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: Previous studies have examined the expression and regulation of tyrosine kinase receptors ( Trks ) in micturition reflexes with urinary bladder inflammation .
### Output Text:
Previous studies have examined the expression and regulation of <span class="chemical">tyrosine</span> kinase receptors ( Trks ) in micturition reflexes with urinary bladder inflammation . 