Renal 6 Flashcards
reasons for AVP secretion
increased osmolarity, decreased blood volume, decreased blood pressure
what are the two components of the renal countercurrent exchange system
countercurrent multiplier
countercurrent exchanger
what is the countercurrent multiplier
the loop of henle
what is the countercurrent exchanger
the peritubular capillaries (vasa recta)
what is responsible for high osmolarity deep in medulla
nephrons and vasa recta of juxtamedullary nephrons that extend deep into medulla
What happens to filtrate as it enters descending limb
Becomes progressively more concentrated as it loses water to the increasingly hypertonic interstitium
- no solutes transported
What happens to filtrate as it grows up ascending limb
Pumps out Na, K, Cl so becomes hyposmotic
- no aquaporin channels
Where does majority of reabsorption take place
Proximal tubule, 75%
Where does 25% of reabsorption take place
Na and K reabsorption occurs in ascending limb of loop of henle
What transporter are on apical surface of ascending limb
Na-K-Cl cotransporter
What tranporters are on basolateral membrane of ascending loop
Na-K ATPase
K-Cl cotransporter
K and Cl leak channels
Where does NKCC transporter on apical membrane of ascending loop use energy from
Energy stored in Na concentration gradient to move Na, K and 2 Cl into epithelial cells
What is target of loop diuretic drugs for treatment of hypertension and edema
NKCC
Prevents ions from entering and less H20 reabsorption
Why doesnt water entering interstitum via descending limb dilute the hyperosmotic medulla
Opposite direction loop of vasa recta picks some solute up and loses some water as it travels by ascending limb creating hyperosmotic blood
Thus creating gradient allowing water from descending to move into vasa recta
What is the main job of multiplier
Create hypertonic interstitium
what is main job of exchanger
Prevent washout (dilution) of hypertonic interstitum
What is the other half of solute in the medulla interstitum
Urea
What substance create hyperosmotic interstitium
Na, Cl, K, urea
What does urea being reabsorbed in the distal portion of nephron create
Recycling loop
How does urea create recycling loop
Constantly moving and readily filtered
Constantly reabsorbed and secreted
What is AVP insertion of water pores in collecting duct mainly driven by
Increased plasma osmolarity= increased AVP release
- also baroreceptors monitoring blood volume and BP
How much NaCl in North American diet
9g each day 155 milliosmoles of Na and 155 of Cl
What is our plasma Na concentration distributed freely between interstitial and plasma (ECF)
135-145 milliosmoles/L
What is responsible for Na excretion
Kidneys
How does Cl get transported
Na absorption is regulated
Cl follows through electrochemical gradient set up by Na or cotransported with Na
What steroid hormone is repsonsible for altering Na reabsorption and K secretion
Aldosterone
What regulates blood Na levels
Endocrine pathway: renin-angiotensin-aldosterone system
What does aldosterone target
Last third of distal tubule and portion of collecting duct in cortex of kidney
Where is aldosterone produced
Adrenal cortex by zona glomerulosa cells
What is the aldosterone receptor
Cytoplasmic mineralcorticoid receptor in P cells
What happens in early response phase to aldosterone (rapid response)
Binding receptor on apical Na and K channels increase their open time
Results in increased Na reabsorption and K secretion
Insertion of pre-existing transporters
What are the channels on the apical membrane
ENaCs : Na
ROMK : K
What is slow response of aldosterone
Transcription of more ENaCs and ROMKs on apical and basolateral NA-K pumps to further reabsorption and secretion
