Sleep and the Brain

Sleep Stages and Neurotransmitters

• Five sleep stages correlate with specific neurotransmitter activity in the reticular formation, crucial for sleep and arousal.
• Damage to the reticular formation can lead to coma or death.

Key Neurotransmitters Involved in Sleep

• Serotonin: Regulates emotions; decreases during sleep onset.
• Norepinephrine: Regulates arousal; also decreases during sleep onset.
• Acetylcholine: Involved in muscle movements; increases during REM (stage R) sleep.
• GABA: Functions as the brain's inhibitory neurotransmitter, aiding movement between sleep stages.

Sleep Cycle Dynamics

• Neurotransmitter levels decline as sleep begins, reaching their lowest in stage N3 (deep sleep).
• Stage R sleep (REM) is initiated by increased acetylcholine, activating the cerebral cortex.
• REM ends with rising serotonin and norepinephrine, preparing for awakening; likelihood of waking after REM is high.
• If not awakened post-REM, neurotransmitter levels drop again, leading to the next sleep cycle.