PAX BEHAVIOR PERSONAL INJURY DISCOVERED AFTER DIVERSION TO DEP ARPT.

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WE WERE ENRTE TO LEXINGTON; KY; DEVIATING TO AVOID TSTMS WHEN THE WX RADAR FAILED AND WE HAD TO RETURN TO BNA; THE DESIGNATED ALTERNATE. WE ENCOUNTERED CLOUD-TO-CLOUD LIGHTNING; RAIN; AND TURB AS WE TRIED TO FIND A RTE AROUND AN E/W LINE OF TSTMS. TURB WAS MODERATE. OUR RADAR WAS SHOWING NUMEROUS LEVEL 4-5 STORMS WITH RADAR SHADOWS. WE WERE IN WHAT WAS PAINTING AS CLR WHEN WE HIT WIND SHEAR WITH A LOSS OF ALT AND AIRSPD. OUR RADAR EITHER BEGAN TO MALFUNCTION OR WAS ALREADY MALFUNCTIONING. WE ASKED ATC AND FINALLY COMPANY DISPATCH FOR A RERTE. AS WE BEGAN THE RERTE THE RADAR SCREEN SHOWED ONLY GREEN WHEN MINS EARLIER WE WERE LOOKING AT LARGE AREAS OF RED. WE DECIDED TO RETURN TO NASHVILLE. DURING DEPLANING A FEMALE PAX COULD NOT STAND UP. MEDICAL HELP WAS CALLED AND THEY RPTED A BUMP ON HER HEAD. WHETHER IT WAS CAUSED BY TURB - - UNKNOWN. NO PAX NOTIFIED THE CREW THE PAX NEEDED HELP UNTIL DEPLANING. OUR DUTY DAY WAS TERRIBLE: BNA-BMI-BNA- TUP-BNA-LEX. OUR ACFT WAS LATE INBOUND. THE KNOB ON OUR XPONDER FELL OFF IN BMI. WX AVOIDANCE CAUSED PROBS WITH ATC BMI-BNA. FREON AIR CONDITIONING FAILED IN TUP; CABIN TEMP 101 DEGS. WE HAD TO SIT OUT A STORM ON THE RAMP AT BNA JUST PRIOR TO BNA-TUP LEG. I HAD MADE 4 MAINT PIREPS ON THE AIRPLANE FOR MINOR PROBS AND GOT AN 'ATTITUDE' FROM THE MECHS. CAPT AND FO HAD A DISCUSSION ON THE PROPER METHOD TO AVOID TURB AND TSTMS BECAUSE THERE WAS NOT AN EASILY REACHED CREW DECISION ON THE BMI-BNA LEG. I FEEL THESE CHAIN OF EVENTS WITH HEAT FATIGUE AND FATIGUE ON THE 5 LEG DUTY DAY WITH WX; PUSHED THE CREW TO THEIR STRESS LIMITS. JUDGEMENT WAS OK BUT WE WERE 'STRESSED OUT.' WE STILL FUNCTIONED OK AS A CREW BUT WE ALMOST HAD TO 'FORCE IT.'