Hypothalamus [hypo, Greek = below; thalamus, Greek = bed]

= part of diencephalon below the thalamus

Origin: neuroectoderm

Boundaries:

1. anterior = lamina terminalis extending from anterior commissure to optic chiasm
2. posterior = line extending from mamillary bodies to posterior commissure
3. lateral = medial thalamus
4. inferior = tuber cinereum (posteriorly) + median eminence (middle) + infundibular stalk (anteriorly)

Function: homeostasis for blood pressure, body temperature, fluid + electrolyte balance, body weight

Regulatory mechanism:

1. endocrine secretion:
   • neuronal stimulation of posterior pituitary gland via infundibulum
   • hypothalamic releasing factors to anterior pituitary gland via portal plexus as a vascular conduit
2. autonomic function
3. emotions