Brain Cell Neuron
The nerve cells that send information to the muscles, organs and glands in our body and control their work are called “neurons”. Most of the neurons are in the outer shell of the brain, namely the gray matter. It is thought that there are over 100 billion neurons in the brain.
There are 50,000 neurons in a cubic millimeter of brain tissue, and among them there are much more (between 10 and 50 times) “glia” cells that nourish and clean them. Neurons are the most important cells of the brain, and the functions of the brain depend on the functioning of neurons. They consist of a large body and its long thin tail-shaped extension, the “axon”.
Electrical signals from neurons are transmitted by axons to other cells at a speed of 100 meters per second. Neurons can sometimes transmit their messages to very distant parts of the body through a single axon. Some axons start from the brain and go all the way to the spinal cord, and their length can reach one meter.
Axons, which are extensions of the nerve trunk, are surrounded by a special sheath called myelin. This sheath allows electrical signals to be transmitted very quickly. In cases where this sheath is damaged, such as in “multiple sclerosis”, some muscles are out of control.
Antenna-like extensions called “dendrites” that come out of the body of the nerve cells perceive signals from other nerves. All of the dendrites in the neuron body are in connection with axons from other neurons.
Thanks to these connections between neurons, called “synapses”, a signal formed in the brain is delivered to the desired part of the body in a very short time. A brain cell can have about 20-30 thousand connections. The total number of connections in the brain is thought to be 10 to the 15th. It is possible to change the number of connections by increasing the work of the brain, thereby improving the capacity of the brain.
In the past, connections between neurons were thought to be fixed. In other words, once a connection was established, it was thought to be continuous and this number was increasing gradually. Recent research has shown that connections are constantly changing. While the total number of connections generally remains constant, some connections are broken; but meanwhile it creates new connections.
This shows that the brain can constantly change its structure according to changing conditions. In the nerve cell, electrical energy is generated by the displacement of positively charged sodium, potassium, and negatively charged chlorine ions.
During this displacement, the opposite poles formed on the inside and outside of the cell damage cause voltage changes, thus releasing electrical energy in the cell. A neuron can generate several hundred electrical signals per second.
These electrical signals formed in the cell membrane are transmitted by the axons towards the end of the axon at a speed of 200-300 kilometers per hour. When electrical signals reach the tip of the axon, they cause the secretion of very special chemical messenger molecules called “neurotransmitters”.
The secretion of these molecules from the end of the axon activates target cells such as other neurons or muscle cells, enabling them to do their job. In a way, neurotransmitters act as messengers that enable the signals coming from nerve cells to be perceived by other cells.
Depending on the structure of the secreted molecule, the tasks performed by the target cell also change.