L70-Hypothalamic Pituitary Relationship Flashcards
Where is the hypothalamus located?
below thalamus between the lamina terminals and mammillary bodies, forming the floor of 3rd ventricle
What does the hypothalamus secrete?
Hypothalamic releasing hormones
What is the median eminence?
Floor of hypothalamus that acts as convergence point for axons
What are the hypothalamic nuclei?
PVN: paraventricular Nucleus POA: Preoptic Nucleus ARC: Arcuate Nucleus SCN: Suprachiasmatic Nucleus SON: Supraoptic nucleus
Which nucleus secretes GnRH?
POA: preoptic nucleus
What nucleus secretes CRH?
PVN: paraventricular/Parvocellular
What nucelus secretes TRH?
PVN: paraventricular
What nucleus secrete GHRH?
Arcuate Nucleus
What nucleus secretes soatostatin?
PeVN : periventricular
What nucleus secretes Dopamin?
Arcuate nucleus
Which peptide hormones use the cAMP second messenger pathway?
CRH, GHRH, Somatostatin
Which peptide hormones use the IP3/DAG/PKC pathway?
TRH, GnRH,
How is GnRH released?
Pulsatile manner and acts through GPCRs
What is Kallman Syndrome?
Genetic disease where GnRH neurons fail to enter CNS
Leads to reproductive failure and anosmia
Can be X linked (Kal1) or Autosomal (Kal2)
GnRH neurons are arrested at the cribiform plate in X linked Kallman Syndrome
Describe the sequence of events in which GnRH activate gonadotrophs
GnRH released from hypophyseal portal system -> bind to GnRH receptor (GPCR) -> activate PLC -> form IP3 and DAG -> mobilize intracellular calcium and activate PKC-> increased LH/FSH release and synthesis
How does GnRH pulse frequency determine LH or FSH transcription?
High GnRH pulse frequency-> LH(Beta) transcription
Low GnRH Pulse Frequency-> FSH (beta) transcription
Which hormones share the same alpha subunit?
FSH-B, LH-B, TSH-B, hCG-B
What is the pituitary blood supply?
Superior hypophyseal artery give rise to capillary plexus in anterior pituitary -> primary capillary plexus in median eminence-> hypophyseal portal veins -> secondary capillary pelxus in pars distalis
Inferior hypophysial artery supplies posterior pituitary
What are the 2 major pathways between the hypothalamus and pituitary?
Tuberoinfundibular System: neurons sending axonal projections to median eminence with hormones targeting anterior pituitary
Neurohypophysial Tract: Neurons whose axons terminate in posterior pituitary
What makes up the anterior pituitary?
Pars Distalis (90%)
Pars Tuberalis
Pars Intermedia
What makes up the Posterior Pituitary
Pars Nervosa
Infundibulum
How is the tissue between anterior and posteiror pituitaries different?
Anterior pituitary is glandular tissue from embryonic foregut
Posterior pituitary is neural tissue from neuroectoderm
What neurons have their axons terminate in the neurohypophysis of the posterior pituitary
Magnocellular Neurons
What is the blood supply of the posterior pituitary?
Inferior hypophysial artery
What are the major hormones released from the posterior pituitary
AVP and Oxytocin
What are Herring Bodies?
Dilations of unmyelinated axons near the terminals found in the neural tissue in the posterior pituitary; This is where hormones are released and are close to fenestrated capillaries
What are pituicytes?
glial like cells of the posterior pituitary
What cell types are found in the anterior pituitary and how do they stain?
Acidophils(lght): somatotrophs, lactotrophs
Basophils(dark): Corticotrophs, Gonadotrophs, Thyrotrophs
Chromophobes(clear): Paracrine actions
What do the acidophils secrete?
Somatotrophs: GH
Lactotrophs: Prolactin (lactation)
What do the basophils secrete?
Corticotrophs: ACTH (stress)
Gonadotrophs: FSH, LH
Thyrotrophs: TSH
How are the anterior pituitary hormone cell types regionally distributed?
TSH centrally and anterior
ACTH centrally and middle and posterior
GH/PRL: anterior to posterior on the sides
