ABSTRACT
Mediation of NI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 3.6.2 Suggested Follow-Up Work . . . . . . . . . . . . . . . . . . . . . . 101
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
For the majority of individuals, most of the air taken in with each inhalation passes through the nasal cavity. Under normal environmental conditions, the air is warmed and humidified as it passes through the upper airway-the nasopharynx and the trachea. A small fraction of the chemical stimuli in the incoming airstream is deposited onto patches of mucus overlying dendrites of the olfactory receptor neurons and endings of the trigeminal nerve. A fraction of these deposited molecules act as stimuli that trigger action potentials in the olfactory nerve (cranial nerve I), branches of the trigeminal nerve (cranial nerve V), or both. An excellent explanation of the anatomy and innervation of the nasal cavity, from the standpoint of chemosensitivity, is provided by Silver and Finger (1991). If both nerves are intact, as is the case in the vast majority of individuals, it is unlikely that nasal irritation (NI) would be experienced in the absence of odor sensation. Thus, a given inhalation and the consequent chemosensory stimulation are likely to produce one of three outcomes: no sensation, odor sensation but no NI, or both odor sensation and NI. The third case is the subject of this chapter.
