Plugin Update Hook

Hi All,

I have a plugin that stores data in the options table, like this:

a:3:{s:13:”enable_ticker”;s:1:”1″;s:15:”enable_editorst”;s:1:”1″;s:16:”editor_style_loc”;s:21:”/css/editor-style.css”;}

However if I updated my plugin with another feature and I wanted it to be enabled by defult after upgrading, how would I go about doing this? (essentially adding another variable to the options string)

I dont think there is an update hook is there?

Thanks
Dan