Editing Lateral line (section)

== Signal transduction ==

[[File:Lateral line rate coding.svg|thumb|center|upright=2.5|Lateral line rate coding indicates direction and sometimes strength of stimulus. One neuromast shown.]]

The hair cells are stimulated by the deflection of their hair bundles in the direction of the tallest "hairs" or [[stereocilia]]. The deflection allows [[Ion|cations]] to enter through a [[Mechanosensitive channels|mechanically gated channel]], causing depolarization or hyperpolarization of the hair cell. Depolarization opens [[Cav1.3|Ca<big><sub>v</sub></big>1.3]] calcium channels in the [[Epithelial polarity|basolateral membrane]].<ref>{{Cite journal |last=Baker |first=Clare |date=June 11, 2018 |title=Insights into Electroreceptor Development and Evolution from Molecular Comparisons with Hair Cells |url=https://academic.oup.com/icb/article/58/2/329/5020173?searchresult=1#186667130 |journal=Integrative and Comparative Biology |volume=58 |issue=2 |pages=329–340 |doi=10.1093/icb/icy037 |pmid=29846597 |pmc=6927855}}</ref> 

[[Hair cells]] use a system of [[signal transduction|transduction]] with [[rate coding]] to transmit the directionality of a stimulus. The hair cells produce a constant, tonic rate of firing. As mechanical motion is transmitted through water to the neuromast, the cupula bends and is displaced according to the strength of the stimulus. This results in a shift in the cell's ionic permeability. Deflection towards the longest hair results in [[depolarization]] of the hair cell, increased neurotransmitter release at the excitatory afferent synapse, and a higher rate of [[signal transduction]]. Deflection towards the shorter hair has the opposite effect, [[Hyperpolarization (biology)|hyperpolarizing]] the hair cell and producing a decreased rate of neurotransmitter release. These electrical impulses are then transmitted along afferent lateral neurons to the brain.<ref name="Flock 1967"/> 

While both varieties of neuromasts utilize this method of transduction, their specialized organization gives them different mechanoreceptive capacities. Superficial organs are exposed more directly to the external environment. The organization of the bundles within their organs is seemingly haphazard, incorporating various shapes and sizes of [[microvilli]] within bundles. This suggests coarse but wide-ranging detection.<ref name="Peach" /> In contrast, the structure of canal organs allow canal neuromasts more sophisticated mechanoreception, such as of pressure differentials. As current moves across the pores, a pressure differential is created, inducing a flow in the canal fluid. This moves the cupulae of the neuromasts in the canal, resulting in a deflection of the hairs in the direction of the flow.<ref>{{cite book |last=Kuiper |first=J. W. |year=1967 |chapter=Frequency Characteristics and Functional Significance of the Lateral Line Organ |title=Lateral Line Detectors; proceedings of a conference held at Yeshiva University, New York, April 16-18, 1966 |editor=P. Cahn |publisher=[[Indiana University Press]] |pages=105–121}}</ref>