Posterior Pituitary Flashcards

1
Q

Where is the pituitary located

A

Under the optic chiasm and hypothalamus in the brain

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2
Q

What are the 2 nucleus found in the posterior pituitary

A

The paraventricular nucleus and the supraoptic nucleus

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3
Q

Where does the posterior pituitary originate

A

From neuronal tissue- large numbers of glial type cells

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4
Q

What hormones does the posterior pituitary secrete

A

Vasopressin
Oxytocin

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5
Q

What is the function of vasopressin

A

It is an anti diuretic hormone which controls water secretion into urine

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6
Q

Where is vasopressin primarily secreted from in the posterior pituitary

A

The supraoptic nuclei

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7
Q

What is the function of oxytocin

A

Expression of milk from the glands of the breast to the nipples and promotes the onset of labour

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8
Q

Where is oxytocin primarily secreted from in the posterior pituitary

A

The paraventricular nuclei

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9
Q

What percentage of the human body is fluid

A

60%

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10
Q

How much of the 60% fluid sits in the extracellular

A

33% or 14L which is divided into intravascular at 3.5L and interstitial at 10.5L

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11
Q

How much of the 60% fluid makes up the intracellular fluid

A

66% or 28L

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12
Q

Where does vasopressin act upon in the nephron

A

The collecting tubule

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13
Q

What is the mechanism of action for vasopressin

A

Vasopressin binds to the membrane receptor which activates cAMP which is a secondary messenger system. This inserts aquaporin-2 water pores into the apical membrane meaning more water is absorbed by osmosis into the blood

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14
Q

Where are osmoreceptors found

A

In the hypothalamus

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15
Q

What doe osmorecptors detect

A

The change in osmolarity

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16
Q

What do baroreceptors located

A

Carotid sinus and aortic arch

17
Q

What do baroreceptors detect

A

Change in pressure

18
Q

What happens when you are dehydrated to restore osmolality

A

Loss of body water increases plasma osmolality which causes increased thirst and increased in AVP neurone firing, this leads to the release of AVP and increased fluid intake, this causes water reabsorption and the restoration of osmolality and circulating sodium concentration

19
Q

What can affect osmolality

A

Sodium
Potassium
Chloride
Bicarbonate
Urea
Glucose at high concentrations
Alcohol
Methanol
Polyethylene glycol/mannitol

20
Q

How can you suppress vasopressin release and thirst

A

Drinking rapidly

21
Q

What is polyuria

A

Large volumes of urine

22
Q

What is polydypsia

A

Large volumes of drinking

23
Q

What is cranial diabetes insipidus

A

Lack of vasopressin

24
Q

What is nephrogenic diabetes insipidus

A

Resistance to vasopressin

25
Q

What are the 2 types of diabetes insipidus

A

Cranial and nephrogenic

26
Q

What can cause cranial diabetes insipidus

A

Destruction of the hypothalamus
Interruption of the connection of hypothalamus to pituitary

27
Q

Why could a person get cranial diabetes insipidus

A

Idiopathic
Tumours
Trauma
Infection

28
Q

What can caused nephrogenic diabetes insipidus

A

Osmotic diuresis
Drugs
Chronic renal failure
Post-obstructive uropathy
Metabolic- hypercalcaemia/hypokalaemia

29
Q

How can you manage cranial diabetes insipidus

A

Treat any underlying condition
Desmopressin

30
Q

How can you manage nephrogenic diabetes insipidus

A

Avoid drugs
High/very high dose of desmopressin
Hydrochlorothiazide

31
Q

What is SIADH

A

Syndrome of anti diuretic hormone secretion
Producing ADH when you shouldn’t be producing it
Too much AVP when it should not be being secreted which causes low blood concentration so low osmolality. This causes urine to be inappropriately concentrated and plasma sodium will be low
Patient must be euvolaemia

32
Q

When does vasopressin start to be secreted

A

When plasma osmolality gets to 280

33
Q

How is SIADH managed

A

Fluid restriction
Sometimes demeclocycline
Vaptans- V2 receptor antagonists
Hypertonic saline
Potential risk of central pontine myelinolysis