Pineal Hormones and Cells
- Melatonin is the main pineal hormone and is secreted mostly at night.
- Night secretion helps signal darkness to the rest of the body.
- Daylight inhibits most melatonin synthesis.
- Arginine vasotocin is a pineal peptide that appears to oppose luteinizing hormone and follicle-stimulating hormone effects.
- Antagonize means to oppose or reduce the action of another signal.
- Serotonin is a molecule made by pinealocytes and used as a precursor for melatonin.
- Histamine and dopamine may be produced in small quantities by pinealocytes.
- Two-step conversion changes most pineal serotonin into melatonin.
- N-acetyltransferase is the enzyme that catalyzes the first step in serotonin-to-melatonin conversion.
- Catalyzes means speeds up a chemical reaction without being consumed by the reaction.
- Light inhibits N-acetyltransferase, reducing melatonin synthesis during daytime.
- Astrocytes are nervous-system support cells, and pineal neuroglial cells resemble them.
- Elongated processes and small dense nuclei are features of pineal neuroglial cells.
- Intermediate filaments help support the structure of neuroglial cells.
- Jet lag occurs when internal circadian timing does not match the local light-dark schedule.
- Melatonin can be used to help treat jet lag by shifting sleep timing.
- Seasonal affective disorder is a mood disorder related to seasonal changes in daylight exposure.
- Shorter winter daylight can alter circadian and mood-related signaling in susceptible people.
- Therapeutic melatonin use depends on timing because the hormone acts as a darkness signal.
- Endocrine integration in the pineal gland shows how environmental light can influence hormone secretion.
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