Brain Structures and Protection

Brain Divisions

  • Cerebrum: Outer portion of the brain.
  • Brainstem: Connects the brain to the spinal cord.
  • Diencephalon: Central portion of the brain.
  • Cerebellum: Located in the posterior portion of the brain.

Protective Structures of the Brain

  • Ventricles: Cavities within the brain filled with cerebrospinal fluid (CSF).
    • Two lateral ventricles.
    • One third ventricle.
    • One fourth ventricle, which drains into the central canal of the spinal cord.
  • Meninges: Layers of tissue that anchor and protect the brain.
    • Dura mater: Tough, double-layered fibrous tissue that blends with the skull.
    • Subdural space: Space below the dura mater.
    • Arachnoid layer: Loose layer resembling a spider's web.
    • Subarachnoid space: Space below the arachnoid layer, containing CSF.
    • Pia mater: Tightly adhered to the brain tissue itself.

Cerebrospinal Fluid (CSF)

  • Formed through the walls of the ventricles from blood plasma.
  • Permeates through the choroid plexus: a network of blood vessels within the ventricles.
  • Protects the chemical environment of neurons.
  • Cushions the brain and spinal cord.
  • Provides buoyancy so the brain can float inside the skull.

Blood-Brain Barrier

  • Diffusion barrier formed by astrocytes surrounding brain capillaries.
  • Prevents certain particles from entering the brain.
  • Necessary for maintaining a stable chemical environment for neurons.

Cerebrum

  • Left and right cerebral hemispheres, separated by the median longitudinal fissure.
    • The left side of the brain controls the right side of the body, and vice versa.
  • Gyri: Raised ridges on the surface of the brain.
  • Sulci: Grooves between the gyri.
  • Fissures: Deep grooves (e.g., median longitudinal fissure).
    • Right and left central sulcus: grooves that go all the way from the top through the bottom.

Lobes of the Brain

  • Frontal lobe: Controls higher executive functioning, reasoning, and decision-making skills.
  • Parietal lobe: Receives sensory information from the body (touch, pain, etc.).
  • Temporal lobes: Receive sensory information for hearing and smell.
  • Occipital lobes: Receive visual information from the eyes.

Functional Areas of the Brain

  • Primary areas: Direct processing of primary sensory or motor input.
  • Association areas: Integrate information from different lobes of the brain.
    • Primary motor area: Controls voluntary movements.
    • Primary sensory area: Receives direct sensory input.
    • Broca's area: Responsible for speech production, located in the frontal lobe.
    • Wernicke's area: Responsible for understanding speech, located in the temporal lobe.

Functions of the Cerebrum

  • Consciousness: State of being aware of surroundings.
  • Intelligence and reasoning, especially involving the frontal lobe.
  • Controls lower brain areas: brainstem, diencephalon, limbic system, and cerebellum.

Brainstem

  • Medulla oblongata:
    • Contains ascending and descending tracts between the spinal cord and higher brain centers.
    • Regulates heartbeat, breathing, vasoconstriction (blood pressure), vomiting, coughing, swallowing, and hiccuping.
  • Pons:
    • Contains bundles of axons between the cerebellum and other parts of the central nervous system.
    • Functions with the medulla for heartbeat regulation.
  • Midbrain:
    • Relay station for tracts between the cerebrum, spinal cord, and cerebellum.
    • Contains superior and inferior colliculi for head, neck, visual, and auditory stimuli control.
    • Reflex centers for visual, auditory, and tactile systems.