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Endocrinology BRS 2 > Disorders of Vasopressin > Flashcards

Disorders of Vasopressin Flashcards

1
Q

What are AVP and oxytocin contained in within the hypothalamus

A

Hypothalamic magnocellular neurons

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2
Q

Where do Hypothalamic magnocellular neurons originate from

A

Supraoptic & paraventricular hypothalamic nuclei

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3
Q

Name the term for production of urine

A

Diuresis

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4
Q

What is the main physiological action of vasopressin (anti diuretic hormone)

A

Stimulation of water reabsorbtion

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5
Q

What does ADH do to urine

A

Concentrates it

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6
Q

Which receptor does ADH act on in the kidney

A

V2 Receptor

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7
Q

What other function does Vasopressin have on blood vessels and what receptor does it act on to do this

A

It is a vasoconstrictor and acts on the V1 receptor

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8
Q

How does ADH act as a vasoconstrictor

A

Stimulates ACTH release from anterior pituitary
V1 receptor on endothelial cells

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9
Q

Describe the basic mechanism of how vasopressin concentrates urine

A

Stimulates the insertion of aquaporin 2 channels in the apical membrane, via binding to the V2 receptor.

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10
Q

Describe the 2 types of stimuli for vasopressin release

A

Osmotic- rise in plasma osmolarity, sensed by osmoreceptors
Non osmotic- Decrease in atrial pressure sensed by atrial stretch receptors

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11
Q

Describe 2 features of the organum vasculosum & subfornical organ which allows it to respond to changes in the systemic circulation.

A

No blood brain barrier
Highly vascularised

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12
Q

Where are the organum vasculosum and subfornical organ located.

A

Around the 3rd ventricle

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13
Q

Describe the mechanism by which osmoreceptors regulate Vasopressin/AVP.

A
  1. Increase in extra cellular NA+
  2. Osmoreceptors release H2O
    3.Osmoreceptors shrink
  3. Increased osmoreceptor firing
    5.AVP gets released from hypothalamic neurons
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14
Q

How is vasopressin release inhibited

A

Via atrial stretch detectors detecting pressure in the right atrium.
(Reduction in blood volume means less stretch of these atrial receptors so less inhibition of vasopressin, vasopressin stimulates water reabsorption via V2 and vasoconstriction via V1)

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15
Q

Why does dehydration cause increased plasma osmolarity

A

When there is less water in your blood, the concentration of particles is greater.

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16
Q

Describe the physiological response to water deprivation leading to thirst.

A

Increased plasma osmolarity leads to stimulation of osmoreceptors which leads to thirst and increased AVP release.

17
Q

How does AVP release lead to a reduction in plasma osmolarity

A

AVP release leads to increased water reabsorbtion from renal collecting ducts which reduces urine volume and plasma osmolarity.

18
Q

A problem with AVP/ADH is indicative of which type of diabetes

A

Diabetes insipidus

19
Q

Define:
POLYURIA
POLYDIPSIA
NOCTURIA

A

polyuria- peeing allot
Polydyspia- drinking allot of water
Nocturia- peeing at night frequently

20
Q

Name the two types of diabetes insipidus

A

Cranial (central) diabetes insipidus
Nephrogenic diabetes insipidus

21
Q

What is cranial diabetes insipidus

A
  • problem with hypothalamus and/or posterior pituitary
  • Unable to make arginine vasopressin
  • aka vasopressin insufficiency
22
Q

What is the treatment for cranial insipidus

A
  • Want to replace vasopressin with something selective for V2 receptor (V1 receptor activation would be unhelpful)
  • Desmopressin
  • Different preparations- tablets or intranasal
23
Q

What is nephrogenic diabetes insipidus

A
  • Can make arginine vasopressin (normal hypothalamus and posterior pituitary)
  • Kidney (collecting duct) unable to respond to it
  • aka vasopressin resistance
24
Q

what is psychogenic polydipsia

A
  • Polydipsia, polyuria, nocturia symptoms
  • Unlike diabetes insipidus- no problem with arginine vasopressin
  • Problem is that patient is drinking water all the time, so passes large volumes of dilute urine
25
Q

How do we distinguish between diabetes insipidus and psychogenic polydipsia?

A

Water deprivation test

26
Q

how do we distinguish between CDI and NDI

A
  • Give ddAVP during water deprivation test- this’ll work like vasopressin
  • CDI- response to ddAVP- urine concentrates
  • NDI- no increase in urine osmolality with ddAVP as kidneys can’t respond
27
Q

Difference in plasma osmolarity between psychogenic polydipsia and diabetes insipidus

A

Psycho poly plasma osmolarity < normal range
Diabetes insipidus plasma osmolarity > normal range

Endocrinology BRS 2 (12 decks)

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