The Suprachiasmatic Nucleus: Your Internal Clock

· February 21, 2019
According to neuroscientists, the suprachiasmatic nucleus is the body's master clock. It regulates your circadian rhythms. Any alterations in this area may lead to insomnia or memory loss.

The suprachiasmatic nucleus is located in the anterior region of the hypothalamus and contains about 20,000 neurons. It works as your internal clock, regulating your sleep/wake cycles. Specifically, it receives stimuli through your retina which allows you to be more or less active depending on the time of day.

Like animals, people are sensitive to changes in their environment. The Earth and its rotation establish the light and temperature patterns that condition your level of activity. Hence, your metabolism is intimately linked to nature, although sometimes it may not seem like it.

Circadian rhythms are biological rhythms that recur naturally every 24 hours. The suprachiasmatic nucleus is one of the most interesting parts of the brain because it mediates circadian rhythms. Specifically, this nucleus is a regulatory center capable of setting in motion neuronal and hormonal events. In turn, it controls important aspects such as rest, energy, body temperature, or hunger.

“Look deep into nature, and then you will understand everything better.”

-Albert Einstein-

The suprachiasmatic nucleus: Location and functions

We actually have two suprachiasmatic nuclei. Both of them are located in each cerebral hemisphere, very close to the hypothalamus. They’re located right above the optic chiasm because they receive signals that the retina captures to regulate a large number of biological processes.

Studies like the one  Dr. Joseph L Bendot carried out call the suprachiasmatic nucleus the brain’s central clock. We know that this brain structure aids important processes such as memory creation or learning.

Enjoying an adequate or restful sleep is essential for our brain and each of its processes. Thus, any malfunction of the circadian system can lead to sleep disorders and even memory loss.

How does the suprachiasmatic nucleus work?

The suprachiasmatic nuclei are complex. The biochemical processes they set in motion are as precise as they are intricate.

  • This area receives information about your surroundings through your retina.
  • Your retina isn’t just full of photoreceptors which you use to distinguish shapes and colors. Additionally, it also has ganglion cells that are rich in melanopsin, a type of pigment.
  • This pigment and its cells carry information directly to the suprachiasmatic nucleus. Later, after analyzing the information, it will send signals to the upper cervical ganglia. These signals will tell the pineal gland or epiphysis to secrete or inhibit melatonin production.
  • If it’s nighttime, the melatonin secretion will increase. In particular, this helps to reduce activation levels and promotes sleep.
Different colored lights shining on an eye.

The suprachiasmatic nucleus is the master clock of the rest of our internal clocks

Ever since a few decades ago, scientists have been discovering more information about this structure thanks to the Drosophila fly. As many of us know, the study of this insect is giving us valuable information on fundamental biology and genetic principles.

Today, we know that the suprachiasmatic nucleus helps us control circadian rhythms. Namely, it does so by coordinating and synchronizing the many other internal circadian clocks. Because, beyond what it appears, both our body and brain have hundreds of mechanisms that regulate infinite processes and behaviors.

The processes that it helps regulate are:

  • Hunger.
  • Digestive processes
  • Hibernation in animals.
  • Body temperature.
  • Hormone production
  • It encourages our brain and body to carry out maintenance and restoration tasks. Specifically, it does so through the REM phase.
A floating woman sleeping in the forest due to her suprachiasmatic-nucleus.

Alterations of the suprachiasmatic nucleus

Many factors can alter the functioning of the suprachiasmatic nucleus. A lot of them stem from our daily habits:

  • Staying awake at night in front of a digital screen.
  • Not following a fixed routine.
  • Jet lag.
  • Living in cities with high pollution levels.

In addition, the suprachiasmatic nucleus has a direct relationship with the pituitary gland and melatonin production. Your hormone levels decrease as you get older. This leads to problems such as sleep disorders, fatigue, memory loss, exhaustion, depression, and more.

In addition, scientists have discovered that neurodegenerative diseases, such as Alzheimer’s, lead to a progressive loss of neurons that make up the suprachiasmatic nucleus.

Therefore, you should start following a regular scheduleLikewise, you should also control your exposure to the blue light that electronic devices emit.

  • Benarroch, E. E. (2008). Suprachiasmatic nucleus and melatonin Reciprocal interactions and clinical correlations. Neurology, 71(8), 594-598.
  • Mirmiran, M., Swaab, D. F., Kok, J. H., Hofman, M. A., Witting, W., & Van Gool, W. A. (1992). Circadian rhythms and the suprachiasmatic nucleus in perinatal development, aging and Alzheimer’s disease. Progress in brain research, 93, 151-163.
  • Moore, R. Y. (2007). Suprachiasmatic nucleus in sleep-wake regulation. Sleep medicine, 8, 27-33.
  • Joseph L. Bedont (2014) Constructing the suprachiasmatic nucleus: a watchmaker's perspective on the central clockworks. Frontiers in Neurology DOI 10.3389/fnsys.2015.00074