Hypothalamus Flashcards
Which 6 hormones are produced by the pars distalis of the adenohypophysis (anterior pituitary)?
- GH
- LH
- FSH
- ACTH
- Prolactin
- TSH
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Which 3 hormones are made by the pars intermedia of the adenohypophysis (anterior pituitary)?
- MSH
- Endorphin
- Dopamine
Which hormones are stored in and release by the pars nervosa of the neurohypophysis (posterior pituitary)?
- Oxytocin
2. AntiDiuretic Hormone/Vasopressin
Describe hypophysis (pituitary) vasculature
- Pars distalis has no direct arterial supply; receives oxygen from hypothalamohypohyseal portal system
- Both anterior/posterior pituitary share a common venous drainage
- Venous blood from the hypothalamus drains to the Pars Distalis of the Adenohypophysis before continuing to the heart
Rostral hypothalamus contains
- Supraoptic area
2. Paraventricular nucleus
Middle hypothalamus contains
- Ventral medial nuclei
2. Arcuate nuclei
Caudal hypothalamus contains
- Mammillary nuclei
2. Caudal nuclei
What are the four hypothalamic inputs?
LARA
- Limbic structures (amygdala)
- Autonomic Nervous System
- Reticular formation of brainstem
- Ascending aminergic pathways (noradrenaline, serotonin, dopamine)
Adrenocorticotrophic hormone (ACTH)
Produced by pars distalis of anterior pituitary
Stimulates adrenal cortex to make cortisol (a glucocorticoid); negative feedback
Corticotropin Releasing Hormone (CRH)
Produced by hypothalamus
Stimulates cleavage of POMC -> release of ACTH from pituitary
Downregulated by cortisol (negative feedback)
Regulation of prolactin
- TRH from hypothalamus stimulates
- Dopamine from hypothalamus inhibits
- Negative feedback: PRL stimulates dopamine release
Regulation of LH and FSH
- GnRH from hypothalamus stimulates release of LH and FSH from anterior pituitary
- Testosterone/estrogen inhibits pituitary and hypothalamus
- Prolactin also inhibits GnRH release
Where are LH and FSH produced?
Gonadotrophin cells of adenohypophysis
Functions of LH
- Ovaries -> stimulates steroid hormone production
- Testicles -> stimulates release of testosterone from Leydig cells
- Stimulates maturation of germ cells
Functions of FSH
- Ovaries -> stimulates granulosa cell development
- Testicles -> stimulates release of androgen binding proteins from Sertoli cells (initiates spermatogenesis)
- Stimulates maturation of germ cells
Regulation of GH
- Stimulated by:
a. GHRH from hypothalamus
b. Thyroxine
c. Grehlin/hypoglycaemia - Inhibited by:
a. Somatostatin from hypothalamus
b. Free fatty acid (negative feedback)
c. IGF-1 from liver (negative feedback)
GH functions
Stimulates production of somatomedin, which promote:
a. T-cell proliferation
b. Calcium absorption
c. Hepatic Glycogenolysis (raises blood glucose)
d. Growth
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TRH is released by the ______ whereas TSH is released by the ______.
TRH - hypothalamus
TSH - pituitary
Where is TRH produced?
TRH - Parvocellular neurons in paraventricular nucleus
Don’t confuse with TSH, which comes from the pituitary
CRH
- Released from hypothalamus
2. Promotes ACTH release from anterior pituitary
GHRH
- Released from hypothalamus
2. Promotes GH/somatropin release from anterior pituitary
TRH
- Released from hypothalamus
2. Promotes TSH, Prolactin, and POMC [ACTH precursor] release from pars intermedia of anterior pituitary
GnRH
- Released from hypothalamus
- Promotes FSH and LH release from anterior pituitary
- Release INHIBITED by prolactin
Somatostatin
- Released from hypothalamus
2. Inhibits GH release from anterior pituitary
