Suprachiasmatic nucleus: the internal clock of the brain

While we often take for granted that the human brain is basically the organ that enables us to think and be aware of things, the truth is that it also performs all kinds of automatic and subconscious functions. It is not simply the biological basis of the human intellect; it is also responsible for a multitude of processes essential to our survival.

The suprachiasmatic nucleus is an example. While certain regions of the brainstem are responsible for activating the heartbeat or regulating body temperature so that our cells do not die, this brain structure acts like our internal clock. Next, we will see what this means exactly and what anatomical features the supraquiasmatic nucleus exhibits / displays.

    What is the suprachiasmatic nucleus?

    By suprachiasmatic nucleus we mean a small structure made up of about 20,000 neurons located in the area of ​​the hypothalamus closest to the face, ie in the lower part of the diencephalon. It is made up of gray matter.

    It should be noted that there is a suprachiasmatic nucleus in each cerebral hemisphereIn other words, two per person on each side of the head.

    His location

    As the name suggests, the suprachiasmatic nucleus it is located above the optic chiasmus, Which is an area at the base of the brain in which the optic nerves cross, passing into the opposite hemibody. It is also possible to locate it by reference to the hypothalamus, since it is located in the anterior part of this cerebral structure, limiting on both sides the third cerebral ventricle.

    The fact that the optic chiasm is located just above the optic nerves is not accidental; in fact, its functioning is linked to the light signals picked up by the retina, as we will see.

    Functions of the suprachiasmatic nucleus

    The main task of the suprachiasmatic nucleus is regulate circadian rhythms which govern the activity levels of the body depending on when we are. Circadian rhythms are the cycles that determine when there is a greater need for rest and when there is a large amount of energy available and therefore we will move more, think better, etc.

    In other words, the suprachiasmatic nucleus is involved in sleep-wake cycles, and makes us more likely to sleep at certain times and wake up at others, for example, and not have the same energy at noon as after the day. having dinner.

    The cycles that regulate the suprachiasmatic nucleus last 24 hours, as evolution did adapt to what lasts a calendar day of the brightness captured through our eyes.

    So when we are exposed to light, it is interpreted by this brain structure as evidence that it is time to stay awake longer, and it is delayed. massive melatonin segregation, A much larger hormone just before we start to sleep and while we stay asleep.

      Mechanism of operation

      When we look somewhere, the light that reflects what our eyes are pointing at is projected onto the retina, a layer of cells inside the eye that some scientists consider to be part of the brain.

      This membrane collects the electrical signals in which the light patterns of what we see are translated, And sends this information to the brain through the optic nerves. The usual route for most of this information is through the thalamus and the occipital lobe, an area where visual information begins to be integrated into larger and more complete units.

      However, some of this information deviates from this path at the level of the optic chiasm, located at the “entrance” of the brain, to reach the suprachiasmatic nucleus. This structure does not recognize the details of light patterns, shapes or movements, but is sensitive to the general amount of light collected by the retinas. This causes commands to be sent to other areas of the body related to circadian rhythms, such as the pituitary gland, located nearby.

      In this way, our body adapts to what are interpreted as environmental demands. After all, if we are designed in such a way as to generate more efficiency during the day, it is best to take advantage of those moments and let the hours of darkness sit, according to the logic of natural selection.

      However, the use of artificial light sources it can turn us against us and, for example, exposing ourselves to the light of a computer screen shortly before bedtime can cause us insomnia despite the fatigue of a long day at work. This causes our body to try and respond to a strange situation for which it was not prepared: days with many more hours of light.

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