Keef 5 Flashcards
How does insulin help w/ K uptake & the avoidance of the dangerous hyperkalemia?
Insulin prompts Na+ to be taken into the cells via Na/H exchanger. With more Na+ inside the cell, the sodium potassium pump is stimulated. This pushes more sodium outside of the cell & pushes more potassium inside the cell.
How does epinephrine help w/ K uptake & the avoidance of the dangerous hyperkalemia?
Epinephrine stimulates the sodium potassium pump.
Which part of the nephron is capable of giving you isotonic urine?
The PCT! The osmolarity is 300 entering it & 300 leaving it! All that happens is that 67% of the salt & water are taken out.
Urine: 300
Which part of the nephron is capable of giving you a hypotonic urine?
The thick ascending limb of the loop of Henle. Here: the H2O permeability is crazy low. However, the Na/K/Cl transporter is working like crazy.
Urine: 150-250
What is the osmolarity of our urine usually? Why?
Hypertonic
B/c of the whole nephron & b/c of the ADH effects in the DCT & the osmotic gradient formed by the loop of Henle. The osmotic gradient pulls water out of the collecting ducts so that by the time you get to the renal papilla the urine is concentrated.
What is the osmolarity in the cortex? At the entrance to the minor calyx?
Cortex: 300
Entrance: 1200
What are the steps to forming the osmotic gradient in the interstitial space of the loop of Henle?
Pump: the salt out of the ascending limb
Equilibrate: passive movement of salt into descending limb & water into interstitial space
Shift: put more water in!
What is the max osmolarity that you can get in the interstitial space from the movement of salt?
600mOsm
How do you get to an osmolarity of 1200 in the interstitial space?
from the movement of urea out of the loop of Henle
T/F as a part of the counter current multiplier…sodium is actively secreted into the descending limb of the loop of Henle
False.
It is passively secreted into the descending limb of the loop of Henle as a part of equilibration.
What is the osmolarity of the blood in the vasa recta that comes from the glomerulus? That goes to the vena cava? That is at the base of the loop?
From glomerulus: 300
To vena cava: 325
Bottom of Loop: 1200
In order to achieve the concentrations of blood it does at each section of the vasa recta:
what happens @ the descending limb?
The ascending limb?
Descending limb: get rid of water & absorb salt
Ascending Limb: absorb water & get rid of salt.
B/c of equilibration: what is the concentration at the bottom of the vasa recta, the loop of Henle & the interstitial space?
1200
Plasma flow exiting the vasa recta is ____ that entering the vasa recta.
2X. B/c of water reabsorption.
T/F Plasma exiting the glomerular capillaries is approximately 20% less than that entering the glomerular capillaries.
true.
20% filtered
What percentage of the renal blood flow goes to the cortex? What percentage goes to the medullary region?
90% goes to the cortex.
10% goes to the medullary region.
After the PCT…what is the concentration of urea?
50% of the original concentration…it is reabsorbed here along w/ sodium & water.
In the DCT…what is the concentration of urea?
110% b/c it is secreted along the loop of Henle.
What part of the nephron is impermeable to urea?
The DCT…this is why the urea becomes super concentrated here.
What is the concentration of urea leaving the collecting tubule? How is this possible?
40%. This is possible b/c of the reabsorption of urea in the collecting duct
How is urea reabsorbed in the collecting duct?
This process is considered facilitated diffusion. It is prompted in the presence of ADH. Remember…this is important in the formation of the conc’n gradient–get to that 1200!!
What ultimately stimulates the synthesis of ADH? What senses this?
An increase in plasma osmolarity.
Sensed by osmoreceptors.
Where is ADH synthesized?
In the supraoptic nuclei & the paraventricular nuclei.
Where is ADH released from?
The posterior pituitary
How does ADH lead to the insertion of aquaporins in the DCT & the increased reabsorption of water?
V2 receptors on the basolateral membrane of the DCT bind ADH.
Gs: adenylyl cyclase is activated
cAMP increases
PKA is activated
Phosphorylation happens; CREB stuff happens–>synthesis of aquaporins is increased in the nuclei
These aquaporins travel to the apical membrane via vesicles.
They are inserted & increase the water permeability of the DCT.
T/F Although the main aquaporins which are formed thru ADH are inserted into the apical membrane–>there are also aqualporins in the basolateral membrane.
True.
What is usu associated with all forms of Diabetes?
Polyuria. Tons of urine.
What does insipidus mean?
dilute
What is Nephrogenic Diabetes Insipidus?
the formation of a bunch of dilute urine b/c the kidney will not respond to ADH.
What is Neurogenic Diabetes Insipidus?
the formation of a bunch of dilute urine b/c not enough ADH is synthesized.
What is SIADH? What are its symptoms?
Syndrome if Inappropriate AntiDiuretic Hormone Release
Too much ADH is released. You retain too much water.
Dilution Hyponatremia is seen here. There is a normal amount of sodium in the body, but there is a low conc’n of sodium b/c of all of the retained water.
What is psychogenic polydipsia?
It is the consumption of excessive amounts of water b/c of a mental issue & a feeling of excessive thirst.
What is diuresis?
more than normal amount of urine flow. V>1
What is antidiuresis?
a normal amount of urine flow in which the urine is hypertonic.
Is diuresis or antidiuresis normal?
Antidiuresis
What is water diuresis? What is a condition that would exhibit this?
excessive urine flow b/c of excessive consumption of water…psychogenic polydipsia
What is osmotic diuresis? What is a condition that would exhibit this? What is a pill that could create this?
more than normal urine flow caused by water being trapped in the tubule by a lot of solutes…
Diabetes Mellitus…there is glucose in the urine…this traps water there!
Mannitol is used as an osmotic diuretic for this very reason.
In water diuresis…is their ADH? What is the conc’n of the urine entering the DCT & exiting the cortex/DCT? Why?
No ADH
150 entering…100 exiting the cortex/DCT
This is b/c the NaCl transporter in the DCT gets rid of solute…but the water can’t follow b/c there are no aquaporins present.
In antidiuresis…is their ADH? What is the conc’n of the urine entering the DCT & exiting the cortex/DCT? Why?
ADH is present.
entering DCT…250
exiting 300.
The NaCl transporter takes salt out. Water can follow & equalize the interstitial gradient of 300 b/c of the presence of aquaporins b/c of the presence of ADH.
What is the max conc’n of urine in the tubules in the cortex? Why?
300
b/c that is the interstitial gradient @ its maximum in the cortex. Can only equalize water. There isn’t a water pump.
What is the conc’n of urine leaving the collecting tubules in water diuresis? Along the collecting tubules, is salt reabsorbed? Urea?
75
Salt is reabsorbed.
urea isn’t reabsorbed.
Water isn’t reabsorbed.
What is the conc’n of urine leaving the collecting tubules in antidiuresis? Along the collecting tubules, is salt reabsorbed? Urea? Water?
1200
Salt & urea are reabsorbed.
Water is also reabsorbed.
In water diuresis, are the following values high or low? V? Uosm? Uurea? Curea?
V-High Uosm-Low Uurea-Low Curea-High **Uurea is low b/c conc'n is low. **Curea is high b/c so much water is exiting & the urea isn't being reabsorbed. It is like putting a hose up to the nephron.
In antidiuresis, are the following values high or low? V? Uosm? Uurea? Curea?
V--Low Uosm-High Uurea-High Curea-Low *b/c there is such a low volume of urine leaving, the clearance of urea is relatively low, even tho the conc'n of urea in the urine is high.
T/F The osmotic gradient in the interstitium is highest in water diuresis.
False.
T/F The osmotic gradient in the interstitium is essential for the formation of both isotonic & hypotonic urine.
False. It is needed for neither of these. It is only needed for the formation of hypertonic urine.
T/F Urea contributes more to the gradient during antidiuresis than during diuresis.
True.
ADH is what prompts urea reabsorption & the formation of the extreme gradient. During diuresis, hypotonic urine is formed & ADH isn’t present/urea isn’t reabsorbed.
T/F The osmotic gradient is formed by passive transport of salt & water.
No. There is active transport involved.
What is the pH range of your urine?
5-7
The conc’n of which 2 electrolytes in your urine depends upon your consumption of them?
sodium
potassium
Which 2 non electrolytes are found in your urine? Which one predominates?
Creatinine
urea
**urea predominates
Why is your urine yellow?
The breakdown of the heme of old red blood cells produces bilirubin…this forms urobilin which is yellow.
