Circadian Rhythms and Sleep
Stages of brain activity during day
(1) Awake -low amplitude high frequency EEG (beta waves) (2) Light sleep -increasing amplitude decreasing frequency EEG (theta waves) (3) Deep Sleep -high amplitude low frequency EEG (delta waves) (4) Rapid eye movement (REM) sleep -low amplitude high frequency EEG (beta waves)
What is narcolepsy? Cataplexy? Hypnagogic hallucinations? Sleep paralysis?
(hyperinsomnia) Daytime sleepiness Disrupted nighttime sleep Fragments of REM sleep -cataplexy-sudden, brief episodes of muscular weakness -hypnagogic hallucinations-vivid dream like hallucinations at the beginning or end of sleep -sleep paralysis-inability to move upon awakening
______ tells you when to sleep, but ______ tells you how much sleep you need What happens during sleep deprivation
*-Circadian Rhythms-* tells you when to sleep; *-Sleep homeostasis- *tells you how much sleep you need. Sleep homeostasis overrides circadian rhythms but eventually the person will fall asleep at anytime
What are the two major types of sleep?
--Non-rapid eye movement (NREM) --Rapid eye movement (REM) REM (rapid eye movement) -dream occur -low amplitude, high frequency oscillations -similar to wakefulness (beta waves) Non-REM (resting) is also called slow-wave-sleep (SWS): -high amplitude, low frequency waves (delta waves) -containing 4 stages of sleep (from stage 1-4)
What do young adult sleep patterns consist of?
-7-8 hours of 90-110 min of each cycle repeating cycles for 5-6 times -4-5% stage 1 -45-55% of total sleep is stage 2 -10-20% stage 3 and 4 (deep sleep) -20% of total sleep is REM sleep -more SWS early in night -progressive lengthening of REM periods
What are hypocretin/orexins?
-Orexins are peptide NTs involved in normal wakefulness -in lateral hypothalamic neurons with projections to primary arousal structures -narcoleptic dogs have mutant oxexin-2 receptors -orexin knock-out mice-immediate onset REm and increased sleep during normal wake periods -tx=stimulants
Interesting links btw REM sleep and depression
-REM deprivation has anti-depressant effects -most anti-depressant drugs reduce REM sleep -REM deprivation can produce cognitive/memory deficits -REM sleep increases ffg new learning
Why do we sleep?
-Sleep enables the body and brain to repair itself after working hard all day -appx 1/3 of our lifespan spend in sleep -brain is 3% of total body weight, but uses almost 1/4 of the energy -going without sleep causes people to be irritable, dizzy, and to have hallucinations and impaired concentration
How can we reduce the impact/effects of jet lag?
-Use melatonin to reset the body clock -Should not be used unless intending to stay in new time zone over 3 days -melatonin is not sleeping pill and does not need a prescription to get -timing is important too...individuals should be allowed to sleep after the melatonin or else they are prolonging their circadian rhythm -adopt local eating times etc to help reset the biological clock as soon as possible
What are the Tx for insomnia?
-behavioral and psychological treatment strategies -benzodiazepine receptors agonists (BzRAs) -other drugs used to treat insomnia -new and emerging pharmacologic treatments -implications for clinical practice
How does sleep architecture change with aging?
-elderly people have shorter total sleeping time each night -elderly people have shorter SWS or even have no stage 4 sleep -elderly people wake up more frequently during night
How does the EEG record brain waves (set-up)?
-electrodes to scalp, low resistance connection -connected to banks of amplifiers and recording devices -voltage fluctuations measured (tens of microvolts) -electrode pairs: measure different brain regions -set of simultaneous squiggles, voltage channels, between electrode pairs Records very small electrical fields generated by synaptic currents in pyramidal cells Generating large EEG signals by synchronous activity
(Neural Mechanisms of sleep) Sleep is an active state mediated by at least what 3 neural systems?
-forebrain: generates SWS -reticular formation (RF): wakes forebrain -pons (locus coeruleus): triggers REM sleep
Theories state that REM is required for normal:
-mental health -motivation -cognitive processing
Neurons producing awaken state are located where? (2)
-neurons in tuberomammillary nucleus (TMN) -neurons in locus coeruleus
What are the characteristics of slow wave sleep?
-progressive decrease in spinal reflexes -progressive reduction in heart rate and breathing rate -reduced brain temperature and cerebral blood flow -increased hormone secretion (eg growth hormone) -synchronised cortical activity
What are the sleep cycles?
-sleep occurs in a recurring cycle of 90-110 minutes and is divided into two categories: non-REM (which is further split into four stages) and REM sleep -there are four stages in the non-REM sleep -there are 5-6 sleeping cycles each night -with increasing in cycles, stage 3 and 4 (deep sleep) getting shorter and REm sleep getting longer
What are the characteristics of REM sleep?
-spinal reflexes absent -rapid eye movements behind closed eyelids -increased body temperature and cerebral blood flow -desynchronised cortical activity -dreams
What is the neural control of SWS in the basal forebrain? inhibited by?
-ventral frontal lobe, anterior hypothalamus -lesions abolish SWS -electrical or heat stimulation can induce SWS activity -these neurons are active at sleep onset --inhibited by NE stimulation
2 phases of shift work consequence of shift work (compromising..) how long does it take to adjust to a 12 hour shift in time
1) phase advance = getting up early or going to bed earlier than normal 2) phase delay = going to bed late or getting up late -by delaying/advancing our rhythms we are compromising our ability to cope in the short term -on average it takes appx 3 days to adjust to a 12 hour shift in time
What are some sleep disorders?
15% of adults have chronic insomnia 24% of adults have chronic sleepiness 25% of motor vehicle accidents with LOC are due to falling asleep 60% of fatal truck accidents are due to sleepiness REM sleep behavior disorder
What is stage 1 of sleep?
Alpha to Theta Waves Non-REM -breathing slows down -disengage from sensation -vivid mental imagery-everyday activities, not bizarre dreams
Describe the awake but drowsy stage of pre-sleep?
Alpha waves Functions: relaxed, harder to concentrate, want to go to sleep Hypnogogic Hallucinations -vivid images, bizarre -jerky movements ---sensation of falling ---bed, gravity, floating
Describe the pre-sleep stage of sleep?
Awake and Alert -beta waves -functions: calm, alert, active, ready to learn -may take about 15 minutes to go through this stage -adjust pillows, comforter, start to relax
What is REM sleep? what kind of waves on graph (their appearance)?
Binocularly synchronous REMs, sawtooth waves -dreaming -muscle atonia (paralysis) -high metabolic activity in brain -irregular breathing (increased risk of apnea or hypoxic events) -increased heart rate variability (increased risk of arrhythmias, pulmonary HTN, and heart attack)
What are EEG rhythms? What are the 4 categories (and their fxns)?
Categorization of rhythms based on frequency -beta: greater than 14 Hz, activated cortex -alpha: 8-13 Hz, quiet, waking state -theta: 4-7 Hz, some sleep states -delta: less than 4 Hz, deep sleep Deep sleep -high synchrony, high EEG amplitude
What is REM sleep behavior disorder? How treated (2 Rxs)?
Characterized by failure to exhibit muscle paralysis during REM sleep Appears to be neurodegenerative disorder w/ some possible genetic component -often associated w/ other neurodegenerative disorders, such as Parkinson's disease Usually treated w/ clonazepam, a benzodiazepine
What is a circadian rhythm?
Circa=appromately, dies= a day -24 hours endogenous cycles or internal body clock Ex> -sleep/wake cycle -body temperature -hormone secretion -drug sensitivity
What is stage 4 of sleep?
Delta waves-100% Non-REM -oblivious to outside world -sleep-walking, sleep-talking occur here -very difficult to wake up but can have activities (answer phone, talk etc) Then you ascend back up through these stages and enter your first dream
What are the symptoms of insomnia?
Difficulty falling asleep Interrupted sleep Waking up early Light sleep poor quality of sleep-not refreshed after sleeping
What is partial arousal?
Eg sleep walking, nightmares -often associated w/ anxiety, psychological disturbance or drug taking -little known about causes -limited capacity for pharmacological treatment of sleep disorders
Describe the neural control of arousal? (2 paths)
Electrical stimulation of the brain stem induces arousal -dorsal path: RF --> to medial thalamus--> cortex -ventral path: RF--> to lateral hypothalamus, basal ganglia, and the forebrain
What can be used to diagnose epilepsy, sleep disorders, other neurological conditions? Measures?
Electroencephalogram (EEG) -measurement of generalized cortical activity -noninvasive, painless
What is hypersomnia (narcolepsy)?
Excessive drowsiness and falling asleep
What is jet lag?
Jet lag is a physiological condition which results from alterations to the body's circadian rhythms resulting from rapid long-distance (east-west or west-east) travel on high-speed aircraft *TIME ZONE changes. NOT north-south travel
AGAIN: What are some facts about jet lag
Jet lag only occurs when flying from east-west or from west-east (change time zones) -not north to south
SCN pathway/fxn
Light inhibits, darkness sitmulates--> retino-hypothalamic tract--> SCN--> pineal gland <---> superior cervical ganglion -stimulation of pineal gland produces the hormone melatonin (sleepy) When light levels are low we produce more melatonin This rhythm affects the sleep wake cycle via the pineal gland
What is melatonin? Under investigation for the tx of?
Melatonin is the principal hormone produced by the pineal gland. Melatonin is under investigation as a tx for a number of conditions, including jet lag, seasonal affective disorder (SAD), depression, and cancer
Define insomnia
Reduction or absence of sleep-transient or persistnet
What do circadian rhythms do? Which model used? (clock vs hourglass)
Regulate when to sleep A two-process model Process C: circadian regulation, behavior independent CLOCK Process S: sleep homeostasis, behavior dependent HOURGLASS
What are the various NTs and their effects on sleep?
Serotonin -site of cell bodies-raphe nuclei -manipulation-increased, decrease -promotes sleep, reduces sleep Norepinephrine -site of cell bodies-locus coeruleus -manipulation-increase -promotes waking, inhibits REM sleep -lesions=abolish loss of muscle tone in REM sleep Dopamine -site of cell bodies-basal ganglia -manipulation-increase, decrease -promotes waking, has variable effects Acetycholine -site of cell bodies-basal forebrain -manipulation-increase, decrease -induces REM, suppresses REM
Sleep is a _____ and an altered state of _______. Associated with?
Sleep is a behavior and an altered state of consciousness -sleep is associated w/ a need to lie down for several hours in a quiet environment ---few movement occur during sleep (eye movements) --the nature of consciousness is changed during sleep ---we experience some dreaming during sleep ---we may recall very little of the mental activity that occurred during sleep We spend about a third of our lives in sleep -a basic issue is to understand the function of sleep
What is the main endogenous rhythmn pacemaker? Where located?
The main pacemaker for endogenous (internal) rhythms is the --suprachiasmatic nucleus-- (SCN). This is a small group of cells located in the area of hypothalamus. It lies just above the optic nerves, therefore it can receive information directly from the eye and the rhythm can be reset by the amount of light entering the eye.
What is stage 3 of sleep?
Theta-Delta-Theta -slow wave sleep -probably a transition stage
What is stage 2 of sleep?
Theta-K complexes-Delta non-REM -brief periods of brain activity -small muscle twitches -breathing rhythmical
What are 2 examples of disrupted biological rhythms?
When external cues change we have to readjust our internal clock -jet lag -shift work
Does the pons control REM sleep?
YES! -lesions ventral to pons abolish REM sleep -electrical or pharmacological stimulation (ACh agonists) can induce or prolong REM sleep -small lesions ventral to LC selectively abolish REM muscle atonia
What is Zeitgebers?
Zeitgeber: an environmental cue such as 24 hour light-dark cycle, resets the circadian rhythm (internal body clock from over 24 hr to exact 24 hr). Altering light/dark cycles produces phase shift and entertainment.
Electrical stimulation of cholinergic nuclei during SWS causes
a shift into REM sleep or arousal/awaken state
How can we reduce the impact/effects of shift work?
by using bright lights as a substitute for sunlight ---dawnson and campbell exposed workers to a 4 hour pulse of very bright light. This appeared to work.
EEGs record what? Large EEGs result from?
very small electrical fields generated by synaptic currents in pyramidal cells -- large EEG signals result from synchronous activity