8.1 Renal Physiology II - Fluid Balance ELECTROLYTES Flashcards
HOMEOSTASIS includes balance of:
- ELECTROLYCE BALANCE
Ion gain each day = ion loss - FLUID BALANCE
water gained daily = water lost - ACID-BASE BALANCE
H+ gain is offset (balanced) by H+ loss
EXCESS of any can be fatal
ISOTONIC
HYPOTONIC
HYPERTONIC
ISOTONIC: salt conc same inside and outside cell, no net movement of water
HYPOTONIC: Higher salt conc. IN cell so water moves IN, cell swells
HYPERTONIC: Higher salt conc. OUTSIDE cell so water moves OUT, cell shrinks
REABSORPTION can occur by:
- CO-TRANSPORTERS (Na/Glucose)
- ACTIVE TRANSPORTERS (use ATP)
- OSMOSIS
- SOLVENT DRAG and Passive DIFFUSION
what is PARACELLULAR TRANSPORT
Movement of substances BETWEEN epithelial CELLS
eg Potassium K+
what is SOLVENT DRAG
movement of Salts BETWEEN CELLS (PARACELLULAR transport) and PULLS WATER with it (moves into interstitial space)
what is TRANSCELLULAR TRANSPORT
Movement of substances ACROSS and epithelial CELL
what is TUBULAR REABSORPTION
substances move FROM TUBULE INTO BLOOD
what is TUBULAR SECRETION
substances move FROM BLOOD INTO TUBULE
what happens in the PCT
REABSORPTION of WATER, IONS and organic nutrients
NO K+ TRANSPORTERS in the
PCT
(no potassium reabsorption here)
GLUCOSE TRANSPORTERS are ONLY in the
PCT
(glucose reabsorption only takes place from PCT)
in PCT what MOVE OUT OF FILTRATE (into PCT CELLS) for REABSORPTION
GLUCOSE
AMINO ACIDS
CHLORIDE
WATER
in the PCT what allows for the TRANSPORT of GLUCOSE, AMINO ACIDS, CHLORIDE and WATER from filtrate into PCT cells for REABSORPTION
NA+
- Na+ moves DOWN conc. gradient into PCT cells and brings GLUCOSE, AMINO ACIDS, CHLORIDE, WATER with it
WATER brought by SOLVENT DRAG (moves with Na+)
Na+-Glucose Transporters
Na+-Amino Acid Transporters
Na+-Cl- Transporters
why does Na+ diffuse into PCT CELLS from lumen, DOWN its conc. gradient
NA+ also being PUMPED OUT via Na+-K+ CO-TRANSPORTER (3 Na+ OUT) into BLOOD
- Na+ REABSORPTION for use
(water reabsorbed with it) - creates conc. gradient for Na+ to diffuse in (carrying other substances)
PCT is the MAIN SITE of … REABSORPTION
WATER
Na+ Reabsorbed, so water moves out with it
what is different about the TRANSPORT of GLUCOSE OUT of FILTRATE
there is a TRANSPORT MAXIMUM
(limits how much glucose can move from filtrate to PCT cells for reabsorption)
as Na+ moves INTO PCT CELLS from lumen, what does it cause to MOVE OUT, INTO LUMEN
Na+ in down conc. gradient moves H+ OUT (into filtrate) AGAINST CONC. GRADIENT
what factors AFFECT REABSORPTION
- RATE of the FLOW OF FILTRATE (how fast filtrate is moving) (faster means less reabsorption)
- CONC. of SMALL MOLECULES in the FILTRATE
(more conc/ more Na+, more reabsorption)
but fixed number of transporters
PCT REABSORBS how much of FILTERED SODIUM
LOOP OF HENLE?
DCT:
COLLECTING DUCT:
65%
LOOP OF HENLE: 25%
DCT: 8%
COLLECTING DUCT: 2% ONLY in presence of ALDOSTERONE
COLLECTING DUCT can REABSORB last 2% of filtered NA ONLY in the presence of…
ALDOSTERONE
how does the PERMEABILITY DIFFER in the LOOP OF HENLE
THIN DESCENDING LIMB:
PERMEABLE to WATER
IMPERMEABLE to SOLUTES
(impermeable to urea)
WATER REABSORBED (moves out)
how does the PERMEABILITY DIFFER in the LOOP OF HENLE
THICK ASCENDING LIMB:
PERMEABLE TO SOLUTES
IMPERMEABLE to water
(moderately permeable to urea)
ACTIVE TRANSPORT of SOLUTES - REABSORPTION
Na+
Cl-
starts to become more permeable to K+ further up
how does OSMOLALITY (conc. of solutes) in FILTRATE CHANGE in the LOOP OF HENLE
down DESCENDING LIMB
- INCREASES (more water out)
up ASCENDING LIMB
- DECREASES as salts can now leave
why do solutes move out of LOOP OF HENLE (ASCENDING LIMB)
BLOOD capillary surrounding it / CIRCULATING has come from EFFERENT ARTERIOLE so has LOW CONCENTRATIONS of SODIUM, CHLORIDE, POTASSIUM
extra SODIUM and CHLORIDE remaining that hasn’t already diffused out will leave ASCENDING LIMB by..
ACTIVE TRANSPORT using ATP or more so K+
K+ moves down conc. gradient OUT OF FILTRATE, MOVES NA+ and CL- with it
(1 K+, 1 Na+, 2 Cl-)
how is BLOOD FLOW / CIRCULATION around the LOOP OF HENLE
going in the OPPOSITE DIRECTION
COUNTER-CURRENT
how is BLOOD FLOW / CIRCULATION around the LOOP OF HENLE
going in the OPPOSITE DIRECTION
COUNTER-CURRENT MULTIPLIER SYSTEM
from ASCENDING LIMB,
SOME K+ STAYS in the…
INTERSTITIAL FLUID
(does not all go into blood)
how is the K+ TRANSPORTER in the ASCENDING LIMB (loop of henle)
ELECTROCHEMICALLY NEUTRAL
(NO ATP required)
LONGER LOOP OF HENLE means..
(other animals)
MORE WATER can be CONSERVED
why does increased GLUCOSE (diabetes) produce more urine volume
- more glucose
- harder for H20 to leave filtrate
- Increased Rate of filtrate flow
- Decreased Na+ & Cl- reabsorption
- Blood less concentrated at ascending limb
- Less water reabsorped
More water in filtrate (retained)
why might high glucose (diabetes) cause proteins in urine
- hypoglycosylation of proteins that make up podocytes
- filtration bed damaged
- proteins and cellular components filter through and enter filtrate
CELLS of the MACULA DENSA can sense what in the DCT (as filtrate leaves loop of henle)
if there is LOW FLUID FLOW or LOW SODIUM CONC in DCT
when MACULA DENSA CELLS sense low fluid flow or low sodium conc in DCT what is the RESPONSE
JUXTAGLOMERULAR CELLS SECRETE RENIN
(top up fluid volume by RAAS SYSTEM)
RAAS SYSTEM
low renal fluid
- KIDNEYS SECRETE RENIN (juxtaglomerular cells)
- LIVER: ANGIOTENSINOGEN
- LUNGS: ANGIOTENSINOGEN I CONVERTED into ANGIOTENSINOGEN II by ACE ENZYME
- ADRENAL CORTEX: ALDOSTERONE
- aldosterone increases SODIUM UPTAKE from DCT and COLLECTING DUCT
what is SECRETED from the PLASMA INTO the PCT LUMEN
AMMONIA NH3
(specific transporters)
