Anatomy (CNS) · MU Sofia

159.160 Diencephalon (Interbrain): thalamus, epithalamus, subthalamus.hypothalamus

Covers the diencephalon and its four parts: the thalamus with its nuclear groups and functions, the epithalamus with the habenular nuclei, pineal body and commissures, the subthalamus with its nucleus and reticular nuclei, and the hypothalamus with its connections, functions and a three-unit nuclear classification.

Inside: 6 sections · 10 labelled pictures · 10 flashcards · 9 min

Topic 17 of 34 in the MU Sofia syllabus for Anatomy (CNS) (Medicine, Year 2). The free AceMed note covers it in 6 sections, about 1,311 words (9 min of reading), with 10 flashcards.

In this note

  1. Introduction
  2. DIENCEPHALON
  3. Thalamus :
  4. The epi- thalamus :
  5. Sub-thalamus
  6. Hypothalamus :

Introduction

159 + 160

DIENCEPHALON

  • 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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