Collecting duct

Question 1

Function of collecting duct?

Answer 1

Similar distal
Acid balance
Regulate H2O and salt reabsorption
Water moves out to hypertonic interstitium

Question 2

What hormone effects collecting ducts?

Answer 2

Vasopressin (ADH)

Question 3

Effect of vasopressin (ADH)?

Answer 3

Promote AQP2

Question 4

How is water reabsorbed in collecting duct?

Answer 4

1) Dilute (hypotonic) fluid enters collecting duct
2) Passes through increasing concentration gradient (hypertonic) in medullary interstitium
3) Cells have tight junctions the collecting duct is impermeable to water
4a) Absence of vasopressin collecting duct is impermeable to water (lots of urine produced)
4b) With vasopressin becomes permeable water is reabsorbed
Collecting duct becomes permeable to urea
Increase water reabsorption through oncotic pressure

Question 5

How does urea increase water reabsorption?

Answer 5

Oncotic pressure

Question 6

What 2 factors influence conc gradient?

Answer 6

1) Efficiency reabsorption
2) Length loop of Henle

Question 7

Where is ADH (vasopressin) synthesised?
secreted from?

Answer 7

Synthesised- hypothalamus
Secreted- posterior pituitary

Question 8

What controls realse ADH?

Answer 8

Osmoreceptors

Question 9

Function of osmoreceptors?

Answer 9

Detect changes in osmolarity
If increased
Release ADH

Question 10

Does alcohol increase or decrease release ADH?

Answer 10

Decrease

Question 11

Does nicotine increase or decrease release ADH?

Answer 11

Increase

Question 12

Is half life of ADH (vasopressin) short or long?
Why

Answer 12

Short
Allow quick adaptations

Question 13

What does ADH do?

Answer 13

Allow expression AQP2 on apical membrane

Question 14

How is water reabsorbed in collecting duct?

Answer 14

1) AQP2 in vesicles
2) ADH stimulate excretion of AQP2
3) Water absorbed through AQP2 channels on apical membrane
4) Use AQP3 and AQP4 channels on basolateral membrane

Question 15

State 2 effects of ADH?

Answer 15

1) Increase expression AQP2 channels- water reabsorption
2) Cause arteriolar constriction- restore bp

Question 16

What stimulates osmoreceptors?

Answer 16

Increase plasma osmolarity
Decrease ECF

Question 17

What does stimulation of osmoreceptors lead to?

Answer 17

Secretion ADH
Increase H2O absorption

Question 18

Why is urea important?

Answer 18

Used produce concentrated urine

Question 19

How does urea allow production of concentrated urine?

Answer 19

Interstitium try keep high urea
Stop osmotic effect water moving back into collecting duct

Question 20

Location of baroreceptors (2)?

Answer 20

Aortic arch
Carotid sinus

Question 21

Name 2 factors stimulate ADH?

Answer 21

Osmolality
Decreased ECF

Question 22

Explain baroreceptor reflex?

Answer 22

1) Baroreceptors detect decrease in ECF
2) Increase aldosterone via RAAS
3) Decrease rate of firing
4) ADH secretion due to less stimulation of hypothalamus
4) Increased permeability of collecting ducts
5) More water reabsorbed

Question 23

What is more sensitive baro or osmorecptors?

Answer 23

Osmoreceptors

Question 24

What is baroreceptor reflex if high BP?

Answer 24

Increased baroreceptor firing
Decrease vasopression secretion