The Suprachiasmatic Nucleus, Our Circadian Center

For neuroscientists, the suprachiasmatic nucleus is the “master watchmaker”. It regulates our circadian rhythms. Any alteration in this area leads to insomnia and memory loss.
The suprachiasmatic nucleus, our circadian center

The suprachiasmatic nucleus is located in the anterior region of the hypothalamus and contains approximately 20,000 neurons. Its function is as fascinating as it is determining: it plays the role of our internal clock, regulating the cycles of sleep and wakefulness. Thus, thanks to the stimuli it receives by the retina, it allows us to be more or less active depending on the time of day we are.

Humans, like animals, are sensitive to changes in their environment. The Earth and its rotation establish the patterns of light and temperature that condition our level of activation. All this facilitates our adaptation. Therefore, our metabolism is, in a way, intimately linked with nature (although it may sometimes seem that it is not).

These circadian rhythms are in turn regulated by some of the most interesting areas of our brain. Thus, regions, such as the suprachiasmatic nucleus, become regulatory “centers” capable of orchestrating precise neuronal and hormonal events to control aspects such as rest, energy, body temperature or hunger.

Let’s take a look at more data on this subject.

suprachiasmatic nucleus illustration

The suprachiasmatic nucleus: location and functions

In fact, we have more than one suprachiasmatic nucleus. We have two, and both are located in each cerebral hemisphere and very close to the hypothalamus. They are also integrated just above the optic chiasm for a specific purpose: to receive signals picked up by the retina in order to regulate a large number of biological processes.

On the other hand, studies, such as that published in the journal Frontiers in Neuroscience by Dr. Joseph L. Bendot, do not hesitate to call the suprachiasmatic nucleus the clockwork brain. In addition, we know that this encephalic structure promotes processes as relevant as memory and learning. Getting adequate and restorative rest is always essential for our brain and each of its processes.

Thus, any dysfunction of the circadian system is linked to diseases ranging from sleep disorders to memory loss (particularly serious in the elderly).

How does the suprachiasmatic nucleus work?

The functioning of the suprachiasmatic nucleus is complex. The biochemical processes they trigger are as precise as they are complicated. However, we can understand their development more easily if we divide them into stages:

  • This area receives information about ambient light through our retina.
  • The retina does not only have photoreceptors to distinguish shapes and colors. It also incorporates ganglion cells, which are rich in a pigment called melanopsin.
  • This pigment and its cells carry information directly to the suprachiasmatic nucleus. Later, after analyzing the information received, it will send signals to the upper cervical ganglion for the pineal gland, or epiphysis, to secrete or inhibit the production of melatonin.
  • If it is dark and there is no solar stimulation, the secretion of melatonin increases to reduce the level of activation and promote sleep.
the retina and suprachiasmatic nucleus

The suprachiasmatic nucleus is the master of the rest of our “internal clocks”

For decades, scientists have learned more about this structure thanks to the Drosophila fly. As we are well aware, this insect and its study offer us valuable information on the fundamentals of biology and genetics.

Today we know that the suprachiasmatic nucleus helps us maintain circadian rhythms by coordinating the synchronization of many other internal “circadian clocks”. Because beyond what it may sound, our body and brain have hundreds of mechanisms that regulate countless processes and behaviors.

The processes that the suprachiasmatic nucleus would help regulate would be as follows:

  • He would control our hunger pangs
  • It would regulate our digestive processes
  • It would promote hibernation in animals
  • It would regulate our body temperature
  • It would also regulate the production of hormones, such as growth hormones
  • It would encourage the brain and our body to perform maintenance and recovery tasks  during the REM phase

Alterations of the suprachiasmatic nucleus

The functioning of the suprachiasmatic nucleus can be affected by many factors. Many of them derive from our lifestyle:

  • Being awake at night in front of our electronic devices
  • Do not follow a fixed routine in our schedules
  • Suffering from jet lag
  • Living in heavily polluted cities

In addition, the suprachiasmatic nucleus has a direct relationship with the pituitary gland and the production of melatonin. As we can guess, it is common as we get older that the levels of this hormone decrease. All of this leads to sleep disturbances, fatigue, memory loss, exhaustion and discouragement, among others.

Neurodegenerative diseases, such as Alzheimer’s disease, have also been found to cause progressive loss of the neurons that make up the suprachiasmatic nucleus.

So let’s try (as much as possible) to take care of our routines. The ideal would be that we start to follow more or less fixed schedules, as well as we regulate our exposure to the blue light of our electronic devices.

 

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