The nervous system of a human body, both central and peripheral, is an integral part of it and plays a crucial role in helping with the regular functioning of the body. Memory and earning are often associated as the functions of its primary functions. Still, from the twitch of your finger to the rhythm of your heartbeat, it is the nervous system which generously contributes to your survival.
Essentially, the development of the nervous system in humans continues throughout their lifetime. Still, majorly it takes place in two folds- firstly, during the “embryonic stage”, which is the beginning of the development of the nervous system in humans, and consists of namely four stages, secondly, during Adulthood.
- The beginning: Embryonic Stage
There are, namely, four stages that are recognized during the development process of the neuron development and the formation of the nervous system during the embryonic stage.
Throughout these formative stages, all cells which form the basis of every organ in our body and its systems that come together to develop a human body ultimately, are created and assigned their designated roles.
The stages of the nervous system are:
Stage 1: Neurogenesis
Neurogenesis is the foundation process of neuronal development stages. Cells that are yet to be differentiated undergo mitosis, during this stage, to produce either stem cells, or neuroblasts. These will ultimately differentiate into multiple types of neurons.
Neurologists consider the neuroblasts and stem cells to be the same. Functionally, they are precursors to what eventually becomes a neuron. The main difference here is that neuroblasts are the showstoppers of embryonic development as a baby. On the other hand, stem cells play a more significant role in neurogenesis when the embryo turns into an adult.
During this stage, cells continue dividing till they eventually form a densely packed layer of cells, the Ventricular Zone. This leads to the formation of three separate zones:
- Ventricular Zone
- Intermediate Zone
- Marginal Zone
Stage 2: Cell Migration
After the completion of the foundation, the second most crucial stage takes place- Cell Migration. This is the stage when things start getting rather exciting and take on a bit more complicated as well.
During this stage, the cells that were previously responsible for the creation of ventricular zones now must travel greater distances. This needs to be done to establish a distinct cell population for further embryonic development. It is essential to know that these migrations are not so random in any way but rather happen to be genetically predetermined.
Another thing which is essential to be kept in mind is that the formation of the three zones, namely Ventricular, Intermediate, and Marginal, is because of these cell movements. This means, even though the formal process of migration may not have started yet, this is the mechanism of formation of these zones.
To wrap this stage in a nutshell, what essentially constitutes Cell Migration is the movement of cells, which are formed during the first stage neuronal development- Neurogenesis, along with the radial glia, from the ventricular zone to the marginal zone. Once they reach their destination, differentiation begins.
Stage 3: Differentiation
Once the cells migrate from the ventricular zone to the Marginal area, the third stage begins- Cell differentiation.
It is essential to mention that the process of differentiation is somewhat different from the normal cell mitosis during the embryonic stage because the embryo’s DNA ends up dictating the nerve cells their specific physiology for future core functions. This is the stage where it is determined which type of nerve cells; they will be ultimate. Once done, this process does not just end here but continues in Stage-4.
Stage 4: Outgrowth
This is another vital stage where the foundational cells of the nervous system genuinely begin to take their actual shape. During this process, differentiation continues to exist and directs the development of the axons and dendrites because each neuron needs a distinct physicality, based on their designated function.
- During Adult Life
As said earlier, neuronal development is an ongoing process which continues to develop throughout the lifespan of a human being. After the completion of the four stages during the embryonic stage, during adult life, there are a few significant developments that take place.
In adults, neuronal development takes place in the hippocampus, which is the region of the brain primarily concerned with memory. This development is crucial for every human being to avoid any irregularities and to ensure the smooth functioning of the body. Both, complete lack of and low rates of neurogenesis in adults are directly associated with the difficulty in differentiating stimuli that may be like each other. In other words, difficulty in distinguishing between things that, for example, smell the same but taste different.
New proteins must be synthesized at the synapses between neurons and dendrites. This is to create the ability to form memories. For the development and functioning of neurons, some of the significant components are miRNA, a non-coding RNA involved in gene expression, circa, Sodium (Na), Potassium (K) and many more.
The low development of the nervous system at this stage can result in problems with long term memory and conditions like depression, PTSD (post-traumatic stress disorder), and even anxiety.
Neuronal development is central to life’s most essential system- the nervous system. From its beginning at the embryonic stage to death, this is the process which gives rise to the very cells that allow us to function as efficient, sentient, and all-around perspective organisms. From the slightest sensation to growth and reaction of the body, the neurons are a significant part of the human growth and development process that we cannot do without.
