Sensory systems - Overview

Senses play a fundamental role in our lives. Sensory systems provide the primary interface between the individual and the environment, facilitating a constant awareness of external stimuli.

It is estimated that every second, our brain receives more than a billion pieces of information from different sensory modalities ^[142]. This incredibly vast number demonstrates the extent to which the nervous system is continuously bound to the environment.

Like many other species, we possess several sensory modalities that detect various physical and chemical properties. For instance, we possess an extraordinary visual system sensitive to light. Through this system, we perceive electromagnetic waves as meaningful images. We also have an auditory system that detects even the slightest variations in air pressure and converts them into understandable sound. Two other chemical systems - olfactory and gustatory - allow us to detect chemical particles and assign them a smell and a taste. Another balancing system informs us (consciously or not) of our position and movements in space.

And above all, we possess an impressive sensory entity: the somatosensory system, which is as vital as vision or hearing, if not more. This system, diffuse and ubiquitous throughout the body ^[39], constantly provides information about our own body, what touches it, and, above all, what threatens it.

Sensory systems are often composed of a receptor organ, a transmission pathway, and a cortical reception and perception area within the brain. Signal transduction occurs at the receptor organ - that is, the conversion of physicochemical properties into electrical signals that can be transmitted by neurons.

The arrival of these electrical signals in the primary cortical areas represents only the first stage of information assimilation within the brain. Indeed, other regions, known as associative cortical areas, are required for the information to acquire meaning; this process is what we call perception.