Structure and function of the hypothalamus

Structure

Small 4g diencephalon structure
Bounded by lamina terminalis anteriorly, 3rd ventricle superiorly and medially, pituitary (via infundibulum) inferiorly, tegmentum posteriorly
Anterior, medial, lateral, and posterior zones

Functions

Anterior zone has 4 main nuclei, 3 of which sound identical
Preoptic nucleus \(\to\) central thermoreceptors, thermostat function, coordinates with posterior area to achieve thermal homeostasis
Supraoptic nucleus \(\to\) receives input from vascular organ of lamina terminalis (central osmoreceptor) \(\to\) secretes ADH to maintain osmotic homeostasis
Suprachiasmatic nucleus \(\to\) regulates circadian rhythm, controls melatonin release from pineal gland
Paraventricular nucleus \(\to\) secretes oxytocin
Lateral zone \(\to\) promotes hunger, wakefulness, heightened emotional states (e.g. aggression)
Medial zone \(\to\) promotes satiety (inhibits lateral zone), sexual behavior. Secretes hormones to anterior pituitary
Posterior zone \(\to\) controls . Receives signals from preoptic nucleus \(\to\) SNS-mediated thermogenesis \(\uparrow\)body temperature

Hormones released via axonal projections to posterior pituitary

The anterior pituitary system

Portal blood flow through superior hypophyseal artery \(\to\) hypothalamic capillaries \(\to\) portal vessels \(\to\) anterior pituitary ensures hormones secreted by medial zone of hypothalamus affect pituitary
Hypothalamic hormone \(\to\) pituitary hormone \(\to\) systemic hormone
TRH \(\to\) TSH \(\to\) T3/4
CRH \(\to\) ACTH \(\to\) cortisol
GHRH \(\to\) growth hormone \(\to\) insulin-like growth factor 1
GnRH \(\to\) FSH and LH \(\to\) oestrogen and testosterone
Dopamine \(\xrightarrow{inhibits}\) prolactin