7. BRAINSTEM

• Brainstem


  Consists of: Midbrain, Pons, Medulla oblongata
• Brainstem


  • Located in posterior cranial fossa
  • Continuous with cerebral hemisphere above
  • Continuous with spinal cord below
• Midbrain


  • Continuous with cerebral hemisphere above
  • Connected to cerebellum by superior cerebellar peduncle
• Pons


  • Connected to cerebellum by middle cerebellar peduncle
  • Contains white matter tracts and gray matter nuclei
• Medulla oblongata


  • Transition from spinal cord to brain
  • Contains vital autonomic cardiovascular and respiratory centers
  • Composed of gray matter, cranial nerve nuclei 9-12, and white matter tracts
• Cranial nerves emerging from brainstem

  • CN III (oculomotor)
  • CN IV (trochlear)
  • CN V (trigeminal)
  • CN VI (abducens)
  • CN VII (facial)
  • CN VIII (vestibulocochlear)
  • CN IX (glossopharyngeal)
  • CN X (vagus)
  • CN XI (accessory)
  • CN XII (hypoglossal)
• Functions of brainstem


  1. Serves as channel for ascending and descending tracts

  2. Contains reflex centers for respiration and cardiovascular system

  3. Contains nuclei of cranial nerves III-XII
• Midbrain


  • Cerebral peduncles (anterior)
  • Tegmentum (posterior)
  • Cerebral aqueduct connecting 3rd and 4th ventricles
• Pons


  • Ventral pons (white matter tracts)
  • Dorsal tegmentum (white matter tracts and gray matter nuclei)
• Medulla oblongata


  • Ventral medulla (olive, pyramidal tracts, cranial nerves 9-12)
  • Dorsal tegmentum (cranial nerve nuclei and white matter tracts)