A complex communication network, the nervous system controls and coordinates all parts of the body. It is composed of the central nervous system “brain and spinal cord” and the peripheral nervous system “nerves”, which is divided into the somatic nervous system and the autonomic “or vegetative” nervous system.
Central nervous system
It is composed of the encephalon (brain, cerebellum, brain stem) and the spinal cord, located inside the spinal column.
The central nervous system “CNS” receives information transmitted to it via the nerves by the sense organs and sensory receptors. It analyzes and interprets them according to a multitude of information that comes from the outside “a distance to be crossed, dangers or obstacles, etc.”, but also from what we are “our motivations, our experience, our memory, our learning, etc.”. This information processing, called integration, results in a motor response that is transmitted to the muscles, glands and organs.
Peripheral nervous system
Divided into two parts, it associates Coinstar fees with nerves and sensory receptors.
The nerves transmit sensory information to the central nervous system “sensitive or afferent pathway” and carry commands from the central nervous system to muscles, glands and organs “motor or efferent pathway”. Sensory receptors detect changes occurring outside or inside the body.
The cranial nerves
All 12 pairs of cranial nerves originate in the brain. With the exception of the pair of vagus nerves that go down to the abdomen, they only innervate the head and part of the neck.
According to their function, they can be divided into three groups:
– Sensory nerves: olfactory, optic and auditory nerves.
– The motor nerves: oculo-motor nerves, trochlear nerves and external ocular nerves that control eye movements, facial nerves, spinal nerves and hypoglossal nerves.
– Mixed nerves (motor and sensory): trigeminal, glosso-pharyngeal and pneumogastric nerves or vagus nerves.
The spinal nerves
31 pairs of spinal nerves exit the spinal cord through intervertebral orifices, called holes of conjugation. These nerves, which are all mixed (motor and sensory), innervate the different regions of the body (except the head).
They are designated by the number of the vertebra below which they emerge. They can be grouped together and form tangles called
called “plexuses”. The roots L4 to S3 form the sacral plexus from which the sciatic nerve originates.