Pineal Gland Function: The pineal is a small gland responsible for producing melatonin, which is secreted in the absence of light and regulates the circadian rhythm.
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Summary of the pineal gland
- It is a small gland located approximately in the center of the brain.
- The hormone it produces is melatonin.
- Melatonin secretion follows a daily cycle.
- Melatonin, among other roles, is related to sleep promotion .
- Melatonin is used in clinical medicine to treat, for example, sleep disorders.
The pineal, formerly called the epiphysis, is a small gland located near the center of the brain . It has a conical shape, its largest diameter is less than 1 cm, and it weighs about 150 mg. The pineal gland is lined externally by the pia mater meninges, from which septa exit the gland and divide it into lobules.
Two cell types predominate in the pineal gland, pinealocytes and astrocytes. Pinealocytes correspond to about 95% of the pineal cells and are the cells responsible for the production of melatonin and some peptides . Among the pinealocytes are astrocytes.
The pineal gland responds to light stimuli received by our eyes , more precisely by the retina, and transmitted to the cerebral cortex. From the cortex, stimuli are relayed to the pineal gland through nerves belonging to the sympathetic system.
pineal gland function
The pineal gland has been known since antiquity. Until the 19th century, studies about it were mainly made by philosophers, and it was related to metaphysical and mysterious functions. Currently, it is known that the pineal gland is involved in the synthesis of melatonin and acts as a pacemaker of the circadian rhythm (24-hour cycle). The gland is recognized as one of the main components of the so-called biological clock system.
In some animal species , the pineal gland plays a role in controlling seasonal fertility. Although the mechanism is not fully understood, it is known that melatonin and other substances produced by the pineal enter the bloodstream and reach the pituitary gland, decreasing the release of the gonadotropic hormone.
It is believed that, in the winter months, when the duration of the dark period is longer, an inhibition of the gonads occurs. In spring, the secretion of gonadotropic hormone overcomes the inhibitory effects promoted by the pineal, and the functioning of the gonads returns to normal. The relationship between the pineal gland and reproduction in humans is not yet known, but it is believed that it may play a role in this important function.
Melatonin is a hormone produced by the pineal gland and synthesized from serotonin in a sequence of reactions . This hormone has a peak production during the night, and its secretion is made into the bloodstream immediately after synthesis. Melatonin, therefore, is not stored.
The beginning of secretion occurs about two hours before the usual bedtime, and the daily production of the hormone follows a rhythmic production synchronized with the cycle of lighting in the environment. Production of the hormone is suppressed by interrupting the dark by artificial light, and ambient light at night can completely block melatonin synthesis.
Unlike other hormones, melatonin is not related to feedback mechanisms . Therefore, its concentration in plasma does not regulate the production of the hormone.
Currently, several functions are described for melatonin, such as immunomodulation, anti-inflammatory, antitumor, antioxidant and circadian rhythm regulatory action. The nocturnal increase in the levels of this hormone in humans has a great influence on sleep promotion.
It is worth noting, however, that melatonin is produced following the same secretion patterns in both nocturnal and diurnal animals, so we should not consider it the sleep hormone, but the darkness hormone, which tells you whether it is day or night. . Melatonin also plays a role in regulating energy balance.
The medical use of melatonin is known to treat problems such as sleep disorders and neurological and degenerative diseases that cause sleep and biological rhythm disturbances. It is also used in jet-lag situations , i.e. when there is a sudden change in the circadian cycle. Jet -lag can be observed when a person travels to a region in a different time zone.