Nephron

Question 1

What does the primary filtrate consist of?

Answer 1

Water
Na+
Cl-
K+
HCO3
Glucose 
Amino Acids 
Creatinine 
Urea

Question 2

What is reabsorbed in the PCT?

Answer 2

Around 100% of glucose and amino acids.
K+
65% of NaCl
65% of Water

Question 3

What is reabsorbed in the thin descending loop of Henle?

Answer 3

Water

Question 4

What is reabsorbed in the thick ascending loop of Henle?

Answer 4

NaCl (25%)

Question 5

What is reabsorbed in the DCT?

Answer 5

Water

NaCl (5%)

Question 6

What is reabsorbed in the Collecting Duct?

Answer 6

Water
NaCl (5%)
Some Urea

Question 7

What is excreted in urine?

Answer 7

Water 
NaCl 
K+
HCO3-
Creatinine 
Urea

Question 8

What can be secreted into the PCT?

Answer 8

Organic Acids - e.g. Antibiotics

Question 9

Describe the RAAS?

Answer 9

The liver produces pro-enzyme Angiotensinogen.
Renin from Juxtaglomerular cells of the kidney convert Angiotensiongen to Angiotensin 1.
When AT1 reaches the lung in the blood stream, ACE from the lung converts it to Angiotensin 2.
Angiotensin 2 causes vasoconstriction (incl. the efferent arteriole of glomerulus). It also causes the Adrenal gland to secrete Aldosterone.
Aldosterone causes increased sodium and water reabsorption in the DCT and CD. It also causes more K+ and H+ to be excreted in urine.

Question 10

Name and give examples of drugs which effect the RASS?

Answer 10

ACE Inhibitors: E.g. Captopril.
Angiotensin 2 Receptor Blockers (ARB’s): E.g. Losartan.
Antimineralcorticoids: Block aldosterone, e.g. Spionolactone.

Question 11

Name the 4 main channels in the nephron and where they are found?

Answer 11

Na/K ATPase - PCT
N/K/2Cl - Thick ascending limb
N/Cl co-transporter - DCT
ENaC - Collecting duct

Question 12

How does the Na/K ATPase channel in the PCT work?

Answer 12

Na/H+ antiporter takes Na into the cell, it is then pumped out by Na/K ATPase on the basolateral side and water follows.

Question 13

How does the N/K/2Cl channel work?

Answer 13

Located on the apical membrane of the thick ascending limb.
Transports Na, K and 2Cl into the cell by active transport.
K+ can then be recycled as it passively moves down a concentration gradient into the lumen. Na then moved into interstitium by Na/K ATPase.
Targeted by loop diuretics.

Question 14

How does the Na/Cl cotransporter work?

Answer 14

Found in the DCT.
Actively transport Na and Cl into the cell.
Na+ is reabsorbed in exchange for K+ (controlled by aldosterone).
Targeted by thiazide diuretics.

Question 15

How does ENaC work?

Answer 15

Sits on the apical membrane of the principle cell of the collecting duct.
Na+ enters the cell from the lumen which stimulates K+ secretion via an apical channel.

Question 16

How do aquaporins work?

Answer 16

ADH causes them to be inserted to the membrane so water can be reabsorbed.
Occurs in response to reduced pressure changes sensed by baroreceptors.
ADH is released from the posterior pituitary.