pgAdmin 1.8 online documentation
pgAdmin Options - Tab 5 (Display)
Show System Objects in the treeview - this option allows objects such as system schemas (e.g. pg_temp*) and system columns (e.g. xmin, ctid) to be included or excluded in the browser tree.
The list of check boxes is used to select which object types to show in the browser tree. By default, only the most commonly used object types are shown. Reducing the number of object types shown can increase the speed of pgAdmin when querying the system catalogs. Use the Default button to reset the list to it's default settings.