Of course it would not be vigorous navigating if all of those turns had been programmed at the same time as the first turn and the FMS was just executing the plan.
Up in the commercial sky is a system of virtual roads. The junctions in those virtual roads are the waypoints.
So to fly from say Newark to Los Angeles a plane will not take off and point the nose directly at Los Angeles, it will have filed a flight plan that defines the virtual roads it intends to take waypoint by waypoint. E.G. Newark> Pittsburg, PA> FortWayne, IN > Springfield, IL > Springfield, MI > Amarillo TX > oh you get the picture... Of course this is not likely to be a straight line.
Waypoints have radio beacons at them and are defined by lat / long so now GPS can also be used to navigate via the waypoints virtually rather than navigating from beacon to beacon.
As the carrier / dispatcher / crew know the flight plan, this is uploaded into the flight management system and once out of the more congested airport airspace in good weather the plane is left to fly from waypoint to waypoint along the planned route.
If you want to deviate from that route (weather etc) you ask permission from the controller in that airspace to exit the corridor (virtual roadway) you are flying on.
A plane like a 777 will both be able to monitor the radio beacon and its gps location and have a check and balance that it has reached a waypoint and set move along the steps and fly to the next waypoint.
As an aside, this is an old fashioned (and clearly safe) way of avoiding mid air collisions). The US is slowly working toward a system where you do literally point the nose of the plane in this example toward LAX and use GPS navigation and ACAS (Airborne Collision Avoidance System) to allow flights to take more efficient routes to their destinations. This should save the airlines some gas money and move the day of peak oil and save us all some bum in seat time when it happens.
http://www.faa.gov/air_traffic/briefing/
http://www.faa.gov/nextgen/
Note to add reading Camachinists point above. Unlike the way you program your GPS with just the destination and the GPS works out a route, here you are telling the GPS the route and the GPS is helping you stick to that route and not decide to take the virtual equivilant of I78 instead of the I80 that you documented in your plan.