Structural Anatomy of the Human Brain

This note covers the basic building blocks and organization of the human brain.

I. Cellular Composition

• The brain consists of two main cell types:

  • Neurons: Specialized cells for processing and transmitting information.

    • They have various shapes and sizes depending on function.
    • Key parts:
      • Cell body: Contains nucleus and organelles for energy and protein synthesis.
      • Dendrites: Receive signals from other neurons.
      • Axon: Transmits signals to other neurons.
      • Axon terminals: Communicate with other neurons.

    Detailed Image of Neuron

  • Glia: Supportive cells for neurons.

    • Outnumber neurons and perform various functions:
      • Provide structure and scaffolding.
      • Maintain neuronal environment.
      • Insulate axons (myelin) for faster signal transmission.
      • Three type of Glia
        • Astrocytes
        • Microglia
        • Oligodendrocytes II. Brain Organization

• Large group of similar and spatially organized neurons form the basis of dissociable brain structure and networks There are three main ways to organize the brain:

• Cytoarchitectural Organization (Brodmann Areas):

  • Based on cell structure and composition.
  • Defined by Korbinian Brodmann in 1909.
  • Still used to locate brain regions in neuroimaging.
  • Applicable to various mammals (human, hedgehog, rabbit, etc.)
  • Brain atlases provide detailed Brodmann area information. (Print & electronic)
  • 

[!Explore More] https://en.wikipedia.org/wiki/Brodmann_area https://www.kenhub.com/en/library/anatomy/brodmann-areas

• Functional Networks:

  • Groups of brain structures connected for specific functions.
  • Examples:
    • Striatum (includes nucleus accumbens, caudate nucleus, putamen) - involved in reward and movement.
    • Medial temporal lobe (hippocampus, entorhinal cortex, perirhinal cortex) - crucial for memory formation.

• Lobes:

  • Rudimentary anatomical classification based on location.
  • Six lobes with generally associated functions:
    • Frontal lobe: involved in planning, decision-making, movement.
    • Parietal lobe: involved in processing touch, spatial awareness.
    • Occipital lobe: involved in processing vision.
    • Temporal lobe: involved in processing hearing, memory, emotion.
    • Limbic lobe: involved in processing emotions and memory.
    • Insular cortex: involved in various functions like taste, self-awareness.

Understanding the brain’s cellular composition and organization is crucial for studying its function and dysfunction.

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Vascular Anatomy of the Human Brain

The Brain Needs a Lot of Energy:

• The brain requires a tremendous amount of energy and oxygen to function properly.
• This is delivered through a complex system of arteries and veins.

Blood Supply System:

• The internal carotid artery is the main supplier of blood to the brain.
  • It originates from the aorta and splits from the common carotid artery.
  • The external carotid artery supplies blood to the face and skull.
• The internal carotid arteries lead to the Circle of Willis.

Circle of Willis:

• This is a ring-like structure formed by arteries at the base of the brain.

• It acts as a distribution hub for blood flow to different brain regions. Blood Distribution from the Circle of Willis:

• Several arteries and veins branch out from the Circle of Willis, each supplying specific brain areas.

  • Listed arteries include:
    • Anterior cerebral artery
    • Middle cerebral artery
    • Posterior cerebral artery
    • Superior cerebellar artery
    • Pontine arteries
    • Anterior inferior cerebellar artery
    • Vertebral artery
    • Posterior inferior cerebellar artery

Cortical Vascular Territories:

• Specific brain regions (cortical territories) are supplied by dedicated arteries from the Circle of Willis.
• These territories have defined boundaries with minimal overlap.
• This specific blood supply is important for neuroimaging techniques.

[!Explore More]