The CNS consists of two main components:
The brain

• The control center of the body, responsible for processing sensory information, coordinating movement, and higher cognitive functions such as thinking, memory, and decision-making.
• It is divided into several regions: the cerebrum, cerebellum, and brainstem, each with specific functions.
  • The cerebrum is further divided into lobes: frontal, parietal, temporal, and occipital, which are involved in various sensory, motor, and cognitive processes.
    The spinal cord
• A long cylindrical structure that acts as a major communication pathway between the brain and peripheral nervous system.
• It consists of 31 pairs of spinal nerves that emerge from it, supplying sensations and movements to specific body regions.
  Anatomy of the Spinal Cord
  The spinal cord extends from:
• Foramen magnum to approximately the L1-L2 vertebrae (lumbar region).
• Enclosed in the vertebral column for protection, providing a bony structure that safeguards it from injury.
  Functions of the Spinal Cord
  Acts as a relay system:
• Information is relayed up to the brain.
• Information is relayed down from the brain.
• Responsible for some reflex actions independently of the brain, such as the knee-jerk reflex, which involves a direct pathway through the spinal cord.
  Key Regions of the Spinal Cord
  Conus medullaris:
• The tapered end of the spinal cord, which signifies where it ends at L1-L2.
  Below the conus medullaris lies the cauda equina:
• A collection of spinal nerves resembling a horse's tail, which continues down the vertebral canal.
  Spinal Cord Enlargements
  Cervical Enlargement:
• Located at the cervical region, responsible for nerves that control the upper limbs.
• It contains increased numbers of motor neurons for controlling the intricate movements of the arms and hands.
  Lumbar Enlargement:
• Located at the lumbar region, responsible for nerves controlling the lower limbs.
• It is essential for coordinating movement and balance in the legs.
  The enlargements occur due to increased nervous tissue needed to control muscle movement in arms and legs.
  Meninges (Protective Layers) of the Spinal Cord
  The meninges are continuous with those covering the brain; composed of three layers:

1. Dura Mater:
   • Tough outer layer that provides strength and protection.
2. Arachnoid Mater:
   • Middle layer, described as 'wetty', which includes a web-like network for cushioning.
3. Pia Mater:
   • Inner layer directly touching the spinal cord, containing many blood vessels that nourish the spinal cord.
     Spaces associated with the meninges:

• Epidural Space:
  • Contains fat and is located above the dura mater, serving as a cushion for the spinal cord.
• Subdural Space:
  • Contains a small amount of serous fluid that acts as a lubricant.
• Subarachnoid Space:
  • Contains cerebrospinal fluid (CSF), which provides buoyancy and protection for the spinal cord.
    Filum Terminale
• Continuation of the pia mater that anchors the spinal cord to the coccyx, helping to stabilize the spinal cord within the vertebral column.
  Lumbar Puncture Procedure
  To withdraw CSF:
• Entry is made into the subarachnoid space, below the spinal cord which ends around L1-L2.
• The lumbar puncture allows access to CSF for diagnostic purposes such as checking for infections or bleeding.
• Care is taken to avoid injury to the spinal cord during this procedure, often performed in a sitting or lying position to minimize risks.