Circadian Rhythms & Sleep (8)

what’s the difference between ultradian, circadian, infradian, and circannual?

• Each of those terms refers to the length of a cycle of SOMETHING

• Ultradian (< day)

  • ex. 2-4 hr vole feeding cycles, sleep cycles go in 90 minutes

• Circadian (about a day)

• Infradian (> day)

  • ex. estrous, menstrual cycles

• Circannual (about a year)

  • ex. squirrel’s body weight, hibernation, seasonal affective disorder (SAD)

how does pain sensitivity change in rats throughout the day? how do we know this?

• Method

  • measured the reaction time of rats to move tail away from hot surface

• Pain Sensitivity Changes

  • least sensitive around 6pm, most sensitive at 2am

  • shows that pain sensitivity changes based on time of day

Explain the injection of the toxic dosages injected in rats and how their mortality fluctuated

• The mortality of rats being injected by deadly poison was different based on time of administration

what does the melatonin cycle look like?

• During the day time, virtually no melatonin

• During night time, melatonin spikes

what are some consequences related to Circadian Rhythms?

• Public safety

  • People have to work during times when their body tells them to SHLUMP

  • ex. Exxon oil spill, gas release in India

• Medical Interventions

  • certain drugs have more effectiveness dependent on time of administration

  • ex. child chemotherapy effectiveness changes based on time of day

• Experimental control

  • can affect outcome of research so account for it

• Educational policy

  • delay start of school day leads to positive effect in learning

• Shift-work

  • more likely to cause accidents late at night

  • they be suffering

• Physiology

what is the history of discovering the existence of an internal endogenous clock?

• DeMarain: plant experiments in 1700s

  • plants opened leaves during day and closed them at night

  • Demarain wanted to know if its light-dependent so it put it in a cellar and it still opened and closed

  • concluded that it came from within plant

• Aschoff bunkers

  • put people into bunkers as an experiment

  • they kept their rhythms even when isolated from outside

• Blind people

  • not aligned with day-night but they still show sleep-wake cycles

• DD (animal studies)

  • studied in animals in complete darkness

how long does it take a hamster to get over jetlag?

• Actogram shows a gradual shift toward day-night cycle

• takes about 5 days to adapt free-wheel running behavior (4 hr delay)

what part of our eyes relates to our circadian rhythm?

• We have a specialized visual system called ipRGC (intrinsically photosensitive retinal ganglion cells)

  • contain melanopsin

Describe the Transcription-translation feedback loop (TTFL)

• per1 transcribed → per1 translated → goes to cytoplasm and forms dimers → dimer goes to nucleus and inhibits transcription → degrades so inhibition is released (loops again)

what is advance sleep phase syndrome? what gene was a determiner is having ASPS?

• makes you go to sleep earlier. affects your sleep phase

• mutation in hPer2 gene will result in ASPS

what is the SCN? what happens when you lesion it? what happens when you isolate the SCN in vitro?

• SCN was theorized to be crucial for circadian rhythm

  • information from eyes made a pitstop at SCN (right above optic chiasm)

• When lesioned . . .

  • healthy animals will lose free-running cycle

    • they start running sporadically

• When in vitro . . .

  • SCN showed evidence of maintaining clock-like features

    • measured by looking at the action potentials of SCN over a 24-hour period

how did researchers restore circadian rhythms in SCN lesioned rats?

they put methamphetamine in their water

what is the current model of the role of the SCN?

• SCN sits atop a hierarchy of clocks

  • normally coordinates entire system

• Additional, weaker clocks throughout brain/body

• Normally dampen without SCN

• Under permissive condition, these can be coordinated

Are individual cells of the SCN capable of maintaining a 24 hour period? How did we answer this question (two ways)?

• Researcher put single SCN cells in vitro:

  • they grew cells on a micro-electrode plate

  • one cell has a circadian rhythm

  • different cells have different period etc.

• Researcher switched from electrical recording (clock output) to clock-gene recording (gear of the clock)

  • used glow-in-the-dark protein from fireflies

    • attached to a clock gene

  • Results:

    • SCN increases/decreases in PER2 protein

Why do West Coast Teams perform better during Monday night football?

• Not because one team is better than the other

  • performance during the week is about even

• Explanation

  • because of jetlag

how do dolphins and whales go to sleep?

• They have specific sides of their brain sleep at a time

what are the characteristics of sleep?

• Decreased activity

• Lowered sensitivity to stimuli

how long does it take a newborn to develop a day-night cycle?

around 6 months

what is a chronotype? how does this change over time?

• Chronotype: characteristic of your sleeping behavior

  • Larks: go to sleep hella early

  • Owls: go to sleep hella late

  • calculated by looking at midpoint between bedtime and wake up time

• Chronotype as child is very low, peaks around 20 years old and decreases over time

what is social jet lag?

• No sleep during the week due to obligations

  • work, school, whatever

• Extra sleep on weekends

  • to catch up

• Could get even less sleep on weekends

  • go to party, go out, social occasions results in sleeping later

what is the difference between Process S vs Process C?

• Process S: sleep debt; homeostasis

  • all-nighter accumulates sleep debt that requires MORE sleep to decrease

• Process C: Circadian

  • This rhythm is still in place even after an all-nighter you will feel more energy the next day

what method did researchers use to induce total sleep deprivation (TSD) in rats?

• Method

  • they put rats in a pot of water standing on a small platform. Everytime they went to sleep they fell in the water, meaning they couldn’t sleep

  • Results

    • They all died within 11-32 days from various causes

    • causes of death include: skin diseases, weight

How does sleep deprivation affect performance in cognitive assessments? what research did we do to conclude this?

• Research

  • Had four groups sleep in lab: total sleep dep, 4h, 6h, and 8h

• Results

  • Total sleep deprivation resulted in poor performance on cognitive tasks

  • 8 hours in bed group (6.5 hours sleep) results in slightly decreased performance over 2-week span

  • 6 hour group showed significant progressive decrease in cognitive performance

    • after 2 weeks comparable to 24 hour sleep deprived person

  • 4 hour group sees comparable performance to 24 hour sleep deprived person in one week

• Self-Reported Sleepiness Score

  • 6 and 4-hour group self-report decent sleep score in spite of decreased cognitive performance

    • suggests they are not aware of how bad it is

what type of EEG waves are associated with being awake?

• Alpha waves

  • relaxed arousal

• Beta waves

  • attentive arousal

what type of EEG waves are associated with Stage 1 and Stage 2 sleep?

• Stage 1 Sleep

  • theta activity

• Stage 2 Sleep

  • Sleep spindle: transient burst of synchronized potential

  • K-complex: transient, high amplitude spike; response to sounds

• Stage 3 Sleep (slow wave sleep)

  • Delta Activity

• Stage 4 Sleep (slow wave sleep)

  • Delta Activity

• REM sleep

  • theta & beta activity

  • characterized by:

    • rapid rolling eye movement

    • desynchronized EEG

    • skeletal muscle atonia

      • shuts down motor activity

      • associated with REM behavioral disorder where person moves around in sleep

    • dreaming

what are the sleep disorders discussed in lecture?

• Insomnia

• Sleep talking/walking

• Night terrors

• REM Behavioral Disorder

• Sleep Paralysis

  • muscle atonia while conscious

what are the different types of insomnia?

• Insomnia

  • onset, maintenance, or terminal insomnia

• Chronic Insomnia

  • difficulty concentrating

  • memory problems

  • auto accidents

  • inability to enjoy family / social relationship

  • 2 fold greater risk for major depression

• Fatal Familial Insomnia

  • prion mutation

  • stop sleeping within 18 months

  • possible insomnia cause of death?

what is narcolepsy? why does this happen? what does the anatomy of narcoleptic brain tell us?

• Characterized by suddenly falling asleep

• Narcolepsy in dogs . . .

  • showed a mutation of orexin/hypocretin receptor

• Anatomy of Narcoleptic Human Brains show . . .

  • sections of brain show that narcoleptic brains do not have mRNA for hypocretin

  • suggests lack of hypocretin is cause of narcolepsy

what’s a good treatment for people with sleep apnea?

• CPAP: continuous airway pressure

  • mask that puts pressure on your respiratory passages so you don’t stop breathing

what neurotransmitters are involved in our sleep cycles?

• Norepinephrine

  • alerts large areas of brain

• Serotonin

• Acetylcholine

  • keep cortex alert

• Histamine

  • keeps us awake

• Adenosine

  • caffeine acts on this

  • alerting effect

What amount of each neurotransmitter is released during REM?

• REM

  • ACh high

  • NE low

  • 5-HT low

what are some theoretical purposes to sleep?

• physiological restoration

• memory and learning

• metabolic processes

• temperature regulation

  • ground squirrels de-hibernate to sleep

what studies have we done to conclude if sleep is essential in consolidating learning?

• Study

  • had participants learn finger tapping task and measured improvement before and after sleeping

  • after sleeping they improved their ability to do task

• Another Study

  • Found a positive correlation between % stage 2 NREM4 sleep and % improvement

• Weaknesses of Studies

  • only measured on specific, simple task

  • definitely can learn without sleep

  • sleep stages still largely based on correlations