As advances in health care progress, more importance is being given to the glands of the endocrine system and the necessity of their proper functioning. Much is still to be researched and understood about the body’s endocrine system, particularly the glands located in the the brain.
The endocrine system consists of a series of glands that secrete particular hormones into the bloodstream. These hormones send messages to the cells of the body, which in turn help to regulate a variety of functions including metabolism, growth and development, tissue function, and mood.
From its unique perch between the brain’s two hemispheres, the endocrine system’s pineal gland secretes melatonin, a derivative of serotonin, which generally contributes to feelings of well-being and happiness. The tiny, pine cone — shaped gland is joined by the habenular trigone and the posterior commissure to make up the epithalamus, which serves to connect the limbic system to other parts of the brain.
The limbic system influences both the endocrine system and the autonomic nervous system and seems to have involvement (which is not entirely well understood) with emotion, behavior, motivation, long-term memory, and olfaction (our sense of smell). Just in this brief description, we get a glimpse of the inextricable relationships amongst our organs, systems, and their functions.
Released by the pineal gland’s pinealocyte cells, melatonin is a powerful antioxidant that fights free radicals that damage neurons (or any cells, for that matter). The amount of melatonin found in spinal fluid is much higher than the amount in our bloodstream, and it controls our circadian rhythm — our sleep and wake cycle. The pineal gland creates more of the antioxidant at night, in the absence of light, which helps to dictate our sleeping patterns.
Studies on the pineal gland and melatonin have contributed to chronobiology, the branch of science which explores rhythms in living organisms. We all know people who strongly identify with being a “morning person” or “night owl,” and chronobiology has ways of assessing these chronotypes. In the dark months of winter, seasonal affective disorder (SAD) seems to be the result of low melatonin levels.
Interestingly, aside from our eyes, the pineal gland is the only other organ in our body that detects light.
Melatonin is produced in response to another hormone called norepinephrine. Recent research shows that while the norepinephrine complex turns up melatonin in the evening (and the resulting sleepiness), dopamine and its receptor form a complex of proteins that does the opposite in the morning. The dopamine receptor on the outside of the pineal gland works alongside norepinephrine receptors to slow the melatonin-secretion signal in the early morning.
Several diseases and conditions are affiliated with melatonin, including insomnia, fatigue, anxiety and, most recently, cancer. Since melatonin protects white blood cells against radiation damage, they provide a boost for the immune system. The blood flow through the pineal gland is very high and second only to the kidney, the body’s natural blood filter. This counts as another unique aspect of the pineal gland, as most other parts of the brain are separated from the bloodstream by the blood-brain barrier system (a separation of circulating blood from the brain extracellular fluid).
The pineal gland also has an effect on our reproductive system. High levels of melatonin in children are thought to inhibit their sexual development, and pineal gland tumors have been linked to the onset of early puberty. In addition, when the gland is damaged, accelerated growth of sexual organs occurs.
Dr. Rick Strassman, who conducted extensive research on near-death experiences in the 1990s, asserts that the pineal gland is also responsible for secreting the naturally occurring psychedelic hormone dimethyltryptamine (DMT). Structurally analogous to both serotonin and melatonin, it is believed DMT might help contribute to the visual effects of natural dreaming, near-death experiences, religious visions, or other altered states.
As we have attempted to understand its functions throughout history, the pineal gland has been associated with mystery and myth. René Descartes, for example, dubbed it the “principal seat of the soul,” suggesting it connected the body and intellect. Further, the philosophy of French writer Georges Bataille holds that the pineal gland can be thought of as a blind spot in Western rationality.