The Command Department on the USS Tomcat NCC 62114 starts with the ships Captain, and going down via the First Officer and Second Officer if one is assigned. Nominally the next in command would be the officers with the most experience, but the setup on the Tomcat it would devate to Operations should no other eligable command personnel are available to take over.
The Senior Command Level is not a Department as such, but it contains the majority of the Senior Staff. While Department Heads (Senior Staff) will have different colour shirts on, all Department Heads are classed at Senior Command Level. On a Starship regardless of its size, the Senior command Level Structure is standard on most ships, but on the USS Tomcat the structure is slightly different to that of the norm as all Department Heads and their subordinated must have a basic working knowledge of other Bridge systems on the ship.