Nervous system
The nervous system is one of the most important and complex systems in the human body.
It has multiple functions, including receiving and processing all the information that comes from
both inside the body and from the environment, in order to regulate the functioning of the
other organs and systems. This action can be carried out directly or in collaboration with the
endocrine system by regulating the release of different hormones.
It is mainly made up of two types of cells, neurons and glial cells.
1. The neuron is the fundamental cell, it is responsible for processing and transmitting
information throughout the entire nervous system.
2. Glial cells (also called glia or neuroglia) are cells that support and protect neurons. Neurons
cannot function in the absence of glial cells.
Although there are neurons with different shapes, depending on the type of task they carry out,
in general, a neuron can be divided into four parts:
1. Cell body or soma: Contains the nucleus and most of the structures that maintain the vital
processes of the cell. Its shape varies according to the different types of neurons.
2. Dendrites: They are extensions of the cell body of neurons that act as receptors for messages
transmitted by other neurons.
3. Axon: Long, thin tube, often covered with a myelin sheath, responsible for carrying
information from the cell body to the terminal buttons.
4. Terminal buttons: It is the external part of the axon. The information that passes from one
neuron to another is transmitted through the synapse, which is a union between the terminal
buttons of the sending neuron and the dendrite of the receiving cell.
Neurons have characteristics that differentiate them from other cells in the body: they have
long extensions and have little ability to regenerate. For this reason, some neurological diseases
can be progressive.
The Nervous System is divided into two parts:
1. Peripheral Nervous System: Formed by the nerve extensions or paths that leave the spinal
cord to the different tissues.
2. Central Nervous System: Made up of the brain (which includes the cerebrum, cerebellum,
and brainstem) and the spinal cord.
The 2 structures that form the CNS are protected by bony envelopes, which are the skull and
the spine, respectively. Both the brain and the spinal cord are covered by 3 membranes that
serve as protection: the dura mater (outer membrane), the arachnoid mater (intermediate
membrane) and the pia mater (inner membrane). These membranes are known as meninges.
Between these membranes, a space is created, called the subarachnoid space, which is filled
with a colorless and transparent liquid, which is called cerebrospinal fluid.
This liquid is made up mainly of proteins, ions, glucose and blood cells that are part of the
immune system and, among its functions, is to allow the exchange of various substances
between the nervous system and the blood, act as a system for the elimination of residual
products, maintain proper ion balance and provide cushioning and mechanical protection.
The cells that make up the central nervous system are arranged in such a way that they give rise
to two classes of substances that are characterized by their color: the gray matter (cerebral
cortex), formed by the bodies of the neurons, and the white matter (area subcortical), formed
mainly by nerve extensions (dendrites and axons), whose function is to conduct information.
Wrapping and protecting the nerve fibers of the CNS is a material made up of proteins and fats
called myelin that facilitates the conduction of electrical impulses between the nerve fibers.