Posted on Oct 16, 2022 112
We have all heard a hundred times that “nerve cells do not recover”. Such a phrase usually wants to stop excessive nervousness in a person - to calm him down. And indeed, until recently, it was considered a scientific fact. But progress is inexorable, because the more we study and discover in certain areas, the more it makes us doubt even seemingly inviolable truths.
Let’s inspect - so are our nerve cells regenerating or not?
As already written above, that nerve cells do not regenerate was believed to be true, and the author of these views - Santiago Ramon y Cajal did not doubt this at all. The assertion was: nerve pathways are unchangeable and fixed, nerve cells die off without the possibility of recovery.
He held this view based on several principles:
- Clinical. Patients diagnosed with neurological diseases associated with CNS lesions do not recover. Alzheimer’s or Parkinson’s disease has a progressive deterioration. Treatment can relieve unpleasant symptoms, but it cannot stop the disease.
- Functional. The CNS handles many complex mechanisms (emergence of emotions, manifestation of reflexes, making movements). Neurobiologists believe such functions require “fine tuning”. Therefore, the emergence of new cells may have disrupted the entire work of the CNS.
- Learning theories. According to scientists, neural networks were formed in learning in humans. When the need to remember something, the information is simply extracted from the right grid. The emergence of new nerve cells in this theory is completely incompatible with memory.
As you can already understand, despite the fundamental basis, the theory has been disproved. More and more new studies and experiments have questioned the discovery of the Spanish neurobiologist. And we had to deal with this question anew - so do these cells regenerate or not?
Neurogenesis has a very rich history, even though the theory is only a little over 60 years old:
- 1962. A radioactive thymidine was discovered in the cells of the dentate gyrus. This substance can only be present in cells capable of division. When thymidine was also found in the brain's hippocampus, this was already a clear call. But experts could not prove that it was neurons that were labeled.
- 1977. They did the experiments again, now with the help of electron microscopy. It was proven that it was the neurons that were labeled.
- 1989. Experiments with canaries led by Fernando Notebaum. At when the bird sang a new song, the formation of neurons in the brain was recorded.
- 2011. It was finally proven that neurogenesis occurs in specific parts of the brain in mammals and humans.
A nerve cell is a rather complex mechanism that accords to its own laws. It has several branched offshoots (dendrites and axons), through which neurons can communicate with each other and with other tissues (e.g. muscles). Disruption of such connections leads to various nerve diseases.
Nerve cells do not divide - it was found experimentally that forced division of neurons led only to their death. This was explained because the neuron had to lose all its connections while dividing.
But in the brain, new neurons appear, forming from the materials of other, dead cells. This is what science calls neurogenesis. Such processes have been recorded in the hippocampus and subventricular zone and occur literally every day - new neurons are constantly formed and then sent to the parts of the brain for which they are intended.
Neurogenesis is one of the most mysterious processes in the brain and not much is known about it. However, there are a few nuances that scientists are sure of.
The emergence of new neurons in the brain can be sped up by:
- a favorable environment;
- moderate exercise;
- taking antidepressants;
- certain hormones (e.g. estrogen).
There are also factors that can slow down this process, namely:
- excessive stress;
- use of glucocorticoids;
- exposure of the body to stress hormones (cortisol);
- natural aging.
Your nerve cells will, of course, recover, but it is still better not to be nervous - otherwise you yourself will inhibit this process.
There are certain diseases that can destroy neurons, slow down their birth or even prevent them from regenerating at all. Among these are:
- Stroke. This is a pathology in which there is an acute disruption of blood flow in the brain. There is a disruption in the connections of some neurons. Individual parts of the brain die off.
- Alzheimer’s disease. A neurodegenerative disease in which a person has progressive functional and cognitive impairment (memory loss, speech impairment, motor disorders).
- Parkinson’s disease. The pathology is characterized by the gradual death of motor neurons that synthesize dopamine.
- Huntington’s disease. This is a genetic disease in which there is degenerative destruction of neurons.
- Epilepsy. A chronic pathology in which periodic synchronous excitation of neurons in a particular area of the brain (the epileptogenic focus) occurs.
Depression. In this pathology, the outgrowths of neurons stop delivering serotonin (the happiness hormone) to the centers. This leads to a persistent worsening of mood. If the treatment is chosen correctly, doctors restore the neural connections and completely rid the person of depression.
At the moment, scientists around the world are dealing with the above pathologies and try to reverse their effects on the brain’s neurons. There is confidence that soon, not only will the answer to the question “why” be announced, but also special drugs will be developed that can cure a person and restore neurogenesis completely.