Central Nervous System Overview

Arachnoid Dura and Its Layers

  • The dura mater consists of two layers:
    • Periosteal layer: forms the interperiosteum of cranial bones.
    • Meningeal layer: adheres to the periosteal layer except in certain locations.
  • These layers separate in specific areas, creating:
    • Venous sinuses: blood-filled spaces that assist in draining blood from the brain.
    • Cranial septa: structures that anchor and divide brain regions.

Cerebrospinal Fluid (CSF)

  • CSF is produced in choroid plexuses located in the ventricles, which are lined with ependymal cells.
  • CSF flows over the brain, providing cushioning and nutrient transport.

Overview of Brain Structure

  • The brain is divided into three major regions:
    • Forebrain: includes the diencephalon (epithalamus, thalamus, hypothalamus, and cerebrum).
    • Midbrain: consists of structural components like the corpora quadrigemina and cerebral peduncles.
    • Hindbrain: includes the pons, medulla oblongata, and cerebellum.

Key Components of the Brain

  • Forebrain:
    • Diencephalon:
    • Epithalamus: contains the pineal gland (secretes melatonin).
    • Thalamus: relays sensory information to the cortex (often referred to as a switchboard).
    • Hypothalamus: regulates the autonomic nervous system and hormones.
    • Cerebrum: outer gray matter known as the cerebral cortex, includes lobes:
    • Frontal, parietal, temporal, and occipital lobes.
    • Insula: a separate lobe involved in taste perception (gustation).

The Insula and Gustation

  • The insula contains the gustatory center, responsible for taste perception.
  • Gustation refers to the sense of taste; olfaction refers to the sense of smell.
  • The insula processes feelings of disgust, linking physical disgust with moral disgust, showing evolutionary repurposing of brain structures.

Cerebral Cortex and Cognitive Functions

  • The cerebral cortex is involved in higher cognitive functions, including:
    • Integration and processing of sensory information.
    • Representation of moral and emotional responses, such as disgust.
  • Gray matter: houses circuits of neurons for data integration, while white matter consists of myelinated axons that connect brain regions.

Types of Fiber Tracts in the Brain

  • Fiber tracts signify connections within the brain:
    • Association tracts: connect regions within the same hemisphere.
    • Commissural tracts: connect the left and right hemispheres (e.g., corpus callosum).
    • Projection tracts: connect the cerebrum to lower brain regions and the spinal cord.

Split Brain Syndrome

  • The corpus callosum can be severed to control seizures, resulting in split-brain syndrome, affecting communication between hemispheres and resulting in unique cognitive and perceptual behaviors.

The Limbic System

  • Cerebral nuclei are deep gray matter structures involved in memory and emotional regulation:
    • The hippocampus focuses on short-term memory transfer to long-term memory.
    • Amygdala: associated with fear, anxiety, and emotional responses; overactivity linked to PTSD.

Spinal Cord Structure & Function

  • The spinal cord is divided into five regions: cervical, thoracic, lumbar, sacral, and a few fibers from the coccygeal region.

General Structure of the Spinal Cord

  • The spinal cord displays two enlargements (cervical and lumbar) representing greater diameter indices.
  • The gray matter contains neuronal cell bodies, while the white matter encompasses ascending and descending tracts of myelinated axons.

Funiculi and Horn Structures in the Spinal Cord

  • Funiculi :regions of white matter (posterior, lateral, anterior).
  • Gray horns house sensory and motor neurons:
    • Posterior horn: contains sensory neurons.
    • Lateral horn: contains visceral motor neurons.
    • Anterior horn: contains somatic motor neurons.

Peripheral Nervous System (PNS)

  • The PNS includes all nerves and ganglia outside the CNS:
    • Nerves: bundles of myelinated axons (sensory and motor).
    • Ganglia: clusters of neuronal cell bodies.
  • Specific cranial nerves (12 total) include crucial functions like olfaction, vision, motor control, and sensory perception.

Summary of Cranial Nerves

  • Notable cranial nerves and their functions include:
    1. Olfactory - Smell.
    2. Optic - Vision.
    3. Oculomotor - Eye movement.
    4. Trochlear - Eye movements.
    5. Trigeminal - Sensory to the face.
    6. Facial - Facial expressions.
    7. Vestibulocochlear - Hearing and balance.
    8. Glossopharyngeal - Tongue and throat.
    9. Vagus - Autonomic functions.
    10. Accessory - Neck and shoulder movement.
    11. Hypoglossal - Tongue movement.