L3 - Brainstem and Cerebellum

Question 1

Nervous System:

Answer 1

Central Nervous System:

• Brain and spinal cord

Peripheral nervous system:

• Somatic (voluntary motor and sensory control)
• Autonomic (involuntary mechanisms e.g. HR, RR, stress etc.)

Autonomic Nervous System:

• Sympathetic (“fight-or-flight”) +
• Parasympathetic (“rest & digest”)
• Heart-rate, respiration, sweating
• Stress, arousal

Question 2

Brainstem:

Answer 2

= ANS functions + relay system

• Medulla
  
  • ANS functions (HR, RR, vasomotor) + reflex centres (cough, sneeze, swallow, vomit)
  • Controls heart-rate, respiration, regulation of blood pressure, body temperature
• Pons
  
  • Relay between Cerebral cortex → cerebellum
  • Some nerves to the face for some facial expressions and eye-movements
• Midbrain

Question 3

Disorders of consciousness (functional MRI is required to distinguish between these):

Answer 3

• Persistent vegetative state = No conscious awareness due to severe upper brain damage (hemispheres and cortex) but preservation of ANS (brainstem unaffected)
• “Locked-in” syndrome = Full conscious awareness but (normal cognitive function/vision/hearing) but unable to move
  • Amyotrophic lateral sclerosis (ALS) or motor neuron disease = Loss of motor neurons to spinal cord
  • Brain injury = Disconnection of brainstem → spinal cord

Question 4

Cerebellum:

Answer 4

• Hindbrain (latin for little brain)
• Sense of balance, coordination of complex movement and motor learning (fine adjustment of movement based on feedback)

Question 5

“Motor Programs” for movement:

Answer 5

Movements planned & programmed in brain before initiation, ike a computer program (theory from 1960’s)

• Brain creates program immediately before movement

OR

• Brain retrieves program for learnt skilled actions (e.g. tennis, signature)

Question 6

Feedback programs:

Answer 6

Brain computes difference of planned actions compared to actual actions performed

• Prediction of expected sensory feedback with actual feedback
• Learning motor skill = ↓ Prediction error (mismatches)

Question 7

Sense of agency:

Answer 7

Feedback matches predictions from planned actions

• Brain links sensory events and self-actions to infer causality
• We can sense that our personal actions cause an event (e.g. can’t tickle ourselves)

Question 8

Summary of evolution:

Answer 8

1. Brainstem + Cerebellum = ANS + Movement coordination
2. Limbic system = Fear/threat learning (amygdala) + Memory & environmental navigation (hippocampus)
3. Cerebral hemispheres (cerebral cortex) = Planning, reasoning & problem solving + Language (temporal) + Visual perception (occipital/parietal lobe) + Motor functions (motor cortex)