Animals　utilize　specialized　sensory　neurons　enabling　the　detection　of　a　wide　range　of　environmental　stimuli　from　the　presence　of　toxic　chemicals　to　that　of　touch.　However,　how　these　neurons　discriminate　between　different　kinds　of　stimuli　remains　poorly　understood.　By　combining　in　vivo　calcium　imaging　and　molecular　genetic　manipulation,　here　we　investigate　the　response　patterns　and　the　underlying　mechanisms　of　the　C.　elegans　phasmid　neurons　PHA/PHB　to　a　variety　of　sensory　stimuli.　Our　observations　demonstrate　that　PHA/PHB　neurons　are　polymodal　sensory　neurons　which　sense　harmful　chemicals,　hyperosmotic　solutions　and　mechanical　stimulation.　A　repulsive　concentration　of　IAA　induces　calcium　elevations　in　PHA/PHB　and　both　OSM-9　and　TAX-4　are　essential　for　IAA-sensing　in　PHA/PHB.　Nevertheless,　the　PHA/PHB　neurons　are　inhibited　by　copper　and　post-synaptically　activated　by　copper　removal.　Neuropeptide　is　likely　involved　in　copper　removal-induced　calcium　elevations　in　PHA/PHB.　Furthermore,　mechanical　stimulation　activates　PHA/PHB　in　an　OSM-9-dependent　manner.　Our　work　demonstrates　how　PHA/PHB　neurons　respond　to　multiple　environmental　stimuli　and　lays　a　foundation　for　the　further　understanding　of　the　mechanisms　of　polymodal　signaling,　such　as　nociception,　in　more　complex　organisms.