submission - Independent Pilots Association

The oscillarrons appear as \ a\es, and the time to complete one full '*'a\e !-ycle is called a
"çrenod." The¡ are dirided rnto th¡ee -sroups by'lengrh of ¡le rh¡thm L'ltradian are rh¡rhms of 20
hours or less. Crrcad¡an encompasses rh¡rhms bet'*een 20-lS hours. and Infradian a.re rh¡rhms
grearer tha¡r l8 hours The laner include rhythms called circaseptan 17 days, t 3 days).
circadiseptan (14 days t 3 days). circavigintan (21 days, t 3 days). circatrigintan (30 days. r 5
days) and ci¡caa¡rnual (one )'ear. t 3 months). According to Haus & Touitou (1994) thcrc is
cvidence of 7 dzy,30 day a¡d annual rhythms in humans, as well as the circadian and ultrdia¡r
rhythms.
Circadian rhythms have bcca recognizcd for dccadcs. Ye¡ thc biological clock that regulatcs thc
24-hour physiological a¡d bcbavioral rh¡hms was not idcntificd until the 1970s. Tbcsc t*o
bilaterally locaæd nrrclci cellcd thc suprachiasmic nuclei (SCN) a¡e locarcd above thc opth
chiasm in thc antcrior hypothalamus. Tbcsc nrrclei arc coosidcred the circadian pæcrnalcs
Destrucrion of thcsc nuclei producc an arrh¡hmia and scverc disruptioo bctwccn bchavior and
physiological pararncæn including the timing of food i¡take and slecp. Thcy appcar not to
rcgulate thc amount of cither of these behaviors (Turck & Recth, 1996).
Signals produccd by the SCli a¡e botb hormonal and neuual. Graflcd nuclei withot¡t ncurd
connections restorc ci¡cadia¡ rhythrns of eating and activiry. Mcluonin sccrctions, howeve¡, a¡t
not restored, suggesti¡g neuÍon control. MelUonin reccPtors bave becu found in thc SC?.f and
appear to bc part of a fecdback mechanism thar causcs shifu i¡ thc ci¡cadia¡ clock. Tbc SO.f has
bee n found to possess its own built-in rh¡hm. Ev'idencc gathercd thus far indicares that SCÎ{
receive i¡for¡ation about the light-dark cycle via t*o neu¡al pathwal's fromthe optic nene. one
from the retinohy'pothalamrc t¡act and the other tfuougb the genicu.lohypothalamic Fact. Tbc laner
path*a' appcå¡s to pro\ide inforrnation or signals tlrat bclp witå recnrr¿i¡¡ænt a.ftcr a shiñ i¡ thc_
lighr-dark c¡cle. Bur reccit rese¿¡ch appea¡s to indicate tàat otler photo receptors may also Þ
inrolred i¡ the entrilrunent process rCampbell & \lurphr. 1998'
Peaii lerels oiph.\srolragrcal functronrng, occur dunng the [rght pha-se of the Ught/dark c¡cle This
sy'nchronizalrr--¡n of ph¡sroloercaJ rh¡thrns enhances *ork pcrformance during the da¡irnc and
supporrs slee p at rughr b¡ rurrung dox n the rne nbolrc thermosut The internal synchronizarion of
rhe ranable metabolrc p¿rram€ters *ith the light/dark cyclc are runed for optimal functioni-og.
Over 100 b'rologr;al rh¡rhrns are geneùcally generated withrn the human body, then enrai¡ed or
synchroruzed to bener *ork in concen 1'Wehr. 199ó; Talahasi, 199ó). The greaær the
synchromzation bet,*'een hormone production. nrclabo[c rale. enzyrnc a¡d neurotransmiue¡
s) nrhesis. r}e hLgher tle amplirude of the rh¡hm and the gre¿ter the communication ber*ecn the
body's cells Thus, tìe maintenance of a suong circadian rh¡hm ca¡ries with it considerable
ramifications for good heållh, *ell-being. and functioning Cw*eiu. 19961.
The suprachiasnuc nuclei, togetlrer'*itb the pineal gland, function as rneøboüc a¡d behavioral
concen conducton n cue *ith enrúonmental facton such as hghVdark. næal timing. social
inreraction, and phrsrcal activity. This synchronization of internal and behavioral *'ith the
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