Lecture 19: theories of sleep and circadian rhythms

How long is a circadian rhythm?

24 hours

what waves occur during wakefulness?

beta waves, 13-30Hz

irregular and low intensity

what waves occur during drowsiness?

alpha waves, 8-12Hz

much more regular, allow the body to calm down

What waves occur during stage 1 sleep?

theta waves, make up 4-5% of total sleep cycle

what waves occur during stage 2 sleep?

sleep spindles and K complexes, make up 45-55% of sleep cycle

no eye movements

are distributed unbalanced throughout the brain, help keep the brain from having too low activity

what waves occur during slow wave sleep?

delta waves, 0.5-3Hz

makes up 16-21% of sleep cycle

what occurs during REM sleep?

rapid eye movements, PGO spikes to occipital lobe, body paralysis (atonia), and dreaming

how does the synaptic homeostasis hypothesis of sleep work?

sleep is important because it allows for the body to prune weak synapses that waste energy, so it creates a more efficient system

what is a circuannual behavior?

a behavior that happens once a year, like migratory birds moving south

What is an ultradian rhythm?

A type of biological rhythm with a frequency of more than one cycle in 24 hours, such as the stages of sleep or blinking, breathing, heart rate

what is the most famous example of a circadian rhythm?

jet lag

what does endogenous mean?

generated from within, rhythms regulated without external stimuli, just using internal clock

what is a free running cycle?

The cycle of activity of an individual that is expressed in a constant environment, slightly longer than 24hours so it shifts each day, like when rats choose to run on the wheel

what is a zeitgieber?

a time giver, cues a 24 hour cycle, light, noise etc

where does the suprachiasmatic nucleus get info from?

the melanopsin retinal ganglion cells, just get info if light is present at all, so if its day or night

Where does the SCN send info to?

the pineal gland, for releasing hormones involved in circadian rhythms for melatonin

what does the pineal gland secrete and when?

melatonin is produced at 9pm and stops at 7:30am

what hormone is the synchronizer of all cells?

melatonin

what are the three grams to measure sleep?

EEG- brain activity

EOG- eye movement

EMG- muscle tension

does dreaming happen in all stages of sleep?

yes! they are probably just more boring in non REM

what is the issue with treating insomnia with barbiturates ?

they are highly addictive and tolerant builds quickly, so they become ineffective

what is the issue with treating insomnia with benzos

they are long lasting and tolerance builds too slowly, meaning people can easily take too much over an extended period of time

what is the best recommendation for treating insomnia?

cognitive behavioral therapy

what are the 3 types of insomnia?

onset, maintenance, termination

What is narcolepsy?

A sleep disorder characterized by uncontrollable sleep attacks. The sufferer may lapse directly into REM sleep, often at inopportune times.

What is sleep paralysis?

brief inability to move just before falling asleep or just after waking, disregulation between state of consciousness and muscle tone

what is the difference between central and peripheral apnea?

central cause is unknown, slowly lose breathing rate

peripheral is caused by obstructed airways, morbid obesity

what is REM sleep behavior disorder?

physically act out vivid, often unpleasant dreams with vocal sounds and sudden, often violent arm and leg movements during REM sleep

where did Bremer cut the cats brain to examine sleep?

1. isolated the forebrain, so a mid colliculus cut, could not have any sensory info so it was comatose

2. isolated the spinal cord from brain, allowed for sleep wake cycles but paralysis

determined sleep was passive

who proved Bremer wrong?

Moruzzi and Magoun

where did Moruzzi and Magoun cut?

mid pons, proved that wakefulness was not just caused by stimulation and sleep was not just caused by lack of stimulation

what is the role of FTG neurons in reticular formation?

long-reaching axons, can shut down parts of the brain

how does the monoamine system function?

similar to FTG neurons, sends projections across the whole brain

what is the role of neuromodulators?

controls the arousal state of the brain

what neurotransmitter is produced by the locus coeruleus?

sends norepinephrine from the roof of the pons to the cortex (NE)

what neurotransmitter is produced by the raphe nucleus?

serotonin from the pons area to the cortex, induces sleep and is the only area to produce serotonin (5HT)

what 2 neurotransmitters controlling sleep wake ccles are produced by the hypothalamus?

orexin and histamine, make the body alert

what inhibits the 3 wake areas of the brain?

the ventrolateral preoptic nucleus, which becomes inhibited by the raphe nucleus, the locus coeruleus, and the hypothalamus during wakefulness

is seratonin fast acting or slow acting

slow acting

is serotonin more active during sleep or wakefulness?

the raphe nucleus produces it during wakefulness

what are the 3 theories of why we sleep?

evolutionary, repair and restore, and learning and memory

how does caffeine work?

as a stimulant, binds to the adenosine that breaks down cAMP, which triggers sleep, so caffeine blocks adenosine so cAMP stays intact

what happens when you deprive a subject of REM sleep or SWS selectively?

they immediately rebound, go into the sleep they were missing upon falling asleep

how did they test learning and memory and sleep?

with rats in a maze and hippocampus place cell activation, rehearse during sleep and if that was disrupted then they didn't remember how to do the maze

what is important to remember about the repair and restore theory?

that the waves during SWS and REM sleep are doing work, when cAMP is broken down the body signals time to sleep, and the body resets the cAMP levels and prunes synapses

Beta waves are characterized by more frequent waves but lower amplitude, whereas alpha waves are characterized by less frequent waves but higher amplitude.

true

how are alpha waves characterized?

less frequent, higher amplitude of drowsiness

how are beta waves characterized?

more frequent, lower amplitude of wakefulness

What examines the motor movement of the eyes during sleep?

EOG

Rising adenosine levels are a signal that you should be going to sleep and caffeine is an antagonist to adenosine.

true, with higher and higher concentrations, adenosine inhibits arousal and causes sleepiness. Then, adenosine levels decrease during sleep.

caffeine works as an antagonist to adenosine (cAMP-ase)