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Kidneys and Hormones > Posterior pituitary > Flashcards

Posterior pituitary Flashcards

1
Q

What is the origin of the two parts of the pituitary?

A

Embryonic

Anterior pituitary - originates from the upwards invagination of the roof of the oral cavity

Posterior pituitary - made from the downward extension of the floor of the brain

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2
Q

What is the name of the upwards invagination of the oral cavity?

A

Rathke’s pouch

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3
Q

What is the name of the downward extension of the floor of the brain?

A

Infundibulum

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4
Q

What is Rathke’s pouch made of?

A

Endocrine glands

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5
Q

What is the Infundibulum made of?

A

Extension of the CNS

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6
Q

What is another name for the posterior pituitary?

A

Neurohypophysis

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7
Q

What two hormones are secreted by the posterior pituitary?

A

ADH

Oxytocin

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8
Q

What two nuclei make up the cells of the posterior pituitary?

A

Paraventricular nucleus

Supraoptic/ Suprachiasmatic nuclei

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9
Q

How are the hormones released from the posterior pituitary?

A
  1. ADH and oxytocin are made in the hypothalamus
  2. Trasport along the hypothalamic-pituitary tract to the posterior pituitary
  3. Released into the blood when hypothalamic neurons fire
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10
Q

What is the most important hormone released by the posterior pituitary?

A

ADH

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11
Q

Structural properties of ADH

A

Loop of 9 amino acids

Connected by disulphide bonds

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12
Q

What are the receptors for ADH?

A

V1 and V2

Both are G-protein coupled receptors

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13
Q

What type of receptors are V1 and V2?

A

G-protein coupled receptors

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14
Q

Where are V1 receptors found?

A

In the smooth muscle

Causes vasoconstriction upon activation

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15
Q

Where are V2 receptors found?

A

In nephrons

Enhances water reabsorption via translocation of aquaporins

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16
Q

What is the main function of ADH?

A

To control plasma osmolality

17
Q

What is osmolality?

A

Concentration of a solution expressed as the total number of solute particles per kilogram

18
Q

What does hyposmolality cause?

A

Cerebral oedema

Serious consequences in the brain since it is entrapped by skull

Increased pressure reduces the blood flow to the brain and causes ischaemia

19
Q

What two mechanisms reduce osmolality if high?

A

Stimulate thirst - drinking water maintains healthy osmolality

Stimulate secretion of ADH

20
Q

Describe how the body responds to hyperosmolality

A
  1. Osmotic sensors in the brain detect high plasma osmolality
  2. Send impulses to the supraoptic nucleus of the hypothalamus
  3. Firing of neurons releases ADH from the posterior pituitary
  4. Nephrons reabsorb more water by insertion of aquaporins
  5. This corrects plasma osmolality
21
Q

Describe how the body responds to hyposmolality

A
  1. Less ADH is formed
  2. Less aquaporin translocation in the nephrons
  3. More water is lost in the urine - less resorption of water
22
Q

What does diabetes insipidus mean in Greek?

A

Much tasteless urine - blood glucose is not high

23
Q

What causes diabetes insipidus?

A

Low ADH secretion - damaged posterior pituitary due to injury/ operation/ tumour

Impaired ADH receptor function - nephrogenic diabetes insipidus

24
Q

What are the symptoms of diabetes insipidus?

A

Polyuria

Polydypsia

25
Q

What is polyuria?

A

Urinary loss of water due to less water reabsorption

Low renal aquaporin

Increased desire to urinate

26
Q

What is polydipsia?

A

Urinary loss of water leads to hyperosmolarity

Stimulates thirst - drink water to regulate plasma concentration

If asleep = die from hyperosmolarity since can’t drink

27
Q

What nucleus in the posterior pituitary releases ADH?

A

Suprachiasmatic nucleus

28
Q

What nucelus in the posterior pituitary releases oxytocin?

A

Paraventricular nucleus

29
Q

Why can high levels of oxytocin mimic ADH effects?

A

They are structurally similar

30
Q

Due to its simple structure, oxytocin can be synthesised artificially

TRUE or FALSE

A

True

31
Q

What is a use for synthetically manufactured oxytocin?

A

Induce labour

32
Q

When is oxytocin released?

A

In response to stretching of the cervix during labour

Stimulation of nipples from feeding

33
Q

What does oxytocin do?

A

Helps with birth and milk ejection

Released in both males and females - used in social bonding

Increases trust between people, increases generosity and involved in romantic attraction and monogamous pair bonding

34
Q

What is the normal range of plasma osmolality?

A

275 - 295 mosmol/kg

Kidneys and Hormones (39 decks)

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