What 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. Circadian rhythms Animals and plants possess endogenous clocks to organize daily behavioral and physiological rhythms in accord with the external day- night cycle The basis for these clocks is believed to be a series of molecular pathways involving “clock” genes that are expressed in a nearly 24- hour rhythm Refers to circa=approximately, and dias=day
The Influences of Circadian Rhythms o Circadian Rhythm o A daily rhythmical change in behavior or physiological process. o About a day o Regular fluctuation from high to low points of certain bodily functions and behaviors o Sleep debt o Deficiency caused by not getting the amount of sleep that one requires for optimal functioning o Affects psychological functions of o Blood pressure o Heart rate o Appetite o Secretion of hormones and digestive enzymes o Sensory acuity o Elimination o Body’s response to medication
Environmental 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 cycles As 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.
About 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
What’s the Endocrine System? A collection of glands that secrete hormones in order to regulate functions within the body.
The Influences of Circadian Rhythms o Suprachiasmatic nucleus (SCN) o A nucleus, situated atop the optic chiasm, in the brain’s hypothalamus that control the timing of circadian rhythms o It contains a biological clock responsible for organizing many of the body’s circadian rhythms. o Lesions do not reduce sleep time, but they abolish its circadian periodicity o Exhibit activity that can be entrained by the light-dark cycle o Transplant SCN, transplant sleep-wake cycle o Melanopsin o A photopigment present in ganglion cells in the retina whose axons transmit information to the SCN, the thalamus, and the olivary pretectal nuclei. o Zeitgebers o A stimulus (usually the light of dawn) that resets the biological clock responsible for circadian rhythms. o Intergeniculate leaflet (IGL) o 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
The Influences of Circadian Rhythms o Control of seasonal rhythms o Pineal Gland o A gland attached to the dorsal tectum; produces melatonin and plays a role in circadian and seasonal rhythms. o Secretes melatonin from dusk until just before dawn o Does not secrete melatonin during daylight hours o Melatonin o A hormone synthesized from serotonin in the pineal gland o Secreted during the night by the pineal body; o Melatonin levels display circadian rhythms controlled by the SCN o plays a role in circadian and seasonal rhythms. o Melatonin is not a sleep aid, but may be used to shift circadian rhythms
Disruptions in Circadian Rhythms Jet lag o When 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 started o Can produce memory deficits that may be permanent o Supplemental melatonin has been shown to be an effective treatment for relapses of psychiatric disorders induced by jet lag o Zeitgebers are accelerated or decelerated o Research 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.
Disruptions in Circadian Rhythms Shift work o When people work during the night and sleep during the day o Shift workers average 2 to 4 hours less sleep than nonshift workers of the same age o Subjective night o The time during a 24-hour period when body temperature is lowest and when the biological clock is telling a person to go to sleep o During 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 altered o Rotating 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 reverse o Modafinil o A wakefulness drug that will help people remain alert without the side effects of stimulants such as caffeine
Can the effects be prevented or minimized? o Both produce a variety of deficits o Can the effects be prevented or minimized? Reducing Jet Lag Gradually shift sleep-wake cycle prior to travel Administer post-flight treatments to promote the needed shift Phase advance following east-bound travel with intense light early in the morning Hamster studies suggest a good early morning workout may also help
Can the effects be prevented or minimized? Reducing the Effect of Shift Changes Schedule phase delays, rather than phase advances Move from current schedule to one that starts later It is easier to stay up later and get up later than to retire and arise earlier Phase advances are harder, explaining why east-bound travel tends to be more problematic Shift 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 home Exposure to appropriately timed bright light or even light of medium intensity has been found to reset young adults’ biological clocks and improve their performance
The Influences of Circadian Rhythms Disruptions in Circadian Rhythms o Subjective night o The time during a 24-hour period when the biological clock is telling a person to go to sleep. o Energy and efficiency are at their lowest points o Reaction time is slowest o Productivity is diminished o Industrial accidents are higher o Daylight savings time in spring is associated with short term 6.5% increase in accidental deaths. o Work schedules o Moving work schedules forward from days to evenings to nights makes adjustment easier o Rotating shifts every three weeks lessens the effect on sleep
Sleep What is it? What Does It Look Like? How does it function? What happens when we sleep? Measurement? How does it change with age?
What is sleep? A state of sustained 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…
Why 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.
Why 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 function Ultimate Explanation sustains our ability to reproduce successfully, by maintaining good health
Why do we sleep? Recuperation theories Sleep is needed to restore homeostasis Wakefulness causes a deviation from homeostasis Circadian theories Sleep is the result of an internal timing mechanism Sleep evolved to protect us from the dangers of the night
What 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.
What 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 waves Stage 4: Rhythmic breathing and limited muscle activity. REM (Rapid Eye Movement) sleep.
NREM Sleep o Non-rapid eye movement sleep. o Four sleep stages 1. Lightest sleep 2. Mid-sleep 3. Deep sleep 4. Deepest sleep o Heart and respiration slow and regular o Little body movement o Blood pressure and brain activity at lowest points of 24 hour period.
Non-REM sleep Stage 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%.
REM (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.
REM Sleep o Rapid eye movement sleep - also known as “active sleep”.20-25% of a night’s sleep o Internally: o Intense brain activity o Brain metabolism increases o Brain temperature rises rapidly o Epinephrine release leads to increases in Blood pressure, Heart rate, respiration o Externally: o Body appears calm o Large muscles become paralyzed o Eyes dart around o Dreaming occurs in 80% of people o Brain conducts -Consolidation of learning (all night studying doesn’t help) o perceptual skills increase after 8-10 hours of sleep o Memory consolidation
REM Rebound o The increased amount of REM sleep that occurs after REM deprivation o Intensity of REM sleep increases o Those with Sleep Deprivation o Proceed more rapidly into REM as REM deprivation increases o More time spent in REM when deprivation is over o Often associated with unpleasant dreams or nightmares o Alcohol, amphetamines, cocaine, and LSD use suppress REM sleep results in REM rebound o Withdrawal results in REM rebounds REM rebound suggests that REM sleep serves a special function
Purpose of REM? Necessary for mental health Inconsistent with the effects of tricyclic antidepressants – block REM Necessary for maintenance of normal levels of motivation Necessary for processing of memories No clear purpose Default Theory of REM REM serves no critical function One can’t stay continuously in non-REM sleep, so we switch between REM and wakefulness When bodily needs exist – wake up No immediate needs – REM No REM rebound seen when lost REM periods replaced with 15-mins awake
How much sleep is requir ed? 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 7.75 hours How long people sleep a day on average:
Variations in Sleep o Infants and young children o have the longest sleep time o Have the highest of REM and slow wave sleep o Ages 6-puberty o Most consistent sleepers and wakers o Sleep and awake same time daily o Adolescents o Sleep patterns are influenced by their schedules o Sleep longer when no schedule conflicts o Poor sleep may contribute to poor school performance
Variations in Sleep Larks and owls Larks Awaken early every morning and leap out of bed with enthusiasm, eager to start the day Body temperature rises rapidly after they awaken and stays high until about 7:30 p.m. Turn in early and have the fewest sleep problems
Variations in Sleep Owls Fumble for the alarm clock and push the snooze button to get a few more precious minutes of sleep Body temperature of an owl gradually rises throughout the day, peaking in the afternoon and not dropping until later in the evening Guthrie and others Compared the performance of several hundred college students classified as larks or owls Found that the larks made better grades in early morning classes, while the owls made higher grades in classes they took later in the day A gene that runs the biological clock is responsible, in part, for the differences between larks and owls
Animal Sleep SPECIES Average total sleep time per day Python18 hours Tiger15.8 hours Cat12.1 hours Chimpanzee9.7 hours Sheep3.8 hours African Elephant3.3 hours Giraffe1.9 hours Animals also have a required certain amount of sleep:
Sleep o Understanding of sleep increased by the study of o Brain waves o Eye movements o Chin muscle tension o Heart rate o Respiration rate Electro-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.
3 Physiological Measures of Sleep By means of Electroencephalogram (EEG) “brain waves” By means of EOG Eye movements seen during rapid eye movement (REM) sleep By means of EMG Loss of activity in neck muscles during some sleep stages
Sleep Polysomnogram o Provides brain wave sleep recordings o Outlined REM and NREM sleep patterns
Beta 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 relaxation Eyes closed, preparing to sleep Theta 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. EEG
Stage 1 similar to awake EEG, but slower low-voltage, high-frequency EEG voltage increases and frequency decreases as one progresses from stage 1 through 2, 3, and 4 Stage 2 – characterized by K complexes – large negative waves Sleep spindles – burst of Hz waves Stages 3 and 4 – delta waves, large and slow Progress to stage 4 sleep and then retreat to stage 1 Sleep Cycle & EEG
Emergent stage 1 differs from initial stage 1 REMs Loss of body core muscle tone Progress through sleep stages in 90 minute cycles More time spent in emergent stage 1 as night progresses Emergent stage 1 sleep = REM sleep Non-REM (NREM) sleep = all other stages Stage = 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 Sleep Cycle & EEG
Physiological Mechanisms of Sleep and Waking Types of neurotransmitter involved 1. Acetylcholine -Two groups of acetylcholinergic neurons located in the pons and basal forebrain. They produce activation and cortical desynchrony when they are stimulated. 2. Norepinephrine- Catecholamine agonists produce arousal and sleeplessness; effects appear to be mediated by the locus coeruleus in the dorsal pons. 3. 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. 4. Histamine - A neurotransmitter implicated in the control of wakefulness and arousal; a compound synthesized from histidine, an amino acid.
Physiological Mechanisms of Sleep and Waking Neural control of arousal Locus coeruleus A 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 nucleus A group of nuclei located in the reticular formation of the medulla, pons, and midbrain, situated along the midline; contains serotonergic neurons.
Physiological Mechanisms of Sleep and Waking Neural control of arousal Tuberomammillary nucleus A nucleus in the ventral posterior hypothalamus, just rostral to the mammillary bodies; contains histaminergic neurons involved in cortical activation and behavioral arousal. Hypocretin A peptide also known as orexin, produced by neurons whose cell bodies are located in the hypothalamus; their destruction causes narcolepsy.
Physiological Mechanisms of Sleep and Waking Neural control of slow-wave sleep Ventrolateral 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 result in total insomnia, coma, and eventual death in rats.
Physiological Mechanisms of Sleep and Waking Neural control of REM sleep PGO 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.
Physiological Mechanisms of Sleep and Waking The executive mechanism Peribrachial 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 both REM sleep is controlled by nuclei in the caudal reticular formation, each controlling a different aspect of REM Magnocellular nucleus - A nucleus in the medulla; involved in the atonia (muscular paralysis) that accompanies REM sleep.
Effects of Sleep Deprivation o Causes o Difficulty concentrating o Attention lapse o General irritability o Decreases cognitive functioning o Impairs learning Recuperation theories predict: Long periods of wakefulness will result in disturbances Disturbances will get worse as deprivation continues After deprivation, much of the missed sleep will be regained What does the research indicate?
Studies 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 performance 3-4 hours of deprivation in one night Increased sleepiness Disturbances displayed on written tests of mood Perform poorly on tests of vigilance 2-3 days of continuous deprivation Experience microsleeps, naps of 2-3 seconds Effects on complex cognitive function, motor performance, and physiological function are less consistent
Sleep-Deprivation Studies with Lab Animals Carousel apparatus used to deprive rats of sleep When the experimental rat’s EEG indicates sleep, the chamber floor moves – if the rat does not awaken, it falls into water Yoked controls – subjected to the same floor rotations Experimental rats typically die after several days Postmortem studies reveal the extreme stress experienced by the experimental rats Carousel apparatus
Theories of Sleep Function o 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. o 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.
Hypothalamus and Sleep During WWI – victims of encephalitis lethargica caused some to sleep continuously and others to sleep little Damage in posterior hypothalamus and adjacent midbrain > excessive sleep Damage in preoptic area and adjacent forebrain > wakefulness
Dreams Dream content Varies by culture, gender, and age Frequently connects with recent experience May help us form memories o REM Dream o An almost continually occurring dream during REM sleep o Has story like qualities o More vivid, visual, and emotional than NREM dreams o NREM Dream o Less frequent than REM dreams o Less memorable than REM dreams o Bizarre Dreams o Biopsychological explanation o Lower amounts of serotonin and norepinephrine lead to less inhibition of impulsive thoughts and actions. o Lucid Dreams o A dream an individual is aware of dreaming and whose content the individual is often able to influence while dreaming.
Lucid Dreams Next time you wake up during a dream, try the following the steps to see if you can engage in lucid dreaming. 1. Relax 2. Close your eyes and focus on an imaginary spot in your field of vision. 3. Focus on your intention to have a lucid dream 4. Tell yourself that you’re going to dream about whatever you want. 5. Imagine yourself in a dream of the type you want to have. 6. Repeat the steps until you fall asleep.
Interpreting Dreams o Sigmund Freud o Freud thought dreams were triggered by unacceptable repressed wishes o Believed dreams satisfy unconscious sexual and aggressive desires and so must be disguised. o Manifest Content – what we experience o The content of a dream as recalled by the dreamer o Latent Content o The underlying meaning of the dream o In recent years o Seen as an expression of a broad range of the dreamer’s concerns rather than sexual impulses.
Interpreting Dreams o Activation-Synthesis Hypothesis o 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 activity Story is synthesized as a consequence of brain activity o People impose meaning on the random mental activity
Sleep Disorders - Parasomnias o Somnambulism (sleepwalking) o occurs during partial arousal from stage 4 sleep. o Sleep terror o happens during partial arousal from stage 4 sleep o usually begins with a piercing scream. o Nightmares o are frightening dreams that occur during REM sleep. o Somniloquy (Sleeptalking) o occurs during any sleep stage o is more frequent among children.
Major Sleep Disorders o Insomnia A sleep disorder characterized by Disorders of sleep initiation and maintenance o Difficulty falling or staying asleep o Waking too early o Sleep that is light, restless, or of poor quality Symptoms can lead to distress and impairment in daytime functioning o Hypersomnia o Disorders of excessive sleep or sleepiness
Major Sleep Disorders o Sleep apnea Periods during sleep when breathing stops and the individual must awaken briefly in order to breathe o 2 types 1. Caused by muscle spasms or atonia 2. Failure of the CNS to stimulate breathing Most commonly seen in males, the overweight, and in the elderly The major symptoms are excessive daytime sleepiness and extremely loud snoring, often accompanied by snorts, gasps, and choking noises Alcohol and sedatives aggravate the condition Can lead to chronic high blood pressure, heart problems, and even death Neuroscientists have also found that it can cause mild brain damage The interrupted sleep experienced by individuals with this disorder affects cognitive as well as physiological functioning
Major Sleep Disorders o Narcolepsy o Also a form of hypersomnia o Characterized by excessive daytime sleepiness and repeated brief uncontrollable attacks of daytime REM sleep, usually lasting 10 – 20 minutes o An incurable sleep disorder o Cataplexy – loss of muscle tone while awake o Sleep paralysis – paralyzed while falling asleep or upon waking o Hypnagogic hallucinations – dreaming while awake o Appears to be an abnormality in the mechanisms that triggers REM o Dreaming and loss of muscle tone while awake – suggest REM intruding into wakefulness o REM without atonia – able to act out dreams – possibly caused by damage to the nucleus magnocellularis or its output
Effects of Long-Term Sleep Reduction The brain is adaptable – may be able to function well with very little sleep One deficit seen with subjects sleeping only 5.5 hours for 60 days Slight deficit in a test of auditory vigilance Other study – no ill effects seen at I year with subjects sleeping 7-18 hours less per week than before study How much sleep do you need? Can this question be answered? Why or why not?