ALL ABOUT KIDNEYS <3

Question 1

What are the 3 main components of the filtration barrier?

Answer 1

1. Endothelial cells- fenestrations
2. Basement membrane- shape, size and charge
3. Epithelial cells (podocytes)- slit pores

Question 2

What are the main determinants of filtration?

Answer 2

1. Permeability of B.M
2. Physical forces driving filtration
3. Mass
4. Charge

Question 3

What is Starling’s equation?

Answer 3

GFR= Kf(Pcap+ONCbc) - (Pbc+ONCcap)

Question 4

What are the average figures for each component of Starling’s equation?

Answer 4

Pcap= 60mmHg
ONCbc= 0
Pbc=20mmHg
ONCcap=30mmHg

Question 5

What happens in autoregulation?

Answer 5

Arterial b.p fluctuates in the range 80-200mmHg
Afferent arteriole constriction/relaxation
Effects the resistance in the afferent arteriole
Counteracts any changes in the GFR caused by the change in b.p

Question 6

What are the 2 main hypotheses explaining autoregulation?

Answer 6

1.Myogenic theory
Stretch receptors
2.Tubuloglomerular feedback theory
rate of flow of tubular fluid
macula densa cells- vasoactive chemicals

Question 7

What is osmolality and how is it calculated?

Answer 7

Osmolality is the measure of concentration of a solution. Units are Osm/kg H2O
Concentration x number of particles it dissociates into

Question 8

Describe counter current multiplication

Answer 8

It is the process of creating differing osmotic gradients in order to reabsorb water from the tubular fluid and produce concentrated urine.
It relies on differing permeabilities in the loop of Henle and collecting ducts.

Question 9

Discuss the difference in handling of Na,CL, Urea and H20 in CCM

Answer 9

Thin DL-
permeable to water, little solute movement
inner medulla- urea enters tubular fluid
Thin AL-
impermeable to water
very permeable to Cl and Na
Thick AL-
impermeable to water
permeable to solute
CD-
very permeable to water
impermeable to solute-
apart from inner medullary CDS- reabsorption of urea

Question 10

Transport proteins and diseases

Answer 10

Bartters syndrome
ROMK,NKCC2,CLCK, Barttin subunit
stops reabsorption of Na and Cl in TAL
Diabetes insipidus
AQ-2/ Vasopressin 
*UT-B mutation-
washing out of urea in IF-
effects counter current exchange

Question 11

What are the normal pH ranges?

Answer 11

7.35-7.45

Question 12

Explain the davenport diagram

Answer 12

metabolic acidosis-
H+ high/
HCO3- low
pH down
metabolic alkalosis-
HCO3- high
pH high
resp. acidosis-
CO2 high
H+ high
resp alkalosis-
CO2 low
H+ low (to make more CO2)
pH high

Question 13

Peripheral chemoreceptors main stimulus

Answer 13

Hypoxia

Question 14

What nerves do the Glomus cells signal to

Answer 14

Vagus, sinus and glossopharyngeal nerves

Question 15

What changes causes an increase in sensitivity of peripheral chemoreceptors?

Answer 15

high pCO2
low pH
low O2

Question 16

Central chemoreceptors main stimulus

Answer 16

Hypercapnia

Question 17

Where are the 2 main locations of the central chemoreceptors

Answer 17

Brain parenchyma

Ventrolateral medulla and other brainstem nuclei

Question 18

What are the properties of the BBB

Answer 18

Separates the blood and brain extracellular fluid (BEF)
Poor ion permeability
CO2 moves across easily

Question 19

What is the buffering power like in the BEF?

Answer 19

Reduced bicarb buffering power
As a result- larger fall in pH in BEF
chronic acid/base disturbance- HCO3- moves across (small qtys) from blood to BEF

Question 20

With a change in plasma pH- what are the differences in response in metabolic and respiratory disorders

Answer 20

Met disorder- small change in BEF pH due to H+ and HCO3- poor ion permeability of BBB
Resp disorder- larger change in BEF pH due to CO2 being freely permeable across the BBB

Question 21

What is the integrated chemoreceptor response to respiratory acidosis?

Answer 21

Central chemoreceptors more important- tonic drive for breathing
However peripheral receptors respond faster

Question 22

What is the integrated chemoreceptor response to metabolic acidosis?

Answer 22

If severe- hyperventilation
Peripheral receptors involved in short term response
Central receptors- longer term

Question 23

3 main renal mechanisms involved in balancing acids and bases

Answer 23

1. HCO3- handling (net reabsorption of bicarbonate)
2. Urine acidification (binding H+ with buffers)
3. Ammonia synthesis

Question 24

What causes respiratory acidosis?

Answer 24

lung disease-

emphysema, chronic bronchitis

Question 25

What causes respiratory alkalosis?

Answer 25

hyperventilation-

due to stress,fear, pain

Question 26

What causes metabolic acidosis?

Answer 26

ingestion of acid

loss of alkaline fluid- diarrhoea, cholera

Question 27

What causes metabolic alkalosis?

Answer 27

ingestion of alkaline fluid

loss of acid- vomiting

Question 28

Symptoms of Liddles syndrome

Answer 28

Hypertension
Hypokalaemia
Metabolic alkalosis

Question 29

What causes Liddle’s syndrome and how is it treated

Answer 29

Gain of function mutation- deletion of proline rich motif (on beta or gamma subunit) which means the protein is no longer degraded correctly
Too much Enac in apical membrane of principal cells
Amiloride is used as treatment

Question 30

Types of diabetes insipidus

Answer 30

Central- impaired AVP production
Nephrogenic- impaired AVP effect
Gestational- AVP metabolised

Question 31

Causes of central and nephrogenic DI?

Answer 31

Central
acquired= head trauma, surgery, infection
congenital= 67 diff mutations associated- impaired transport of AVP from hypothalamus to posterior pituitary
Nephrogenic
acquired= lithium, some antibiotics, acute and chronic renal failure
congenital= mutations in AVPR2 gene/ AQP2 gene

Question 32

Treatments of DI

Answer 32

Central- desmopressin
Nephrogenic- modulatory drugs
pharmacological chaperones