Diurnal or Cir Card Ian Rhythms

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Diurnal or Diurnal or CircardianCircardian RhythmsRhythmsDiurnal or Diurnal or CircardianCircardian RhythmsRhythms

6/19/2010 1ICLS/SILLIMAN UNIVERSITY/ Ms. Gissele C. Palero



Colin Pittendrigh(1919-1996)

³many organisms on³many organisms on

Earth operate under a Earth operate under a

circardiancircardian (roughly(roughly2424--hour)hour)

schedule«which is schedule«which is

innate«´innate«´




Diurnal or Circardian RhythmsDiurnal or Circardian Rhythms

secretion rates of many hormonessecretion rates of many hormones

rhythmically fluctuate up and down as arhythmically fluctuate up and down as a

function of timefunction of time it is the most endocrine rhythmit is the most endocrine rhythm

CircardianCircardian ± ± around a dayaround a day

DiurnalDiurnal ± ± dayday--nightnight




Diurnal or Circardian RhythmsDiurnal or Circardian Rhythms

causes repetitive oscillation in hormonecauses repetitive oscillation in hormone

levels that arelevels that are very regular every 24 hoursvery regular every 24 hours

caused bycaused by endogenous oscillatorsendogenous oscillatorsparticularly theparticularly the pineal glandpineal gland




Pineal glandPineal gland

andandCircardian RhythmCircardian Rhythm




Pineal glandP

ineal gland

tiny, pinetiny, pine--cone shaped structure in thecone shaped structure in the

center of the braincenter of the brain secretessecretesmelatoninmelatonin (1959) to keep the(1959) to keep the

body¶sbody¶s inherent circardian rhythms ininherent circardian rhythms in

synchrony with lightsynchrony with light--dark cycledark cycle




Tryptophan 5-hydoxytryptophan

5-hydroxytryptamine

(serotonin)

N-Acetyltransferase

+Acetyl-Co-A

N-Acetyl-5-hydroxytryptamine

(N-acetylserotonin)

6-Hydroxymelatonin (liver )

N-Acetyl-5-methoxytryptamine

(melatonin)

Other metabolites (brain)




Suprachiasmatic NucleusSuprachiasmatic Nucleus

(SCN)(SCN) ((suprasupra= above;= above; chiasmachiasma= cross)= cross)

master biological clockmaster biological clock that serves asthat serves as

thethe pacemaker pacemaker for the body¶sfor the body¶s circardiancircardian

rhythms consisting of arhythms consisting of a cluster of nervecluster of nerve

cell bodies in the hypothalamuscell bodies in the hypothalamus aboveabove

thethe optic chiasmoptic chiasm, the point at which part, the point at which part

of the nerveof the nerve fibersfibers from each eye crossfrom each eye cross

to the opposite half of the brainto the opposite half of the brain




SCN¶s circardian oscillationSCN¶s circardian oscillation

specificspecific self self--starting genesstarting genes within the SCN within the SCN

neurons set in motion a series of eventsneurons set in motion a series of events

that brings about thethat brings about the synthesis of clocksynthesis of clock

proteins in the cytosolproteins in the cytosol surrounding thesurrounding the

nucleusnucleus





as the day wears on, theas the day wears on, the clock proteinsclock proteins

continue tocontinue to accumulate to reach a criticalaccumulate to reach a critical

massmass and areand are transported back in thetransported back in the

nucleusnucleus. Here they block the genetic. Here they block the genetic

process responsible for their production.process responsible for their production.





As the block proteins dwindle, the cycle As the block proteins dwindle, the cycle

repeatsrepeats Each cycleEach cycle takes about a day.takes about a day.




PathologyPathology

May be the site of pinealomas or

germinomas

S/S:-increased intracranial pressure-visual abnormalities

- ataxia

-Parinaud¶s syndrome (upward gazepalsy, absent pupillary light reflex, wide

based gait, paralysis of convergence)




Parinaud¶s syndrome




PathologyPathology

Results primarily fromResults primarily from deficiency of deficiency of

hypothalamic hormoneshypothalamic hormones

Tx: surgical removal or decompressionT

x: surgical removal or decompressionradiation therapyradiation therapy

hormone replacementhormone replacement


Diurnal or Cir Card Ian Rhythms

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