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REN > L07: Urine Concentration Dilution > Flashcards

L07: Urine Concentration Dilution Flashcards

1
Q

Whereabouts in the nephron does water get reabsorbed back into the blood

A

Descending limb of loop of henle

Collecting duct

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2
Q

What is the main determinant hormone of the urine concentration

A

ADH

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3
Q

What is ADH also known as

A

Vasopressin

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4
Q

Where is ADH synthesised

A

Hypothalamus

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5
Q

Where is ADH secreted from

A

Posterior pituitary gland

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6
Q

Where does ADH act on

A

Collecting duct

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7
Q

What does ADH do in term of express channels

A

It expresses aquaporin 2

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8
Q

Describe the process of absorption of water when ADH increases aquaporin 2 in the apical membrane

A

1) water moves in through AQP2 in the apical membrane

2) water then moves out of the cell though the basolateral membrane via aquaporin 3

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9
Q

What receptors do ADH bind to when they are released from the posterior pituitary gland

A

V2 receptors

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10
Q

What happens intracellular when ADH binds to V2 receptors

A

V2 receptors or coupled to Gs proteins
Gs proteins Stimulate adenylyl cyclase to create CAMP (2nd messenger)
CAMP stimulates the nucleus to transcribe AQP2 synthesis
CAMP then stimulate protein kinase A to insert the synthesised AQP2 into the apical membrane

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11
Q

Therefore what is the concentration of the urine like when there is ADH

A

Concentrated

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12
Q

Therefore what is the concentration of urine when there is no ADH

A

Dilute

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13
Q

What happens to the flow rate of urine when there is no ADH

A

High

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14
Q

What happens to the flow rate in the nephron when there is ADH

A

LOW as we are not producing urine

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15
Q

What does urea do in terms of osmolalility

A

Contribute to medullary osmolarity when it gets reabsorbed from the loop of henle

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16
Q

What happens to urine when there is low urea

A

Urine is dilute

17
Q

What results in low urea

A

Protein starvation

18
Q

What hormone regulators the expression of UT-A1 (urea transporter)

A

ADH

19
Q

What receptor does ADH bind to stimulate the expression of UT-A1

A

V2 receptors the basolateral membrane

20
Q

What happens intracellularly when ADH binds to V2 receptors

A

1) Gs is activated which stimulates adenylyl cyclase to produce CAMP
2) CAMP increases transcription and synthesis of UT-A1
3) CAMP stimulates protein kinase A to insert UT-A1 into the apical membrane

21
Q

What is diabetes insipidus

A

Low ADH secretion
Or
Loss of ADH sensitivity due to loss of function of V2 receptors

22
Q

What are the symptoms of diabetes insipidus

A 
Polyuria 
Dehydration 
Hypo aloe is 
Polydipsia (drinking too much)
Hypernatreamic
23
Q

Due to the 2 different causes of diabetes insipidus, what are the 2 types of diabetes inspidus

A

Central diabetes insipidus

Nephrogenic diabetes insipidus

24
Q

What is diabetes insipidus due to

A

Lack of secretion of ADH

25
Q

What are the causes of central diabetes insipidus

A

Head injury
Tumours in pituitary gland
Infection

26
Q

What is the treatment of central diabetes insipidus

A

Give ADH analogue called desmopressin to replace ADH

27
Q

What is nephrogenic diabetes insipidus due to

A

Loss of sensitivity to ADH in V2 receptors

28
Q

What are the causes of nephrogenic diabetes insipidus

A

Toxicity
Hypercalcaemia
Genetic mutation to V2 receptors

29
Q

What is the treatment to nephrogenic diabetes insipidus

A

Thiazides diuretic: increase aquporin expression

Law salt diet

30
Q

What does SIADH stand for

A

Syndromes inappropriate ADH

31
Q

In terms of SIADH what are the levels of ADH like

A

High

32
Q

What are the causes of SIADH

A

Head injury

33
Q

What are the symptoms of SIADH

A

Concentrated urine

Hyponatremic because water dilutes sodium

34
Q

What is the treatment for SIADH

A

Fluid restriction

Aquaretic drugs

35
Q

What does aquoretic drugs cause

A

Water loss without salt loss

36
Q

What is a aquaretic drug

A

V2 receptor antgonist

37
Q

Where does aquaretic drugs act in the nephron

A

Late portion of the distal tubule

Collecting duct

38
Q

Why do we administer a low salt diet to someone who has nephrogenic diabetes insipidus

A

They have a low sodium because they are losing a lot of water
To treat hypernatremia we tell them to restrict salt in the diet

REN (19 decks)

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