Session 3

Question 1

What are the 2 different types of nephrons?

Answer 1

Cortical nephrons

Juxtamedullary nephrons

Question 2

What is the arrangement of capillaries around the cortical nephrons?

Answer 2

Randomly arranged

Question 3

What is the arrangement of capillaries around the juxtamedullary nephrons?

Answer 3

Vasa Recta (Made of descending and ascending branches)

Question 4

Where is the Glomerulus always?

Answer 4

In the cortex of the Kidney regardless of which type of nephron it is

Question 5

What substances are filtered from the blood in the Glomerulus?

Answer 5

H2O
Salts
Small molecules

Question 6

What are the 3 layers that make the filtration barrier?

Answer 6

Capillary endothelium
Basement membrane
Podocyte layer

Question 7

What is the capillary endothelium permeable to?

Answer 7

Water
Salts
Glucose
Filtrate moves between cells

Question 8

What are the properties of the Basement membrane?

Answer 8

Acellular gelatinous layer of collagen/glycoproteins (Repel protein movement because they are negatively charged.)
Permeable to small proteins

Question 9

What are the properties of the Podocyte layer?

Answer 9

Pseudopodia interdigitate forms filtration slits (So big molecules cannot fit through)

Question 10

What are the 3 forces involved in plasma filtration?

Answer 10

Hydrostatic pressure in the capillary (Favours filtration)
Hydrostatic pressure in the Bowman's capsule (Opposes filtration)
Osmotic pressure (Difference between the capillary & tubular lumen. Slight Oncotic pressure too. Opposes filtration)

Question 11

Define tubular reabsorption

Answer 11

Solutes and H2O are removed from the tubular fluid and transported into the blood. (Reabsorption as these have already been absorbed once in GI tract)

Question 12

Define tubuar secretion

Answer 12

Transfer of materials from peritubular capillaries to renal tubular lumen. (Mainly caused by active transport.)
Usually a small amount are secreted and are either in excess or natural posions

Question 13

Define Transcellular movement

Answer 13

The substance transports through the cell

Question 14

Define Paracellular movement

Answer 14

The substance transports through the intracellular space (i.e. Parallel to the cell)

Question 15

What is reabsorbed in the Proximal Convoluted Tubule?

Answer 15

99% H2O
99.5% Na+
100% Glucose
50% Urea

Question 16

What drives the unregulated reabsorption in the Proximal Convoluted Tubule?

Answer 16

Osmotic and driven by Na+ uptake

Question 17

What are the Na+ transporters in the PCT?

Answer 17

Na/H antiporter

Na/Glucose symporter

Question 18

What are the Na+ transporters in the Loop of Henle?

Answer 18

Na/K/2Cl symporter

Question 19

What are the Na+ transporters in the early DCT?

Answer 19

Na/Cl Symporter

Question 20

What are the Na+ transporters in the later DCT & Collecting ducts?

Answer 20

Epithelial Na+ channels

Question 21

What does SGLUT do?

Answer 21

It is in the PCT and moves 2Na+/1 Glucose into the blood against the concentration gradient for Glucose

Question 22

What is the renal threshold for Glucose?

Answer 22

200mg/100ml

Question 23

How are molecules secreted into the PCT?

Answer 23

Passive carrier mediated diffusion across the Basolateral membrane down favourable concentration/electrical gradients created by the Na+/K+ pump

Question 24

Define filtration fraction

Answer 24

Proportion of substance that is actually filtered

FF = GFR/RPF

Question 25

How can GFR (Glomerular filtrate rate) give you an indication of how well the kidneys are working?

Answer 25

Measures the substance as its filtered so use a substance that is not reabsorbed or secreted as it passes through the kidney to get an indication of how well its working

Question 26

Define clearance rate

Answer 26

The volume of plasma from which any substance is completely removed by the kidney in a given amount of time Clearance rate = (Urine conc of substance x urine flow rate) / plasma conc of substrate

Question 27

How is GFR autoregulated?

Answer 27

Myogenic response of the smooth muscle cells in the walls of the Afferent arteriole

Question 28

What is the myogenic response when blood pressure increases?

Answer 28

The afferent arteriole constricts

Question 29

What is the myogenic response when blood pressure decreases?

Answer 29

The afferent arteriole dilates

Question 30

What is TGF?

Answer 30

Tubular glomerular feedback

Question 31

How does TGF work?

Answer 31

A change in tubular flow rate as a result of changes in GFR cause a change in the concentration of NaCl that reaches the DCT

Question 32

What cells in the DCT detect changes in NaCl concentration?

Answer 32

The Macula densa cells (TGF response works via a concentration dependent salt uptake through NaK2Cl co transporters in the apical membrane of the MD cells)

Question 33

What is the response if NaCl is high?

Answer 33

Adenosine is released (Vasoconstriction occurs to drop GFR)

Question 34

What is the response if NaCl is low?

Answer 34

Prostaglandins released (Vasodilation occurs to increase GFR)