Editing Chemoreceptor (section)

== Classes ==
There are two main classes of chemoreceptor: direct and distance.{{Citation needed|date=July 2010}} 
* Examples of ''distance chemoreceptors'' are:
**[[olfactory receptor neuron]]s in the [[olfactory system]]: Olfaction involves the ability to detect chemicals in the gaseous state. In vertebrates, the olfactory system detects [[odor]]s and [[pheromone]]s in the nasal cavity. Within the olfactory system there are two anatomically distinct organs: the main olfactory epithelium (MOE) and the [[vomeronasal organ]] (VNO). It was initially thought that the MOE is responsible for the detection of odorants, while the VNO detects pheromones. The current view, however, is that both systems can detect odorants and pheromones.<ref>{{cite book |doi=10.1007/400_2008_4 |pmid=19145414 |chapter=Extraordinary Diversity of Chemosensory Receptor Gene Repertoires Among Vertebrates |title=Chemosensory Systems in Mammals, Fishes, and Insects |volume=47 |pages=57–75 |series=Results and Problems in Cell Differentiation |year=2009 |last1=Shi |first1=P. |last2=Zhang |first2=J. |isbn=978-3-540-69918-7 }}</ref> Olfaction in invertebrates differs from olfaction in vertebrates. For example, in insects, olfactory sensilla are present on their antennae.<ref name="Chapman RF 1998 Chemoreception ">{{cite book |last1=Chapman |first1=R. F. |chapter=Chemoreception |pages=636–654 |chapter-url=https://books.google.com/books?id=jHUCdbgW4MAC&pg=PA636 |title=The Insects: Structure and Function |date=1998 |publisher=Cambridge University Press |isbn=978-0-521-57890-5 }}</ref>
* Examples of ''direct chemoreceptors'' include: 
** [[Taste receptor]]s in the [[gustatory system]]: The primary use of gustation as a type of chemoreception is for the detection of tasteants. Aqueous chemical compounds come into contact with chemoreceptors in the mouth, such as taste buds on the tongue, and trigger responses. These chemical compounds can either trigger an appetitive response for nutrients, or a defensive response against toxins depending on which receptors fire. Fish and crustaceans, who are constantly in an aqueous environment, use their gustatory system to identify certain chemicals in the mixture for the purpose of localization and ingestion of food. 
**Insects use contact chemoreception to recognize certain chemicals such as cuticular hydrocarbons and chemicals specific to host plants. Contact chemoreception is more commonly seen in insects but is also involved in the mating behavior of some vertebrates. The contact chemoreceptor is specific to one type of chemical.<ref name="Chapman RF 1998 Chemoreception "/>