Chapter 10 Flashcards
what are the three biological clocks?
- circadian rhythms (24 hours): key for regulation of sleep cycles; enable us to anticipate an event before that event
- ultradian rhythms repeat more than once a day
- infradian rhythms repeat less frequently than once a day
what are biological clocks?
internal clocks that guide timing of behavior and biological processes
- every animal has own endogenous clock
- rest by light or other physical cues
what is zeitgeber?
any cue an animal uses to synchronize its activity with the environment
what is a free-running biological clock
rhythm of behavior shown by animal deprived of external cues about time of day
- results in animal’s behavior governed by biological clock (most time is longer than 24 hrs)
where is the biological clock located?
located in suprachiasmatic nucleus (SCN) in hypothalamus above optic chiasm
- lesions of SCN eliminate circadian rhythms of drinking, locomotion, and hormone secretion
- isolated SCN cells continue to show circadian rhythm for days or weeks
what is the retinohypothalamic pathway?
light-dark cycles set the biological clock
- biological clock reset by light and SCN stimulated by light
- light information from eye reaches SCN directly via retinohypothalamic pathway
what is the retinohypothalamic pathway made of?
specialized ganglion cells directly transmit light information from eye to SCN
- these cells are sensitive to light and contain melanopsin
what does melatonin do?
SCN informs pineal gland when it’s dark
- pineal gland secrete melatonin (key for promoting sleep)
- blind individual must take melatonin
- bight light reduce melatonin production while darkness increase melatonin production
how does our circadian rhythm change?
at puberty, it shift so get up later in day
- as we get older, we. get up earlier
what is used to determine what stage of sleep someone is in?
EEG activity is used to determine what stage of sleep a person is in
what is the brain activity in normal and just before sleep?
normal waking state: characterized by presence of beta wave
just before sleep (drowsiness): alpha waves increase
what is stage 1 of sleep?
transition period between wakefulness and sleep
- begins when sleepers drift off
- waves of smaller amplitude and irregular frequency begin
- vertex spikes (sharp waves) appear
- heart rate slows, muscles relax, eyes roll slowly -> last several minutes
what is stage 2 of sleep?
- breathing becomes more regular
- less sensitive to external stimulation
- EEG have burst of brain activity called sleep spindles (burst of 12-14 Hz waves) and K-complexes (sharp negative EEG potentials)
what is stage 3 of sleep?
slow wave sleep where sleeps are hard to awaken
- EEG reveal large regular delta waves (large amplitude with slow waves about 1 per second)
what is REM sleep?
eye dart rapidly under closed eyelids -> dreaming
- paralysis of motor systems (muscles relaxed)
- EEG show beta wave
how many times do we cycle through the stages of sleep?
most people cycle through about 5 times
- total sleep time ranges from 7-8 hours with half is stage 2 sleep and 20% is REM sleep
- cycles last 90-110 minutes with cycles early in night have more stage 3 and later cycles have more REM
what are dreams?
products of consciousness during sleep
- during dream, confusion of images and fantasies with reality
- spend 6 years of lives dreaming
what are different REM dream?
vivid drams occur during REM sleep
- visual imagery: sounds, smell, and emotions -> feel like it’s there
nightmares: long, frightening dreams that awaken from REM
what are the different brain areas associated with dreams?
- more visual cortex activity (vivid visual imagery)
- more amygdala activity (emotional content)
- more M1 activity (“feeling” that we are acting)
- more brain stem activity (preventing acting out dreams)
- less PFC activity (illogical content)
why do we have dreams?
activation-synthesis theory: dreams are result of brain’s attempts to make sense of random brain activity by synthesizing activity with stored memories
what are non-REM dreams?
report thinking about problems rather than seeing themselves in mental movie
- night terrors: sudden arousals from stage 3 marked by fear and autonomic activity
- remember sense of crushing feeling on chest but don’t recall vivid dream
- common in children
what can sleep deprivation lead to short term?
can impair function
- lead to microsleep (where people fall asleep for seconds or minutes)
what are long term effects of sleep deprivation?
effects on cognitive performance and hippocampus activity
- hippocampus activity decreased with sleep deprivation
- hippocampus is key for memory so impair memory and cognitive performance
how does less sleep lead to cognitive impairment?
poor sleep associated with Alzheimer’s disease
- as we age, amount of stage 3 sleep declines dramatically (at 60, it’s half as much as 20 & disappears by 90)
- lack of stage 3 leads to memory impairment and loss of growth hormone so cognitive decline
how does the glymphatic system factor into sleep?
glymphatic clearance occurs primarily while we sleep (most active in stage 3)
- may protect against Alzheimer’s disease, stroke, and multiple sclerosis
what parts of the brain generate sleep?
- forebrain system: generates SWS
- brainstem system: generates wakefulness in forebrain
- pontine system: triggers REM sleep
- hypothalamic system coordinates other three
how does the forebrain generate SWS?
generated by basal forebrain
- neurons in region become active at sleep onset and release GABA
- GABA receptors also stimulated by general anesthetics which produce slow waves like SWS
what wakes the forebrain?
reticular formation wakes forebrain
- electrical stimulation of area will wake sleeping animal and lesions of area produce persistent sleep
- forebrain and reticular formation regulate SWS and wakefulness
what triggers REM sleep?
subcoeruleus (area of pons) responsible for REM sleep
- some neurons in area only active during REM sleep
- inhibit motor neurons & disable motor system during REM sleep
how does the hypothalamus control other systems?
release hypocretin that controls other sleep systems -> loss leads to disorganized sleep
what is narcolepsy?
symptoms: frequent, intense daytime sleep attacks, demonstrate cataplexy (sudden loss of muscle tone -> collapse), do not go through SWS before REM, and experience hallucinations and sleep paralysis
treatment: altertness drugs and psychostimulants
what causes narcolepsy?
humans with it lost 90% of hypocretin neurons
- normally prevent transition from wakefulness directly into REM sleep)
- key for governing sleep and wake cycles
what is the hypothalamic sleep center?
hypocretin neurons project to basal forebrain, reticular formation, and subcoeruleus
- axons also go to tuberomammillary nucleus (inhibition induces SWS)
- contains hypocretin switch to determine wakefulness, non-REM sleep or REM sleep
what is sleep paralysis?
brief inability to move just before falling asleep or just after waking up
- may experience hallucinations (something is crushing chest)
- never last more than a minute
- pontine center may be continuing to impose muscle paralysis after wakefulness
what are non-REM sleep disorders?
sleep disorders in children: night terrors and sleep enuresis (bed-wetting)
- somnambulism (sleep walking): occurs during stage 3
what is REM behavior disorder?
organized behavior in person who appears asleep (acting our their dream)
- pontine center may not be able to impose muscle paralysis
- may be followed by early symptoms of Parkinsons’s disease or dementia
- widespread damage of disease begins in brainstem region that imposes muscle atonia
what is insomnia?
having trouble falling asleep or staying sleep
- sleep-onset insomnia: difficulty falling asleep caused by situational factors
- sleep-maintenance insomnia: difficulty staying asleep punctuated by frequency nighttime arousals caused by drugs or neurological and psychiatric factors
what is sleep apnea?
breathing may cease for minute or so (blood O2 levels drop)
- caused by: muscles in chest & diaphragm relax too much and changes in pacemaker respiratory neurons in brainstem) -> accompanied by snoring
- increase risk of cognitive decline or Alzheimer’s disease by more than 2 fold; also hypertension, cvd, and depression
what is SIDS?
sudden unexpected death of healthy infant who stops breathing during sleep
- raises from sleep apnea due to immature respiratory pacemaker system or arousal mechanisms
- associated with abnormalities in brainstem serotonin systems
- putting babies to sleep on back reduces incidents
how do sleeping pills work?
bind to GABA receptors throughout brain
side effects: produce marked changes in sleep patterns that persist for days after use; become ineffective; lead to daytime drowsiness and memory gaps
what are sleep hygiene examples?
better sleep is achieved through good sleep habits
Ex: develop regular routine to exploit circadian clock; avoid daytime naps & having caffeine at night; bedtime routine in quiet, dark environment; avoid use of phones and laptops at bedtime
