KEY wk 9, lec 3 Flashcards
division of water in body
2/3 intracellular
1/3 extracellular (20% blood plasma. 80% interstitial fluid)
fluid and salt go into ECF easily not ICF
–> water expands both
–> saline expands ECF
–> salt expands ECF and shrinks ICF
nephron reabsorb vs excrete
eabsorb essential substances such as water, glucose, amino acids, and ions while secreting waste products like urea, creatinine, and excess ions into the tubular lumen for excretion in urine.
passive diffusion
move down [ ] gradient without energy
lipid soluble substances (i.e. urea), gases, small ions, water
facilitated diffusion
carrier proteins or channels move molecules down concentration gradient without energy
i.e. glucose and amino acids
active transport
move against [ ] gradient via ATP
Na+/K+ ATPase pump (sodium out, k in)
secondary active transport (symport and anti port)
active transport; coupled movements of 2+ molecules
symport: same direction (sodium glucose cotransporter SGLT) (Na-3HCO3 symporter for bicarbonate)
anti port: opposite (sodium calcium exchanger, sodium in, ca out) (Na-H anti porter)
endocytosis vs exocytosis
Endo: engulf extracellular substance via invagination of cell membrane = form vesicle
exocytosis: reverse; vesicles with substance fuse with membrane and release content into extraceullar space
extraceullar vs intracellular ions in both
extracellular:
lots: Na+, Cl-
some: Ca2+, HCO3-, protein
intracellular
lots: K+, PO4 and organic anions
fair bit: Mg2+, protein
~100 of Na+, Cl- in extracellular
~30 of HCO3- in extracellular
~100 K+ in intracellular
water gain and loss
insensible= not aware of (NOT sweat)
input: food, drink, metabolism
output: insensible via skin and lung, sweat, feces, urine
2 routes for transporting substances in renal tubules
transcellular: apical transporter –> cytoplasm –> basolateral surface –> peri-tubular capillaries
paracellular: across tight junctions, in ECF space between cells
what cells are in the collecting tubules
principal and intercalated cells
parts of the tubule and their function
PCT- reabsorb nutrients ans 60% of water and most solutes
loop of henle thin limb: passive reabsorb water (descending) and NaCl (ascending)
loop of henle thick tiling: ionic gradient for countercurrent multiplication; dilutes urine, makes interstitial hypertonic
DCT: Na+, Cl-, water balance
collecting tubules: principal cells for absorption of Na+, K+, water and intercalated cells for acid.base and K+ homeostasis
main thing for osmolality in ECF
NaCl
ICF has how much water
2/3 of body osmotic content and therefore water
(1/3 in ECF)
but ECF and ICF is osmotic equilibrium bc water crosses cell membranes easily
water transport in tubules
move from what osmolality
always reabsorbed; never secreted
moves from low to high osmolality
na, cl and water
water and salt are freely filterable at renal corpuscle ‘
cl is passive and because of electroneutrality (- and +) its tied to Na trasnport
where does majority of Na, Cl and water get reabsorbed? how much?
2/3 in proximal tubule
where does sodium get reabsorbed
what goes to urine
65% in proximal tubule
25% un thin ascending limb and thick ascending limb of henle
little bit in DCT and collecting duct ~10%
NONE in descending thin limb of henle loop
urine= <1% of total filtered sodium
all nephron segments have what for active transceullar sodium reasbosption? keeps sodium [ ] in intracellular space ____, despite the negative charge inside the lumen (that’s why need ATP for Na+ to go against electrochemical gradient)?
Na-K-ATPase pump
low
what anions balance out sodium (cation)
mainly chloride, some bicarbonate
main reabsorption of chloride
proximal tubule
Cl- gets transported where
intracellular (even through negative inside)
–> need energy to move against gradient
how to excrete water in excess of salt and vice versa
seperate reabsorption
-the same in proximal tubule, but differs beyond
-water reabsorbed in descending henle
-Na reabsorbed in ascending henle
sodium reabsorbed in loop of henle is always ____ than water
greater