Lecture 3: Hypothalamus-Pituitary Relationship Flashcards
What are the 5 important nuclei of the hypothalamus?
1) PVN (paraventricular nucleus)
2) POA (Preoptic nucleus)
3) ARC (arcuate nucleus)
4) SCN (superchiasmatic nucleus)
5) SON (supraoptic nucleus)
What are the 5 important nuclei of the hypothalamus?
1) PVN (paraventricular nucleus)
2) POA (Preoptic nucleus)
3) ARC (arcuate nucleus)
4) SCN (superchiasmatic nucleus)
5) SON (supraoptic nucleus)
What differentiates the different hypothalamic nuclei?
enzymes
True or false: the hypothalamus lies inside the blood brain barrier?
FALSE; the floor of the hypothalamus sits at the medial eminence (ME) which is outside the BBB and is the convergence point for axons
Which nucleus controls sleep?
SCN
Which nucleus controls feeding behavior/satiety?
ARC
Which nucleus controls thirst?
PVN
Which nucleus controls reproduction?
POA
Which nucleus controls mood/emotion/stress?
PVN/ARC
Which nucleus controls body temperature?
POA
Which nucleus controls blood pressure?
PVN
What 7 hormones are released from the hypothalamus?
1) GnRH
2) GnIH
3) CRH
4) TRH
5) GHRH
6) Somatostatin
7) Dopamine
Which nucleus releases GnRH?
POA
Which nucleus releases CRH and TRH?
PVN
Which nucleus releases GHRH and Dopamine?
arcuate nucleus
What is the pituitary target of dopamine?
lactotrope - prolactin
What is the pituitary target of GnRH/GnIH?
gonadotropes - FSH and LH
What is the pituitary target of CRH?
corticotrope - ACTH
What is the pituitary target of TRH?
thyrotrope - TSH
What is the pituitary target of GHRH and Somatostatin?
Somatotrope (GH)
What is the function of Somatostatin?
to INHIBIT GH
What is the function of Somatostatin?
to INHIBIT GH
Which hypothalamic hormones act via cAMP second messengers?
CRH, GHRG, Somatostatin (GHIH)
Which hypothalamic hormones act via IP3/DAG/PKC second messengers?
TRH, GnRH
Which hypothalamic hormones act via IP3/DAG/PKC second messengers?
TRH, GnRH
Describe neurons that release GnRH?
cell bodies in forebrain, axons in median eminence
very few of them; only 1500-2000
How large is GnRH?
decapeptide (10aa)
What is Kallman Syndrome?
rare genetic disease where GnRH neurons fail to enter the CNS. Characterized by anosmia and reproductive failure (these neurons originate in olfactory placode)
What is Kallman Syndrome?
rare genetic disease where GnRH neurons fail to enter the CNS. Characterized by anosmia and reproductive failure (these neurons originate in olfactory placode)
Where do GnRH neurons originate?
nose, have to migrate thru cribiform plate to get to brain
What is the hypophyseal portal system?
vascular connection between the hypothalamus and pituitary
discovered because when pituitaries were transplanted to other locations, they stopped secreting hormone
What pattern is GnRH released in?
PULSATILE fashion throughout the day
pulsatility required for turnover of receptors
How is LH pulsatility fashioned after GnRH?
occurs slightly after GnRH burst
What 2 hormones does GnRH stimulate release of from the pituitary?
LH and FSH
What subunit remains the same across TSH, FSH, LH, hCG? What changes?
alpha stays the same
beta changes
What determines whether FSH or LH is released from pituitary in response to GnRH?
pulse frequency
more pulses –> more LH
(fewer pulses –> more FSH)
Which GnRH stimulated intracellular pathway stimulates hormone release? synthesis?
IP3/Ca++ –> hormone release
DAG/PKC –> hormone synthesis
What are the 2 major pathways of hypothalamic-pituitary connection?
1) tuberoinfundibular system
2) neurohypophysial tract
What is the tuberoinfundibular system?
all neurons that send axonal projections to the median eminence. Hormones target the anterior pituitary thru the capillary system
What is the neurohypophysial tract?
all neurons whose axons terminate in posterior pituitary (cell bodies still in hypothalamus)
The pituitary gland sits in what bony structure in the brain?
sella turcica
The pituitary gland sits in what bony structure in the brain?
sella turcica
What are the 3 parts of the anterior pituitary?
1) Pars distalis
2) Pars tuberalis
3) Pars intermedia
What are the 2 parts of the posterior pituitary?
1) Pars nervosa
2) Infundibulum (stalk)
What are the 2 parts of the posterior pituitary?
1) Pars nervosa
2) Infundibulum (stalk)
Which half of the pituitary is derived from from neural tissue? Which half is more glandular?
Posterior (neurohypophysis) - neural tissue
Anterior (adenohypophysis) - glandular
Which half of the pituitary is referred to as the adenohypophysis?
Anterior (A and A)
glandular - cords of epithelial cells
Which half of the pituitary is referred to as the neurohypophysis?
Posterior
neural - terminal axons and glial cells
What is the major blood supply in the posterior pituitary?
inferior hypophysial artery (NOT part of portal system)
What are the 2 hormones produced by the posterior pituitary?
AVP and oxytocin
What are magnocellular neurons and where are they?
cell bodies in hypothalamus; axons extend into the posterior pituitary
What kind of capillaries are found in the posterior pituitary?
fenestrated (axons terminate near them)
What are herring bodies and where are they found?
dilations of unmyelinated axons near terminals. They are found in the posterior pituitary right near the capillaries
What do Herring bodies contain?
AVP or oxytocin plus binding protein, neurophysin
Where is the median eminence and why is it important?
floor of the 3rd ventricle, outside of the BBB. It is the interface for all hypophysiotrophic hormones
What are the 5 major anterior pituitary cell types?
1) Somatotrophs (GH)
2) Lactotrophs (prolactin)
3) Corticotrophs (ACTH)
4) Gonadotrophs (LH/FSH)
5) Thyrotrophs (TSH)
What two anterior pituitary cell types are classified as acidophils? (also the most abundant in the anterior pituitary? 40%)
1) somatotrophs (GH)
2) lactotrophs (prolactin)
What 3 anterior pituitary cell types are classified as basophils? 10%
1) corticotrophs (ACTH)
2) gonadotrophs (LH/FSH)
3) thyrotrophs (TSH)
What makes up the remaining 50% of ant. pit. mass?
Chromophobes (responsible for paracrine actions)
