Ch.5,6-Distal Nephron, Hormones Flashcards
What % of the filtered load of WATER and SALT makes it all the way to the Distal Nephron (both Distal Tubule and Collt Tubule)
10% of both
What does ADH regulate in the Distal Nephron?
WATER!!! more ADH=more H2O reabsorption
What does Aldosterone regulate in the Distal Nephron?
SALT!!!! more Aldosterone=more NaCl reabsorption
HOW does ADH do its job in the collecting tubule?
ADH makes the collecting duct permeable to H20. KICK it out of the Kidney to KEEP it in the body!! ANTIDIURESIS
What happens to the collecting duct when ADH is NOT present??
Collecting duct is IMPERMEABLE to H20…MORE water peed out…DIURESIS
Which Apq type does ADH move to the ______ membrane of the collecting duct? WHAT G-protein messenger is used??
Aqp-2….luminal….uses cAMP (more cAMP=more Aqp-2)
Which channels are “super-glued” to the BL membrane in the Collecting duct?
Aqp-3
Is the ADH/Aqp-2 process reversible??
YES! less ADH=less Aqp-2’s
Which Aqp’s do we see in the Proximal Tubule?
Aqp-1’s
Which region of the nephron DOES NOT have Aqp’s?
The Ascending Limb (luminal portion)
Review: Which region is most active in the reabsorption of Na+?? What is used on the Luminal and BL membranes to make this happen?
Cortical Collecting Duct….Selective Na+ transporters used on the membrane,
What does the Cortical Collecting Duct secrete?
K+
What are the 3 things Aldosterone is doing to promote Na reabsorption? (think aldosterSLOWone)
1.make more Na+ channels 2.make more Na+/K+ pumps 3.Boost ATP production (via Krebs cycle)
Aldosterone and ______ have similar affinity for the mineralocorticoid receptor.
cortisol (a GLUCOcorticoid!)
What is used to combat the Cortisol/Aldosterone dilemma?
11-Beta-HydroxySteroid Dehydrogenase Type 2 (hahaha our longest name yet!!!)
Mutations in 11-Beta-HydroxySteroid Dehydrogenase Type 2 can lead to ______ and _______.
NaCl retention and hypertension (cause Cortisol is frontin’ on Aldosterone’s receptors, yo)
What does PTH do to the Distal Tubule? (2 methods) (which membrane)
promotes more Ca2+ reabsorption…1. Make more Ca2+ATPase’s and 2. More Na+/Ca2+ exchangers (BOTH on BL membrane)
What mechanism do we use to create the medullary hypertonic intersitium? What magical fluid does it use?
CounterCurrent Multiplication…pre-[ ] tubular fluid
What are the 3 steps to CounterCurrent Multiplication?
1.Reabsorption and retention of NaCl in the ascending limb 2.Reabsorption of H2O in the descending limb (remove w/ vasa recta) 3.Proximal tubule sends Isotonic fluid into the Lof H, now the fluid is hypertonic in the ascending limb
After the countercurrent multiplication, which has more of an osmotic gradient: vertical or horizontal?
Vertical has a 275 gradient > horizontal 200 gradient
Urea Recycling: The _____/_____ ______ collecting tubule cannot reabsorb urea.
Cortical/outer medullary collecting tubule
What happens to [Urea] in the presence of ADH? (2 things)
- [Urea] increases in the collecting tubule (you are reabsorbing H2O)….2.FARTHER down the collecting tubule ADH makes Urea more permeable so it moves to the interstium (then back into the ascending limb (REDUCE–>REUSE–>RECYCLE, learn it, live it, love it)
What happens to Urea in the ABSENCE of ADH?
No ADH=low [Urea]=low urea reabsorption=high urea excretion
What does HIGH ADH do to Urea excretion?
High ADH=High Urea Reabsorption=Low Urea Excretion
What does Low ADH to to Urea excretion?
Low ADH=Low Urea Reabsorption=High Urea Excretion
What does low ADH do to Medullary Osmolarity?
Low ADH=Low Medullary Osmolarity
What are the 3 main functions of the Vasa Recta during ‘CounterCurrent Exchange”?
1.Nutrient supply 2.Remove the reabsorbed H2O and NaCl 3.NET-preserve the hypertonic gradient of the medullary interstitium
In countercurrent exchange, how does the osmolarity of the plasma flowing in compare to the osmolarity of the plasma leaving the medulla?
in isotonic 300mOsm….vs….out more hypertonic 320 mOsm
Main idea of urea and protein: how do cells survive in the denaturing environment of urea?
By expanding and contracting (Aqp’s)
Since water in MUST EQUAL water out, what is the ONLY output that we can TIGHTLY control?
Urine output!
What is max diuresis (low ADH)? (in L/day AND mOsm/kg)
20-25 L/day & 50-75 mOsm/kg
What is max antidiuresis? (high ADH) (in L/day AND mOsm/kg)
0.5 L/day & 1200-1400 mOsm/kg
What is another name for ADH?
AVP-Argenine VasoPressin
ADH/AVP is synthesized in neural cell bodies located in _______ and _______ nucleii of hypothalamus.
SupraOptic & Paraventricular
Wait, which general part of the brain is ADH/AVP synthesized again?
the Hypothalamus :)
Where is ADH/AVP stored once synthesized?
the PURSE! posterior pituitary (not the flat peg/anterior pituitary)
What is ADH secretion regulated by?
Hypothalamic OsmoReceptors
Which has a more SENSATIVE effect on ADH release…plasma osmolarity OR plasma volume?
Plasma Osmolarity….Osmoreceptors are MUCH more sensitive then the Volume Receptors