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BRS - Endo > Pituitary Gland > Flashcards

Pituitary Gland Flashcards

1
Q

What is a hormone?

A

A “messenger” carried from the production organ to the affecter organ via the blood stream.

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2
Q

What are the two types of hormones?

A

Peptide + Steroid

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3
Q

How are peptide hormones synthesised?

A

synthesised first as prohormones (long peptide chains) which require further processing (cleavage by enzymes, etc.) in order to ACTIVATE them.

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4
Q

How are steroid hormones synthesised?

A

synthesised in a series of reactions from cholesterol.

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5
Q

How are peptide hormones stored?

A

stored in vesicles (regulatory secretion)

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6
Q

How are steroid hormones stored?

A

released immediately, not stored (constitutive secretion)

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7
Q

What receptors do peptide hormones bind to?

A

bind to receptors on cell membranes + transduce signal using 2nd messenger systems.

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8
Q

What receptors do steroid hormones bind to?

A

bind to intracellular receptors to change gene expression directly.

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9
Q

Where does the pituitary gland sit in the brain?

A

in the sella turcica of the sphenoid bone

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10
Q

What gland and cns landmark is the pituitary gland inferior to?

A

hypothalamus and optic chiasm (kind of)

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11
Q

What is another name for the anterior pituitary gland?

A

adenohypophysis

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12
Q

What is another name for the posterior pituitary gland?

A

neurohypophysis

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13
Q

What are the two main parts of the pituitary gland?

A

anterior and posterior

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14
Q

What is the anterior pituitary gland made of?

A

anatomically distinct from the hypothalamus, made up of 5 different types of endocrine cells

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15
Q

What are the 5 different types of endocrine cells?

A 
Somatotrophs
Lactotrophs
Corticotrophs
Thyrotrophs
Gonadotrophs
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16
Q

How is the anterior pituitary gland regulated?

A

by the hypothalamic parvocellular neurones

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17
Q

What are parvocellular neurones?

A

short neurones / neurosecretory cells that terminate in the median eminence + release hypothalamic releasing/inhibitory factors into the capillary plexus of the median eminence in order regulate the APG.

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18
Q

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

A

by the hypothalamo-pituitary portal system

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19
Q

What is the hypothalamo-pituitary portal system?

A

system of blood vessels that transport hypothalamic releasing/inhibitory factors to the APG

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20
Q

How does the hypothalamo-pituitary portal system work?

A

the factors are released into the portal system
→ transported to the APG
→ they stimulate or inhibit release of hormones from APG endocrine cells
→ these hormones leave the gland via the blood

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21
Q

What hormone(s) do somatotrophs release?

A

growth hormone / somatotrophin

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22
Q

What hormone(s) do lactotrophs release?

A

prolactin

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23
Q

What hormone(s) do thyrotrophs release?

A

thyroid stimulating hormone (TSH) / thyrotrophin

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24
Q

What hormone(s) do corticotrophs release?

A

adrenocorticotrophic hormone (ACTH) / corticotrophin

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25
What hormone(s) do gonadotrophs release?
luteinising hormone (LH), follicle stimulating hormone (FSH)
26
What hypothalamic hormone / factor stimulates the somatotrophs?
growth hormone releasing hormone (GHRH)
27
What hypothalamic hormone / factor inhibits the somatotrophs?
somatostatin
28
What hypothalamic hormone / factor inhibits the lactotrophs?
dopamine
29
What hypothalamic hormone / factor stimulates the thyrotrophs?
thyrotrophin releasing hormone (TRS)
30
What hypothalamic hormone / factor stimulates the corticotrophs?
corticotrophin releasing hormone (CRH)
31
What hypothalamic hormone / factor stimulates the gonadotrophs?
gonadotrophin releasing hormone (GRH)
32
What are the main target cells of the growth hormone?
general body tissues (especially the liver)
33
What are the main target cells of the prolactin?
breasts (lactating woman)
34
What are the main target cells of the thyrotrophin?
thyroid
35
What are the main target cells of the gonadotrophins (LH + FSH)?
testes / ovaries
36
What are the main target cells of the adrenocorticotrophic hormone?
adrenal cortex
37
What is an optic chiasm?
where fibres of the nasal (medial) nerve cross over
38
How can a pituitary tumour affect the vision? What kind of tumour specifically?
the tumour can compress the optic chiasm, specifically a suprasellar tumour
39
What visual defect can a pituitary tumour cause?
bitemporal hemianopia - when you lose peripheral vision / the outer halves of vision from left + right eyes
40
How can a tumour cause bitemporal hemianopia?
compression or lesion of the optic chiasm, preventing transmission of sensory information from the lateral visual fields to the occipital lobe
41
What is Step 1 of the neuroendocrine reflex arc for milk production in the mammary glands?
mechanical stimulation of the nipple and surrounding area activates afferent pathways
42
What is Step 2 of the neuroendocrine reflex arc for milk production in the mammary glands?
afferent signals integrated in the hypothalamus and inhibit dopamine release from dopaminergic neurones
43
What is Step 3 of the neuroendocrine reflex arc for milk production in the mammary glands?
less dopamine in the hypothalamic-pituitary portal system causes less inhibition of the anterior pituitary lactotrophs therefore more prolactin is released
44
What is Step 4 of the neuroendocrine reflex arc for milk production in the mammary glands?
increased prolactin in the plasma increases milk secretion in the mammary glands
45
What is the direct mechanism of action for the growth hormone?
- anterior pituitary gland's somatotrophs release GH (somatotrophin) which directly affects body tissues, stimulating growth + development + metabolic actions, etc.
46
What is the indirect mechanism of action for the growth hormone?
- anterior pituitary gland's somatotrophs release GH (somatotrophin) which targets the liver - liver releases IGF-1 AND IGF-2 (insulin-like growth factor / somatomedin) - they target body tissues, stimulating growth + development + metabolic actions, etc.
47
What are IGF-1 AND IGF-2?
insulin-like growth factors / somatomedin - hormone released by liver
48
What effects can a pituitary tumour have on growth hormone?
too much growth hormone
49
What is the effect of too much GH before puberty?
gigantism
50
What disorder is caused by too much GH after puberty?
acromegaly
51
What is gigantism?
abnormal growth in height due to excessive GH + IGF-1 while the epiphyseal growth plates of bones are still open
52
What is acromegaly? What are some features of acromegaly?
excessive growth - coarsening of facial features, macroglossia (prominent nose), prognathism (large jaw), increased hand, feet and finger sizes, sweatiness, headaches, enlarged lips.
53
What is the difference between gigantism + acromegaly? Why?
acromegaly has no abnormal increase in height, occurs after puberty when the epiphyseal plates at the end of long bones have fused.
54
What is the posterior pituitary gland made up of?
neuronal tissue - it's anatomically continuous with the hypothalamus
55
What hormones does the posterior pituitary gland produce?
Arginine Vasopressin (AVP, also known as the ADH hormone) + Oxytocin
56
How are these hormones produced?
by stimulation of hypothalamic magnocellular neurones
57
What are magnocellular neurones?
long neurones / neurosecretory cells that originate in the supraoptic (AVP) + paraventricular (oxytocin) nuclei in the hypothalamus
58
How are these hormones transported to the bloodstream?
hypothalamic magnocellular neurones secrete AVP and Oxytocin in the hypothalamus + transport hormones down the stalk to posterior pituitary gland where they diffuse into blood capillaries, then the bloodstream.
59
What is another name for AVP (arginine vasopressin)?
ADH (anti-diuretic hormone)
60
What is the main purpose of AVP? Why?
Stimulation of water reabsorption in the renal collecting duct, in order to concentrate urine
61
What is "diuresis"?
Production of urine
62
What other functions does AVP have?
also a vasoconstrictor + stimulates ACTH release from anterior pituitary gland
63
How does vasopressin concentrate urine?
- vasopressin binds to v2 receptors in the kidneys, causing a cascade of reactions involving G protein, adenylate cycles, CAMP, protein kinase A, etc. - aquaporin-2 reabsorbs H2O from urine + aquaporin-3 releases it back into the plasma
64
What is the function of oxytocin when delivering a baby?
Released to uterus at parturition, targets myometrial cells + stimulates contraction to help the delivery of the baby
65
What is the function of oxytocin during lactation?
Released to breasts during lactation, targets myoepithelial cells + stimulates contraction + starts ejection of milk
66
How is oxytocin used to help woman struggling in labour?
Giving women analogues of oxytocin helps them deliver babies.
67
What is the neuroendocrine reflex arc for milk ejection?
- mechanical stimulation of the nipple + surrounding area activates afferent pathways - afterent signals integrate in the hypothalamus + stimulate oxytocin releasing activity - action potentials travel down oxytocin neurones + oxytocin is released into the bloodstream - increased oxytocin in plasma = increased milk ejection

BRS - Endo (9 decks)

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