UC San Diego

In this chapter, basic aspects of the anatomy, physiology, and chemical responsiveness of the human trigeminal system were reviewed. Additionally, studies demonstrating that ocular trigeminal sensitivity may be similar to intranasal trigeminal sensitivity were reviewed. Among other topics addressed were the functional dissociation of CN I and CN V responses, the application of modern structure-activity studies in predicting irritative responses of volatiles, and an assessment of potential functional interactions between CN I and CN V. It is apparent from the material reviewed in this chapter that the trigeminal system is generally less sensitive to volatile agents than the olfactory system, and very few, if any, odorants fail to stimulate CN V at high enough concentrations. It is pointed out that knowledge of the factors responsible for nasal and ocular irritation is not only of theoretical interest, but of practical interest as well, particularly in relation to environmental concerns.