Topography of the Brain

Summary

• Parts of the brain
  • Lobes
  • Sulcus and gyrus

Parts of the brain

• Broadly, there are 4 main regions of note in the brain:

1. Cerebral hemispheres (aka telencephalon, cerebrum )
   • Separated by longitudinal fissure
   • Each hemisphere contains a cavity called the lateral ventricles
   • There are multiple regions within the hemispheres (see ‘lobes of the brain’ below)
2. Diencephalon
   • Surrounds the 3rd ventricle
   • Composed of:
     1. Epithalamus (pineal gland)
     2. Dorsal thalamus
     3. Hypothalamus
     4. Thalamus
3. The brainstem
   • Lies within middle/posterior cranial fossae
   • Made up of 3 parts:
     • Midbrain (Mesencephalon)
       • Most rostral part of the brainstem
       • Between the middle/posterior cranial fossae
       • Contains cerebral aqueduct
     • Pons
       • Middle part of brainstem
       • Lies in posterior cranial fossa
       • Part of the 4th ventricle
     • Medulla oblongata
       • Caudal part of brainstem
       • Continuous with spinal cord
     • The main parts of the brain. Note that the forebrain includes both telencephalon (cerebrum) and diencephalon.
4. Cerebellum
   • Below tentorium cerebri
   • 2 hemispheres joined by the vermis

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Lobes of the cerebral hemispheres

• There are six main areas of the cerebrum to consider (FM SPOT):
  • Frontal lobe – responsible for planning and personality
  • Motor Cortex – movement
  • Sensory Cortex – sensations
  • Parietal lobe – spelling, calculations, perception
  • Occipital lobe –Vision
  • Temporal lobe – Memory, language
• Connected by corpus callosum
  • This unites hemispheres via commissural fibres
  • Also have other commissures

    

• The sulci and gyri are part of the cerebral cortex (i.e. the surface of the brain)
  • Sulcus – depressions
  • Gyrus – ridges

    

  • Certain fixed sulcus’/gyrus’ serve as landmarks of separations between lobes
    • Central sulcus separates parietal and frontal lobes
    • Pre-central gyrus – contains the primary motor cortex
    • Post-central gyrus –  contains the primary sensory cortex

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