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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
Where are hypothalamic hormones secreted into?
Primary capillary plexus
26
Which circulation is linked to the primary capillary plexus?
The portal hypophyseal circulation
27
Where do the parvocellular neurones terminate (site of primary plexus)?
Median eminence
28
How are the hypothalamic releasing/inhibitory factors transported to the anterior pituitary?
The portal hypophyseal circulation | Primary capillary plexus to the secondary capillary plexus
29
Where is the median eminence located?
Infundibulum
30
What type of cells comprise the anterior pituitary gland?
Endocrine cells thyrotropes, lactotropes, corticotropes, somatotropes and gonadotropes
31
What are the 5 classes of endocrine cells found in the anterior pituitary?
``` Lactotrophs Somatotrophs Gonadtrophs Thyrotrophs Corticotrophs ```
32
Which plexus releases hypothalamic inhibitory/releasing factors into the anterior pituitary gland?
Secondary capillary plexus
33
Which releasing hormone stimulates the release of TSH?
Thyrotropin-releasing hormone (TRH)
34
What effect does TRH(Thyrotropin-releasing-hormone) have on anterior pituitary?
Stimulates the release of thyroid-stimulating-hormone
35
Which endocrine cell do TRH act on?
Thyrotrophs
36
Which hormone is secreted by somatotrophs?
Growth hormone
37
Which hormone is secreted by lactotrophs?
Prolactin
38
Which hormone is secreted by thyrotrophs?
Thyroid-stimulating hormone
39
Which hormones are secreted by gonadotrophs?
``` Lutenising hormone (LH) Follicle-stimulating hormone ```
40
Which hormone is secreted by corticotrophs?
Adrenocorticotrophic hormone
41
What is the target organ of growth hormone?
General body tissue, particularly the liver
42
What is the target organ of prolactin?
Mammary gland
43
What is the target organ of TSH?
Thyroid gland
44
What is the target organ of LH?
Testes and ovaries
45
What is the target organ of FSH?
Ovaries
46
What is the target organ of ACTH?
Adrenal cortex
47
Which hormone inhibits the secretion of growth hormone?
Somatostatin
48
Which hormone stimulates the release of growth hormone?
Stimulates: GHRH Inhibits: Somatostatin
49
Which hormone stimulates the release of TSH?
Thyrotropin-releasing hormone
50
Which hormone stimulates the release of ACTH?
Corticotrophin-releasing hormone
51
Which hormone stimulates the release of LH & FSH?
gonadotrophin-releasing hormone
52
What typical condition arises due to a pituitary tumour?
Bitemporal hemianopia
53
Why does bitemporal hemianopia occur?
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
Which nerve bundle is compressed due to an adenoma?
Optic chiasm
55
Describe the neuroendocrine reflex arc for prolactin:
**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
Which molecule inhibits the release of prolactin?
Dopamine
57
What is released upon growth hormone receptor activation of the liver?
IGF-1 (Somatomedin)
58
What is IGF-1?
Mediator of growth hormone stimulated somatic growth, binding to target receptors
59
How do pituitary gigantism occur?
Refers to growth hormone excess that occurs before epiphyseal growth plate fusion. Patient has elevated levels of serum growth hormone and IGF
60
Which hormones are elevated in pituitary gigantism?
Growth hormone and IGF
61
What is acromegaly?
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
What are the clinical features for gigantism?
``` Coarsening of facial features Macroglossia Prominent nose Proganthism Sweatiness Frequent headache Bitemporal hemianopia Obstructive sleep apnoea ```
63
What is obstructive sleep apnoea?
Osseous and soft tissue changes surrounding the upper airway results in narrowing and subsequent collapse during sleep, disruption to sleep patterns
64
What test can be used to diagnostically confirm an adenoma?
MRI scans
65
How does an oral glucose tolerance test diagnose a pituitary adenoma?
Raising glucose levels using an OGTT, would cause **reduction in growth hormone plasma concentrations, patients with acromegaly do not respond**
66
How can a blood test be used for diagnostics of adenoma?
Growth hormone and IGF-1 measurements
67
How are the posterior pituitary hormones stored?
Neurosecretory vesicles (Herring bodies)
68
Which tissues present in the hypothalamus?
Neural tissue
69
Which magnocellular hypothalamic neurones secrete AVP?
Supraoptic
70
Which nuclei secrete oxytocin?
Paraventricular nuclei
71
Which region of the posterior pituitary contain Herring bodies?
Pars nervosa
72
What stimulates the release of AVP or oxytocin?
Excitation of hypothalamic magnocellular neurones
73
Which neurosecretory cells secrete ADH?
Magnocellular neurones (Supraoptic)
74
What is the effect of ADH?
Increases the permeability of the distal convoluted tubule and collecting duct to water
75
Which receptors does ADH bind to?
Specific V2 G protein-coupled receptors of the cell surface membrane
76
What intracellular effect does ADH have in the collecting duct?
Triggers adenylate cyclase activity to form cyclic-AMP, secondary messenger enables **protein kinase A to active aquaporin-2 and 3 genes**
77
Which water channels are synthesised upon ADH activation?
Aquaporins
78
Which side does aquaporins-2 insert itself in?
Tubular lumen
79
What effect does oxytocin have?
Stimulates uterine contractions, and dilation of cervix Milk ejection
80
When are oxytocin receptors in the uterus synthesised at the highest rate?
During pregnancy within the uterus, the smooth muscles become more sensitive
81
What feedback loop does oxytocin exhibit?
Positive feedback mechanism
82
How is the positive feedback loop of oxytocin initiated?
Cervical stretching
83
Which hypothalamic nuclei releases oxytocin?
Paraventricular nuclei

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