Renal

Question 1

Driving force for facilitators and diffusion

Answer 1

Electrochemical gradient

Question 2

How is the electrochemical gradient made?

Answer 2

Na+/K+ ATPase pumping in 2K+ and pumping out 3Na+

Question 3

Absorption of Na+ causes what in the lumen?

Answer 3

Osmotic and electric gradient between lumen and interstitium

Question 4

How does osmolarity effect H2O movement?

Answer 4

Water follows solutes to keep the solutions iso osmotic

Question 5

H2O moves via what type of pathway?

Answer 5

Transcellular and paracellular pathways in leaky tight epithelia
ONLY transcellularly in tight tight epithelia

Question 6

Na transport in tight tight epithelia

Answer 6

ENaC which is driven by Na+/K+ ATPase activity/electrochemical gradient
only transcellular

Question 7

Salivary acinar cells produce …. fluid

Answer 7

iostonic (same concentrations of NaCl as our blood)

Question 8

In secretory epithelia, what is the additional transporter?

Name, where, what it does

Answer 8

Na+/H+/2Cl- cotransporter
Basolateral membrane
Pumps them all into the cell, builds up Cl- gradient inside

Question 9

What is the electric and osmotic effect of Cl- movement into the lumen?

Answer 9

Negative lumen potential, pulls Na+ paracellularly and therefore creates the osmotic gradient and pulls water paracellularly and transcellularly

Question 10

What is the mechanism of water secretion in leaky secretory epithelia?

Answer 10

Na/K ATPase generates the electrochemical gradient using ATP as a primary active transporter
Na+/K+/Cl- are all pumped into the cell using NKCC1
Na and K are pumped back out to the interstitium
Cl- conc increases inside the cell, creating a conc gradient
Cl- facilitators on the apical side (CTFR) allow Cl- to flow down its conc gradient into the lumen
Cl- conc increases in lumen, causing a build up of negative charge
Na+ flows paracellularly into lumen to balance charge
This creates an osmotic gradient between lumen and interstitium and pulls water paracellularly

Question 11

Na transporters in leaky epithelia

Answer 11

SGLT1 and SGLT2

Question 12

Which parts of the nephron have leaky epithelia?

Answer 12

PCT and thinDL

Question 13

Leaky absorbative epithelia function is to:

Answer 13

Absorb glucose using the sodium gradient on the apical side of the cell

Question 14

Main function of the kidney

Answer 14

Maintain blood pressure via water and ion homeostasis

Question 15

Main function of the kidney

Answer 15

Maintain blood pressure via water and ion homeostasis

Filter blood from waste products and drugs

Question 16

What is in normal urine?

Answer 16

95-98% water
creatinine
Urea
H+, NH3
Na+, K+
drugs

Question 17

How much urine do we make a day?

Answer 17

1.5L/day = 1mL/min

Question 18

What is in pathological urine?

Answer 18

Glucose
Protein
Blood
Haemoglobin
Leukocytes
Bacteria

Question 19

The juxtaglomerular

Answer 19

Juxtaglomerular cells and macula densa with the afferent arteriole

Question 20

What type of capillary endothelium is in the filtration barrier?

Answer 20

Fenestrated endothelium

Question 21

What is the filtration barrier composed of?

Answer 21

Fenestrated capillary endothelium
Basement membrane
Epithelial podocyte

Question 22

What are the driving forces for filtration?

Answer 22

Glomerular capillary blood pressure

Osmotic force due to the proteins in plasma

Question 23

What is the net glomerular filtration pressure?

Answer 23

Pgc - Pbs - OsmF

= 16mmHg

Question 24

Which filtration driving force/ pressure at PCT is the highest?

Answer 24

Glomerular capillary blood pressure (60mmHg)

Question 25

Which forces are opposing filtration?

Answer 25

Fluid pressure from Bowman's space | Osmotic force due to the proteins in plasma

Question 26

Filtration at the kidney results in a hypo, iso or hyper-osmotic primary filtrate?

Answer 26

Iso-osmotic

Question 27

What are the substances suitable for determining the filtration rate?

Answer 27

Inulin | Creatinine

Question 28

Clearance definition

Answer 28

Volume of plasma that was cleared from a substance per unit time

Question 29

Clearance equation

Answer 29

``` C = (UxV)/P Clearance = (Conc of substance in the urine x urine output) / concentration of substance in plasma ```

Question 30

GFR approx value

Answer 30

132mL/min | 7.9L/h

Question 31

What makes something a good substance for determining the filtration rate?

Answer 31

``` Something that is: Freely filtered NOT reabsorbed NOT secreted NOT metabolised NOT toxic ```

Question 32

What is filtration at the kidney?

Answer 32

Filtered at the filtration barrier | - everything is slightly filtered at the barrier

Question 33

What is secretion at the kidney?

Answer 33

Active transcellular secretion of substances into the urine from the PCT Usually secretion of drugs Substance is fully secreted so there is no more of it in the blood

Question 34

What is re-absorption at the kidney?

Answer 34

Re-uptaking things that are filtered either partially (K+, Na+) or fully (glucose)