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GOATED BRS > Pituitary gland > Flashcards

Pituitary gland Flashcards

1
Q

What are hormones?

A

Chemical messengers secreted from glands, and bind to target receptors to elicit an activator or inhibitory response within the target cell, carried by the circulatory system

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2
Q

How are peptide hormones synthesised?

A

Synthesised as pro-hormones requiring further processing (cleavage) to activate.

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3
Q

How do peptide hormones enter the cell?

A

Peptide hormones are polar, therefore are impermeable to the phospholipid bilayer of the cell surface membrane, therefore bind to receptors to transduce a secondary messenger system

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4
Q

How are peptide hormones stored?

A

In secretory vesicles

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5
Q

What type of secretion are peptide hormones?

A

Regulatory secretion

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6
Q

Why are steroid hormones membrane permeable?

A

Proteins contain a sterol group, thus can dissolve in phospholipid bilayer and diffuse into the cell

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7
Q

How are steroid hormones stored?

A

Released immediately

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8
Q

What is the term used to describe the secretion of steroid hormones?

A

Constitutive secretion

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9
Q

Which types of intracellular receptors do steroids bind to?

A

Type 1: Cytoplasmic intracellular receptor
Type 2: Nuclear

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10
Q

Which pituitary gland is continuous with the hypothalamus?

A

Posterior pituitary gland

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11
Q

How is the anterior pituitary gland anatomically distinct in comparison the posterior pituitary gland?

A

The anterior pituitary gland is distinct and not continuous with the hypothalamus; there is no presence of neural tissue

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12
Q

How is the pituitary suspended from the inferior side of the brain?

A

By the pituitary stalk

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13
Q

What is another term for the pituitary stalk?

A

Infundibulum

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14
Q

Where does the pituitary gland reside?

A

Sella turcica of the sphenoid bone

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15
Q

What is a supra-sella tumour?

A

Pituitary tumour above the sell-turcica (fossa)

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16
Q

What is another term for the anterior pituitary?

A

Adenohypophysis

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17
Q

What is Rathke’s pouch?

A

Piece of tissue that forms the anterior pituitary gland, composed of glandular epithelium

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18
Q

Which region of the anterior pituitary gland secretes majority of hormones?

A

Pars distalis

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19
Q

Which epithelial layer separates the pars anterior from the posterior lobe in the pituitary gland?

A

Pars intermedia

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20
Q

What is the term for the portal circulation in the hypothalamus and pituitary gland?

A

Hypophyseal portal circulation

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21
Q

What is the neurohypothysis?

A

Posterior pituitary gland

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22
Q

Which hormones are secreted from the posterior pituitary gland?

A

Oxytocin and ADH

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23
Q

Which nuclei secrete oxytocin and ADH within the posterior pituitary gland?

A

ADH: Supraoptic
Oxytocin: Paraventricular
(Both magnocellular)

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24
Q

Which neurones secrete hypothalamic hormones into the primary capillary plexus?

A

Parvocellular hypothalamic neurones

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25
Q

Where are hypothalamic hormones secreted into?

A

Primary capillary plexus

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26
Q

Which circulation is linked to the primary capillary plexus?

A

The portal hypophyseal circulation

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27
Q

Where do the parvocellular neurones terminate (site of primary plexus)?

A

Median eminence

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28
Q

How are the hypothalamic releasing/inhibitory factors transported to the anterior pituitary?

A

The portal hypophyseal circulation

Primary capillary plexus to the secondary capillary plexus

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29
Q

Where is the median eminence located?

A

Infundibulum

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30
Q

What type of cells comprise the anterior pituitary gland?

A

Endocrine cells
thyrotropes, lactotropes, corticotropes, somatotropes and gonadotropes

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31
Q

What are the 5 classes of endocrine cells found in the anterior pituitary?

A 
Lactotrophs
Somatotrophs
Gonadtrophs
Thyrotrophs
Corticotrophs
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32
Q

Which plexus releases hypothalamic inhibitory/releasing factors into the anterior pituitary gland?

A

Secondary capillary plexus

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33
Q

Which releasing hormone stimulates the release of TSH?

A

Thyrotropin-releasing hormone (TRH)

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34
Q

What effect does TRH(Thyrotropin-releasing-hormone) have on anterior pituitary?

A

Stimulates the release of thyroid-stimulating-hormone

35
Q

Which endocrine cell do TRH act on?

A

Thyrotrophs

36
Q

Which hormone is secreted by somatotrophs?

A

Growth hormone

37
Q

Which hormone is secreted by lactotrophs?

A

Prolactin

38
Q

Which hormone is secreted by thyrotrophs?

A

Thyroid-stimulating hormone

39
Q

Which hormones are secreted by gonadotrophs?

A 
Lutenising hormone (LH)
Follicle-stimulating hormone
40
Q

Which hormone is secreted by corticotrophs?

A

Adrenocorticotrophic hormone

41
Q

What is the target organ of growth hormone?

A

General body tissue, particularly the liver

42
Q

What is the target organ of prolactin?

A

Mammary gland

43
Q

What is the target organ of TSH?

A

Thyroid gland

44
Q

What is the target organ of LH?

A

Testes and ovaries

45
Q

What is the target organ of FSH?

A

Ovaries

46
Q

What is the target organ of ACTH?

A

Adrenal cortex

47
Q

Which hormone inhibits the secretion of growth hormone?

A

Somatostatin

48
Q

Which hormone stimulates the release of growth hormone?

A

Stimulates: GHRH
Inhibits: Somatostatin

49
Q

Which hormone stimulates the release of TSH?

A

Thyrotropin-releasing hormone

50
Q

Which hormone stimulates the release of ACTH?

A

Corticotrophin-releasing hormone

51
Q

Which hormone stimulates the release of LH & FSH?

A

gonadotrophin-releasing hormone

52
Q

What typical condition arises due to a pituitary tumour?

A

Bitemporal hemianopia

53
Q

Why does bitemporal hemianopia occur?

A

Adenoma engulfs the entirety of the sella turcica, the superior optic chasm is compressed (region where decussation occurs)

Fibres from optic retinae are therefore compressed, thus no sensory stimulation from the lateral fields to primary visual cortex

54
Q

Which nerve bundle is compressed due to an adenoma?

A

Optic chiasm

55
Q

Describe the neuroendocrine reflex arc for prolactin:

A

Mechanical stimulation of the nipple touch and sensory receptors, activating afferent pathways.
Action potentials traverse along the axons, through the ascending sensory pathways

Afferent signals integrated in the hypothalamus, and inhibit dopamine release from dopaminergic parvocellular neurones

Reduced concentration of dopamine in the hypothalamic-pituitary gportal system, result sin reduction of inhibition of anterior pituitary lactotrophs

Increased plasma prolactin increases milk secretion in the mammary glands

56
Q

Which molecule inhibits the release of prolactin?

A

Dopamine

57
Q

What is released upon growth hormone receptor activation of the liver?

A

IGF-1 (Somatomedin)

58
Q

What is IGF-1?

A

Mediator of growth hormone stimulated somatic growth, binding to target receptors

59
Q

How do pituitary gigantism occur?

A

Refers to growth hormone excess that occurs before epiphyseal growth plate fusion.
Patient has elevated levels of serum growth hormone and IGF

60
Q

Which hormones are elevated in pituitary gigantism?

A

Growth hormone and IGF

61
Q

What is acromegaly?

A

Attributed to a growth hormone producing a tumour within the anterior pituitary gland, whereby somatotroph cells secrete excessive concentrations of growth hormone, elevated levels of IGF-1

Epiphyseal growth plates have fused

62
Q

What are the clinical features for gigantism?

A 
Coarsening of facial features
Macroglossia
Prominent nose
Proganthism 
Sweatiness
Frequent headache
Bitemporal hemianopia
Obstructive sleep apnoea
63
Q

What is obstructive sleep apnoea?

A

Osseous and soft tissue changes surrounding the upper airway results in narrowing and subsequent collapse during sleep, disruption to sleep patterns

64
Q

What test can be used to diagnostically confirm an adenoma?

A

MRI scans

65
Q

How does an oral glucose tolerance test diagnose a pituitary adenoma?

A

Raising glucose levels using an OGTT, would cause reduction in growth hormone plasma concentrations, patients with acromegaly do not respond

66
Q

How can a blood test be used for diagnostics of adenoma?

A

Growth hormone and IGF-1 measurements

67
Q

How are the posterior pituitary hormones stored?

A

Neurosecretory vesicles (Herring bodies)

68
Q

Which tissues present in the hypothalamus?

A

Neural tissue

69
Q

Which magnocellular hypothalamic neurones secrete AVP?

A

Supraoptic

70
Q

Which nuclei secrete oxytocin?

A

Paraventricular nuclei

71
Q

Which region of the posterior pituitary contain Herring bodies?

A

Pars nervosa

72
Q

What stimulates the release of AVP or oxytocin?

A

Excitation of hypothalamic magnocellular neurones

73
Q

Which neurosecretory cells secrete ADH?

A

Magnocellular neurones (Supraoptic)

74
Q

What is the effect of ADH?

A

Increases the permeability of the distal convoluted tubule and collecting duct to water

75
Q

Which receptors does ADH bind to?

A

Specific V2 G protein-coupled receptors of the cell surface membrane

76
Q

What intracellular effect does ADH have in the collecting duct?

A

Triggers adenylate cyclase activity to form cyclic-AMP, secondary messenger enables protein kinase A to active aquaporin-2 and 3 genes

77
Q

Which water channels are synthesised upon ADH activation?

A

Aquaporins

78
Q

Which side does aquaporins-2 insert itself in?

A

Tubular lumen

79
Q

What effect does oxytocin have?

A

Stimulates uterine contractions, and dilation of cervix

Milk ejection

80
Q

When are oxytocin receptors in the uterus synthesised at the highest rate?

A

During pregnancy within the uterus, the smooth muscles become more sensitive

81
Q

What feedback loop does oxytocin exhibit?

A

Positive feedback mechanism

82
Q

How is the positive feedback loop of oxytocin initiated?

A

Cervical stretching

83
Q

Which hypothalamic nuclei releases oxytocin?

A

Paraventricular nuclei

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