the brainstem

Question 1

what is the brain stem?

Answer 1

the oldest part of the brain
largely to do with survival and basic functions
controlls the autonomic nervous system
around 8cm long
10/12 cranial nerves join the CNS here

Question 2

what are the 3 main subdivisions of the brain stem?

Answer 2

• 3 main subdivisions:
  Midbrain (mesencephalon)
  Pons (metencephalon)
  Medulla (myencephalon)

Question 3

what are the two major components of the midbrain?

Answer 3

• Tectum
  ○ Dorsal auditory and visual system
• Tegmentum
  ○ Rostral end of the reticular formation
  ○ Sleep, arousal, muscle tome, movements and vital reflexes.
  Reticular activation system= RAS

Question 4

what is the midbrain?

Answer 4

• Top of brain stem
• Also known as mesencephalon
• Contains rostral end of RF: damage to this area can result in loss of consciousness or coma
• Two major parts:
  Tectum = “Roof”
  Tegmentum = “Covering”

Question 5

what is reticular formation?

Answer 5

• Reticulum= “little net”- netlike structure
• Large interconnected network of nuclei and neurons
• Runs through the core of the brainstem
• Receives and integrated input from all regions of CNS
  Only part of brain essential to life

Question 6

what are the pons (metencephalon)?

Answer 6

• Latin for bridge
• Connection between cerebrum and cerebellum
• Origin of 4 cranial nerves
• Helps coordinate movement
• Core is reticular formation
• All the way down from the midbrain

Question 7

what is the medulla oblongata (myencephalon)?

Answer 7

• “oblong marrow”
• Most caudal portion of brain stem
• Terminal of brain stem
• Conduit for nerve tracts
• Centre for vital functions such as heart rate, blood pressure and breathing
  Nuclei of the 4 inferior cranial nerves

Question 8

what are the important structures of the midbrain?

Answer 8

• Tectum – relaying audio and visual information
• Inferior colliculus – auditory info
• Superior colliculus – visual info
• Tegmentum – motor centre
• Red nucleus – from brain centres to SC
• Substantia nigra – projects to basal ganglia.

Question 9

what is the red nucleus (midbrain)

Answer 9

Role in muscle tone, posture, gait

Question 10

what happens if the pons become damaged?

Answer 10

• Damage to pontine nucleus or cerebellar peduncles: impaired coordination of movement and/or posture
• Locked-In Syndrome: Lesions in ventral pons render the individual quadriplegic.
• Look like they are in a coma except are able to move their eyes (if given an eye communicating device they can communicate)
• Total locked-in syndrome eyes are paralyzed, as well

Question 11

what happens if the medulla becomes damaged?

Answer 11

• Partial damage can result in Wallenberg syndrome
• Symptoms include: difficulty swallowing (Dysphagia), slurred speech, facial numbness and facial pain