In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: Nociceptin , also known as orphanin FQ , is an endogenous ligand for the orphan opioid receptor - like receptor 1 ( ORL1 ) and involves in various functions in the central nervous system ( CNS ) .
### Output Text:
<span class="chemical">Nociceptin</span> , also known as <span class="chemical">orphanin FQ</span> , is an endogenous ligand for the orphan opioid receptor - like receptor 1 ( ORL1 ) and involves in various functions in the central nervous system ( CNS ) . 