Feel the wind on your body and in your hair. Rub a surface with your fingers and feel its roughness or smoothness; retract your arm instantly if the surface is hot. Light, sounds, volatile molecules, heat, vibrations, gravity: when they come into contact with us, these stimuli are continuously transformed into information by receptors scattered throughout the body. This information travels in the form of an electrical signal along a very dense network of nerves, from the periphery towards the Central Nervous System, where it is integrated and processed. The CNS establishes priorities, the level of attention to certain stimuli, transforms information into sensations, light into images, mechanical waves into sounds, heat into pain.
Not only that: the CNS also arises our intention, our action on the world. Grab the pen, write a poem. Take a run and throw the ball. Dive into the sea, swim, hold your breath. When we make a voluntary movement, the electrical impulses from the cortex to the muscles travel on that same system of nerves. Just as sensory stimuli are filtered and processed upon entry, movement is refined and harmonized by a series of nerve structures as it travels from the center to the periphery.
The nervous system also takes care of a great many needs or more basic needs, regardless of our will. While we are intent on relating to the world, it keeps us in balance, regulates posture, allows us to focus on an object and ignore background noise. Like an orchestra conductor, he coordinates and harmonizes in an extremely fine way the complex intertwining of physiological systems responsible for maintaining our homeostasis. It is in fact involved in many visceral functions such as breathing, heart function, blood pressure, digestion, erection.
Ultimately, the nervous system mediates our relationship with the outside world, through the nerves. and with the internal one, through the sympathetic and parasympathetic autonomic nervous system.