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.