max cos it shud be reabsorbing all the gluc
In diabetics how does transport max, excretion and absorption relate to each other
the amount filtered is above transport max, so they will have gluc in their urine.
At transport max what do we need to see with reabsorption
At transport max,black dots coming in, spokes full and able to reabsorb every molecule
At transport max,every molecule is reabsorbed, and nothing is excreted so no black dots in urine.one more molecule above Tm then one thing would be excreted. At Tm u will not excrete anything
In reabsorption and excretion, what does splay depend on
Splay is the reason why we have the curve and this in reference to the heterogeneity of nephrons
.Comparing the cause of this in the Reabsorbed curve and excrete curve…
some will have shorter prox tubules,
while some will have longer,
or shorter or longer nephrons or some may have more transporters or fewer transporters.
.
Which type of nephrons reaches transport max sooner, the shorter ones or the longer ones?
The ones with shorter nephrons will reach Tm sooner…..we will see gluc in the urine a little sooner cos of the splay
what kind of substances does prox tube reabsorb
organic substances,eg Glucose Amino acids Acetate Krebs cycle intermediates Water-soluble vitamins Lactate Acetoacetate GWAAALK
each need to be coupled to sodium
What is the components of an active transport medium
They are active..use Energy Atp
They manifest a Tmax
Well above what is normally filtered
They manifest specificity
They are inhibitable by drugs and disease
they are on the Apical membrane.
They all use secondary active transport with the same process…couple with sodium
what is filtered load
The filtered load is how much of a substance will be filtered into the nephron from the blood.
For freely filtered=Gfrx x plasma concentration
what ion has the highest filtered load
NA,about 99% is absorbed
What are the varying % of reabsorption in the nephron and location
Prox tubule will reabsorb(60-75)
Loop of Henle—15-20)
Distal tubule 5%
Collecting tubule 5-7%
which of the membrane does the process of reabsorption start on and which channel is involved in the prox tubule
BASOlateral membrane and this is the na/k pump
explain the process of sodium reabsorption, what, where it starts from and what channels that are involved in the prox tubule
Starts on the Basolateral membrane with na/k pump.
NA moves out of the cell into the blood and the conc in the cell is now low
.NA on the Apical membrane goes down its conc gradient into the cell pull with it Gluc using the SGLT1/2 transporter.
Na then goes into the blood using the na /k pump.
Gluc goes into the blood using Glut 2 transporter.
all the organics will be coupled to na to be absorbed
what transport mechanism is used to reabsorb Na/Gluc in the prox tubule
Na and gluc is being absorbed all into the cell in the prox tubule…via symporters
What mechanism is used to absorb Na/H in the prox tubule
na/H is absorbed using antiporters or countertransport..this also happens in the prox tubule for acid-base regulation
what is the benefit of na/h pump
this happens in the prox tubule for acid-base regulation
Explain the process of absorbing chloride and what pathway does it use.
Na and k is +ve charges with gluc neutral…
going into the blood.
There should be a negative charge pulled to counterbalance this.
Hence chloride is pulled by the electrical gradient through the paracellular pathway…(Chloride is through paracellular route.)
what follows sodium when pulled into the blood
water
what does TF/P mean?
Tubular fluid concentration/plasma concentration
During absorption what changes occur in the amount of mass, the concentration of the solute while moving down the proximal tubing
Although the AMOUNT(Mass) of sodium in the tubular fluid decreases markedly along the proximal tubule, the CONCENTRATION of sodium (and totally osmolarity) remains relatively constant because water permeability of the proximal tubules is so great that water reabsorption keeps pace with sodium reabsorption.
what would be the value of TF/Plasma ratio if they are the same on the correlation graph and whats the meaning of this
tubular fluid to plasma ratio(conc of tubular fluid/conc plasma), if they are the same hence the number of that ratio, will be 1.
what happens to bicarb, amino acid and gluc on the graph of TF/P
Bicarb, amino acid, and Gluc get reabsorbed quickly at the beginning of the tubule and their TF concentration becomes very low couple with loss of mass.
what happens to TF/p of chloride as we go down the prox tubing
Cl is above 1 cos of the delay that exist and the electrical gradient needed to move it…..so cl will be a little more conc than sodium.
when na and water gets pulled out ..the conc of cl goes up, waiting for the electrical gradient to be established to pull the chloride
what happens to TF/P of Inulin as we go down the proximal tubing
Inulin…
as sodium is reabsorbed water gets pulled out, hence the concentration of inulin goes up.
Inulin gets filtered, not reabsorbed and not secreted.
Reabsorbing sodium and water, anything not reabsorbed its concentration will go up.
Explain permeability of water and solute in the loop of Henle
Descending limb is permeable to water
Impermeable to the solute. Hence concentrating segment and no solute reabsorption here
Ascending Limb is permeable to solute and Impermeable to water, hence Dilutional Segment and solute reabsorption here
in the loop of Henle, what is Na coupled to in the ascending limb
K and cl
What’s the process of K+ and cl transport in the ascending limb of the loop of Henle
Basolateral
Na out go into blood using na/k pump ,k in creating the conc gradient low conc inside cell
Apical 1 Na in 1 K in total of 2+ charges 2 Cl- also pulled into balance the cell with -2 charges
NA pumped out into Baso membrane
Transporters will allow cl and k to be reabsorbed
Transporter here is still secondary active
What cells are used for reabsorption in the distal tubule?
Principal cells
EXplain the process of Na and chloride reabsorption in the Distal Tubule, channels involves
Happens in the principal cell..
Start on baso mem,na/k ATPase,na out k in.
sodium conc low hence na on the apical membrane moves in via symporter with cl..
cl goes through cl channel and moves out into the blood,
Na also moves into the cell and Na goes through the na/k pump and gets reabsorbed with chloride together.
ALdosteron’s action is in the distal tubule. Explain the process of aldosterone action in the distal tubule
Aldosterone retains sodium in the distal tubule by increasing the amount of sodium reabsorbed.
This is a steroid hormone, its lipophilic meaning it can cross the membrane. It comes into the cell and inside the cell, there is aldosterone receptor that can go into the nucleus and cause the nucleus to make a bunch of new protein…..1.)more sodium/potassium ATPase that will go on the basolateral membrane…pump out more sodium creating a stronger gradient.
2.)Na channel on the apical membrane. This will cause the Na to go into the cell, which will be pumped out of the basolateral membrane through the na/k ATPase.water will follow this na route into the blood, which will be Na /water into the blood which increases blood volume. hence increase in b/p
What tubule do we have potassium secretion and through what process
K channel is also opened on the apical membrane when aldosterone initiates the creation of na/k pump on the basolateral membrane and Na channel on the apical membrane. This new Chanel causes potassium to go out of the cell, causing potassium secretion.
What are the effects of aldosterone in the distal tubule and the First part of collecting duct? during low b/p and low blood vol
Aldosterone is released during low b/p and low blood vol…increases bv and b/p and secreting potassium in the process,so its gonna have potassium effects …this is in the distal tubules and the first part of the collecting duct.
What is the mechanism of action of diuretics in the kidney
Diuretics will stop the nacl transporter(na/cl symporter) on the distal tubule on the apical membrane
and some will block the sodium channel on the apical membrane.
They will both block the reabsorption of sodium in the distal tubule if no Na reabsorbed, sodium remains in urine,
waters stay with it, hence increasing urine vol, decreasing blood vol and hence reducing b/p
How does the osmolarity and mass of solute in the proximal tubule compare to that in the Bowmans capsule
Bowman’s space osm..300mosm
Proximal tubule end …. Should be the same..there is no conc change,mass reduced…300mosm(reabsorption happens here)
How does the osmolarity and mass of solute in the Descending limb compare to that in the Bowmans capsule
Descending limb…impermeable to the solute, permeable to water…more conc here(hyperosmotic) from pulling out water…
if its long loop henle it can be conc up to 1200mosm(Juxtamedullary nephron), a short one will not be that much, but it will be more than 300mosm.
How does the osmolarity and mass of solute in the Ascending limb compare to that in the Bowmans capsule
Top of ascending limb..less conc..hypoosmotic..
Impermeable to water, solutes permeable..pulling solutes out but not allowing water to leave.
Less conc than plasma.
How does the osmolarity and mass of solute in the distal limb compare to that in the Bowmans capsule
End of Distal tubule ..rest of reabsorption
Conc becomes the same conc that entered,na, cl and water entered might be diluted but same conc(about 100mosm) losing mass(same conc it entered, not losing conc .)
How does the osmolarity and mass of solute in the collecting duct compare to that in the Bowmans capsule
Collecting duct conc can be dilute. Hypoosmotic (about 100).And then may need to be conc by Adh
Do we have high or low ECF K
Low
Do we have high or low ICF K
ICF, we have a large number of tissue stores of potassium
What happens to tissue stores of potassium when insulin is given
Every time insulin is used will release tissue stores of potassium.
Will all K be absorbed in the colon?
Potassium reabsorbed in the colon…not all will be reabsorbed but will inturn will be secreted.
Will potassium be secreted or reabsorbed in the distal tubule or cortical collecting duct during High/Normal potassium levels?
The secretion of potassium may happen in the distal tubing and collecting duct…
What’s the process of potassium reabsorption
Paracellular pathway used for potassium reabsorption
Bulk flow in the proximal tubule will bring in many things and water and potassium gets caught in the water and pulled between cells and other things in a paracellular pway and that how we get potassium.
Name 3 actions of aldosterone when its secreted
K Chanel on the apical membrane,
More na/k ATPase on the basolateral membrane
Na channel in the apical membrane
where does potassium reabsorption happen
Reabsorption of potassium happens in the ascending limb of the loop of henle.(na/k/cl transporter) and potassium gets reabsorbed this way
Via the principal cells how does potassium get absorbed and secreted
Increases basolateral Na/K ATPase activity, pumping more K into the cells. K is then secreted into the lumen through apical aldosterone sensitive channels
Slide 43 and 48 review pls
Whats is the process of reducing potassium levels and increasing sodium reabsorption per aldosterone
If k level increases.levels go up, aldosterone gets secreted, in the distal tubule, which opens up all the pumps
(k channel,na channel, ATPases of na/k) hence decreasing potassium conc and increasing sodium reabsorption
NAme the 3 medium that ca works on
Gi tract,kidney and bone
What are the effects of low calcium level on PTH, Kidney, Gi, and bone
Low ca level will cause:
release of PTH from ur parathyroid gland, increase ca reabsorption in the kidney
(no more secretion of calcium also),
in the bones it will cause bones to breakdown ca storage,
will also increase the amount of vitd , which will increase ca absorption in the Gi tract.
What are the effects of high calcium level on PT, Kidney, GI, and the bone
Upon the rise of ca, there will be an opposite move, inhibition of PTH, no breakdown of ca stores and no absorption in the Gi tract…leading to excretion of ca in the urine
What are the Changes in PTH activity in relation to calcium levels
PTH: no ca…pth released…ca reabsorption increased.
Too much ca..no PTH released…no reabsorption happening.
What locations can calcium be absorbed in
Calcium reabsorbed in the prox tubule 60%, loop of Henle 20% (Ascending)and distal tubule 10%
What’s the Effect of PTH on ca and phosphate binding and availability if calcium
Ca in the bone is coupled with phos…
when ca is bind to phos ca is not active(in the blood),
so we need to increase ca and decrease phosphate, so we have more bioactive ca and more ca in the blood.PTH increases the amount of ca be reabsorbed but decreases the amount of phosphate reabsorbed so we have more bioactive ca.
What is the location of PTH
Most parathyroid receptors are in the prox tubule and distal tubule
On the Ascending loop of Henle, what is the process of ca Absorption
In the loop of Henle (ascending limb) Apical membrane we open up ca channel, inside cell calcium level is low,,,
calcium comes into the cell.
On the basolateral membrane, there is a ca ATPase primary active transport
…all the calcium that comes in…gets pumped out into the blood
…the two channels are regulated by PTH
what are the Two channels ain the Ascending limb of the loop of Henle that is used for ca reabsorption and what are their locations
CA-ATPase..Basolateral membrane
CA-Chanel Apical membrane
On the Descending limb of the loop of Henle, what is the process of ca Absorption
On the descending limb
there is a ca Chanel on the apical membrane, ca rush in
on the Basolateral, membrane we will have a ca ATPase and also a ca/na transporter both allow ca to cross the basolateral membrane into the plasma
Know slide 60
now
What are the characteristics of Inulin
Freely filtered at the Glomerulus Not reabsorbed Not secreted at the nephron Not metabolized or produced by the kidney Does not Alter GFR Not Endogenous
What are the characteristics of Creatinine that makes it better for clearance(GFR) determination than inulin
A byproduct of skeletal muscle metabolism
Endogenously produced in an amount proportional to the muscle mass
Small amount secreted by the tubule, so clearance is a slight overestimate of GFR
AMount excreted normally exceeds the amount filtered by 10%(due to secretion)
Compare GFR and Clearance if there is reabsorption
GFR>Clearance
Compare GFR and Clearance if there is secretion
Clearance >Gfr
Compare GFR and Creatinine Graph
LOwer GFR Increase Plasma creatinine and vice versa
GFR=1/Pcr
If plasma creatinine is 1, what is Gfr
1/1=100%
If plasma creatinine is 2, what is Gfr
1/2=50%
Normal plasma creatine is ? and why
1mg/dl, this is kept low because it’s removed by filtration
characteristics of PAH
- Highly secreted, It’s filtered and then it moves from the blood into urine(Secretion)
- Will all exit through the ureter
What will the Clearance of PAH Tell us
Renal Plasma Flow
How do the kidneys maintain water balance
Through Na/water reabsorption and excretion, water goes where sodium goes
Name some of the end products of metabolism and their parent substances
Protein-Urea
Nucleic Acid-Uric Acid
Muscle creatinine–Creatine
How does the kidney regulate arterial blood pressure?
NA and water reabsorption increases the blood volume
hence an increase in blood pressure.
VAsoactive substances a; also release by the kidney to increase bp
Regulation of Red Blood Cell Production by the kidney
Erythropoietin is released by the kidney and control Erythrocyte production by the bone marrow
What regulates the secretion of erythropoietin
Secretion is regulated by the partial pressure of oxygen in the kidneys
Regulation of Vitamin D Production by the kidney
Kidney converts 25 hydroxy vitamin D3 to 1-25 hydroxy vitamin D3
1.Expose skin to UV radiation…
Vit d increases calcium absorption
Name some Metabolic processes by the kidney
Carbohydrate synthesis stopped,body make new glucose from Amino acids and glycerol
Ammoniagenesis ….creating NH3 by the kidney…and excrete the vast amount of acids/substances that we take in
Name some components of the functional area of the kidney
Renal cortex…Renal Pyramid…renal medulla..renal papillae..minor calyx…major calyx
Does Glomerulus have a venule? Y/N
N
What is the functional unit of the kidney
Nephron
How much filtration does the nephron do in 1 day
180L/Day
What makes up the renal corpuscle
Glumeruls and the Bowmans capsule
Where does filtration happen?
Renal corpuscle
Proximal tubule function
Reabsorption about 60-75% happens here
Distal tube function
rest of reabsorption…15-20% happens here
The function of loop on henle
create and maintain a medulla osmotic gradient
The function of the collecting duct
Functions as the concentrating mechanism of the nephron….
And dilution of the urine
Explain how ADH concentrates and dilutes urine
on the collecting duct, Adh opens aquaporin channels
Allows water reabsorption which goes back in the bloodstream , increases blood volume and increasing blood pressure….also concentrating the urine in the process.
Water moves to a more conc area…adh works with more conc outside the collecting duct…allowing water to come out.
Cells are the same before the distal convoluted tubule.
name the 2 cells found in the DCT
Principal cells (primary cell type) Intercalated cells(Acid-base cells)
Name the part of the nephron in the medulla and the part in the cortex
Cortex-Proximal tubule,connecting tubule,Distal tubule,Bowmans capsule
Medulla-Loop of Henle, collecting duct.
The function of macula densa cells
Macula Denser cells function as sensor cells , looking for a drop in the amount of fluid from the Nephron…they stimulate Juxta Glumerula cells to release renin into the bloodstream to go into the medulla
Explain The Process of Renin to increase BP
Low b/p—renin release…converts ang to ang 1…vasoconstrictor and also converts to ang2…vasoconstrictor and stimulate aldosterone(adrenal cortex) to reabsorb sodium and water, thereby increasing blood volume and increasing blood pressure and also stim Adh in the pituitary gland
Name the 2 types of Nephron, the capillary associated with them and their location
Juxtamedullary nephron-Vasa Recta(Long)(Deep)(Cortex)
Cortical Nephron-Peritubular capillary(Short)(superficial)
The Most common Nephron we have is
Cortical nephron
The Loop of Henle maintains the Osmotic gradient, what is the important factor here.
The length of the loop of Henle
What is the track of renal blood flow through the kidney
afferent arteriole (site of regulation)—-glomerular capillaries—-efferent arteriole
what % of the cardiac output goes to the kidney?
20%, 1L/min
Does whole blood or plasma get filtered
Plasma
what is the rate of RPF
600ml/min
whats filtration
the process by which water and solutes leave the vascular system through the filtration barrier and enter Bowman’s space
Whats secretion
the process of moving substances into the tubular lumen from the cytosol of epithelial cells that form the walls of the nephron
whats reabsorption
the process of moving substances from the lumen across the epithelial layer into the surrounding interstitium
In most cases, the reabsorbed substances then move from the interstitium into surrounding blood vessels (two step process
Explain the process of urine formation
Filtration: Filtered…plasma gets out of the glomerulus into the nephron
Reabsorption: Some filtrate will be moved back into the blood.
Secretion: Move the thing we want to excrete into the tubular lumen
What is the composition of the glomerular filtrate
The glomerular filtrate is very much like blood plasma, however, it contains very little total protein
No Blood cells
Consists mainly of inorganic ions and
low-molecular-weight organic solutes in virtually the same concentrations as in the plasma.
What are freely filtered substances
Substances that are present in the filtrate at the same concentration as in the plasma are said to be FREELY FILTERED
low-molecular-weight components of blood are freely filtered Ions (Na, K, CL, HCO3) Neutral organics (glucose and Urea) Amino acids Peptides (insulin and ADH)
What is GFR
The volume of filtrate formed per unit time=GFR
180L/day (125ml/min)…know this…normal GFR
they possess arterioles that’s why they can filter more
Name the three types of cells in the glomerulus
Endothelial cells, Mesangial cells, and podocyte cells
What are Components of the Endothelial cells, and whats their mechanism of filtration
lines all the blood vessels and capillaries, smallest position of blood vessels.
In all capillaries they have fenestration(space between our endothelial cells) that are too small to let things through(cells and protein), so things go through based on size
What are Components of the podocyte /foot cells, and whats their mechanism of filtration
they are cells around the glomerulus, squeezing the interdigitated protocytes has space (space between the foot)….forming Filtration slit or slit pore and only lets thing out based on sized.
What are Components of the mesangial cells, and whats their mechanism of filtration
Modified smooth muscle cell in the base have the Mesangial cells sits in the glomerular and then lay down extracellular matrix ..which is the Glomerular basement membrane…this cell is a Highly negative charge….
These cells keep things out based on charge…
What is the Kf and what can affect this?
This is a constant based on surface area…
.. losing nephrons changes this.
losing the kidney also drops GFR.
Can be changed by glomerular disease and drugs
Mesangial contraction can also affect this reducing flow and hence decreased surface area and decreased Gfr.
What are the forces favoring filtration
Hydrostatic pressure of the Glomerular capillary
what happens to GFR with Constriction of Afferent arteriole
will lead to a Decrease in the Hydrostatic pressure in GC and decrease GFR
what happens to GFR with Constriction of Efferent arteriole
will increase Hydrostatic pressure, thereby Increasing GFR
The outcome of Dilating Afferent Arteriole
allows more blood in and Hydrostatic pressure increase…Gfr Increases..
Dilating Efferent arteriole what happens
Drop in Cap Hydrostatic pressure which drops ur GFR.
dilate Afferent and Constrict Efferent
Double increase in hydrostatic pressures)
Obstruction anywhere along the tubule or in the external portions of the urinary system can cause what effects to the pressures.
increase hydrostatic pressure in Bowman’s capsule
Decrease GFR
Comes from the fluid and the tissue that is in the bowman space in the nephron(Obstruction in the nephron, like kidney stone within the nephron, can cause a backup in the nephron and backup in the Bowman space, which increase hydrostatic pressure in bowman space , which can decrease GFR
A decrease in arterial plasma protein concentrations will lower?
lower arterial oncotic pressure and increase GFR
Anything that causes a steeper rise in oncotic pressure will tend
to do what?
to lower filtration pressure and hence GFR
This is from proteins in the Glomerular,
Liver failure can cause a drop in the amount of protein thereby decreasing oncotic pressure, the drop will increase GFR since we are decreasing the opposition
What is Filtered load?
Amount of substance filtered per unit time.
What is the Myogenic response
Tubuloglomerular Feedback(Juxtaglumerular feed back…per Renin-Ang 2
How does Adh work during increase blood osmolarity
Inc blood osm—>Adh released into blood…..>stimulates drinking response—
water in—Adh increases water reabsorption….plasma osmolarity goes down to normal levels
Diabetes insipidus….make a lot of urine…no water reabsorption…remains in urine…making lots of urine.
whats the osmolarity of the cortex and the Medulla,Bowmans space ,End of proximal tubule
Cortex …300mosm…
Medulla starts at 300mosm..can get conc to 1200mosm
BS…300,Prox tubule..300
Is the descending limb Hyperosmotic or hypo and why
Hyperosmotic cos of high water permeability
It can go up to 1200 depending on the lenght of loop of henle
Is the ascending limb Hyperosmotic or hypo and why
Hyp0-osmotic,cos of solute permeability,diluting segment..100-150
Distal tubule conc
Hypoosmotic….cos solute and water reabsorbed co conce same
Collecting duct hypo or hyperosmotic
Hypoosmotic b4 Adh action 100-150
If u don’t have adh…no water channels open. Water stay in urine, no water or solute moved. Hypo-osmotic urine…100-150mosm with no adh
Things that affect adh release
Low b/p
Sweat
Evaporation and expiration
Cold
In the medullary counter-current system, what establishes the cycle
the repeated cycle in whichna/k/cl activates an osmotic gradient and solutes are transported out of the thick ascending limb of Henle (which raises the osmolar concentration of the interstitial fluid) and then water is reabsorbed from the thin descending limb (which further concentrates the tubular fluid entering the thick ascending limb). This cycle is repeated until the full interstitial gradient (from 300 mosm/L in the cortex to 1200 mosm/L in the deep medulla) is established.
During counter current, why does urea remain in the tubular fluid
urea remains in the tubular fluid while water is reabsorbed from the descending limb, contributing to the tubular fluid osmolarity
Is the movement of water and equilibration in the counter current active or passive?
Movement is passive, equilibration is active
More fluid we move, more gradient we create
what are the drivers in the Countercurrent system
Diff in permeability is important and the transporters on the ascending limb are the drivers of concentration
Tmax of trans can only create a difference of 200 between inside and outside and the more fluids moved, the more conc
What % of renal osmolarity does urea contribute
Urea contributes about 40% of the osmolarity of renal medullary interstitium
What parts of the nephron are impermeable to urea
Ascending Loop, Distal tubule, and Cortical Collecting Duct are relatively impermeable to urea
What part of the Nephron is permeable to urea
Intermedullary collecting ducts very permeable to urea (even more so with ADH)
Proximal tubule: Some reabsorption takes place
Descending limb: Diffusion into
The function of Vasa recta
In the medulla, preserves conc gradient created in the medulla.
Helps to preserve hyperosmolarity of the renal medulla
What are the special characteristics of the Vasa Recta that helps preserve Hyperosmolarity
- Medullar blood flow is low:Only 5% of the RBF is through the vasa recta, creating a sluggish flow.
- Vasa Recta serve as countercurrent exchangers……loop henle exchanges solute.
The concentration of urine depends on 3 Factors namely?
Depends on plasma level of ADH(depends on the osmotic gradient in the medulla
The osmolar concentration of interstitial fluid surrounding the collecting ducts(depends on urea)
Urea recycling
Vasa Recta: This high concentration in the ascending vasa recta, in turn, facilitates the entry of water from the ascending tubules. The combined interactions of tubular permeability and the vasa recta create the standing osmotic gradients in the cortex
What are the major sources of water loss
Urine losses is the major source of water loss at normal temp
Sweat is the major source of water loss during high temp and exercise followed by resp
what would happen for ADH to be released
Adh released if ecf conc up…water reabsorption and ecf down
Compare plasma osmolarity and urine flow per graph
Decrease osm …inc urine….
Inc osm…..low urine.
What effects would increase plasma flow have on vaso recta and hence Adh
Normal Vasa recta counter-current present,
but the flow is slow…
.high vasorecta flow will wash away conc gradient.
Plasma volume goes up with too much water
…vasorecta blood flow high …gradient washed away..adh present and aquaporin channels open,can only create dilute urine
After giving saline, explain urine flow
Saline(has salt)…..flow rate of urine not up and osmolarity the same….isosmotic makes it more difficult..cos na needs to be regulated too.
Willl take much longer to get rid of vol…..
Formula for excretion
Excretion= Filtration- Reabsorption+ Secretion
To change sodium excreted and Na reabsorbed what should you change
GFR
To change sodium level what should you change
Filtration and reabsorption
What is the relationship of GFR with sodium excreted
Higher Gfr, Higher sodium excretion
Lower Gfr Lower sodium excretion
Alter gfr to change sodium excretion
IF plasma vol and b/p is down what are some of the changes that will happen to raise these back up
Vaso constrict and inc oncotic pressure will decrease gfr which will decrease sodium filtration/excretion,and increasing water reabsorb and increase blood volume and b/p
What’s the mechanism for VAsa recta to create a high osmotic gradient
The vasa recta or straight arterioles of kidney are a series of straight capillaries that lie parallel to the loops of Henle of the juxtamedullary nephrons ( Fig. 17.22 ). Only 5% of the RBF is through the vasa recta, creating a sluggish flow. As the capillaries descend into the medulla, the blood becomes more concentrated by solute entry from the interstitium. This high concentration in the ascending vasa recta in turn facilitates the entry of water from the ascending tubules. The combined interactions of tubular permeability and the vasa recta create the standing osmotic gradients in the cortex (300 mOsm/L), juxtamedullary zone (600 mOsm/L), and deep medulla (1200 mOsm/L).
Neurohumoral control of renal sodium reabsorption
Sympathetic nerves
RAAS
Aldosterone
ANP….ANF
In what way will sympathetic nerves act to increase blood pressure
inc Renin secretion
inc afferent and efferent arteriole constriction
INC sodium reabsorption in proximal tubule..to increase na reabsorption…na excretion dcreases
Action of ANg 2 in the proximal tubule
Ang 2 will increase sodium reabsorption in the proximal tubule…..(Na/H) exchanger, Acid regulator on the apical membrane)
The action of anp/anf
Anp wants to increase sodium excretion.
High blood volume….decrease renin, decrease aldosterone, turns off those hormones…(work to increase Gfr and decrease sodium reabsorption
Action of ADH on distal tubule and collecting duct
Distal tubule/CD adh will open sodium channel on apical membrane..sodium in and water follows and vol increases
ACtions that happen upon large volume of water in the body and large blood volume?
Large blood vol…..anp secreted… decrease sympathetic.. inc water and na excretion. .inc gfr.. decrease na reabsorption…
Stretched atria..anp high… shut off renin, ang2, symp off.. adh.. aldosterone. renin… Gfr up…excrete na up…no na reabsortption. .no water reabsorption… working to increase sodium and water excretion…
High vol and low con urine
Plasma vol shud decrease.
ACtions that happen upon low volume of water in the body and large blood volume?
Low volume …(decrease sodium causes)…keep water ..inc na reabsorption. Decrease GFR…
Low b/p ..sympathetic activity RAAS inc ,BARORECEPTORS inc..adh inc….anp off..
Sympathetic activity will constrict veins, decreases gfr ..decrease ns excretion.
Ang 2…constriction vaso..dcrease gfr..decrease na excretion..release aldosterone..works on prox tubule to inc na reabsorption. Decrease na and water excretion(na/h ex)
aldosterone…distal tub/collecting..dec na/water excretion…opening channels on the distal tubule
Adh..inc water reabsorption,dcrease water excretion..open aquaporin channels..
Low volume of urine…… high conc urine(high reabsorption, filtered little)
Things that can cause acid gain are?
ingestion of acid contained in foods (e.g., acidic drinks and proteins), cell and protein metabolism, hypoventilation, and diarrhea (loss of HCO 3 −) sulfuric acid, phosphoric acid, and keto acids
Things that cause acid loss
hyperventilation,
vomiting,
urinary acid excretion.
Ecf Acid buffers are
Bicarb The most, phosphate , protein
Intracellular buffers are
Proteins,phosphate,Na/H pump,K/H pump(Antiporter),Ammonia
How does The kidneys control the amount of base (free bicarbonate) present in the ECF.
generating new bicarbonate if low
by excreting excess bicarbonate (e.g., in alkalosis) if high
What does the reabsorption of bicarb depend on
is dependent on the secretion of H+ into the tubular lumen
Which cells secrete bicarb
Intercalated cells of the collecting duct secrete bicarb and its excreted via the HCO3/cl exchanger and hence H+ accumulated with loss of Hco3 and reduction of ph.
Should we buffer acid secreted from collecting duct?
Acid secreted into the CDs must be buffered by ammonia or phosphate (to minimize acidification of the urine and allow continued secretion of H + )
What controls urine PH
Free H + is secreted into the lumen of the proximal tubules, TALH loop, and CDs. When secreted, it binds to ammonia to become ammonium; it can also be incorporated into phosphates to become a titratable acid (TA) . This production of ammonium and TA buffers the H + in the CDs, control urine pH
What is the main source of acid excretion
TAs are the main source of acid excretion
What controls the base and free bicarb present in the ECF
The kidneys control the amount of base (free bicarbonate) present in the ECF
In acidosis explain the ion movement that happens
k+/H(facilitated diffusion)Higher H conc outside, need to move into the cell for K to move out of the cell(needs to have the ability to switch, this is acidosis…vice Versa will be alkalosis.
Acid-base change in the body also has a potassium change
What controls the Co2 conc
Respiratory
Will a change in H+ content change bicarb or co2 levels?
Bicarb
ARe Bicarbs freely filtered and do they all get absorbed or secreted or excreted?
Freely filtered
Typical plasma concentration- 24 mmol/L
Normal GFR 180 L/Day(same as plasma cos its freely filtered)
4320 mmol/day
Essential that virtually all of the filtered bicarbonate be reabsorbed except during alkalosis
What part of the kidney absorbs or secretes Bicarb
Prox tubule absorbs bicarb, Ascending loop of Henle and the collecting duct reabsorb Bicarb
distal tubule/secretes bicarb
What’s the net product of bicarb absorption in the proximal tubule
No H+ excretion and no bicarb excretion with this process of Bicarb reabsorption in the prox tubule.
state the stages of absorption of Bicarb in the proximal tubule and the transporters and products involved
Starts inside the cell with an enzymatic process.
Carbonic anhydrase takes co2 and water(inside cell) and turns it into hco3 and h ions
The hydrogen ions goes out the apical membrane with the na/h exchanger…..na in using (secondary active transport)antiport
H+hco3=co2 +water..(this bicarb is the one that was filtered,combines with H+ to form co2 and water go in the opposite direction..no longer in the lumen neutralized into water)
Hco3 that was made inside the cell transport through the basolateral membrane through na/Hco3 exchanger into the blood.
Filtered bicarb is reabsorbed….net zero
Bicarb disappeared from blood,the one from cell replaces it in the blood.
Hydrogen ion from Apical membrane is just water now,so it does not add any acid to this.
Using the chloride exchanges on the basolateral membrane state the process of bicarb absorption in the proximal tubule
Chloride exchanger is the same process only that it uses Hco3-cl antiporter on the basolateral membrane to get into the blood.
Atp is used for the Na/H antiporter.
State the process of bicarb Absorption in the Distal tubule, Type A
After enzymatic action to produce H and Hco3,
H+ move into the tubular lumen via apical membrane. Through 2condary active transport…with Atp energy((H+ out , K+ in) and another H+ pumped out in the second Chanel with Atp.
Hco3 in the cell goes out to the interstitium and chloride come in … via hco3/cl channel.
Intercalated cells secrete acids or bases
State the process of bicarb Absorption in the Distal tubule, Type B
Same transporter different membranes ..secrete bicarb, when we have too much base and need to get rid of base. (alkalosis)
What happens it there is a base Load
Excrete bicarb via distal tubule or go into acute tubular necrosis due to alkalosis
What cells secrete hydrogen
alpha intercalated cells
When there is an acid load what happens to bicarb
Acid load will reduce the amount of bicarb in the blood
The kidney needs to replace the lost bicarbonate by generating new bicarb.
H+ ions are secreted and combine with a base of buffers other than bicarbonate.
This generates a NEW bicarbonate ion.
Explain the process of H secretion, location,type of cells and buffering of that hydrogen when released into the lumen
In the Distal tubule(Intercalated type A cells)….
Inside cell….H out via channel(ATP) or h/k channel, hsco3 out via cl channel
H+ is secreted and combines with (phos)buffer
Explain the process of Titratable acids formation and where it occurs
DT(Intercalated type A cells)….
Inside cell….H out via channel(AtP) or h/k channel, hsco3 out via cl channel
H(buffer) is secreted and combines with phos)buffer
Phosphate gets excreted after combining with H to form Titratable acids. And new bicarb is made in the blood.
Only issue is that u have to have TA in the tubular lumen…(this is in finite capacity)
The secondary mechanism is NH4 if TA is exhausted…and will make new bicarb and put into the blood when NH4 is made
If TA is expended, how do we excrete H+?
AMmonium
What are the products of catabolism protein by liver
Catabolism of protein by the liver generated CO2, water, urea, and glutamine.
Explain the process of formation of NH4 from glutamate and how ammonium is used to Buffer
Protein catabolism—Glutamine(filtered)—Proximal cells(Through enzyme process)—Converted into NH4 and Hco3….Nh4 into prox tubule(Urine),bicarb into interstitium(Blood)
what is the net acid excretion
Titratable acids
NH4
NAE= TA+ NH4- HCO3(acid –Base
On the excretion rate bar graph
if no acid in the urine , what happens
Normally diet is acidotic
No bicarb in the urine.
Get rid of acid via TA and Nh4
Net acid is black bar
what happens with acid load on the excretion rate graph
Take acid in ,will..excrete acid…make hco3 and put in blood as u do
TA can only go up by so much , but NH3 goes up a lot.
For base loaded….base is excreted…per net acid excretion
what are the things that can cause acid gain
Acid gain- decreased respiration, keto acids(product of anabolic metabolism in starvation and dm, renal failure(kidney removes acid ,if it fails ..then acids cannot be removed
ANIon and summary
Acid gain or base loss?
Difference in concentration between the major cation (Na)(ecf), and major plasma anions (Cl and HCO3)(ECF)
AG=Na- (Cl+HCO3)
Normal 8-12
Acids are an anion, and as they grow, so does the AG
WHat is the scenario of loosing base when there is No change in Anion gap
Bicarb loss…will be replaced by chloride….no change in anion(if anion does not change….means u lost base)(Bicarb replaced by Chloride
what is the scenario for acid gain if anion gap is high
When we gain acid,Na is gained….and Anion gap is high…..gained Acid.
Whats alkalosis and what avenues can they happen
Results from the loss of fixed acid or gain of HCO3
Loss of fixed acid- hyperventilation/vomitting
Gain of HCO3_, bicarb overdose, chronic diuretic usage
Kidneys regulate plasma concentrations of HCO3 by two processes
- Reabsorption of filtered HCO3
2. Generation of new HCO3
