3What is Circadian Rhythms? Circadian rhythms refer, collectively, to the daily rhythms in physiology and behavior. They control the sleep-wake cycle, modulate physical activity and food consumption, and over the course of the day regulate body temperature, heart rate, muscle tone, and hormone secretion. The rhythms are generated by neural structures in the hypothalamus that function as a biological clock.Animals and plants possess endogenous clocks to organize daily behavioral and physiological rhythms in accord with the external day- night cycleThe basis for these clocks is believed to be a series of molecular pathways involving “clock” genes that are expressed in a nearly 24- hour rhythmRefers to circa=approximately, and dias=day
4The Influences of Circadian Rhythms A daily rhythmical change in behavior or physiological process.About a dayRegular fluctuation from high to low points of certain bodily functions and behaviorsSleep debtDeficiency caused by not getting the amount of sleep that one requires for optimal functioningAffects psychological functions ofBlood pressureHeart rateAppetiteSecretion of hormones and digestive enzymesSensory acuityEliminationBody’s response to medication
5Environmental cues: activity and rest =growth, maintenance, hormonal fluctuations.too Earths rotation--light-dark cycle, on 24-hour circadian system. Activity-non-activity (circadian rhythms) can be further subdivided up into smaller time activity-rest units,called, ultradian cyclesAs wakefulness (alert), stage 1 sleep, stage 2, stage 3 and stage 4 (Non-Rem) and Rem (rapid eye movement sleep), also called active of paradoxical sleep.
6About life, students….Its about circles..i.e. cycles…all the way down…we live inside of circular space..cycles within cycles within cycles…as in life cycle..sleep cycles, menstrual cycles, hormonal cycles..time cycles..midnight(when and where morning and night are simultaneously one, a beginning and an end at the same instant.. Where beginning and ending is the same, is it Friday or Saturday
7What’s the Endocrine System? A collection of glands that secrete hormones in order to regulate functions within the body.
8The Influences of Circadian Rhythms Suprachiasmatic nucleus (SCN)A nucleus, situated atop the optic chiasm, in the brain’s hypothalamus that control the timing of circadian rhythmsIt contains a biological clock responsible for organizing many of the body’s circadian rhythms.Lesions do not reduce sleep time, but they abolish its circadian periodicityExhibit activity that can be entrained by the light-dark cycleTransplant SCN, transplant sleep-wake cycleMelanopsinA photopigment present in ganglion cells in the retina whose axons transmit information to the SCN, the thalamus, and the olivary pretectal nuclei.ZeitgebersA stimulus (usually the light of dawn) that resets the biological clock responsible for circadian rhythms.Intergeniculate leaflet (IGL)A part of the lateral geniculate nucleus that receives information from the retina and projects to the SCN; terminals release neuropeptide Y at the SCN
9The Influences of Circadian Rhythms Control of seasonal rhythmsPineal GlandA gland attached to the dorsal tectum; produces melatonin and plays a role in circadian and seasonal rhythms.Secretes melatonin from dusk until just before dawnDoes not secrete melatonin during daylight hoursMelatoninA hormone synthesized from serotonin in the pineal glandSecreted during the night by the pineal body;Melatonin levels display circadian rhythms controlled by the SCNplays a role in circadian and seasonal rhythms.Melatonin is not a sleep aid, but may be used to shift circadian rhythms
10Disruptions in Circadian Rhythms Jet lagWhen traveling, you reach your destination at a time when it is daylight there, but it would have been time to go to sleep at the place you startedCan produce memory deficits that may be permanentSupplemental melatonin has been shown to be an effective treatment for relapses of psychiatric disorders induced by jet lagZeitgebers are accelerated or deceleratedResearch indicates that frequent flyers, such as this airline employee, are just as likely to suffer from jet lag when crossing several time zones as travelers who are on their first inter-continental journey.
11Disruptions in Circadian Rhythms Shift workWhen people work during the night and sleep during the dayShift workers average 2 to 4 hours less sleep than nonshift workers of the same ageSubjective nightThe time during a 24-hour period when body temperature is lowest and when the biological clock is telling a person to go to sleepDuring subjective night, energy and efficiency are at their lowest point, reaction time is slowest, productivity is diminished, and industrial accidents are significantly higher Zeitgebers unchanged, but sleep-wake cycle must be alteredRotating work schedules forward from days to evenings to nights makes adjustment easier because people find it easier to go to bed later and wake up later than the reverseModafinilA wakefulness drug that will help people remain alert without the side effects of stimulants such as caffeine
12Can the effects be prevented or minimized? Both produce a variety of deficitsCan the effects be prevented or minimized?Reducing Jet LagGradually shift sleep-wake cycle prior to travelAdminister post-flight treatments to promote the needed shiftPhase advance following east-bound travel with intense light early in the morningHamster studies suggest a good early morning workout may also help
13Can the effects be prevented or minimized? Reducing the Effect of Shift ChangesSchedule phase delays, rather than phase advancesMove from current schedule to one that starts laterIt is easier to stay up later and get up later than to retire and arise earlierPhase advances are harder, explaining why east-bound travel tends to be more problematicShift workers who temporarily reside at their work places, such as workers on offshore oil rigs, appear to adjust more easily to the demands of night work than those who live at homeExposure to appropriately timed bright light or even light of medium intensity has been found to reset young adults’ biological clocks and improve their performance
14The Influences of Circadian Rhythms Disruptions in Circadian RhythmsSubjective nightThe time during a 24-hour period when the biological clock is telling a person to go to sleep.Energy and efficiency are at their lowest pointsReaction time is slowestProductivity is diminishedIndustrial accidents are higherDaylight savings time in spring is associated with short term 6.5% increase in accidental deaths.Work schedulesMoving work schedules forward from days to evenings to nights makes adjustment easierRotating shifts every three weeks lessens the effect on sleep
16Sleep What is it? What Does It Look Like? How does it function? What happens when we sleep? Measurement?How does it change with age?
17What is sleep?A state ofsustained immobility or quiescence in a characteristic posture accompanied by reduced responsivity to external stimuli;Immobility need not be absolute as dolphins, seals and whales may float or swim while asleep…most sleep with eyes closed but not all;Cattle may sleep with eyes open..horses and elephants sleep while standing…
18Why do we sleep? The answer: no one really knows for sure! Some believe that sleep:gives the body a chance to gain strength from the day's activities but in reality, the amount of energy saved by sleeping for even eight hours is tiny - about 50 kilocalories, the same amount of energy in a piece of toast!We have to sleep because it is needed to sustaining normal levels of cognitive skills such as speech, memory, and innovative and flexible thinking.sleep plays an important part in brain development.
19Why Do We Sleep?Proximate Explanation:Because we begin to “feel” tired..melatonin Need to consolidate energy and experiences;Need to avoid predators;Need to restore body cells and promote protein anabolism;Maintain hormonal secretions, immune functionUltimate Explanationsustains our ability to reproduce successfully, by maintaining good health
20Why do we sleep? Recuperation theories Circadian theories Sleep is needed to restore homeostasisWakefulness causes a deviation from homeostasisCircadian theoriesSleep is the result of an internal timing mechanismSleep evolved to protect us from the dangers of the night
21What Happens When We Don’t Sleep? A good way to understand the role of sleep is to look at what would happen if we didn't sleep.Lack of sleep:Serious effects on our brain’s ability to function (cognitive functioning)If you have ever not slept for an entire night, you'll feel grumpy, groggy, irritable and forgetful. After just one night without sleep, concentration becomes more difficult and attention span shortens a great deal.Continues lack of sufficient sleep the part of the brain that controls language, memory, planning and sense of time is severely affected, practically shutting down.17 hours of continuous sleeplessness leads to a decrease in performance that is equivalent to a blood alcohol level of two glasses of wine(0.05%).Effect on emotional and physical health –excessive daytime sleepiness - linked to stress and high blood pressure.may increase the risk of obesity because chemicals and hormones that play a key role in controlling appetite and weight gain are released during sleep.
22What happens when we sleep? What happens every time we get a bit of shut eye?Sleep occurs in a recurring cycle of 90 to 110 minutes and is divided into two categories:Non-REM (which is further split into four stages)Stage 1:half awake and half asleep (light sleep)Stage 2: The breathing pattern and heart rate start to slow down.Stage 3: Brain begins to produce delta wavesStage 4: Rhythmic breathing and limited muscle activity.REM (Rapid Eye Movement) sleep.
23NREM Sleep Non-rapid eye movement sleep. Four sleep stages Lightest sleepMid-sleepDeep sleepDeepest sleepHeart and respiration slow and regularLittle body movementBlood pressure and brain activity at lowest points of 24 hour period.
24Non-REM sleepStage 1:Half awake & half asleep. A transition period of drowsiness between waking & sleeping. Slow rolling eye movements. Body temperature drop. Muscle activity slows down, Heart rate slows and slight twitching may occur. The period of light sleep (we can be awakened easily at this stage). (10 min)Stage 2: Lasts around 20 minutes. The breathing pattern and heart rate start to slow down. Somewhat more deeply asleep. This period accounts for the largest part of human sleep.Stage 3: Brain begins to produce delta waves [a type of wave that is large (high amplitude) and slow (low frequency) - Delta waves reach 20%]. Slow wave sleep begins. Breathing and heart rate are at their lowest levels.Stage 4: Rhythmic breathing and limited muscle activity. If we are awakened during deep sleep we do not adjust immediately and often feel groggy and disoriented for several minutes after waking up. Some children experience bed-wetting, night terrors, or sleepwalking during this stage. Delta waves reach nearly 100%.
26REM (Rapid Eye Movement) sleep The first Rapid Eye Movement (REM) period usually begins about 70 to 90 minutes after we fall asleep.We have around three to five REM occurrences a night.Although we are not conscious, the brain is very active - often more so than when we are awake.This is the period when most dreams occur. Our eyes dart around, and our breathing rate and blood pressure rise.However, our bodies are effectively paralyzed nature's way of preventing us from acting out our dreams.After REM sleep, the whole cycle begins again.
29REM SleepRapid eye movement sleep - also known as “active sleep”.20-25% of a night’s sleepInternally:Intense brain activityBrain metabolism increasesBrain temperature rises rapidlyEpinephrine release leads to increases in Blood pressure, Heart rate, respirationExternally:Body appears calmLarge muscles become paralyzedEyes dart aroundDreaming occurs in 80% of peopleBrain conducts -Consolidation of learning (all night studying doesn’t help)perceptual skills increase after 8-10 hours of sleepMemory consolidation
30REM ReboundThe increased amount of REM sleep that occurs after REM deprivationIntensity of REM sleep increasesThose with Sleep DeprivationProceed more rapidly into REM as REM deprivation increasesMore time spent in REM when deprivation is overOften associated with unpleasant dreams or nightmaresAlcohol, amphetamines, cocaine, and LSD use suppress REM sleep results in REM reboundWithdrawal results in REM reboundsREM rebound suggests that REM sleep serves a special function
31Purpose of REM? Necessary for mental health Inconsistent with the effects of tricyclic antidepressants – block REMNecessary for maintenance of normal levels of motivationNecessary for processing of memoriesNo clear purposeDefault Theory of REMREM serves no critical functionOne can’t stay continuously in non-REM sleep, so we switch between REM and wakefulnessWhen bodily needs exist – wake upNo immediate needs – REMNo REM rebound seen when lost REM periods replaced with 15-mins awake
32How much sleep is required? There is no set amount of time that everyone needs to sleep, since it varies from person to person.Results from the sleep profiler indicate that people like to sleep anywhere between 5 and 11 hours, with the average being hoursHow long people sleepa day on average:
33Variations in Sleep Infants and young children Ages 6-puberty have the longest sleep timeHave the highest of REM and slow wave sleepAges 6-pubertyMost consistent sleepers and wakersSleep and awake same time dailyAdolescentsSleep patterns are influenced by their schedulesSleep longer when no schedule conflictsPoor sleep may contribute to poor school performance
34Variations in Sleep Larks and owls Larks Awaken early every morning and leap out of bed with enthusiasm, eager to start the dayBody temperature rises rapidly after they awaken and stays high until about 7:30 p.m.Turn in early and have the fewest sleep problems
35Variations in Sleep Owls Fumble for the alarm clock and push the snooze button to get a few more precious minutes of sleepBody temperature of an owl gradually rises throughout the day, peaking in the afternoon and not dropping until later in the eveningGuthrie and othersCompared the performance of several hundred college students classified as larks or owlsFound that the larks made better grades in early morning classes, while the owls made higher grades in classes they took later in the dayA gene that runs the biological clock is responsible, in part, for the differences between larks and owls
36Average total sleep time per day Animal SleepAnimals also have a required certain amount of sleep:SPECIESAverage total sleep time per dayPython18 hoursTiger15.8 hoursCat12.1 hoursChimpanzee9.7 hoursSheep3.8 hoursAfrican Elephant3.3 hoursGiraffe1.9 hours
37Sleep Electro-oculogram (EOG) Electromyogram (EMG) Understanding of sleep increased by the study ofBrain wavesEye movementsChin muscle tensionHeart rateRespiration rateElectro-oculogram (EOG)An electrical potential from the eyes, recorded by means of electrodes placed on the skin around them; detects eye movements.Electromyogram (EMG)An electrical potential recorded from an electrode placed on a muscle.
383 Physiological Measures of Sleep By means of Electroencephalogram (EEG)“brain waves”By means of EOGEye movements seen during rapid eye movement (REM) sleepBy means of EMGLoss of activity in neck muscles during some sleep stages
40Sleep Polysomnogram Provides brain wave sleep recordings Outlined REM and NREM sleep patterns
41EEGBeta activity - Irregular electrical activity of 13–30 Hz recorded from the brain; generally associated with a state of arousal.Alpha activity- A smooth electrical activity of 8–12 Hz recorded from the brain; generally associated with a state of relaxationEyes closed, preparing to sleepTheta activity - EEG activity of Hz that occurs intermittently during early stages of slow-wave and REM sleep.Delta activity - Regular, synchronous electrical activity of less than 4 Hz recorded from the brain; occurs during the deepest stages of slow-wave sleep.
43Sleep Cycle & EEG Stage 1 similar to awake EEG, but slower low-voltage, high-frequencyEEG voltage increases and frequency decreases as one progresses from stage 1 through 2, 3, and 4Stage 2 – characterized byK complexes – large negative wavesSleep spindles – burst of Hz wavesStages 3 and 4 – delta waves, large and slowProgress to stage 4 sleep and then retreat to stage 1
44Sleep Cycle & EEG Emergent stage 1 differs from initial stage 1 REMs Loss of body core muscle toneProgress through sleep stages in 90 minute cyclesMore time spent in emergent stage 1 as night progressesEmergent stage 1 sleep = REM sleepNon-REM (NREM) sleep = all other stagesStage = slow-wave sleep (SWS)During REM: REMs, loss of core muscle tone, low- amplitude/high-frequency EEG, increased cerebral and autonomic activity, muscles may twitch
46Physiological Mechanisms of Sleep and Waking Types of neurotransmitter involvedAcetylcholine -Two groups of acetylcholinergic neurons located in the pons and basal forebrain. They produce activation and cortical desynchrony when they are stimulated.Norepinephrine- Catecholamine agonists produce arousal and sleeplessness; effects appear to be mediated by the locus coeruleus in the dorsal pons.Serotonin (5-HT) - Appears to play a role in activating behavior; almost all of the brain’s serotonergic neurons are found in the raphe nucleus. These neurons are located in the medullary and pontine regions of the brain.Histamine - A neurotransmitter implicated in the control of wakefulness and arousal; a compound synthesized from histidine, an amino acid.
47Physiological Mechanisms of Sleep and Waking Neural control of arousalLocus coeruleusA dark color group of noradrenergic cell bodies located in the pons near the rostral end of the floor of the fourth ventricle; involved in arousal and vigilance.Raphe nucleusA group of nuclei located in the reticular formation of the medulla, pons, and midbrain, situated along the midline; contains serotonergic neurons.
49Physiological Mechanisms of Sleep and Waking Neural control of arousalTuberomammillary nucleusA nucleus in the ventral posterior hypothalamus, just rostral to the mammillary bodies; contains histaminergic neurons involved in cortical activation and behavioral arousal.HypocretinA peptide also known as orexin, produced by neurons whose cell bodies are located in the hypothalamus; their destruction causes narcolepsy.
50Physiological Mechanisms of Sleep and Waking Neural control of slow-wave sleepVentrolateral preoptic area (VLPA)A group of GABAergic neurons in the preoptic area whose activity suppresses alertness and behavioral arousal and promotes sleep.Destruction of this area has been reported to resultin total insomnia, coma, and eventual death in rats.
51Physiological Mechanisms of Sleep and Waking Neural control of REM sleepPGO wave (pontine, geniculate, occipital):Bursts of phasic electrical activity originating in the pons, followed by activity in the lateral geniculate nucleus and visual cortex, a characteristic of REM sleep.
52Physiological Mechanisms of Sleep and Waking The executive mechanismPeribrachial area -The region around the brachium conjunctivum, located in the dorsolateral pons; contains acetylcholinergic neurons involved in the initiation of REM sleep.Carbachol - A drug that stimulates acetylcholine receptors.Medial pontine reticular formation (MPRF)-A region that contains neurons involved in the initiation of REM sleep; activated by acetylcholinergic neurons of the peribrachial area.Similarities between REM and wakefulness suggest that the same brain area might be involved in bothREM sleep is controlled by nuclei in the caudal reticular formation, each controlling a different aspect of REMMagnocellular nucleus - A nucleus in the medulla; involved in the atonia (muscular paralysis) that accompanies REM sleep.
53Effects of Sleep Deprivation CausesDifficulty concentratingAttention lapseGeneral irritabilityDecreases cognitive functioningImpairs learningRecuperation theories predict:Long periods of wakefulness will result in disturbancesDisturbances will get worse as deprivation continuesAfter deprivation, much of the missed sleep will be regainedWhat does the research indicate?
54Studies of Sleep Deprivation in Humans Does sleep loss affect your performance?We tend to be poor judges of the effects of sleep deprivation on our performance3-4 hours of deprivation in one nightIncreased sleepinessDisturbances displayed on written tests of moodPerform poorly on tests of vigilance2-3 days of continuous deprivationExperience microsleeps, naps of 2-3 secondsEffects on complex cognitive function, motor performance, and physiological function are less consistent
55Sleep-Deprivation Studies with Lab Animals Carousel apparatus used to deprive rats of sleepWhen the experimental rat’s EEG indicates sleep, the chamber floor moves – if the rat does not awaken, it falls into waterYoked controls – subjected to the same floor rotationsExperimental rats typically die after several daysPostmortem studies reveal the extreme stress experienced by the experimental ratsCarousel apparatus
56Theories of Sleep Function Restorative theory, holds that being awake produces wear and tear on the body and brain, and sleep serves the function of restoring the body and mind.Circadian theory of sleep is based on the premise that sleep evolved to keep humans out of harm’s way during the dark of night and possibly from becoming prey of some nocturnal predator.
57Hypothalamus and Sleep During WWI – victims of encephalitis lethargica caused some to sleep continuously and others to sleep littleDamage in posterior hypothalamus and adjacent midbrain > excessive sleepDamage in preoptic area and adjacent forebrain > wakefulness
59Dreams Dream content REM Dream NREM Dream Bizarre Dreams Lucid Dreams Varies by culture, gender, and ageFrequently connects with recent experienceMay help us form memoriesREM DreamAn almost continually occurring dream during REM sleepHas story like qualitiesMore vivid, visual, and emotional than NREM dreamsNREM DreamLess frequent than REM dreamsLess memorable than REM dreamsBizarre DreamsBiopsychological explanationLower amounts of serotonin and norepinephrine lead to less inhibition of impulsive thoughts and actions.Lucid DreamsA dream an individual is aware of dreaming and whose content the individual is often able to influence while dreaming.
60Lucid DreamsTry It 4.1Next time you wake up during a dream, try the following the steps to see if you can engage in lucid dreaming.RelaxClose your eyes and focus on an imaginary spot in your field of vision.Focus on your intention to have a lucid dreamTell yourself that you’re going to dream about whatever you want.Imagine yourself in a dream of the type you want to have.Repeat the steps until you fall asleep.
61Interpreting Dreams Sigmund Freud Freud thought dreams were triggered by unacceptable repressed wishesBelieved dreams satisfy unconscious sexual and aggressive desires and so must be disguised.Manifest Content – what we experienceThe content of a dream as recalled by the dreamerLatent ContentThe underlying meaning of the dreamIn recent yearsSeen as an expression of a broad range of the dreamer’s concerns rather than sexual impulses.
62Interpreting Dreams Activation-Synthesis Hypothesis Dreams are the brain’s attempt to make sense of the random firing of brain cells during sleep.Cortex creates a story in an effort to make sense of the brain’s activityStory is synthesized as a consequence of brain activityPeople impose meaning on the random mental activity
63Sleep Disorders - Parasomnias Somnambulism (sleepwalking)occurs during partial arousal from stage 4 sleep.Sleep terrorhappens during partial arousal from stage 4 sleepusually begins with a piercing scream.Nightmaresare frightening dreams that occur during REM sleep.Somniloquy (Sleeptalking)occurs during any sleep stageis more frequent among children.
64Major Sleep Disorders Insomnia Hypersomnia A sleep disorder characterized byDisorders of sleep initiation and maintenanceDifficulty falling or staying asleepWaking too earlySleep that is light, restless, or of poor qualitySymptoms can lead to distress and impairment in daytime functioningHypersomniaDisorders of excessive sleep or sleepiness
65Major Sleep Disorders Sleep apnea Periods during sleep when breathing stops and the individual must awaken briefly in order to breathe2 typesCaused by muscle spasms or atoniaFailure of the CNS to stimulate breathingMost commonly seen in males, the overweight, and in the elderlyThe major symptoms are excessive daytime sleepiness and extremely loud snoring, often accompanied by snorts, gasps, and choking noisesAlcohol and sedatives aggravate the conditionCan lead to chronic high blood pressure, heart problems, and even deathNeuroscientists have also found that it can cause mild brain damageThe interrupted sleep experienced by individuals with this disorder affects cognitive as well as physiological functioning
66Major Sleep Disorders Narcolepsy Also a form of hypersomnia Characterized by excessive daytime sleepiness and repeated brief uncontrollable attacks of daytime REM sleep, usually lasting 10 – 20 minutesAn incurable sleep disorderCataplexy – loss of muscle tone while awakeSleep paralysis – paralyzed while falling asleep or upon wakingHypnagogic hallucinations – dreaming while awakeAppears to be an abnormality in the mechanisms that triggers REMDreaming and loss of muscle tone while awake – suggest REM intruding into wakefulnessREM without atonia – able to act out dreams – possibly caused by damage to the nucleus magnocellularis or its output
67Effects of Long-Term Sleep Reduction The brain is adaptable – may be able to function well with very little sleepOne deficit seen with subjects sleeping only 5.5 hours for 60 daysSlight deficit in a test of auditory vigilanceOther study – no ill effects seen at I year with subjects sleeping hours less per week than before studyHow much sleep do you need?Can this question be answered?Why or why not?