keep up in WordNet English dictionary

1. keep in safety and protect from harm, decay, loss, or destruction
   "We preserve these archeological findings"; "The old lady could not keep up the building"; "children must be taught to conserve our national heritage"; "The museum curator conserved the ancient manuscripts"
   conserve  preserve  maintain  keep up 
   
2. keep informed
   "He kept up on his country's foreign policies"
   keep up  keep abreast  follow 
   
3. prevent from going to bed at night
   "The anticipation of the trip kept the children up all night"; "I kept myself up all night studying for the exam"
   keep up 
   
4. maintain a required pace or level
   "He could not keep up and dropped out of the race"
   keep up 
   
5. lengthen or extend in duration or space
   "We sustained the diplomatic negotiations as long as possible"; "prolong the treatment of the patient"; "keep up the good work"
   prolong  sustain  keep up 
   

keep up in English Wiktionary