Daily changes in light intensity major environmental

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Unformatted text preview: ynchronized with acAvity levels driven by surrounding environment 9 Circadian Rhythms •  The internal clock that regulates circadian rhythms is synchronized, or entrained to the daily Light ­Dark (LD) cycle and other social and environmental cues. •  Endogenous Period of the biological clock is ~ 24.2 hours •  The Aming of sleep usually bears a characterisAc relaAonship to the environment and to other circadian rhythms in the body. •  Daily changes in light intensity –  Major environmental cue used to adjust SCN master clock –  Photoreceptors in reAna pick up light signals and transmit them directly to SCN –  SCN relays message regarding light status to pineal gland 10 Visual System SCN 24-h LD Cycle Eye Retina Optic Chiasm Lateral Geniculate Visual Cortex 11 Human SCN 12 Melanopsin PhotosensiAve Ganglion Cell: A New ReAnal Photoreceptor 13 Sleep without a Biological Clock 14 Clinical Laboratory Values 15 SAmulus ­Response (SR): Time of Day Responses A. 100 75 50 25 Chemotherapeutic Agent 2 6 10 14 18 22 B. 100 75 50 25 Radiation C. 100 75 50 25 0 2 6 10 14 18 22 Bacterial Infection 2 6 10 14 18 22 Time of Day (hr) 16 Jet Lag 17 SR: Light and the RegulaAon of...
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