Odorous molecules are perceived by the human olfactory system. This system is defined as the mechanism allowing humans to perceive different smells.
First, the very light odorous molecules are introduced into the nasal cavity; and the decoding begins.
This transduction begins when odorants bind to specific receptors on the outer side of the eyelashes: this linkage can be done directly or via mucus G proteins that bind the molecules and transport them to the receptor neurons located on the eyelash membrane. In this association, a G protein found in the receptors is released. It activates an adenylyl cyclase to produce cyclic AMP (cAMP). In turn, cAMP acts and opens a channel allowing molecules of Na + and Ca 2+ that depolarize the neuron (depolarization = association of electric charges in a body under the influence of an electric field). Thus the increase of Ca 2+ causes the opening of a second channel: Cl - channel, which contributes to most of the depolarization forming the receptor potential. This depolarization amplified by a current Cl- activated by calcium (Ca 2+) extends passively from the eyelashes to the region of the axonal cone (= constant extension of the nerve cell which will allow the transmission of the information to the bulb) of the neuron where the emission of action potentials is transmitted to the olfactory bulb. The information carried by the neuron after depolarization is decoded by this axonal cone.
Once these olfactory signals come out of the epithelium, the axons (= extensions) of the receptor cells gather and form a multitude of bundles that together make up the olfactory nerve. This nerve is defined as the junction between the entire mucus, epithelium and axonal cone, and the olfactory bulb. This bulb is essentially characterized by the presence of glomeruli forming a mass of nerve tissue capable of receiving the primary information from the cone.
