Diencephalon

Diencephalon:
Central area of forebrain surrounded by cerebral hemispheres (considered subdivision of cerebrum). Consists of three symmetrical structures (thalamus, hypothalamus, epithalamus)  enclose third ventricle

Thalamus:
2 egg/oval shaped masses of gray matter on each site of third ventricle; about 30mm long and 15mm wide; major part of diencephalon (80%).
consist of a complicated collection of interconnected neurons; has a number of nuclei, whose function is not clearly established
functions to relay and process large amounts sensory inputs to the sensory cortex for interpretation and the inputs to and from the cerebral motor cortex and lower motor centres – it is the ‘central switching station’ of the brain

Hypothalamus:
small structure located below thalamus and on top of brain stem, in centre of limbic system (forms wall and floor of third ventricle) – has diverse functions
inferiorly has a short stalk (infundibulum) to attach to pituitary gland; controls pituitary via neuropeptides (eg oxytocin, vasopressin or ADH)
has many converging and diverging pathways of neurons; as good blood supply (allows sampling of blood chemistry)
has a number of nuclei and fibre tracts  each has specific function
responsible for body homeostasis via control of autonomic nervous system and endocrine systems; regulates body temperature, food intake, gastrointestinal activity, thirst, hormonal outputs of anterior pituitary gland, water balance, blood pressure, sleep-wake cycles and circadian rhythms, emotional behaviour

Epithalamus:
dorsal part of diencephalon – roof of third ventricle
consists of habenular nucleus (small groups of neurons that integrates olfactory, visceral and somatic afferent pathways; acts as relay for limbic system) and pineal gland (gland  secretes melatonin)

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