Anatomy Bones and Muscles · MU Pleven

133. Diencephalon – thalamus, epithalamus, metathalamus.

Covers the diencephalon's division into dorsal and ventral parts, then the thalamus: its surfaces, its five nuclear groups and their relay functions, and the metathalamus. Closes with the epithalamus, including the habenular nuclei and commissure, the posterior commissure and the pineal body. Includes several labelled pictures and a note on the habenular nuclei's neurotransmitters.

Inside: 3 sections · 5 labelled pictures · 10 flashcards · 5 min

Topic 132 of 236 in the MU Pleven syllabus for Anatomy Bones and Muscles (Medicine, Year 2). The free AceMed note covers it in 3 sections, about 725 words (5 min of reading), with 10 flashcards.

In this note

  1. DIENCEPHALON
  2. Thalamus:
  3. The epi-thalamus:

DIENCEPHALON

159 +160

  • The diencephalon is a central part of the brain.

It is divided by a hypothalamic sulcus which extends from the interventricular foramen to the cerebral aqueduct into:

  • Dorsal part: including thalamus and epithalamus.
  • Ventral part: including hypothalamus and subthalamus.
  • The cavity of the diencephalon is the 3rd ventricle.

Thalamus:

  • It is an oval mass of grey matter situated on each side of the diencephalon extending between the anterior commissure and the base of pineal gland. It has:
  • 2 ends: anterior end (lying posterior to the Interventricular foramen) and posterior expanded end (the pulvinar).
  • Superior surface: forming part of the floor of lateral ventricle (the cavity of the cerebral hemisphere).
  • Inferior surface: separated from hypothalamus by the hypothalamic sulcus.
  • Lateral surface: separated from lentiform nucleus (one of the basal nuclei) by the internal capsule (see white matter of the cerebral hemispheres).
  • Medial surface: forms the lateral wall of the 3rd ventricle. Both medial surfaces are connected by a projection of grey matter (inter-thalamic adhesion), but no fibers cross the midline.

Thalamic nuclei and their functions:

Thalamus is the gateway of the cerebral cortex, as it relays all sensations (except smell) and acts as filter which passes on only a small portion of the arriving sensory information. It also controls the activities of basal nuclei (part of the cerebrum) and cerebral cortex by relaying information between them.

Thalamus has five major groups of nuclei:

  • Nuclei of the anterior group: they form part of the limbic system (a system concerning with emotion and motivation).
  • Nuclei of the medial group: they receive and relay sensory information from other parts of thalamus. They also provide awareness of emotional states by making connections between emotional centers of the hypothalamus and frontal lobes of the cerebral hemispheres.
  • Nuclei of the ventral group: they relay information from basal nuclei and cerebellum to somatic motor areas of the cerebral cortex, and also relay sensory information about (touch, pressure, pain, temperature, and sense of position) to the sensory areas of the cerebral cortex.
  • The posterior group: includes pulvinar nuclei and geniculate nuclei:
  • Pulvinar nuclei: integrate sensory information for projection to association areas of the cerebral cortex.
  • Medial geniculate nucleus: relays auditory information from special receptors of inner ear to the auditory areas of the cerebral cortex.

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