Nervous System Anatomy

• Central Nervous System (CNS)

  brain and spinal cord
• Peripheral Nervous System (PNS)


  Spinal and cranial nerves
• Cranial nerves


  - branch off the brain or brain stem

  - 12 pairs

  - Designated by name/roman numeral

  - carry sensory/afferent - or motor /efferent

  - or both (mixed nerve)
• I Olfactory


  (S) sense of smell
• II Optic


  (S) vision
• III Oculomotor


  (M) - controls 4 of the 6 muscles of eye movement

  - pupils and lens
• IV Trochlear


  (M) - controls 1 of the 6 muscles of eye movement
• V Trigeminal


  (B)

  - s - skin of face

  - m - muscles of mastication
• VI Abducens


  (M) controls 1 of the 6 muscles of eye movement
• VII Facial


  (B)

  - s - taste from anterior 2/3 of the tongue

  - m - muscles of facial expression
• VIII Vestibulocochlear


  (S) sense of hearing and equilibrium (balance)
• IX Glossopharyngeal


  (B)

  - s - taste of posterior 1/3 of tongue

  - m- muscles of swallowing and salivary glands
• X Vagus


  (B)

  - s - taste from posterior throat, sensory from esophagus

  - m - visceral organs
• XI (spinal) accessory


  (M) Trapezius, SCM
• XII Hypoglossal


  (M) muscles of tongue
• Spinal Cord


  - a bundle of nerve tissue

  - base of the brain to about L2

  - Travels within vertebral canal

  - 2 way connection between brain and spinal nerves

  - Has 3 structures protecting it
• 3 structures protecting spinal cord

  - bone

  - meninges

  - cerebro-spinal fluid
• Bone


  In form of vertebral column
• Meninges


  - connective tissue - 3 layers

  - outermost layer - dura mater(string mother)

  - middle layer - arachnoid mater(cobweb like)

  - inner layer - pia mater(gentle mother) - directly on cord surface
• CSF


  cerebrospinal fluid

  - between arachnoid and pia

  - deep to arachnoid (subarachnoid space)

  - ventricles of the brain makes csf
• All structures


  Also surround the brain in form of skull
• Spinal segment


  - each segment gives off a pair of spinal nerves

  - nerve roots extend away from spinal nerves
• Nerve roots


  - exist below each vertebra

  - 7 cirvical

  - 12 thoracic

  - 5 lumbar

  - 5 sacral

  - 1 coccygeal

  In total 31
• Conus medullaris


  Inferior end of spinal cord at about L2

  
• Cauda Equina


  "horse's tail"

  - collection of nerve roots that extend below L2

  
• Filum Termínale


  Extension of pia mater that anchors spinal cord to coccyx

  
• Cervical and lumbar(limbo-sacral) enlargements

  Increases number of neurons to supply appendages
• Inside of spinal cored is made up of

  White and grey matter
• Grey matter forms-


  "H" of spinal cord

  
• Posterior horns


  Cell bodies of sensory neurons

  
• Anterior horns


  Motor neurons

  
• Lateral horns


  Only T1-L2

  - autonomic motor neuron cell bodies

  
• Central canal


  Down the center of the cord- carries CSF

  
• White matter..


  Surrounds grey matter

  - myelinated axons

  - organized into columns or tracts

  - carry descending (motor/efferent) or ascending (sensory/afferent) info

  
• Reflex


  automatic, rapid response to an "emergency" situation
• Reflex Pathway


  - receptor

  - sensory neuron

  - CNS(interneurons maybe)

  - motor neuron

  - effector - usually a muscle but can be gland or organ

  
• Brain


  - same covering as spinal cord

  - bone(skull), meninges, CSF

  - 100 billion neurons

  - cerebrum, cerebellum, brainstem

  
• Cerebrum


  2 halves (cerebral hemisphere)

  
• Cerebellum


  - "little brain"

  - 2 halves (cerebellar hemisphere)

  
• Brainstem


  3 parts (midbrain, pons, medulla oblongata)