🔑 Key Definitions
Serotonin (5-HT): Monoamine neurotransmitter synthesized from tryptophan; involved in mood, sleep, appetite, and sensory perception
Tryptophan: Essential amino acid precursor to serotonin; must be obtained from diet
Pineal Gland: Small endocrine gland that converts serotonin to melatonin
Melatonin: Hormone derived from serotonin that regulates sleep-wake cycles and circadian rhythms
Tryptophan: Essential amino acid precursor to serotonin; must be obtained from diet
Pineal Gland: Small endocrine gland that converts serotonin to melatonin
Melatonin: Hormone derived from serotonin that regulates sleep-wake cycles and circadian rhythms
🧠 Serotonin Synthesis
- Tryptophan: Essential amino acid from dietary protein (turkey, milk, etc.)
- → 5-HTP: Tryptophan hydroxylase converts tryptophan (rate-limiting step)
- → Serotonin (5-HT): Aromatic amino acid decarboxylase completes synthesis
- → Melatonin: In pineal gland, serotonin converted to melatonin for sleep regulation
📊 NE in Multiple Functions
- Stress Response: NE released during fight-or-flight; increases heart rate, blood pressure, alertness
- Feeding Behavior: NE in hypothalamus influences hunger and satiety
- Reward Pathways: Interacts with dopamine in motivation and reinforcement
- Depression: Low NE contributes to lack of energy, motivation, and positive affect in depression
📊 Pineal Gland Function
- Location: Small gland near center of brain (epithalamus)
- Serotonin → Melatonin: Converts serotonin to melatonin at night
- Circadian Regulation: Melatonin release increases at night, promotes sleepiness
- Light Sensitivity: Receives input from SCN about light/dark cycles
💡 Exam Tips
- Tryptophan is essential amino acid - must come from DIET
- Synthesis: Tryptophan → 5-HTP → Serotonin (5-HT) → Melatonin (in pineal)
- NE has diverse roles: stress, feeding, reward, mood
- Pineal gland makes melatonin FROM serotonin at night
- Depression involves BOTH low NE and low serotonin
- Remember: 5-HT is abbreviation for serotonin (5-hydroxytryptamine)