Hypothalamic-pituitary relationship (L3) Flashcards
Relative anatomical location of the hypothalamus
Between the lamina terminalis and the mammillary bodies
Median eminence
Forms a base at the base of the third ventricle; convergence point for hypothalamic hormone release to the pituitary
What regulates sleep?
Suprachiasmatic nucleus
What regulates feeding behavior/satiety?
Arcuate nucleus
What regulates thirst?
Paraventricular nucleus
What regulates reproduction?
Preoptic nucleus
What regulates circadian rhythms?
The suprachiasmatic nucleus
What regulates mood/stress?
Paraventricular and arcuate nuclei
What regulates body temperature?
Preoptic nucleus
What regulates blood pressure?
Paraventricular nucleus
Location for cell bodies for gonadotropin releasing hormone (GnRH)
Scattered throughout brain, but mostly concentrated in the preoptic nucleus
How many GnRH neurons do humans have?
Only 1500-2000, which is relatively few
How are downstream effects mediated by GnRH?
Through GPCRs
How long is GnRH?
10 amino acids
In what manner is GnRH released?
Pulsatile; OBLIGATORY
Incidence of Kallmann syndrome
Rare; 1/8,000 men, 1/40,000 women
Clinical manifestations and causes of Kallmann syndrome
Anosmia and reproductive failure; failure of GnRH neurons to enter the CNS
Heritability of Kallmann syndrome
X-linked: Kal1
Autosomal: Kal2
From where do GnRH neurons migrate during fetal development?
From olfactory placode through cribriform plate into forebrain
Downstream effects of GnRH binding to its GPCRs
Activation of PLC cleaving PIP2 to IP3 and DAG, leading to increased intracellular Ca2+ and PKC activation.
GAP
GnRH-associated peptide: part of prohormone for GnRH
High pulse frequency with GnRH
Preferentially releases leutinizing hormone (1 pulse every 30-60 minutes)
Slow pulse frequency with GnRH
Preferentially releases FSH (once every 2-3 hours)
Superior hypophysial artery
Gives rise to the capillary plexus - “portal plexus” of the anterior pituitary
Inferior hypophysial artery
Supplies the posterior pituitary
Course of the superiorhypophysial artery
Breaks into primary capillary plexus that supplies the median eminence, then drains into the hypophyseal portal veins and secondary capillary plexus that supplies the pars distalis
Tuberoinfundibular system
All neurons that send neurons to the median eminence, and hormones then target the anterior pituitary through the capillary system
Neurohypophysial tract
Neurons whose axons terminate in the posterior pituitary
Parts of the anterior pituitary
Pars distalis (90%) Pars intermedia Pars tuberalis
Parts of the posterior pituitary
Pars nervosa
Infundibulum (stalk)
Derivations of the anterior pituitary
Glandular tissue derived from embryonic foregut
Derivations of the posterior pituitary
Neural tissue from neuroectoderm
Axons from the __ __ terminate in the neurohypophysis
magnocellular neurons
Herring bodies
Dilations of unmyelinated axons near the terminals; site of hormone release in the posterior pituitary
Herring bodies are in close proximity to what structures
Fenestrated capillaries
Pituicytes
Small, darkly stained cells; glial-like cells of the posterior pituitary
Acidophils
Somatotrophs and lactotrophs
Basophils
Corticotrophs, gonadotrophs, and thyrotrophs
Chromotrophs
Appear clear on stain; have paracrine actions
Topographical distrubution of cell types in the anterior pituitary
TSH near top
ACTH in middle
GH/PRL on the sides
FSH/LH throughout
