Major Parts Of The Brain

Embryonic brain

Yes, the above photo is of a walnut.

With over 20 billion neurons, each collecting and organizing information from thousands of other neurons simultaneously, the brain is far more complicated than any computer.

To begin our journey of

the inside of the mind we start at embryology. The central nervous system begins as a hollow tube filled with fluid. Within week 3, this cavity expands into enlarged chambers called ventricles, there are three;

  • Proencephalon
  • Mesencephalon
  • Rhombencephalon

Image result for brain stemBy week 4 these further separate into distinct structures. 

  • Proencephalon
    • Telencephalon
      • At birth this is considered to be the cerebrum.
    • Diencephalon
      • Has a ‘roof’ (the epithalamus) and ‘walls’ (the right and left thalamus). The eyes form from each side of the diencephalon.
  • Mesencephalon
    • Does not divide but the walls do thicken and the central canal becomes similar to spinal cord.
  • Rhombencephalon
    • Metencephalon
      • Anterior portion of this structure becomes the pons, the posterior into the cerebellum.
    • Meylencephalon
      • This forms the medulla oblongata.

There are six major parts inside the adult brain; the cerebrum, diencephalon, mesencephalon, pons, medulla oblongata, and the cerebellum. The mesencephalon, pons and medulla oblongata make up the brain stem (truncus cerebri) while the cerebrum and cerebellum surround this. The brain stem processes info to and from the cerebrum and cerebellum.


In order from inferior to superior, details of these regions are as follows;

  • Medulla Oblongata
    • Connects the brain stem to the spinal cord
    • Relays sensory information from the spinal cord to the thalamus
    • Connects major centers that regulate autonomic functions such as heart rate, blood pressure and the digestive system
  • Pons
    • Connects the cerebellum to the brain stem
    • Contains nuclei (bundles of cell bodies in the CNS) that control somatic and visceral motor functions
  • Related image
    The parts of the diencephalon

    Mesencephalon (Midbrain)

    • Nuclei here process auditory and visual information
    • Coordinates reflexive somatic motor responses to visual and auditory stimuli
    • Contains centers that maintain levels of consciousness
  • Diencephalon (three parts)
    • Epithalamus: includes the pineal gland that secretes hormones (endocrine
    • Thalmus (right and left): sensory information is relayed and processed here.
    • Hypothalamus: This has centers for emotion. It connects to the pituitary gland that uses hormones whereby linking the endocrine and nervous system
  • The Cerebellum
    • This automatically adjusts motor movements based on sensory stimuli.
  • The Cerebrum
    • The cerebrum is made of grey matter on the outside (cerebral cortex) and white matter.
    • The structure is wrinkled with sulci into ridges named gyri.
    • This is responsible for conscious thought, memory storage, complicated motor functions and intellect.

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