A B737 PLT ATTEMPTING TO CLOSE ENG ANTI-ICE VALVES MISTAKENLY TURNED OFF ALL HYD PWR. FLT ATTENDANT INJURIES RESULTED WHEN HYD PWR RESTORED.

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THE FO WAS FLYING THE ACFT AND THE CAPT WAS THE PM. AT 24000 FT; IN DSCNT INTO ZZZ ARPT (ABOUT 70 MI FROM ARPT) THE FO INEXPLICABLY TURNED OFF ALL HYD PUMPS IN THE ACFT; PUTTING THE ACFT INTO MANUAL REVERSION. THE ACFT WAS ALREADY IN AN ABNORMALLY NOSE LOW ATTITUDE; AND NOSE DOWN ATTITUDE WAS INCREASED AFTER HIS ACTIONS. ALL HYD PUMPS WERE TURNED OFF BY THE FO IN A RUSHED AND UNVERBALIZED ACTION WHILE THE CAPT WAS INVOLVED IN OTHER DUTIES TALKING ON THE RADIO AND REFERRING TO VARIOUS ARPT CHARTS. THE FO DID NOT MAKE ANY EFFORT TO COORDINATE OR VERIFY HIS ACTIONS WITH HIS FELLOW CREW MEMBER. THEREFORE; THE CAPT WAS COMPLETELY UNAWARE OF THE QUADRUPLE HYD PUMP FAILURE. THE FO MISTAKENLY THOUGHT HE WAS TURNING OFF THE ENG ANTI-ICE SWITCHES; AND ADDITIONALLY CANCELED THE MASTER CAUTION WARNING WITHOUT NOTIFYING THE CAPT OF THAT ACTION; UNDER A FURTHER MISTAKEN IDEA THAT THE MASTER CAUTION HAD SOME RELATION TO THE ANTI-ICE SWITCHES. WHEN THE ACFT REACHED AN ALARMING NOSE-DOWN ATTITUDE; THE CAPT TOOK CTL OF THE ACFT (WHILE STILL UNAWARE OF THE HYD FAILURE). THE CAPT IMMEDIATELY RECOGNIZED THE MANUAL REVERSION SITUATION WHEN ATTEMPTING TO RECOVER THE ACFT AND DISCOVERED ALL 4 HYD PUMPS IN THE OFF POS. THE FO AT THIS POINT ALSO PULLING BACK ON THE CTL WHEEL WITH CONSIDERABLE FORCE; SO WHEN THE HYD PUMPS WERE TURNED ON (AND THE CAPT RELEASED PRESSURE ON THE CTL COLUMN) THE FO DID NOT RELEASE THE COLUMN AND A STRONGER THAN NORMAL PULL-UP RESULTED WHEN ALL PUMPS WERE TURNED BACK ON. THE STRONG PULL-UP RESULTED IN NO PAX INJURIES; HOWEVER; 2 FLT ATTENDANTS WERE KNOCKED TO THE FLOOR AND INJURED. 1 FLT ATTENDANT WAS ONLY INJURED SLIGHTLY; AND THE OTHER FLT ATTENDANT INJURED HER ARM; BUT WAS ABLE TO CONTINUE ON THE NEXT FLT. ADDITIONAL TRAINING FOR THE FO TO BE MORE CAREFUL WHAT SWITCHES HE TURNS OFF AND ON; AND TO NOT DO SO IN A MANNER THAT IS UNNOTICEABLE TO THE CAPT. SUPPLEMENTAL INFO FROM ACN 765246: WE BROKE OUT BELOW THE CLOUDS AND I THOUGHT I TURNED THE ENG HEAT BACK OFF (L HYD PUMPS ACTUALLY); I GLANCED UP TO CHK THAT THE VALVES HAD CLOSED AND NOTICED THAT THE LIGHTS ILLUMINATED TO THE L OF MY HAND AND I PROCEEDED TO TURN OFF THE ENG ANTI-ICE (R HYD PUMPS). IN THE SECONDS TO FOLLOW I THOUGHT I LOST MY VNAV PATH AS I WAS NOW CLRED TO 11000 FT. THE AIRPLANE WAS NOW ABSENT HYDS AND WAS NOSING DOWN AND ACCELERATING. I WAS CONCERNED ABOUT GETTING MY VNAV PATH BACK AS THE CAPT QUICKLY AND ACCURATELY RECOGNIZED A FLT CTL PROB AND HE PUNCHED OFF THE AUTOPLT. IN THE PROCESS OF SIMULTANEOUSLY MANUALLY RAISING THE PITCH AND TURNING THE HYDS BACK ON; I INDUCED A MODERATE TURB. I WILL NEVER MOVE AN OVERHEAD SWITCH AGAIN WITHOUT FIRST CONFIRMING VISUALLY I HAVE INDEED GRABBED THE CORRECT SWITCHES.