There are few body parts with as several names as the pineal gland, and even fewer shrouded in as much mystery. Our heads have a small endocrine gland which produces hormones responsible for modulating our sleep patterns.
The gland is right at the center of the brain, between the two halves of the brain, at the thalamus joint. The gland is shaped like a cone and hence, called the pineal gland. Pineal gland is a small structure, about the size of a pea, situated approximately in the center of the head.
Because it is one of the few obviously unpaired structures in the brain, the seventeenth-century French philosopher René Descartes (1596 to 1650) suggested that it was the seat of the soul, mediating subjective experience and intervening in the machinery of the brain in situations of free will and moral choice.
In reality, the pineal gland is essentially part of the visual system. In mammals it responds indirectly to light because it receives messages along fibers from nerve cells of the suprachiasmatic nucleus of the hypothalamus, which themselves receive signals from the eye via fibers of the optic nerve.
Believers say that the pineal gland, once activated to its full potential can let us travel through dimensions, look through the future and have the supreme knowledge of every unknown mystery of the universe.
René Descartes once described the pineal gland as “the principal seat of the soul.” Though medical knowledge has vastly progressed since then, here are a few things you might not have known about this critical organ.
1. The pineal gland is part of your endocrine system. Though located in your brain, the pineal gland is actually a crucial part of your endocrine system, which regulates major bodily processes such as growth, metabolism, and sexual development through the release and control of hormones.
2. In reality, it produces a single—but key—hormone. As scientists have learned more about the functions of the pineal gland, they’ve learned it synthesizes the hormone melatonin from the neurotransmitter serotonin. Melatonin production determines your sleep-wake cycles and is purely determined by the detection of light and dark. The retina sends these signals to a brain region known as the hypothalamus, which passes them on to the pineal gland. The more light your brain detects, the less melatonin it produces, and vice versa. Melatonin levels are highest at night to help us sleep.
3. Its shape influenced its name. This itty-bitty little gland, located very deep in the center of the brain, gets its name from its pinecone-like shape, most recently from the French (pinéal, or “like a pinecone”), itself from the Latin for pinecone (pinea). However, at about one-third of an inch long in adults, it’s smaller than your average pinecone.
4. Melatonin is also critically involved in reproduction. It inhibits the release of pituitary reproductive hormones, known as gonadotropins, from the pituitary gland, affecting male and female reproductive organs. In this way, melatonin—and therefore the pineal gland—regulates sexual development.
5. It’s been called the “third eye.” The pineal gland was commonly dubbed the “third eye” for many reasons, including its location deep in the center of the brain and its connection to light. Mystic and esoteric spiritual traditions suggest it serves as a metaphysical connection between the physical and spiritual worlds.
6. It’s been recognized as important since the ancient Greeks. Though the pineal gland wouldn’t be fully understood until the 20th century, descriptions of its anatomical location are included in the writings of Galen (ca. 130-ca. 210 CE), a Greek doctor and philosopher.