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30 Cards in this Set
- Front
- Back
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What time scale is an infraradian rhythm?
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A period longer than 24h
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What time scale is an ultraradian rhythm?
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A period under 24h
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What is the name for the phenomenon where a rhythm exists in the absence of environmental cues?
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Free Running
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What is the name for an external environmental cue?
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Zeitgber
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Which brain nucleus is responsible for generation of circadian rhythms?
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Suprachiasmatic nucleus (just above the optic chiasm)
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What is the predominant zeitgber?
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Light
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What are the two modes of regulation to the central oscillator?
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Negtive feedback (down regulates its own expression) and Post transcriptional control
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How do zeitgbers reset the central rhythms?
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Zeitgbers act on the negative feedback loop. Either degrade a componenyt whos levels decrease in the day or one whose levels decrease at night
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What time of day are the frequency of SCN action potentials at their highest?
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Middle of the day
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Name a hormonal; neuromodulator that can entrian clock genes?
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Melatonin.
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How does melatonin shift the clock genes? -
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Shifts the rhythm os SCN firing
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Why does jet lag occur?
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State of internal desynchronisation.
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What cells from the eye send direct input about light to the SCN?
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Melanopsin containing ganglion cells
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Which neurotransmitter activates NMDA receptors on the SCN and increases their firing rate?
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Glutamate
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What is a peripheral oscillator?
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Found in all body cells - cannot maintain rhythmicity in the absence of the SCN. They are entrained by neiral and hormonal influence controlled by the SCN
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How is ovulation controlled in the rat?
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LH surge occurs at night (nocturnal mating) plus ovulation is also determined on the length of the luteal phase thus it is both centrally and peripherally controlled
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Where is melatonin released from?
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The pineal gland
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When are concentrations of melatonin low?
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During daylight hours
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When are melatonin concentrations high?
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During nighttime hours
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Which cells secrete melatonin?
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Pinealocytes
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What triggers melatonin secretion?
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Sympathetic adrenergic innervation (darkness) via thee superior cervical ganglion
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Where are melatonin receptors?
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SCN and anterior pituitary
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What does increased melatonin trigger in sheep?
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GnRH neurons to increase their pulse frequency
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At what age does puberty occur in ewe lambs?
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6-7 months
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Name 4 things influencing onset of puberty
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Genetics, Nutritional Status, Season, Stress
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Which cattle breeds large or small reach puberty sooner?
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Small
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Give an example of how an environmental cue could trigger puberty.
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Male urine can trigger female puberty (mice, rats, sheep, goats, pigs and cows)
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What hormone may be associated with puberty onset?
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Leptin - low levels, low fat, reproductive activity arrested.
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What is a sign that a mare is in oestrus?
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Clitoral winking, raised tail
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Name some signs that a ***** (female dog for the purpose of flashcard exchange!) is in oestrus?
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Restless, disobedient, vulva licking, leave house to access dogs, increased polyuria. Alpha females more aggressive to those in her pack.
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