• Diencephalon: forms central core of forebrain, surrounded by cerebral hemispheres. Made of 3 paired structures: 1) thalamus, hypothalamus, and epithalamus.
  • Thalamus: egg-shaped (known as the inner room) has midline connection called interthalamic adhesion
  • ***EVERY part of the brain that communicated with the cerebral cortex must relay its signals through a nucleus of the thalamus.
  • Hypothalamus: an inferior portion of the diencephalon. Lies between optic chiasma (point of crossover between cranial nerves II/ optic nerve) and the mammillary bodies (rounded bumps)
  • Hypothalamus contains many nuclei and regulates activities of the visceral organs


  • Control of ANS. Controls heart rate, blood pressure, movement of the digestive tube, secretion of sweat glands/ salivary glands.
  • Control of emotional response. Lies at the center of the emotional part of the brain. (limbic system)
  • Regulation of body temperature. Body’s thermostat
  • Regulates hunger/ thirst sensations. Mediates feeling of hunger and thirst
  • Control of motivational behavior. Controls behavior of rewarding/ pleasure. (i.e eating and sex)
  • Regulation of sleep-wake cycle. (contains the suprachiasmatic nucleus)- body’s biological clock. Determines day and night cycle (circadian) rhythms.
  • Controls endocrine system.
  • Formation of memory.
  • Control from the hypothalamus is carried through the periaqueductal gray matter/ medulla’s reticular centers
  • Epithalamus: MOST dorsal part of the diencephalon. Contains pineal gland (hormone-secreting organ) This gland will secrete melatonin. Prepares the body for nighttime.

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