Easiest is probably to hold Ctrl and while holding it press [ and S in succession. This will find and select the current file in the Solution Explorer. Then just expand it to see the definitions it contains. If you want, you can right click the class (the node under the source file, not the source file node itself), and click either "Scope to This" or "New Solution Explorer View" to display just the selected class in the Solution Explorer.
You probably have a different version than I have. I have an enterprise licence. You can rebind keys under Tools -> Options -> Environment -> Keyboard. In my editor, the action is called "SolutionExplorer.SyncWithActiveDocument".