Questions and Answers
Which part of the Suprachiasmatic Nucleus (SCN) contains the main pacemaker neurons?
Ventrolateral (core)
What is the main source of outputs to the rest of the hypothalamus?
Dorsomedial (shell)
What is the main stimulus for entrainment of the Suprachiasmatic Nucleus (SCN)?
Light
What is the intrinsic period for nocturnal animals?
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What gland secretes melatonin and interacts with the SCN to regulate rest-activity?
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What affects pacemaker function and has a limited distribution in the mammalian brain?
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What determines melatonin production, controlling seasonal reproduction and affecting the function and size of gonads?
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What is important for health, as maintaining a constant schedule for sleeping and eating helps the brain and body function their best?
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What affects the temporal organization of function, but does not alter the amount of activity?
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What mediates the majority of circadian photoreception in the retina?
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What is the role of the intergeniculate leaflet (IGL) in relation to the Suprachiasmatic Nucleus (SCN)?
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What is the approximate tau for diurnal animals?
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Which component of the Circadian Timing System (CTS) transduces entraining information?
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What is the role of the Suprachiasmatic Nucleus (SCN) in the CTS?
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What happens when there is ablation of visual pathways in relation to the CTS?
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What percentage of the genome in specific organs is rhythmically controlled and synchronized by the SCN?
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What is the main sense for diurnal animals according to the text?
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What is the approximate recovery period for some rhythms after Suprachiasmatic Nucleus (SCN) transplantation?
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What is the main function of the Output pathways in the Circadian Timing System (CTS)?
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What is the main role of the pacemakers in the Circadian Timing System (CTS)?
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What is the effect of Suprachiasmatic Nucleus (SCN) ablation on circadian function?
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What is the primary function of the photoreceptors and pathways in the Circadian Timing System (CTS)?
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What is the main role of the Circadian Timing System (CTS) in relation to environmental adaptation?
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Study Notes
Circadian Rhythms and the Role of the Suprachiasmatic Nucleus (SCN)
- Suprachiasmatic Nucleus (SCN) is located at the base of the hypothalamus and has two parts: dorsomedial (shell) and ventrolateral (core).
- The ventrolateral SCN contains the main pacemaker neurons and receives primary entrainment afferents.
- The dorsomedial SCN is the main source of outputs to the rest of the hypothalamus and develops in late gestation in rats.
- Retrograde tracers injected into the eye are detected in retinal ganglion cells, SCN, and intergeniculate leaflet (IGL).
- The SCN affects a wide variety of functions and ablation alters the temporal organization of the function, but the amount of activity remains the same.
- Light is the dominant stimulus for entrainment and specialized retinal ganglion cells containing melanopsin mediate the majority of circadian photoreception in the retina.
- Nocturnal animals have an intrinsic period, called tau, of about 23.5 hours and diurnal animals have a tau of about 24.5 hours.
- The pineal gland secretes melatonin and interacts with the SCN to regulate rest-activity.
- Melatonin affects pacemaker function and has a limited distribution in the mammalian brain.
- Day length determines melatonin production, which controls seasonal reproduction and affects the function and size of gonads.
- The relationship between the cellular clocks of different tissues is important for health, and maintaining a constant schedule for sleeping and eating helps the brain and body function their best.
- Good medicine requires good timing, and more than double the survival rate when treatments are administered at the optimum time of day.
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