renal 2 Flashcards
what can happen to tubular fluid after filtration
Reabsorption and secretion
what are the modes of transport in secretion and reabsorption
Transcellular (through tubular cells)
Paracellular (between tubular cells
what is the diffusion of water
Osmosis
what regulates the rate of osmosis in membrane transport
Aquaporins
what type of trasnport proteins are found in faciliated diffusion
Ion channels Transport proteins - uni - symp - anti
what are the types of vesicular transport
Endocytosis
Exocytosis
where can Sodium be reabsorbed in the nephron
All but one segment
- ocurs in:
- the proximal tubule(most)
- ascending limbs of loop of henle
- distal tubule
- collecting duct
how does Glucose and amino acids get reabsorbed in the proximal tubule
Glucose and amino acids reabsored using Na symporters
what keeps intracellular Na low in the proximal tubule
active transport on the basal side
how does water and solutes move in the proximal tubule
paracellular transport to keep the osmolarity of the tubular fluid constant
what does Na reabsorption occur with
With bicarbonate reabsorption using an Na/H antiporter
how is Bicarbonate reabsorbed
Not direct since H seceretion leads to HCO3 reabsorption
how is H secretion related to HCO non direct reabsorption
- Ca reaction produces H and HCO3 in tubule cell
- HCO3 transported into blood
- H transported into tubular fluid where it recombines with filtered HCO3
why is it important that the proximal tubular has transporters for organic cations and anions
to secrete drugs that are often organic ionic compounds, often bound to plasma proteins(not filtered)
- need to be secreted
what is the pro/con of transporters in the proximal tubule for drugs
low specificity so do lots of drugs, but are easily saturated
what all is resorbed in the proximal tubule
2/3 Na, Cl, water, and small proteins by endocytosis
K and divalent cation reabsored by solvent drag
All amino acids and glucose reabsored
Bicarbonate reabsored due to Na/H transporter
what all is secreted in the proximal tubule
Organic ions (Drugs)
what is reabsorbed in the loop of henle
25% of filtered Nacl
15% of water reabsorbed
what can and cannot pass through the descending thin limb
impermeable to slat
Permeable to water
what can and cannot pass through the ascending thin limb
impermeable to water
permeable to salt
how does reabsorption occurin the thin desending and ascending limb
passive
what happens to the fluid in the ascending thick limb
Fluid is diluted
what transport protein is found in the apical membrane in the ascending thick limb
Na, K, 2Cl symporter (goes into the cells)
what transport protein is found in the basolateral membrane in the thick ascending limb
Na K ATPase (Na out of cell, K into cell)
does solvent drag pull monovalents and divalents in the tick ascending limb
No, paracellular transport
how does paracellular transport occur in the thick ascending limb
tubular fluid becomes positive when Cl reabsored
- cations diffuse along electrical gradient
what is the concentration of solutes in the loop
Hyopsmotic
how does fluid leveling the loop become hyperosmotic urine
Countercurrent mechanisms to create an osmotic gradient
what hormone leads to concentration of tubular fluid
acting of ADH/Vasopressin in the collecting duct
what are peritubular capillaries pereable to
NaCl and water
what happens to plasma osmolarity as the capillaries follow the loop
changes, but eventually leaves in a vein as a normal osmolarity
what does the inital segment of the distal tubule reabsorb
about 8% of filtered NaCL
how does the inital segment of the distal tubule reabsorb NaCl
NaCl symporter in apical membrane
Na K ATPase in basolateral membrane
how does sodium reabsorb in the latter half of idstal tubule and collecting duct occur
Similar to the inital segments
what are the types of cells in the collecting duct and late distal tubule
primcipal cells
intercalated cells
what is found on principle cells of the late distal tubule and collecting duct
Epithelial sodium channels
what do epiethlial sodium channels do
Reabsorb Na and secrete K
what is the importance of principle cells of the late distal tubule and collecting duct
Na reabsorption driving paracellular Cl reabsorbtion
K secreted due due to NaK APTase activity in the basal membrane
what is the roll of intercalated cell in the late distal tubule and collecting duct
Acid-base balance
reabsorb K
what hormones aid in regulate blood volume
ADH/Vasopressin
Natuiuretic pepetides
what releases Vasopressin/ADH
posterior pituitary
what causes a release of ADH
- by change in osmolality of body fluid at set point 275-290 mOsm/kgH2O
- change in blood volume/pressure
what responds to a change in low blood pressure to lead to a release of Vaopressin/ADH
baroreceptors in left atrium and large pulmonary vessels
what responds to a change in high blood pressure to lead to less Vasopressin/ADH
baroreceptors in aortic arch and carotid sinus
what is the action of ADH/vasopresin
- Increase permeability of the late distal tubule and collecting duct by increasing aquaporins in the apical membrane (basolateral is freely permeable to water)
- increase permeability of medullary collecting duct to urea
what is diuresis
Low ADH
what happens in Diuresis
Solutes reabsorbed in distal tubule and collecting duct, but no water reabsorption
- urine dilute as 50 mOsm/Kg H2O
what is Antidiuresis
ADH high
what happens in ANtidiuresis
Water reabsored as fluid passes through collecting duct
- urine concentrated up to 1200 mOsm/kg H2O
what does the renin-angiotensin-aldosterone system stimulate
Events that increase reabsorption of sodium and water (combat volume contraction)
what is renin release
responding to a drop in perfusion pressure
decrease in NaCL delivery to macula densa
Sympa input to juxtaglomerular cells
what does renin do
Converts angiotensinogen to angiotensin I
what converts Angiotensin I to Angiotensin II
angiotensin converting enzyme
what is the effect of angiotensin II
Vasoconstriction
Stimulates release of ADH
increase sympa activity
Stimulate aldosterone secretion
what does aldosterone from the adrenal cortex do
increase NaCl reabsorption in the distal tubule and collecting duct by increasing transport protein synth
when are natriuretic peptides secreted
when the heart dilates (during volume expansion)
where does atrial natriuretic pepetide come from
the atria
where does brain natriuretic peptide come from
Ventricles
what are the effects of natriuretic peptides
vasodilation of afferent arterioles
Vasoconstriction of efferent arterioles
inhibit renin and aldosterone
inhibit ADH secretion
what is the net efffect of natriuretic peptides
increase excretion of NaCl and water
why is it important to regulate potassium
major determinant of membrane resting potential
- affect electrically excitable cells
what does hyperkalemaia lead to
depolarize V
what does hypokalema
hyperpolarize V
what does a change in K do to the heart
causes cardiac arrhythmias
what happens to ingesting K
fast shifted into cells mediated by insulin, epinephrine, and aldosterone
how much ingested K is excreted by the kidney
90-95%
is K freely filtered in the Glomerulus
yes
where is K reabsorbed
67% in the proximal tubule
Thick ascending limb
how is K reabsorbed in the proximal tubule
paracellular transport/solvent drag like Na
how K reabsorbed in the thick ascending limb
Na, K, 2Cl symporter and paracellular transport (non solvent drag)
how is K secreted in the late distal tubule and collecting duct
- K secreted by principal cells depending on ATPase activity, K gradient, apical K permeability
- intercalated cells reabsorb K when Potassium is depleted
what are the factors that affect excretion of Potassium
Plasma K
Flow rate of tubular fluid
how does plasma K change the excretion of Potassium
increased K simulates Aldosterone release
aldoserone increase Na/K ATPases in principle cells
what does an increase in flow rate do to K secreteion
Increases K secertion
why does in creased flow lead to an increase in K secretion
local response to bending of cilia
how does increased flow increase K secretion
increased flow
increased Na in collected
Na reabsorption
favors increased K secretion
does reabsorption of K in proximal tubule and thick ascending limb change a lot dpending on poassium presence
No
wha does secretion increase if plasma K is high
increases in distal tubule and cortical collection
where does reabsorption of K occure when plasma concetrations are low`
distal tubule
cortical collecting duct
