Nerve cells make up the nervous tissue that forms the organs and structures of the nervous system: brain and spinal cord, ganglia and nerves. There are two types of nerve cells: neurons and glial cells.
Neurons
There are about 86 billion neurons in the human brain, although many of them die throughout life, they are already known to be capable of regeneration. These cells are highly specialized in processing information.
Structure
Neurons have a more voluminous region called the cell body , where the nucleus and other organelles are located, from which branches form dendrites . The neuron has an extension called an axon that also has branches.
Neuron Function
The function of neurons is to carry out the transmission of nerve impulses , which occurs through a process that involves chemical (synapses) and electrical phenomena.
The electrical signals are transmitted along the neuron, leaving the cell body toward the axon. Changes in the electrical charge in the neuronal membrane occur , generating a difference in electrical potential called action potential .
The synapses occur between two neurons with the help of chemicals called neurotransmitters.
Glial Cells
Glial cells represent more than 80% of the constitution of nervous tissue, and are therefore much more numerous than neurons.
Importance of Glias
Glia accompany neurons providing nutrients, protection and helping to support tissue .
In recent years, however, studies have shown that they are much more important and participate in countless nervous system processes, including modulating electrical impulses . They are also responsible for neurogenesis , that is, the formation of new neurons .
Types of Glial Cells and Their Functions
Glial cells, also called gliocytes, can be of two types: microglia or macroglia.
Microglia
The microglia have a function similar to that of macrophages, cells of the immune system, they make phagocytosis of cellular debris in nervous tissue. Its activation is related to degenerative diseases of the nervous system.
Macroglias
There are three types of macroglia most well-known: astrocytes, oligodendrocytes and Schwann cells.
- The astrocytes are the most commonly found, making up about half of the brain. There are several subtypes related to different functions, especially the metabolism of neurotransmitters, their uptake and the functioning of synapses;
- The oligodendrocytes participate in the process of myelination of neurons, namely the formation of the myelin sheath that surrounds and protects axons;
- The Schwann cells are responsible for the formation of the myelin sheath such as oligodendrocytes. They wrap around the axons.