hmmm did it have a domed shell like a helmet or was it flatter (like an RES)?
About how big was it? Did its head look to big for its body? was it mostly yellow or mostly another color with only some yelllow on it? Did you pic it up? Did its underside shell have a hinge?
according to the state these are the turtles native to tennessee:
do a google image search for each and see if it looks like any of them (there should be plenty of pics of each use EITHER the scientific name OR the common name when you search):
TURTLE, COMMON MAP (GRAPTEMYS GEOGRAPHICA )
TURTLE, COMMON MUD (KINOSTERNON SUBRUBRUM )
TURTLE, COMMON MUSK (STERNOTHERUS ODORATUS )
TURTLE, FALSE MAP (GRAPTEMYS PSEUDOGEOGRAPHICA )
TURTLE, LOGGERHEAD MUSK (STERNOTHERUS MINOR )
TURTLE, MISSISSIPPI MAP (GRAPTEMYS KONII )
TURTLE, PAINTED (CHRYSEMYS PICTA )
TURTLE, SMOOTH SOFTSHELL (TRIONYX MUTICUS )
TURTLE, SNAPPING (CHELYDRA SERPENTINA )
TURTLE, SPINY SOFTSHELL