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Introduction to Brain and Behavior [NOTES] Part 9 -- I got a 92% in the course

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Department
Psychology
Course
PSB 2000
Professor
All Professors
Semester
Winter

Description
Circadian rhythms  Endogenous Rhythms  Circadian rhythms: rhythms that last about a day; human’s last around 24 h • Waking and sleeping • Hormone secretion • Urine production • Eating and drinking • Sensitivity to drugs  Age is an important factor • People around 20 like to go to bed late and wake up late → Not just leaned  Why? To prepare for changes in environment before they occur • Sunrise/Sunset • Temperature changes (day to night, seasonal)  Zeitgeber  A stimulus that can affect or reset the biological clock • Bright light: when you get up in the middle of the night to go to the bathroom/get a drink of water, you don’t turn the lights back on because it wakes you up some  Examples • Temperature • Exercise • Noise • Meals • Bright light  Jet lag  Problem is that our endogenous rhythm doesn’t match external time  Easier to travel West (stay up later than normal and “sleep in”) than East (have to go to bed early and wake up early)  Flight attendants on long trips across several time zones for > 5 years  • Smaller than average hippocampus: adjusting to jet-lag is stressful, and stress increases stress hormones and these can be toxic to the hippocampus especially • Some memory impairment  Shift work: people who work out-of-synch with regular sleep-wake cycle  Duration of sleep depends on when you go to bed (sleep less if you go to bed in the morning or afternoon)  For those who work night shift, try to sleep during day, but it is difficult • Other circadian rhythms (like temperature) do not adjust to new attempted sleep- wake cycle • You can’t just choose to be nocturnal  Lighting conditions can be helpful, but do not override basic drive to sleep at night and be active in day  Biological clock: Suprachiasmatic nucleus  Main control center for sleep and temperature circadian rhythms; cells fluctuate their activity every 24 hours  Brain transplants that prove the SCN contains a clock: • Hamsters with mutant gene causing 20 hour (instead of 24 hour) rhythm remove SCN from normal adult hamsters  replace with SCN tissue from fetal mutant hamsters  adult recipients produce 20 hour rhythm  Clock genes:  Activated, transcribed, proteins are made, bound together, and then the proteins go back to the nucleus and tell the nucleus to stop (negative feedback, takes 24 hours)  Makes proteins: per, time, clock  Small amount in the morning, increase as the day goes on  High levels (in association with another protein, “clock”) “make flies sleepy” and negatively feedback to turn genes off  Cycle begins again in the morning  Light disrupts the process: bright light flash in the night inactivates tim and resets clock  Some sleep disorders linked to problem with these genes  How does light impact the biological clock?  Retinohypothalamic pathway: • Projection that goes directly from the retina to the SCN providing it with information about light; from the retina to the hypothalamus  Melatonin  Hormone secreted by pineal gland; starting 2-3 hours before bedtime; peaks around bedtime; makes us sleepy  Pineal gets information about light (indirectly) from retina and SCN and melatonin feeds back SCN • Taken in afternoon, melatonin phase-advances the biological clock • Melatonin seems to make the cells of SCN more sensitive zeitgebers  Tumor here can make people stay awake for days  Pineal is critical for seasonal rhythms • As nights get longer, releases more melatonin  acts on many regions of the brain to change behavior and physiology to prepare for winter • As days get longer (spring), releases less melatonin; antigonadotropic; less of it means more reproductive behavior ( more important in seasonal breeders than humans…and in the interest of full disclosure, some seasonal breeders are fertile when the days are longer; others when the days are shorter) Study Questions • Define circadian rhythm and zeitgeber. Know examples of each. What is the purpose of endogenous rhythms? • Circadian rhythms: rhythms that last about a day • Sleep cycle, urine production, hormone secretion, sensitivity to drugs • Zeitgeber: a stimulus that can effect or reset the biological clock • Temperature, exercise, noise, bright light, food • What are jet lag and shift work, and what are some effects of these situations on people? • Jet lag: moving from West to East and throwing off your circadian rhythm because you lost three hours of your day • Some hippocampus damage due to stress hormones; some memory impairment • Shift work: working overnight rather than during the day • It’s impossible to just decide to be nocturnal so the night shift is very difficult to adjust to; other circadian rhythms cannot adjust as well • What is the significance of the suprachiasmatic nucleus (SCN)? What is the behavioral result of a lesion of the SCN? How did brain transplants help prove the role of the SCN? • It is the main control center for sleep and temperature circadian rhythms; it can alter length of your day; brain transplants can alter the length of your circadian rhythm • What are some genes and proteins involved in sleep, and how are they involved? • Melotonin: peaks at bedtime; makes us sleepy • Clock genes: increase as the day goes on, makes you sleepy, bright light can interrupt it • What is the retinohypothalamic pathway? In what way does it contribute to circadian rhythms? From what retinal cells does it project and where does it go? • Pathway that goes right from the retina to the SCN that provides information about light Sleep  Function of sleep  Energy conservation • When we would be relatively inefficient • Probably “original” purpose (even bacteria have circadian rhythms) • Species differ in their amount of sleep depending on how much time they devote to hunting/gathering, and how safe they are (inquiring minds) • But sleep deprivation affects cognitive processes much more than physical ones  Restoration • GABA is released during sleep and sleep deprivation increases GABA in neurons • Deprivation: dizziness, bad concentration, hand tremors, irritability, hallucinations • Low metabolic demands, so brain can rebuild proteins and replenish glycogen stores • But this really just requires rest, not just sleep → Cramming and pulling an all-nighter is not as effective as studying as then going to sleep  Memory • Learn something  sleep  have better performance • Brain areas active during learning = brain areas active during sleep • Short term memory can “take out the trash”; also “hardwire” traces destined for long- term memory storage • Genes that are upregulated during sleep belong to the neurotrophin family, as well as genes for synaptic physiology  What makes us sleep?  Melatonin (circadian)  Clock genes/proteins  Accumulation of a chemical  Neural control; hypothalamus • Part of the hypothalamus is inhibitory to wakefulness promoting regions in the brainstem and forebrain • The wakefulness and sleep promoting regions in the brain directly inhibit one another; provides for a quick transition  Stages of sleep  4 stages of non-REM sleep • 3&4 are slow wave  Stage 1 is very similar to being awake – alpha; brain activity is still high but is declining  Stage 2: brain activity still decreasing; K complexes – which serve to protect a person from being awakened by a sudd
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