Renal Phys--> Connecting segment and Collecting duct

Question 1

Which two types of cells are found in the Collecting segment and collecting duct?

Answer 1

Principle cell

Intercalated cell

Question 2

What is another name for this area?

Answer 2

Aldosterone sensitive distal nephron

Question 3

What is the principle’s cell main role?

Answer 3

Absorb Na and Cl resorption

K excretion

Question 4

What the primary role of the intercalated cell?

Answer 4

H+ and HCO3- excretion

Some K resorption

Question 5

What the regulatory channels in this area?

Answer 5

ENAC
ROMK
Aqueporin 2 (AQP2)

Question 6

At this point what should have all been removed from filtrate?

Answer 6

All glucose, AA’s and Bicarb

10% of water left

Question 7

What is the Na resorption here? Significance?

Answer 7

Variable 0-4.99%

- First area that is directly controlled to determine urinary electrolyte conc.

Question 8

What affect does aldosterone have on the principle cell?

Answer 8

Lipophillic so passes through lipid bilayer easily

• binds to SRE (Steroid response element)
• Increases number and Activity of ENAC
• Increased sodium resorption
• Caveat= more K+ excreted

Question 9

What then is the stimulus for Aldosterone release?

Answer 9

Low Na

High K+

Question 10

What else can act like aldosterone? When is it seen?

Answer 10

Cortisol

Prednisone–> why you get puffy on steroids

Question 11

What is little syndrome?

Answer 11

Pseudohyperaldosteronism

• leads to increase ENAC
• HTN
• K wasting

Question 12

What percent of Na is controlled by aldosterone?

Answer 12

2%

Question 13

What does the sympathetic NS control?

Answer 13

Stimulates Na uptatke in proximal tubule
         a. increase Na-K-ATPase
         b. Increase Na-H+ anti-porter 
Controls afferent and efferent tone 
- thus reduces RPF and GFR

Question 14

What are 3 signaling pathways which stimulate renin release?

Answer 14

1. Sympathetic input
2. Decrease stretch of afferent arteriole
3. Decrease Cl delivery to to Macula Densa

Question 15

What are the actions of AgII?

Answer 15

1. vasoconstrict
2. Stimulate prox tubule to increase Na resorption and increases ENAC
3. Salt appetite via CNS
4. Stimulates aldosterone
5. Increase sympathetic activity

Question 16

What does the macula densa sense?

Answer 16

• Flow
• Cl-
• Regulate Renin release and GFR
• Tonically active

Question 17

What does decreased Cl- to macula densa cause?

Answer 17

Means decrease GFR or decrease sodium

• Prostaglandin release
• Renin release triggers RAAS