Tubules- Physiology Flashcards
This is the pathways of water and solutes when they are transported through both the apical and basolateral membranes of a cell.
Transcellular pathway
This is the pathway of water solutes when it is transported through the junctional spaces between the cells.
Paracellular pathway
This is the term for when once the water and solutes are in the interstitial fluid, they are transported all the way through the peritubular capillary walls into the blood by ultrafiltration.
Bulk flow
This is the use of specific ATPase transporters to move substances against an electrochemical gradient.
Primary active transport
In secondary active transport, what must be established by a secondary ATPase to cause movement of a substance against an electrochemical gradient?
A gradient
This is the movement of solutes down their gradient,
Passive transport
When a substance is moved down its gradient with the helping hand of a carrier protein, what is it called?
Facilitated diffusion
This is the saturation of the specific transport systems involved when the amt of solute delivered to the tubule exceeds the capacity of the carrier proteins.
Transport maximum
If a substance exceeds the transport maximum, which is normally reabsorbed completely in the tubules, what do u see in the pee?
The substance, which u normally wouldnt see
Is the transport of water passive or active across cells?
Passive
When water is reabsorbed in the PCT, there is a high gradient established for which ion?
Cl-
Cl- is also reabsorved through the tubular epithelial cells because of the electrical drive from which ion that’s absorbed?
Na+
Urea is pretty big, which causes a ↓ reabsorption rate, resulting in how much % urea reabsorbed?
50%
How much Water and NaCl are reabsorbed at the PCT?
65%
What is reabsorbed in the descending LH?
Water (20%)
How much NaCl is reabsorbed in the descending LH?
NOTHING. ONLY WATER. HAHHAHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHA!
When in the LH does water reabsorption stop?
at the thin ascending LH
What % of NaCl and K is reabsorbed in the thick ascending LH?
25%
How much NaCl is reabsorbed in the early DCT?
5%
The pricipal and intercalated cells of the late DCT reabsorb which substances?
NaCl, K, HCO3- and water
Which hormone controls the level of H2O reabsorption in the collecting duct (CD)?
Antidiuretic Hormone (ADH)
What is reabsorbed in the CD to raise the osmolality of this region to concentrate the urine more?
Urea
Glucose, proteins, and AA’s are completely reabsorbed in which segment of the nephron?
PCT
The NKCC channels in the thick ascending LH absorb which ions?
Na+
K+
2 Cl-
After the NKCC channels reabsorb K, it leaks out again through which channels to cause the reabsorption of Ca and Mg?
ROMK
Which drug is almost completely removed in the plasma and excreted, so it can be used to estimate RPF?
PAH
Loop diruetics (furosemide, ethacrynic acid, and bumetanide) target which carrier?
NKCC on the thick ascending LH
Thiazide diuretics target whcih carrier protein?
NaCl in the early DCT
What is the target for spironolactone and eplerenone for K+ sparing?
Aldosterone R
they’re competitive antagonists
What is the target for Amiloride and Triamterene for the K+ sparing?
ENaC channel (Na+) on luminal membranes
What are the 2 influences on the peritubular capillary hydrostatic pressures?
Arterial pressure
Arterial resistance
SANS increases the reabsorption of which ion from the PCT, thick ascending LH, and DCT?
Na+
The sans also constricts the renal arterioles, which cause which change in GFR?
↓ GFR
Aldosterone stimulates the reabsorption of which ion from the principal cells?
Na+
Aldosterone stimulates the secretion of which ion from the principal cells?
K+
Aldosterone stimulates the secretion of which ion from the intercalated cells?
H+
ADH causes the recruitment and insterion of which proteins int he luminal membrane of the CD to cause ↑ water reabsorption?
Aquaporins
What does ANP do to Na reabsorption?
Blocks it
PTH increases the reabsorption of which ion from the DCT and LH?
Ca++
PTH activates the Gs pathway to decrease the reabsorption of which substance?
Phosphate
This is the volume of plasma that is completely cleared of the substance by the kidneys per unit time.
Renal Clearance
What is the equation for clearance rate?
Cs = (Us x V)/Ps
Us- urine concentration of substance
V- urine flow rate
Ps- plasma concentration
What is the equation for GFR using inulin?
GFR = (Uinulin x V)/Pinulin
What is the equation for clearance ratio, using inulin?
CR = Cs/Cinsulin
What is the equation for ERPF, using PAH?
ERPF = C(PAH) = [U(PAH) x V]/P(PAH)
What is the eqn for RPF?
RPF = C(PAH)/E(PAH) = [U(PAH) x V/P(PAH)]/{[P(PAH) - V(PAH)]/P(PAH)}
E(PAH) = urine PAH extration ratio
lol do u like that?
What is the eqn for RBF?
RBF = RPF/(1-Hct)
What is the eqn for excretion rate?
ER = Us x V
What is the eqn for reabsorption rate?
RR = filtered load - excretion rate = (GFR x Ps) - (Us x V)
What is the eqn for secretion rate?
SR = ER - FL
How much water is taken in each day through liquids or food?
2100 mL/day
How much water is synthesized in the body each day as a result of oxidation of carbs?
200 mL/day
SOOOOOOOOOOOOOOOOOOOOOO the total intake of water each day is what?
2300 ml/day
How much water do we lose each day to respiration and the skin (insensible)?
700 mL/day
How much water is lsot in sweat?
100mL normally but i can increase if ur a sweaty bitch
How much water is lost in poop?
100 mL/day normally.
10000 ml/day for me.
How much water is lost in pee per day?
from 0.5-20L/day
Diarrhea causes the loss of Na, leading to which condition of low Na?
Hyponatremia
Which drugs can cause excess Na loss, leading to hyponatremia?
Diuretics (typically thiazides)
This is the condition where there is undersecretion of aldosterone, leading to Na loss.
Addisons disease
True or False: in SIADH there is too much water retention leading to dilution of Na leading to Hypernatremia.
True
ok yeah i didnt know how to make a flashcard for this lol.
So if you can’t secrete ADH, the excessive loss of water will lead to what Na condition?
HYPERnatremia
What condition is when there is damage to the posterior pituitary, causing the inability to secrete ADH?
central diabetes insipidus
What is it called when there is appropriate ADH release but the kidneys cannot respond to it?
nephrogenic diabetes insipidus
How will sweating cause hypernatremia?
Lose water –> ↑ [Na]
This is the syndrome where there is hyperaldosteronism causing ↑ Na reabsorption and thus hypernatremia.
Conn’s syndrome
What is the osmolarity of the filtrate in the PCT?
300
What is the osmolarity of the filtrate in the descending LH?
increases from 300 –> 600
Why does the osmolarity of the filtrate increase in the descending LH?
water leaves and salt stays in the pee
What is the osmolarity of the filtrate in the ascending LH?
decreases from 600 –> 100
Why does the osmolarity of the filtrate decrease so much from themedullary LH to the DCT?
cuz salt leaves and water stays
What is the osmolarity of the filtrate in the DCT?
100
What is the maximum concentrating ability of the kidneys in osmolarity?
1200 mOsm/L
In the countecurrent mechanism, the tubule pumps out ions and urea into the interstitum, creating a large gradient for what?
Water
Where does water flow to equalibrize the high somolarity from the coutnercurrent mechanism?
From the CD –> interstitum
A loop diruetic will inhibit the NKCC transporter, causing what change in water drive?
less driving force to leave –> ↑ urine volume
Where is urea reabsorbed in the nephron?
PCT and medullary CD
Reabsorption of urea will increase the drive for what other substance to be reabsorbed?
Water
An increased protein diet will cause what change in the urine concentration?
↑ protein –> ↑ urea –> ↑ reabsorption of urea –> ↑ concentration of urine
Once reabsorbed from the CD, urea can then re-enter the nephron at which points to keep a little cycle action going?
medullary portions of the LH
Is medullary blood flow from the vasa recta high or low?
Low (keeps solutes there)
True or False: the vasa recta has a single osmolarity, unlike the LH which varies from cortex –> medulla.
FALSE. The vasa recta is the same shape as the LH and has the same weird osmolarities
Receptors in what location shrink when osmolarity increases?
Anterior pituitary
The anterior pitutary then tells the suproptic nuclei what’s up, which then signals which location?
Posterior pituitary
What does the posterior pituitary release?
ADH
What will cause baroreceptor firing to increase ADH secretion?
decreased arterial pressure (hemorrhage)
Will vomiting increase or decrease ADH release?
increase a ton
Does nicotine and morphine increase or decrease ADH release?
Increase
Does alcohol increase or decrease ADH release?
inhibit
u pee a lot while drinking
Which form of diabetes insipidus will respond to Desmopressin, central or nephrogenic?
Central
Which nuclei in the hypothalamus are responsible for thirst?
Lateral nuclei
What are the 2 locations that sense osmolarity to tell the lateral hypothalamic nuclei that you’re thirsty?
Tractus solitarii nuclei
Area postrema
True or False: there is a massive change in plasma Na concentration when the aldosterone systme is blocked, as you can no longer take in Na+.
False. it barely changes cuz whenever Na is reabsorbed, water follows. its a balance.
True or False: there is a massive change in plasma Na concentration when ADH and thirst systems are blocked.
True
You take in 50-200mEq/day of what ion?
K+
What is normal K concentration in the extracellular fluid?
4.2 mEq/L
This is the condition where there is failure to rapidly ride the ECF of ingested K.
Hyperkalemia
Too much loss of K will cause what?
Hypokalemia
Case: pt presents with massive myoglobinuria and increased urine CK. He also has malaise, hyperventilation, metabolic acidosis, and most importantly, cardiac arrhythmia that’s msot likely leading to sudden death. What is his problem?
Hyperkalemia
↑ Mb and CK from muscle cells popping, which release a ton of K into the ECF –> hyperkalemia
In addition to HTN and arrhythmias, what skeletal muscle abnromalities can be a result from hypOkalemia?
Muscle cramps
Flaccid paralysis
Rhabdomyolisis
Does insulin increase or decrease K uptake into cells?
Increase
So are diabetics typically hyperkalemic or hypokalemic?
Hyperkalemic (no insulin to get rid of the ECF K)
Does aldosterone increase or decrease K uptake into cells?
Increase
Does beta-adrenergic stimualtion increase or decrease K uptake into cells?
Increase
Does acid (H+) increase or decrease [K] in the ECF?
increase
Case: pt presents with cardiac arrhythmias post-marathon. What is happening to his K levels in the ECF?
↑ K from SkM lysis –> hyperkalemia
If there’s an increased intracellular osmolarity, will there be an increase or decrease of K within the cell?
increase
What are the 2 places K is reabsorbed along the nephron?
PCT and thick ascending LH
Where is K SECRETED in the nephron?
DCT/CD
Does an increase or decrease in Na/K ATPase in the principal cells increase K secretion?
Increase Na/K ATPase –> ↑ K secretion
What are the 3 ways that stimulate K secretion?
- ↑ [K] in ECF.
- ↑ aldosterone
- ↑ tubular flow
Which receptor does aldosterone stimualate to cause K secretion and Na reabsorption?
Na/K ATPase
Why does an increased Na intake not change K excretion?
cuz it both ↓ aldosterone (↓ K secretion) but ↑ tubular flow rate (↑ K secretion)
What does acid inhibit cause an increase in [K] in the ECF?
Na/K ATPase
What are 2 drugs that inhibit the aldosterone R to spare K secretion?
Eplerenone and Spironolactone
What are 2 drugs that inhibit the ENaC channel on the luminal membrane to spare K+ secretion?
Amiloride
Triamterene
Thiazide and loop diuretics inhibit receptors, leading to what severe K imbalance?
Hypokalemia
What is a normal Ca++ levels in the plasma?
2.4 mEq/L
What mg/dL determines hypocalcemia?
< 8.5 mg/dL
What mg/dL determines hypercalcemia?
> 10.3 mg/dL
This is the condition of hypocalcemia where there are spastic muscle contractions from ↑ excitability of nerve and muscle cells.
Hypocalcemic tetany
from ↑ permeability of neuronal membranes to Na+
What is the main issue with hypercalcemia?
Cardiac arrhythmias
What are the 3 ways PTH stimulates ↑ [Ca++] in the blood?
1, Stimulating bone resorption
- Activation of vitamin D (↑ GI absorption)
- Directly ↑ renal tubular Ca++ reabsorption
Whenever you reabsorb what ion in the nephron do u reabsorb Ca++?
Na+
What % of Ca++ is excreted?
1%
What mechanism does Ca++ reabsorption in the thick ascending?
Passive mechanisms secondary to Na+ reabsorption
So a loop diuretic will do what to Ca++ reabsorption?
↓
How is Ca++ reabsorbed in the DCT?
active transport independent of Na+ reabsorption
What will thiazide diuretics do to Ca++ reabsorption?
increase Ca++ reabsorption
So which type of diuretics (loop or thiazide) do u use with osteoporotic pts with HTN?
Thiazide diuretics
Does metabolic acidosis or alkalosis increase Ca++ reabsorption?
Acidosis
What is the cap (in mM/min) of Ca++ reaborption of Phosphate in the nephron?
1 mM/min
Does PTH increase or decrease phosphate excretion?
Increase
Although PTH causes bone resorption and thus ↑ phosphate dumping, what does it do to the transport maximum on the renal tubules to ↑ phosphate excretion?
↓ the transport max
This is the term for increased Na excretion from elevated blood pressure.
Pressure natriuresis
This is the term for the effect of increased blood pressure causes a raise in urinary volume excretion.
Pressure diuresis
Which form of HTN (acute or chronic) causes a 2-3 fold increase in urinary Na output?
Chronic
Increased capilalry hydrostatic pressure, ↓ plasma colloid osmotic pressure, ↑ permeability of the capillaries, and obstruction of the lymph vessels can lead to what abnormality?
edema
What does the SANS do to GFR?
↓ GFR by constricting the afferent arteriole
What does the SANS do to tubular reabsorption of Na and Water?
↑
What does the SANS trigger the release of to increase tubular reabsorption?
RAAS system
After eating your Thanksgiving meal, what happens to the SANS?
Reflex inhibition leading to rapid elimination of excess fluid
When the control of ATII of naturesis is fully functional, how much change in blood pressure is needed to increase the sodium excretion drastically?
A little change
If ATII levels cannot eb decreased in response to increased Na intake (like in HTN), how much change in BP is needed to change the Na excretion?
A good amount
Does ADH have an effect on Na+ excretion?
No
Cardiac atrial muscle fibers make this protein when the atria are stretched to act on the kidneys to cause small increases in GFR and ↓ of Na reabsorption by the CD.
ANP
What happens to the kidneys in heart failure?
They retain volume in an attempt to return the arterial pressure and CO toward normal
If you increase circulation capacity (varicose veins), what do the kidneys retain until blood volumes increase to fill the extra capacity?
Na and water
Nephrotic syndrome resulting in edema causes what compensation of the kidney?
Retains Na and water until plasma volume is restored to normal
These are molecules containing hydrogen atoms that can release hydrogen ions in solutions.
acids
These is an ion or molecule that can accept a H+.
base
This is the excess removal of H+ from the body fluids (↑ in pH).
Alkalosis
This is the excess addition of H+ from the body fluids (↓ in pH).
Acidosis
What is the normal pH for the blood?
7.4
What are the 3 ways the body can buffer changes in pH?
Chemical acid-base buffer systems
Respiratory center
Kidneys
Which enzyme convers CO2 + H2O –> H2CO3?
Carbonic Anhydrase
How is acid buffered by the bicarbonate buffer solution (give the eqn)?
↑H + HCO3- –> H2CO3 –> CO2 + H2O
How is base buffered by the bicarbonate buffer solution (give the eqn)?
NaOH + H2CO3 –> NaHCO3 + H2O
What is the Henderson-Hasselbalch eqn to calculate the pH of a sln?
pH = 6.1 + log[(HCO3-)/(0.03 x PCO2)]
What does an ↑ in respiration rate do to pH?
↑ by ↑ CO2 blow-off
These are acids that can be excreted from the lungs, like H2CO3.
Volatile acids
These are acids that cannot be excreted by the lungs, like ketoacids or lactic acid.
Nonvolatile acids
How does the body get rid of nonvolatile acids?
The kidneys excrete them
What is the transporter on the luminal membrane of the PCT, thick ALH, and DCT to secrete H+?
Na/H antiporter
What form of energy transport does H+ use on the PCT, thick ALH, and DCT to secrete H+?
Secondary active transport from Na+ gradient set up by Na/K ATPase
What always gets reabsorbed whenever H+ is made inside the tubule cell to be secreted?
HCO3-
From the DCT onwards, how is H+ secreted by the intercalated cells?
Primary active transport
H+ ATPase
When all the H+ in the pee buffers with the free HCO3-, what 2 systems kick into place to buffer the excess H+ ions?
Phosphate and ammonia buffer systems
The phosphate and ammonia buffer systems buffer the free H+ but also give rise to the net GAIN of what ion to be reabsorbed?
HCO3-
In the phosphate buffer system, the NaHPO4- in the pee can buffer acid and be excreted as what salt?
NaH2PO4
In the PCT, thick ALH, and DCT, which AA is delivered form the liver to the kidneys to buffer H+?
Glutamine
In the CD, the H+ is secreted by primary active transport into the pee, whcih combines with what from the intercalated cell?
NH3
So in both forms of the ammonia buffer system, what is excreted as a salt to buffer H+?
NH4+ + Cl-
An increase in PCO2 causes what change to H+ secretion?
↑ H+ secretion
more CO2 to be broken down and secreted
Does an increase or decrease in the RAAS system ↑ H+ secretion?
↑ RAAS –> ↑ H+ secretion
A patient with Conns syndrome will cause what change, acidosis or alkalosis?
Alkalosis
↑ aldosterone –> ↑ H+ secretion
What is the compensatory response to respiratory acidosis?
an increase in plasma HCO3-from the addition of new bicarbonate to the extracellular fluid by the kidneys
What is the compensatory response to metabolic acidosis?
the lungs compensate by increasing ventilation rate. This decreases PCO2. The kidneys also add new bicarbonate to the extracellular fluid
What is the compensatory response to respiratory alkalosis?
the kidney compensates by increasing excretion of HCO3-
What is the compensatory response to metabolic alkalosis?
the lungs compensate by decreasing respiratory rate (↑ PCO2) and the kidneys increase renal HCO3- excretion
What happens to the H+, HCO3-, and CO2 levels in respiratory acidosis?
H+: ↑
HCO3-: ↑
CO2: ↑
What happens to the H+, HCO3-, and CO2 levels in Metabolic acidosis?
H+: ↑
HCO3-: ↓
CO2: ↓
What happens to the H+, HCO3-, and CO2 levels in respiratory alkalosis?
H+: ↓
HCO3-: ↓
CO2: ↓
What happens to the H+, HCO3-, and CO2 levels in metabolic alkalosis?
H+: ↓
HCO3-: ↑
CO2: ↑
What causes respiratory acidosis?
↓ ventilation
What causes metabolic acidosis?
Diarrhea, diabetes, ingesting acids, renal failure
What causes respiratory alkalosis?
↑ ventilation
What causes metabolic alkalosis?
Vomiting, diuretics, excess aldosterone, ingestion of alkaline drugs
What is the Tx for acidosis?
Tums
What is the Tx for alkalosis?
give ammonium chloride by mouth
This is when there are 2 or more underlying causes for acid-base disturbance and disorders are not accompanied by appropriate compensatory responses.
Mixed acid-base disorder
This is the difference between the unmeasured anions and unmeasured cations in the plasma.
Anion gap
What is the eqn for the plasma anion gap?
Anion gap = [Na+] - [HCO3-] - [Cl-]
In metabolic acidosis, plasma HCO3 is reduced, so what much increase to maintain electrostability?
Cl-
In hyperchloremic metabolic acidosis, is the anion gap increased, decreased, or normal?
Normal
Matabolic acidosis from increased nonvolatile acids does what to the anion gap, increase, decrease, or keep it normal?
Increase
Diarrhea, renal tubular acidosis, carbonic anhydrase inhibitors, and Addisons cause what?
hyperchloremic metabolic acidosis
