Some information about our bodies.

The third eye of human beings-pineal gland

▲ First of all, the pineal gland is the third eye of the human body. It seems incredible to say that the human body has a third eye. In fact, biologists have long found a hole in the skull of an extinct ancient animal. At first biologists were puzzled by this, but later it was confirmed that it was the eye frame of the third eye. Studies have shown that no matter birds and animals, frogs, turtles and snakes, or even human ancestors, they all had a third eye. Only with the evolution of biology, this third eye gradually moved from the skull to the brain and became a "hidden" third eye. Although the pineal gland moved into the dark cranial cavity. "Seclusion" and "isolation" make it impossible to observe the colorful world directly. However, because it has performed the function of clearing the third eye of human beings, it can still feel the light signal and respond with its original "unique stunt". For example, people will feel comfortable and energetic, and sleep less on sunny days. On the contrary, when it is cloudy and drizzling, people will be depressed, unhappy and often want to sleep. This phenomenon is exactly what the pineal gland is doing.

Because pineal cells are rich in 5- hydroxytryptamine, they are converted into melatonin under the action of special enzymes, which is a hormone secreted by pineal gland. It was found that the secretion of melatonin was limited by light. When exposed to strong light, melatonin secretion decreased; Melatonin secretion increases under dark light. However, melatonin in the human body will be suppressed for a long time. On the contrary, when there is less melatonin in the human body, "people are happy when they are happy." From this point of view, it is not surprising that people's emotions are affected by light.

▲ Secondly, the pineal gland is the control center of the "biological clock" of the human body. Because the secretion of melatonin is regulated by light and shade, the periodic alternation of light and shade in the day-night cycle will cause the secretion of melatonin to change periodically day and night. Experiments confirmed that the concentration of melatonin in plasma decreased during the day and increased at night. The pineal gland sends a "time signal" to the central nervous system through this day-and-night secretion cycle of melatonin, which in turn triggers a number of "biological clocks" related to time or age. Such as people's sleep and awakening, ovulation in menstrual cycle and the arrival of puberty. Recently, it has been found that the running cycle of human intelligence biological clock is 33 days, emotional biological clock is 28 days, and physiological biological clock is 23 days. The distribution of these three biological clocks is also carried out by the pineal gland.

▲ Melatonin is a hormone secreted by the pineal gland, which can affect and interfere with many nerve activities of the human body, such as sleep and awakening, mood and intelligence. Obviously, the pineal gland plays an "intermediary" role between nerve signals and hormone signals. Therefore, the pineal gland performs the function of a nerve excitation transducer in the human body. This is also the third function of the pineal gland.

▲ The pineal gland can synthesize peptide hormones such as GnRH, TRH and 8 spermine-oxytocin. GnRH in the pineal gland of many mammals (rats, cows, sheep, pigs, etc.). ) is 4- 10 times higher than that in the hypothalamus of the same animal. Some people think that the pineal gland is a supplementary source of GnRH and TRH.

However, we think that the function of the pineal gland is far from this, and our understanding of the pineal gland is still superficial. Because it is buried deep in the cranial cavity, it adds objective difficulties to our research on it. But in any case, with the deepening of research, its "true face" will eventually appear in front of people.

Some existing speculations about the role of pineal gland;

Speculation ability

The pineal gland of modern organisms is degraded to a certain extent, among which human beings belong to the more degraded category. Animals in nature can cope with natural disasters in advance, but humans are usually unaware of it. So some people speculate that the pineal gland is in charge of premonition ability, and this ability of human beings has deteriorated; According to the fact that the pineal gland can respond to light waves, it is speculated that the pineal gland can also respond to some rays in a special way. In addition, in ancient times, clergy often put large gems corresponding to the pineal gland in their crowns. When performing divination and other ceremonies, they would let the light shine on Tang Yin or the eyebrows and soul, pointing to the pineal gland; Eyebrows have always been considered as a place of concentration. When people encounter bad luck, they will call it "Black Tang Yin". I wonder if these are coincidences.

Biological significance of pineal gland

Pineal cells are dominated by sympathetic postganglionic fibers from the superior cervical ganglion, which can stimulate sympathetic nerves and promote the synthesis and secretion of melatonin in the pineal gland. The secretory function of pineal gland is closely related to light. Continuous light can make the pineal gland smaller and inhibit the secretion of pineal gland cells, while darkness can promote the secretion of pineal gland. Because the secretion and synthesis of melatonin are regulated by light and darkness, its secretion changes in circadian rhythm. In human plasma, its secretion is the lowest at 12 noon and the highest at midnight. In addition, its periodic secretion is obviously related to the sexual cycle and menstrual cycle of animals and people. The pineal gland may send a "time signal" to the central nervous system through the secretion cycle of melatonin, thus affecting the biological effects of sleep, awakening and other time, especially the periodic activity of thalamus-pituitary-gonad axis.

The way in which light inhibits melatonin secretion from the mammalian pineal gland is roughly as follows: Because the pineal gland is dominated by cervical sympathetic postganglionic fibers, when light is projected on the retina and part of its information is transmitted to the suprachiasmatic nucleus, the suprachiasmatic nucleus transmits light information to the sympathetic subconsciousness through the medial forebrain bundle, and then to the superior cervical ganglion through the spinal cord, thus inhibiting the activity of the pineal gland. Therefore, destroying the suprachiasmatic nucleus, cutting off the nerve connecting the sympathetic ganglion in the neck, or cutting off the sympathetic ganglion in the neck will make the rhythmic activity of the pineal gland disappear with the change of light and shade. Illumination and stimulation of optic nerve, or direct stimulation of suprachiasmatic nucleus, inhibit the activity of cervical sympathetic ganglion, and then the activity of pineal gland is weakened.

Because the activity of pineal gland is obviously influenced by light, the seasonal change of pineal gland of animals living at the poles is particularly significant. In the summer when the sun doesn't set, the activity of the pineal gland almost stops. In the long and dark winter, pineal gland activity is extremely enhanced, producing a large number of melatonin, thus inhibiting reproductive activities. Perhaps it is for this reason that Eskimos living in the Arctic, due to the lack of light in the dark in winter, increase the secretion of melatonin and inhibit the hypothalamus-pituitary-ovary system, so women stop menstruating in winter, and the menarche of Eskimo women can appear at the latest at the age of 23. In recent years, it has been found that light, like natural light, can inhibit the secretion of melatonin in pineal gland, thus weakening the inhibition of gonadal development and leading to precocious puberty.

Scientists in Japan and the United States have proved that the biological clock of bird activity is located in the pineal gland cells through the study of bird pineal gland. They found that the activity of birds was inhibited by melatonin. During the experiment, Japanese scientists took the pineal gland of chickens fed alternately with light and dark for 12 hours, cultured it and dispersed it into cells, and then observed the activity of enzymes needed to synthesize melatonin in light and dark environment. The results show that each pineal gland and its scattered cells have the function of biological clock, and they can remember the laws of light and shade and gradually adapt to the new laws. American scientists successfully transplanted the first bird biological clock. They found in the experiment that if the pineal gland of sparrows is removed, the circadian rhythm of their activities will be lost and they will become active all day. For example, when the pineal gland of one sparrow is transplanted to another sparrow whose pineal gland has been removed, the activity rhythm will be restored, which is consistent with the original activity rhythm of the sparrow given the pineal gland.

The pineal gland is a flat cone-shaped body about 7×4mm2, located in the posterior upper part of thalamus and attached to the posterior part of the third ventricle with a stalk. The pineal gland develops in childhood, generally shrinks gradually after 7 years old, and calcium salts are deposited in adulthood.

The main hormone of pineal gland is melatonin, which belongs to indole compounds, and its secretion shows obvious daily cycle changes. Melatonin in amphibians can promote skin discoloration. In mammals, this effect has disappeared. The physiological function of melatonin may inhibit gonadotropin secretion, gonadal activity, sexual maturity and prevent children from precocity through hypothalamus or pituitary gland.