submission - Independent Pilots Association

Thc oscillarions appcar as saves. and thc tirnc to complcte one full $a\e !-ycle'is callcd a
"p€nd." Thc¡ are dirided rnto tfuce groups b¡ lcngrh of ¡he rh.rrhm. l-ltradian are rh¡rhms of 20
hours or lcss. Crrcadran encompasscs rh¡rhms bc¡seen l0-:S hor¡n. urd lnfndiarì arÊ rhrrhrns
gre¡rcr rhan lt hours. Thc lancr includc rhythms callcd circascptan (7 da¡s, t 3 days).
circadisepan (14 days t 3 days). circavigintan (21 days. :3 days). circauigintan (30 days. t 5
days) and circaannud (onc yea¡. r 3 months). According to Har¡s & Tor¡itor¡ (1994) tbcre is
cvidcnce of 7 day. 30 day and annual rh¡hms in humanr as well as tlr cúcadian and ultradian
rh¡hms.
Ci¡cadia¡r rhythrns b¡ve bcco rccognizcd for dccadcs. Yct tbc biologicel çl6t th¡r regulecs rbe '
z4-bcrrr ptysiologicel eod bcbavioral rhythms wrs not idcotificd r¡otil üc l97os. Tbcsc trc
bitucrally locarcd nræþi crllcd thc supræhircmiç a¡¡cþi (SCI\Ð r¡e læ¿cd ¡bove ùÊ optic
chiasm in thc ütcrior bypotheh¡rr¡s. TbcsÊ nælci r¡e osidc¡cd thc circedirn pcn¡¡|cr1
Destrucrion of tl¡csc nr¡clei producc an arräytbmia and scvere disnt¡io bdu¡cca behavior urd
physiologicd paranrtcrs i¡rcluding the timing of food i¡take and slecp. TÞy appcar Dot ro
regulatc ¡hc anrcunt of eithcr of thcsc bchaviors (Tu¡ek ¿1, Rccrà. 19961.
Signals produccd by ttrc SCN arc botb bormood u¡d ncurd. Gr¿ñcd nr¡clci without ncr¡nl
coûrctioos restorc circadian rbythms of cating and activiry. Melrtoni¡ rcrctions, howeve¡, a¡e
not rcstorcd. $gges¡i¡g ncuron cootrol. Melaronin r€ccptors bave boco for¡od in thc SC.I\I rDd
appcar ro bc parr of a fecdback rncchaoism thal causcs shifu in tþ ci¡cadi¡¡ clock. Tbe SCI.I has
bccn found to posscss is own built-in rh¡hm. Evidencc gatbered thus fa¡ indicarcs rha¡ SC.¡{
receive i¡formation about thc hght-dark cycle viatrlo ncural patbways fromthc optic ner\e. one
from rhe retinohypothala¡nic tract and thc othcr through t-be geruculohypotåalamic trztct. TÞ taner
parh*'ay appcå¡s to pro\ rde rnfo¡mati_on or signals that bclp witb ¡ecorra¡¡¡ænt afrcr a shifi rn tbc
iigl',r-a"rk c¡cle. Bur rccent rc-s¿a¡ch appca¡s to ind¡care tbat othcr phoro re.-eptors ma)' also be
inrol.ed n the ent¡a:nmcnt process lCampbcll & \l,rrph¡. 1993'
Peak leicls of ph¡srolo_eical functroning occur dunng thc Lght phase of ûre lighr/dark c¡'cle This
sy'nchronÍzatron o[ph¡srologicd rh¡'thrns enhances *ork pcrfornrancc dr.urng the da¡irrr urd
suppons slccp at rught b¡ nurunt do* n ¡ìc rrr¡abolrc tlrcrmo;ut The in¡croal synchronizauon of
rhc ra¡¡ablc np¡ebolic p:ìra¡Tìctcrs *'ith the light/dark cyclc are runed for opumal functioning.
Ovcr l0O biological rh¡rhrns are gcnctically gerrcratcd within thc human body, then eouai¡cd or
synchronized to bener *'ork in conccrt 1-Wchr. 199ó:TaÌabasi. 1996). Tlr greatcr the
synchronization bctrrecn hormonc production. nre¡abolic rate. enzyn¡c a¡d ocu¡ot¡ansmicc¡
s¡'nthesis. rlrc higher thc amplirude of the rb¡hm and thc tÌe¿ter thc communicarion bcn¡eco the
body's cclls. Thus, the maintenancc of a stront circadian rhythm c¿rrics *itl it considcrablc
ramifications for good health. *cU-bcing. and functioning Cw-eh¡. 19961.
The suprachiasrruc nuclei. togctìcr w'ith the pineal gland. function as nrubolic and bchauioral
concen conduc¡ors in cue *'ith cnr'ûonmcntal factors such as tight/duk. nral timing. social
interaction. and physical activiry. This syncfuonization of in¡ernal and behaviord r*'irh rhc
Lilerature Reyie¡ Page 22