Central Nervous System

Central Nervous System

1. Brain

   • Made of inner portion of white matter & an outer portion called the cortex
   • Consists of cerebrum, cerebellum and and brain stem
     • the cerebrum is the largest part of the brain
       • its referred to as the forebrain
     • the midbrain connects the cerebrum to the pons and cerebellum
     • the hindbrain is made up of cerebellum, pons, and the medulla oblongata
       • the cerebellum is the largest part of the hindbrain

2. Spinal Cord

   • this is an elongated slender structure that extends from the brain to the to the level of L1/L2
     • 18-20 inches long in an adult
     • connects to 31 pairs of spinal nerves
     • the spinal cord and nerves work together to transmit and receive sensory, reflex and motor messages to and from the brain.
       • The spinal cord ends in a pointed structure called the conus medullaris
         • the filum terminale is a delicate strand the extends from the terminal tip to the coccygeal segement
           • Nerves below the termination of the spinal cord are referred to as the cauda equina because they resemble a horses tail

3. Meninges

   • the meninges are 3 continuous protective layers that enclose the brain and spinal cord.
     • The inner layer is the Pia Mater
       • this layer is very vascular and closely adheres to the brain and spinal cord
     • The outer layer is the Dura Mater
       • this is the strong fibrous covering brain and spinal cord
         • it is made of an inner and outer layer
           • this layer is separated from the arachnoid by the subdural space and from the vertebral periosteum by the epidural space
             • the dura mater extends below the spinal cord to the second sacral segement
     • The middle layer is the Arachnoid
       • this delicate layer is separated from the pia mater by the subarachnoid space
         • Some of these spaces are wider than other and are known as arachnoid cisterns
           • the widest is known as the cisterna magna
         • the ventricles of the brain and the subarachnoid space contain cerebrospinal fluid (CSF)
           • CSF surrounds the brain and spinal cord and cushions all the central nervous system structures

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