Ch 9: Sleep And Biological Rhythms Flashcards
Electromyogram (EMG)
An electrical potential recorded from an electrode placed on or in muscle
Electro-oculogram (EOC)
An electrical potential from the eyes, recorded by means of electrodes places on skin around them
- Detects eye movements
Alpha Activity
Smooth electrical activity of 8-12 Hz recorded from brain
- Associated with state of relaxation - Regular, medium-frequency
Beta Activity
Irregular electrical activity of 13-30 Hz recorded from brain
- Assciated with state of arousal - Desynchrony
Stage 1
- A transition between sleep and wakefulness
- Presence of theta activity
- Experience hypnic jerks
- Lasts about 10 minutes
Theta activity
EEG activity of 3.5-7.5 Hz that occurs intermittently during early stages of slow-wave lseep and REM sleep
Hypnic jerks
Muscle contractions followed by relaxation
Stage 2
- Theta activity
- Sleep spindles
- K complexes
- Lasts about 15 minutes
Sleep spindles
Short burst of waves of 12-14 Hz
K complex
Sudden, sharp waveforms
Stage 3
- Slow-wave sleep
- High amplitude delta activity
- Deepest stage of sleep
- Last about 1 hour
Slow-wave sleep
NREM sleep characterized by synchronous EEG activtiy during its deeper stages
Delta activity
Regular, synchronous electrical activity of less than 4 Hz recorded from brain
- Occurs during deepest stages of slow-wave sleep
REM sleep stage
- Dreams
- Easily awoken by meaningful stimuli
- REM sleep paralysis occur because most of our spinal and cranial motor neurons are strongly inhibited
- At same time cerebral blood flow and O2 consumption are accelerated
REM sleep
Period of desynchronized EEG activity during sleep, at which time dreaming, rapid eye movements, and muscular paralysis occurs
- penile erection or vaginal secretion
Sleep Cycles
- Sleep alternates between periods of REM and NREM sleep
- Each cycle is about 90 minutes, containing 20-30 minute period of REM sleep
- Most slow-wave sleep occurs during first half
- Later is more stage 2 sleep
REM and Dreaming
- Lucid dreaming- awareness that they are dreaming and aren’t awake
- Eye movements may be related to visual imagery in dreams
- Brain mechanisms active during dream are same as in real life
Prefrontal Cortex: REM
- Low cerebral blood flow activity
- Reflects lack of organization and planning thast occur in dreams
Extrastriate Cortex: REM
- High cerebral blood flow activity
- Reflects visual hallucinations during dreaming
Striate Cortex: REM
- Low cerebral blood flow activity
- Lack of visual input
Brain Activity for Slow-Wave Sleep
- Brain activtiy can accompany dreamlike imagery
- Decreased throughout brain compared to waking
- Decreased blood flow to thalamus and cerebellum
- Localized increases of cerebral blood flow in visual and auditory cortexes
When trying to regain sleep […]
- can never regain all sleep lost
- slow-wave sleep and REM sleep are prioritized over other stages
Fatal Familial Insomnia
Inherited neurological disorder
Progresive insomnia
Results in damage to portins of thalamus
Destroy after 12 months
Sleep destroys […]
Free radicals and prevents their damaging effects
Sleep enhances […]
Removal of other neurotoxins from brain through glymphatic system— connections interstitial fluid surrounding cells and CSF
Cognitive Activity
Permits brain to rest and recover from its daily cognitive activity
- Slow-wave sleep increases after day or weeks of intense cerebral activity
Functions of REM sleep
REM sleep is controlled by regulatory mechanisms
- Deficiency in REM sleep is made up later - Call rebound phenomenon
Highest proportion of REM sleep is during most active phase of brain development, infancy, and childhood
Rebound Phenomenon
Increased frequency or intensity of phenomenon after it has been temporarily suppressed
REM sleep facilitates consolidation of […]
Nondeclarative memories
Slow-wave sleep facilitates consolidation of […]
Declarative memories
- brain rehearses newly learned information during slow-wave sleep
Adenosine
If wakefulness is prolonged, adenosine accumulates, inbiting neural activity
- lower glycogen—> increase in adenosine —> inhibitory effect on neural activity
- Genetic factors affect duration of slow-wave sleep
- Variability in gene that encodes adenosin deaminase
Acetylcholine
- Involved in arousal of cerebral cortex
- 2 groups of ACh neurons produce activation and cortical desynchrony
- One group of ACh neurons control activity of hippocampus
- Found in pons, basal forebrain, and medial septum
Norepinephrine
- Catecholamine agonists produce arousal and sleepiness
- Effects mediated by noradrenergic system of locus coeruleus
- Noradrenergic LC neurons increase vigilence
- Affects widespread and important regions of brain
- High during wakefulness
Serotonin
- Plays role in activating behavior
- Almost all of brain’s serotonerigic neurons are in raphe nuclei
- Stimuli causes locomotion and cortical arousal
- Most active during waking
Histamine
- Histaminergic neurons are located in tubertomammillary nucleus (TMN) of hypothalamus
- Directly increases cortical activation and arousal
- Indirectly increases release of ACh
- High during waking
Orexin
- Projects to almost every part or brain with excitatory activity
- High during alert or active waking, especially exploratory activity
- Modafinil
- Located in lateral hypothalamus
Modafinil
- drug to treat narcolepsy
- produces alerting effects by stimulating release of orexin
Control of sleep is […]
Homeostatic
Conscious attempt to control sleep is […]
Allostatic
- reactions to stressful events override homeostatic control
Preoptic Area
- Region of anterior hypothalamus
- Suppress activity of arousal neurons
- Majority of sleep neurons are in ventrolateral preoptic area (vIPOA)
- Activity of these neurons increases during sleep
Ventrolateral preoptic area (vIPOA)
Group of GABAergic neurons in preoptic area whose activity suppresses alertness and behavioral arousal and promotes sleep
Flip-flop circuits
- reciprocal inhibition characterizes known as flip-flop
- Either sleep neurons are active and inhibit wakefulness neurons, or wakefulness neurons are active and inhibit sleep neurons
- Impossible for neurons in both regions to be active at same time
Role of Orexin in Flip-Flop Circuit
Orexin- releasing neurons are involved in homeostatic, allostatic, and circadian factor
- Receive excitatory signals during the day - Receive signal from brain mechanisms that monitor nutritional state - Receive sleep signals
REM Flip-Flop
- REM-ON and REM-OFF regions are interconnected
- REM-ON during waking results in cataplexy (paralysis)
- REM-OFF during sleep leads to physically acting out dream
Sublaterodorsal Nucleus (SLD)
Regionof dorsal pons, just ventral to LC, that forms REM-ON portion of REM sleep flip-flop
Ventrolateral Periaqueductal Gray Matter (vIPAG)
Region of dorsal midbrain that forms REM-OFF portion of REM sleep flip-flop
Primary Insomnia
Difficulty falling asleep after going to bed or after awakening during night
Secondary Insomnia
Inability to sleep due to mental or physical condition
Insomnia Treatment: Nonpharmacological Interventions
CBT progressice relaxation techs and changes in sleep hygiene
Insomnia Treatment: Pharmacological Interventions
- Hypnotics, BDZs, and over-the-counter antihistamines
- Chronic use can lead to tolerance and rebound insomnia
Sleep Apnea
- Cessation of breathing while sleeping, disrupting sleep
- Nearly all people have occasional episodes, but doesn’t interfere with sleep
Narcolepsy
Sleep disorder characterized by period of irresistible sleep, attacks of cataplexy, sleep paralysis, hypnagogic hallucinations
Sleep Attack
Irresistable urge to sleep during the day, after which person awakens feeling refreshed
- Generally lasts for 2-5 minutes
Cataplexy
Complete paralysis that occurs during waking
- Muscle weakness, could lead to temporary paralysis - Precipitated by strong emotional reactions or sudden physical effort - Loss of muscle tone is caused by massive inhibition of motor neurons in spinal cord
Sleep Paralysis
Paralysis occuring just before person falls asleep
- Inability to move just before onset of sleep ot on waking - Hypnagogic hallucinations
Physiological Basis of Narcolepsy
- Relatively rare
- Caused by hereditary autoimmune disorder
- Strongly influenced by unknown environmental factors
- Symptoms of narcolepsy treated with drugs
- Treatment: Ritalin and Modafinil (stimulants or antidepressant drugs)
REM Sleep Behavior Disorder
Neurological disorder in which person doesn’t become paralyzed during REM sleep and thus acts out his dream
REM Sleep Behavior Disorder Characteristics
- Paralysis doesn’t occur during REM sleep
- Act out dreams
- Genetic component
- Neurodegenerative
- Usually treated by clonazepam
Slow-Wave Sleep Maladaptive Behaviors
- Bedwetting (nocturnal enuresis)
- Sleepwalking (somnambulism)
- Night terrors (pavor nocturnus)
Sleep- Related Eating Disorder
Disorder in which person leaves his/ her bed and seeks out and eats food while sleepwalking, usually without memory
- Usually responds well to DAergic agonists or topiramate (antiseizure medication)
Circadian Rhythms
Daily rhythmical change in behavior or physiological process
- some are passive responses to changes in illumination
Zeitgebers
Stimulus (usually light of dawn) that resents biological clock that is responsible for circadian rhythms
Suprachiasmatic Nucleus
Nucleus situatioed atop optic chiasm that contains biological clock that is responsible for organizing many of body’s circadian rhythms
- Receive light info from environment and uses it to entrain behaviors to 24-hour light/dark cycle - Provides primary control over timing of sleep cycles
Visual system projects from […] to […] via […]
Visual system projects from retina to SCN via retinohypothalamic pathway
[…] provide info about ambient light levels that synchronizes circadian rhythms
Melanopsin
Melanopsin
Photopigment present in ganglion cells in retina whose axons transmit info to SCN, the thalamus, and olivary pretectal nuclei
Efferent axons of SCN terminate in […]
Subparaventricular zone (SPZ)
- Projections to vIPOA are inhibitory and inhibit sleep - Projections to orexinergic neurons are excitatory and promote wakefulness
- SCN can also control rhythms by secretion of chemicals that diffuse through the brain
Advanced Sleep Phase Syndrome
4 hour advance in rhythms of sleep and temporary cycles, apparently caused by a mutation of gene (per2) involved in rhythmicity of neurons of SCN
Delayed Sleep Phase Syndrome
4 hour delay in rhythms of sleep and temporary cycles, possibly caused by mutation of gene (per3) involved in rhythmicity of neurons of SCN
Melatonin
Hormone secreted by pineal gland at night in response to input from SCN
Pineal Gland
Gland attached to dorsal tectum
- produces melatonin and plays role in circadian and seasonal rhythms
Hypnagogic Hallucinations
Possibility of dreaming while lying awake, paralyzed
Shift Work and Jet Lag
Internal circadian rhythms controlled by SCN become desynchronized with the external environment
