Nervous control of the gills

The fishgillisahighlycomplexorganthatperformsawidevarietyofphysiological processes andreceivesextensivenervousinnervationfrombothafferent(sensory) and efferent(motor)fibres.Innervationfromthelattersourceincludesautonomic nerve fibresofspinal(sympathetic)andcranial(parasympathetic)originwhose primary roleistoinducevasomotorchangeswithintherespiratoryornonrespiratory pathways ofthegillvasculature.Autonomiccontrolofthegilloccursbynervefibres identified asadrenergic,cholinergic,andmorerecentevidenceindicatesthat nonadrenergic–noncholinergic (NANC)nervefibres,suchasthosethatexpress amines, peptides,ornitricoxide,mayalsoplayanimportantrole.Thedistribution and physiologicalfunctionofNANCnervefibres,however,islessclear.Thisreview primarily discusseshistochemicalstudiesthathavecharacterizedthenervous innervation andautonomiccontrolofthegillvasculature.Inaddition,supporting evidence fromrecentstudiesfortheefferentcontrol,ormodulation,ofother homeostatic processesinthegillisexamined.