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Endocrine systems and Reproduction Emily > 001 introduction to endocrine systems and reproduction and the hypothalamo-pituitary axes > Flashcards

001 introduction to endocrine systems and reproduction and the hypothalamo-pituitary axes Flashcards

1
Q

what is a primary endocrine disorder?

A

where the production of the hormone is not functioning properly
- e.g. Cushing’s disease

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2
Q

what is a secondary endocrine disorder?

A

where there is a lack of a particular hormone or the hormone

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3
Q

what is the anatomical location of the pituitary gland?

A
  • base of brain, protected by sphenoid bone
  • connected to the hypothalamus via the pituitary stalk
  • just inferior to the optic chiasm ( clinically important for pituitary tumours)
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4
Q

what is the embryological development/origin of the anterior pituitary gland?

A
  • upgrowth from roof of the mouth called Rathke’s pouch
  • ’ adenohypophysis’
  • not neural origin
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5
Q

what is the embryological development/origin of the posterior pituitary gland?

A
  • grows down from neural tissues from basal floor of the diencephalon
  • ’ neurohypophysis’
  • of neural origin
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6
Q

what is the anatomy of the posterior pituitary gland?

A
  • smaller of the 2 lobes
  • neurons in the hypothalamus (including periventricular and supraoptic nucleus) send projections down through the pituitary stalk and terminate in the posterior pituitary gland
  • these nerve endings release chemicals that directly enter the blood via the plexus supplied by inferior hypophyseal artery
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7
Q

what are the 2 nuclei that feed into the posterior pituitary gland?

A
  • paraventricular nucleus = sits at base of 3rd ventricle
  • supraoptic nucleus = just next to optic chiasm
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8
Q

what is the artery that supplies the posterior pituitary gland?

A
  • inferior hypophyseal artery which forms a plexus which hormones enter the bloodstream through
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9
Q

what is a?

A

optic chiasm

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10
Q

what is b?

A

infundibulum (connecting stalk)

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11
Q

what is c?

A

hypothalamic-hypophyseal tract

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12
Q

what is d?

A

axon terminals

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13
Q

what is e?

A

inferior hypophyseal artery

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14
Q

what is f?

A

supraoptic nucleus

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15
Q

what is g?

A

paraventricular nucleus

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16
Q

what are the 2 posterior pituitary hormones?

A
  • oxytocin
  • anti-diuretic hormone (ADH) / vasopressin (AVP), 2 names as it has 2 receptors
  • called neurohypophyseal hormones
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17
Q

what is the process of releasing hormones from the posterior pituitary gland?

A
  • hormones oxytocin/ADH are synthesized in the magnocellular neurones of the periventricular and supraoptic nuclei in the hypothalamus
  • the hormones are transported down the axons in the infundibulum in the hypothalamic-hypophyseal tract into the posterior pituitary gland and stored in the axon terminals
  • they are stored here until action potentials from the hypothalamus fire to release the hormones into the blood
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18
Q

What are the neurons called in the PVN and SON that produce oxytocin and ADH?

A

magnocellular neurones

19
Q

what is the median eminence?

A

area of fenestrated blood vessels which act as a funnel which ship contents of hypothalamus down into the anterior pituitary

20
Q

what is the process of releasing hormones from the anterior pituitary gland?

A
  • hypothalmaus neurons are stimulated and secreat releasing or inhibiting hormones e.g. TRH, CRH…
  • these hormones travel down the median eminence / primary capillary plexus into the anterior pituitary gland where they either stimulate or inhibit hormones made there
  • the anterior pituitary gland then secretes hormones into the secondary capillary plexus which enters the general circulation e.g. TSH, ACTH
21
Q

what are the 5 different cell populations in the anterior pituitary?

A
  • thyrotrophs = TSH
  • gonadotrophs = LH/FSH
  • corticotrophs = ACTH
  • somatotrophs = GH
  • lactotrophs = prolactin
22
Q

what hormones does the anterior pituitary produce/secrete (6)?

A
  • TSH = thyroid stimulating hormone
  • LH = luteinising hormone
  • FSH = follicle-stimulating hormone
  • ACTH = adrenocorticotrophic hormone
  • GH = growth hormone (somatotrophin)
  • Prolactin
23
Q

what hormones do the hypothalamus produce/secrete?

A
  • GHRH = growth hormone releasing hormone
  • GnRH = gonadotropin-releasing hormone
  • CRH = corticotropin-releasing hormone
  • TRH = thyrotropin-releasing hormone
  • Dopamine (affect prolactin)
24
Q

what are the general structures of TSH, LH, FSH?

A
  • heterodimeric glycoproteins
  • common alpha subunit
  • specific to hormone Beta subunites
25
Q

what is the general structure of ACTH?

A
  • peptide
  • 39 amino acid cleaved fragment of POMC
26
Q

what is the general structure of GH and prolactin?

A
  • 3D peptides
  • 190 amino acids
  • internal disulfide bonds
  • homologous receptors
27
Q

what part of the pituitary is pars nervosa?

A
  • posterior pituitary gland
28
Q

what part of the pituitary is pars distalis?

A
  • anterior pituitary gland
29
Q

what part of the pituitary is pars intermedia?

A
  • intermediate lobe
  • separates anterior and posterior glands
  • closely associated with posterior, separated from anterior via hypophyseal cleft
30
Q

what hormone does the pars intermedia of the pituitary gland secrete?

A
  • MSH = melanocyte-stimulating hormone
31
Q

describe the pathway/ dual control of GH secretion

A
  • hypothalamus secretes GHRH –> stimulates GH secretion from anterior pituitary gland –> liver to produce IGF-1
  • negative feedback loop of IGF-1 to turn off hypothalamus and anterior pituitary
  • GH release is also controlled by somatostatin which is produced near GHRH neurons
  • somatostatin inhibits GH production
  • stress also inhibits GH production
32
Q

why is prolactin an exception?

A
  • instead of being stimulated or inhibited by the hypothalamus, it is under dominant negative control by dopamine (from arcuate nucleus)
  • so more dopamine = less prolactin
33
Q

what are the 3 steps of the hypothalamo-pituitary-thyroid (HPT) axis?

A
  • hypothalamus secrete TRH –> Stimulates anterior pituitary gland to secrete TSH –> stimulate thyroid to produce thryoid hormones (T3,T4)
  • negative feedback loop
34
Q

what are the 3 steps of the hypothalamo-pituitary-gonadal (HPG) axis?

A
  • hypothalamus secretes GnRH –> stimulates anterior pituitary gland to secrete LH/FSH –> stimulates gonads to produce progesterone/testosterone/oestrodiol
  • negative feedback loop
35
Q

what are the 3 steps of the hypothalamo-pituitary-adrenal (HPA) axis?

A
  • hypothalamus secretes CRH –> stimulates anterior pituitary gland to secreted ACTH –> stimulates adrenal gland to produce cortisol
  • negative feedback loop
36
Q

what 2 factors can override negative feedback of the hypothalamus-pituitary axes?

A
  • higher centres of the brain
  • chronic stress = CRH, GcRH, GHRH all affected
37
Q

what can cause pituitary gland defects? (5)

A
  • cranial trauma
  • tumours
  • inflammation/infection
  • midline defects e.g. septo-opticdysplasia
  • defects in migration of hypothalamic neurons e.g. Kallman’s syndrome when GnRH hormones do not migrate = don’t go through normal puberty
38
Q

what can cause hyposecretion of anterior pituitary hormones?

A
  • adenohypophyseal cells are sensitive to radiation, particularly somatotrophs (GH)
  • other than that it is very rare, very specific diseases
39
Q

what can cause hypersecretion of anterior pituitary hormones?

A
  • pituitary tumours
  • specific hormones syndromes e.g. cushings diseases, hypothyroidism, acromegaly
  • ectopic, tumours else where in the body
40
Q

where is oxytocin secreted from?

A
  • posterior pituitary gland
  • ovaries
  • testes
41
Q

what is the general structure of oxytocin?

A
  • 9 amino acid peptide hormone
  • differs from ADH by 2 aa
  • packaged into granules with ADH and secreted along with carrier proteins called neurophysics
42
Q

what are the 3 main actions of oxytocin?

A
  • stimulation of milk ejection
    -stimulation of uterine contractions at birth
  • acts within brain to establish maternal behaviour and bonding
  • all positive feedback
43
Q

what are the neural reflexes that mediate oxytocin positive feedback?

A
  • suckling reflex = act of nursing / suckling on mother nipple cause reflex to stimulate oxytocin release from neurons to stimulate milk ejection
  • Fergusson reflex = stimulation of uterine smooth muscle contractions during birth

Endocrine systems and Reproduction Emily (2 decks)

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