Cell Physiology of Solute Recovery and Consequences of Solute Recovery

Question 1

What are the three main zones of the nephron?

Answer 1

1. Proximal Tubule
2. Loop of Henle
3. Distal Tubule

Question 2

How is sodium recovered in the proximal tubule?

Answer 2

3Na+ is actively removed from the cell into the blood through the Na/K pump. 1 Na+ passively enters the cell from the filtrate and 1 H+ leaves the cell through SLC9A3

Question 3

How is sodium recovered in the distal tubule.

Answer 3

3Na+ is actively removed from the cell into the blood through the Na/K pump. 1 Na+ and 1 Cl- passively enter from the filtrate through SLC12A3.

Question 4

How is potassium recovered in the loop of henle?

Answer 4

K+ can diffuse from the epithelial cell to the blood which creates a concentration gradient to power 2Cl-, Na+, and K+ to enter the epithelial cell through Na-K-Cl cotransporter SLC12A2. K+ can enter the filtrate through the ROMK channel if potassium levels are high.

Question 5

How are amino acids recovered in the proximal tubule?

Answer 5

Neutral amino acids diffuse into the epithelial cells through SLC6a18/SLC6a19 along with 2Cl- and Na+. These amino acids are actively exported from the cell into the blood. Fuled by sodium potassium pump pumping sodium out of the cell.

Question 6

How is glucose recovered in the proximal tubule (plus a little in loop of henle)?

Answer 6

Glucose is actively transported out of the cell and passively enters the epithelial cell from the filtrate through SLC5A1/SLC5A2 along with Na+. This is rate limited and if there is too much glucose in the blood it will bgin to be excreted instead of resorbed, this is why there is glucose in the urine of patients with diabetes mellitus.

Question 7

How are organic cations removed from the blood?

Answer 7

Cations passively transport into the cells of the nehpron and then passively drift out into the filtrate through SLC9A3.

Question 8

How are organic anions removed from the blood?

Answer 8

SLC13A3 actively pushes organic anions into the cell from the blood and they passively drift out.

Question 9

Why are organic anions (e.g. methotrexate, furosemide, and penicillin) dangerous for the kidney?

Answer 9

Orgnaic anions are pushed in from the blood and drift out passively to the filtrate. This means if the drifting out os weak then levels may accumulate to toxic levels as they will continue to be actively pushed in.

Question 10

How is phosphate recovered in the proximal tubule?

Answer 10

SLC34A1 passively allows Na+ and phospahte to enter the cell from the filtrate and the sodium potassium pump powers it by removing sodium.

Question 11

How is calcium recovered by the kidney?

Answer 11

It leaves the filtrate paracellular, passive, and driven by osmosis transport.

Question 12

How is water recovered by the kidney?

Answer 12

Moves through aquaporins due to osmosis due to removal of ions. Hypertonic zone is formed to continue to pull water out. Urea adds to heprtonicity.

Question 13

what reguates the reuptake of urea in the collecting duct?

Answer 13

Vasopressin

Question 14

What regulates how many aquaporins on the collecting ducts there are to absorb water?

Answer 14

Vasopressin

Question 15

Where is the hypertonic zone?

Answer 15

Loop of Henle

Question 16

What are the anatomical units of the kidney going from outside in?

Answer 16

Cortex>medulla>papilla>minor calyx>major calyx>pelvis>ureter

Look at a photo

Question 17

Why is the kidney vulnerable to ischaemia?

Answer 17

The arterioles and vanules run parallel to each other which means that oxygen gets shunted from artery to vein without reaching capillaries.

Question 18

What is produced ny the kidney to increase the number of red blood cells?

Answer 18

Erythropoietin

Question 19

What are the two ways blood pressure is sensed and controlled by the nephron?

Answer 19

1. Myogenic mechanism sensing a stretch in the afferent artiriole to protuct against surges.
2. tubuloglomerular feedback of how well the nephron is functioning.

Question 20

How does the macula densa work?

Answer 20

If there is high blood pressure, then the filtrate will move faster and less salt will be recovered, the macula densa cells then pump out more salt as there is more left for them. This causes juxtaglomerular cells to release adenosine which constricts the afferent arteriole, lowering the pressure.