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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
Q

What hormone(s) do gonadotrophs release?

A

luteinising hormone (LH), follicle stimulating hormone (FSH)

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26
Q

What hypothalamic hormone / factor stimulates the somatotrophs?

A

growth hormone releasing hormone (GHRH)

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27
Q

What hypothalamic hormone / factor inhibits the somatotrophs?

A

somatostatin

28
Q

What hypothalamic hormone / factor inhibits the lactotrophs?

A

dopamine

29
Q

What hypothalamic hormone / factor stimulates the thyrotrophs?

A

thyrotrophin releasing hormone (TRS)

30
Q

What hypothalamic hormone / factor stimulates the corticotrophs?

A

corticotrophin releasing hormone (CRH)

31
Q

What hypothalamic hormone / factor stimulates the gonadotrophs?

A

gonadotrophin releasing hormone (GRH)

32
Q

What are the main target cells of the growth hormone?

A

general body tissues (especially the liver)

33
Q

What are the main target cells of the prolactin?

A

breasts (lactating woman)

34
Q

What are the main target cells of the thyrotrophin?

A

thyroid

35
Q

What are the main target cells of the gonadotrophins (LH + FSH)?

A

testes / ovaries

36
Q

What are the main target cells of the adrenocorticotrophic hormone?

A

adrenal cortex

37
Q

What is an optic chiasm?

A

where fibres of the nasal (medial) nerve cross over

38
Q

How can a pituitary tumour affect the vision? What kind of tumour specifically?

A

the tumour can compress the optic chiasm, specifically a suprasellar tumour

39
Q

What visual defect can a pituitary tumour cause?

A

bitemporal hemianopia - when you lose peripheral vision / the outer halves of vision from left + right eyes

40
Q

How can a tumour cause bitemporal hemianopia?

A

compression or lesion of the optic chiasm, preventing transmission of sensory information from the lateral visual fields to the occipital lobe

41
Q

What is Step 1 of the neuroendocrine reflex arc for milk production in the mammary glands?

A

mechanical stimulation of the nipple and surrounding area activates afferent pathways

42
Q

What is Step 2 of the neuroendocrine reflex arc for milk production in the mammary glands?

A

afferent signals integrated in the hypothalamus and inhibit dopamine release from dopaminergic neurones

43
Q

What is Step 3 of the neuroendocrine reflex arc for milk production in the mammary glands?

A

less dopamine in the hypothalamic-pituitary portal system causes less inhibition of the anterior pituitary lactotrophs therefore more prolactin is released

44
Q

What is Step 4 of the neuroendocrine reflex arc for milk production in the mammary glands?

A

increased prolactin in the plasma increases milk secretion in the mammary glands

45
Q

What is the direct mechanism of action for the growth hormone?

A
  • anterior pituitary gland’s somatotrophs release GH (somatotrophin) which directly affects body tissues, stimulating growth + development + metabolic actions, etc.
46
Q

What is the indirect mechanism of action for the growth hormone?

A
  • 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
Q

What are IGF-1 AND IGF-2?

A

insulin-like growth factors / somatomedin - hormone released by liver

48
Q

What effects can a pituitary tumour have on growth hormone?

A

too much growth hormone

49
Q

What is the effect of too much GH before puberty?

A

gigantism

50
Q

What disorder is caused by too much GH after puberty?

A

acromegaly

51
Q

What is gigantism?

A

abnormal growth in height due to excessive GH + IGF-1 while the epiphyseal growth plates of bones are still open

52
Q

What is acromegaly? What are some features of acromegaly?

A

excessive growth - coarsening of facial features, macroglossia (prominent nose), prognathism (large jaw), increased hand, feet and finger sizes, sweatiness, headaches, enlarged lips.

53
Q

What is the difference between gigantism + acromegaly? Why?

A

acromegaly has no abnormal increase in height, occurs after puberty when the epiphyseal plates at the end of long bones have fused.

54
Q

What is the posterior pituitary gland made up of?

A

neuronal tissue - it’s anatomically continuous with the hypothalamus

55
Q

What hormones does the posterior pituitary gland produce?

A

Arginine Vasopressin (AVP, also known as the ADH hormone) + Oxytocin

56
Q

How are these hormones produced?

A

by stimulation of hypothalamic magnocellular neurones

57
Q

What are magnocellular neurones?

A

long neurones / neurosecretory cells that originate in the supraoptic (AVP) + paraventricular (oxytocin) nuclei in the hypothalamus

58
Q

How are these hormones transported to the bloodstream?

A

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
Q

What is another name for AVP (arginine vasopressin)?

A

ADH (anti-diuretic hormone)

60
Q

What is the main purpose of AVP? Why?

A

Stimulation of water reabsorption in the renal collecting duct, in order to concentrate urine

61
Q

What is “diuresis”?

A

Production of urine

62
Q

What other functions does AVP have?

A

also a vasoconstrictor + stimulates ACTH release from anterior pituitary gland

63
Q

How does vasopressin concentrate urine?

A
  • 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
Q

What is the function of oxytocin when delivering a baby?

A

Released to uterus at parturition, targets myometrial cells + stimulates contraction to help the delivery of the baby

65
Q

What is the function of oxytocin during lactation?

A

Released to breasts during lactation, targets myoepithelial cells + stimulates contraction + starts ejection of milk

66
Q

How is oxytocin used to help woman struggling in labour?

A

Giving women analogues of oxytocin helps them deliver babies.

67
Q

What is the neuroendocrine reflex arc for milk ejection?

A
  • 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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