Sleep Mechanisms

1
Sleep Mechanisms

• Ascending Reticular Activating System
• Projects Up Wakefulness
• Possibly uses the intralaminar nuclei of the
  Thalamus (diffuse projections)

2
NREM Sleep

• Thalamus makes the rhythms
• ThalCort neurons (excitatory)
• TRN -gt Thalamus (inhibition)
• Feedback Loop
• Some TRN cells are activated just like spindles,
  necessary for spindles

3
NREM sleep cont

• Hyperpolarized ThalCort neurons shift to a burst
  firing mode
• They can no longer trasmit sensory information
  nearly as well
• ACh or NE can wake up these cells in the
  thalamus (get them out of burst mode)

4
REM Sleep

• Heart of REM sleep is in the pons
• ACh increases REM
• 5HT, NE supresses REM
• Dorsal Raphe N. (REM off due to 5HT activation)
• Locus Coeruleus (REM off due to NE activation)

5
REM muscle paralysis

• REM starts
• N. Pontis Oralis Activated
• Activates the Bulbar Inhibitory Reg.
• Activates Spinal Interneurons
• Inhibit Alpha Motor Neurons

6
Disorders

• Cataplexy Paralysis when awake
• mimicked by putting ACh agonist into N. Pontis
  Oralis
• Narcolepsy Chronically Falling Asleep
• often brought on by intense excitation