Glomerular filtration & regulation of renal blood flow

Question 1

What is the total % body weight for kidneys?

Answer 1

0.5%

Question 2

Main functions of the kidney

Answer 2

1. Control volume & composition of body fluids
2. To get rid of waste material from body
3. Acid-base balance
4. As an endocrine organ- EPO, Renin & Vit D

Question 3

What can’t the nephron do?

Answer 3

Regenerate new nephrons

Question 4

What are the 2 major stages of urine formation?

Answer 4

Glomeruli produce the liquid; tubules modifies its volume & composition

Question 5

Why should glomerular filtration be fast?

Answer 5

So that the waste products can be removed fast enough so their blood level can be kept low.

Question 6

How much urea is produced in a day?

Answer 6

36 g/ day
Normal plasma urea is 0.2g/litre
So 180 litres of plasma need to be filtered per day
(180 L x 0.2g/l = 36g)

Question 7

What is the glomerular filtration rate (GFR)?

Answer 7

120 ml/min

Question 8

What is proteinuria?

Answer 8

Protein in the urine.

Also a sign of renal/urinary tract disease

Question 9

What is the role of the glomerular membrane?

Answer 9

Sieves out solutes from plasma by molecular size.

Question 10

What forces drive the filtration?

Answer 10

The imbalance of starling forces

Question 11

What happens to the kidney when there is an increase in blood pressure?

Answer 11

The renal plasma flow (RPF) and GFR remain relatively constant.

Question 12

What is needed to help GFR and RPF constant?

Answer 12

Bayliss myogenic response - direct vasoconstriction of afferent arteriole with an increase in perfusion pressure.
Tubuloglomerular feedback (TGF)- Flow dependent signal detected in macula densa, which alters the tone of the afferent arteriole.

Question 13

What is the Bayliss myogenic response?

Answer 13

F= change in P/ R

Where F is blood flow, P changes in pressure, R is resistance

Question 14

What happens when there is an increase in perfusion pressure?

Answer 14

Immediate increase in vessel radius (few seconds only) then blood flow goes up briefly.

Question 15

What does NaCl do?

Answer 15

Elicits an ATP signal by macula densa. This leads to the contraction of the afferent arteriole.

Question 16

What control is the glomerular filtrate rate under?

Answer 16

Extrinsic- Noradrenaline, Vasoconstrictor to reduce the GFR
This happens in 3 conditions
-By Standing upright
-Heavy exercise
-Hemorrhage & other forms of clinical shock
To conserve physical stress

Question 17

What is Tubulo-glomerular feedback (TGF)

Answer 17

Second mechanism contributing to autoregulation

Question 18

What contributes to intrinsic control?

Answer 18

Autoregulation of GFR by Bayliss myogenic response & TGF

Question 19

What are the 2 major clinical disorders of the GFR?

Answer 19

1. Glomeruli too leaky to plasma protein: nephrotic syndrome
   Conditions - Proteinuria, Hypoproteinaemia, Oedema (responds well to steroids)
2. GFR too low - Chronic glomerulonephritis - nonfunctioning glomeruli

Question 20

What GFR indicate renal failure?

Answer 20

<30ml/min