Circadian Rhythm & Bodily Rhythms

• Circadian rhythm refers to the body's biological clock
• It operates on an approximate 24-hour cycle

Bodily Rhythms

• Bodily rhythms change physiological processes within a 24-hour cycle
• Melatonin, a hormone, doesn't cause drowsiness, it signals sunset to the body
• As you fall asleep, body temperature decreases, conversely, body temperature rises with activity
• Alertness also fluctuates as part of the circadian rhythm
• Rhythms are produced by an internal, endogenous clock, and is the internal response to stimuli

Zeitgeber

• A zeitgeber is a cue that synchronizes the body with the environment
• It is German for "time-giver"
• Sunlight, tides, exercise, meals, and environmental temperature can act as zeitgebers
• These cues help to understand what needs to happen

Biological Clock

• A biological clock was studied by a man who studied circadian rhythms while living without a watch in a cave, in the dark, without time
• This is how human chronobiology came to be
• There was a sense of warped time
• The sleep/wake cycle was found to be approximately 24 hours and 30 minutes
• This proved the existence of an internal clock, which persists even without environmental cues

Jet Lag

• Jet lag disrupts the circadian rhythm
• Disruption is when the internal circadian rhythm does not match the external environment, which includes what you see outside
• Traveling west causes "Phase-delays", and it's easier to stay awake longer rather than sleep earlier
• Traveling east involves "Phase-advances", so going to bed earlier is required but is more difficult for the internal clock

Shift Work

• Sleep duration is dependent on when sleep occurs
• Working at night does not reliably shift the circadian rhythm
• People can adjust to night work
• Recent reports indicated that 22 people shifted to night work, and the genetic fine-tuning was lost at night
• Rhythmic genes became out of sync, controlled by the suprachiasmatic nucleus (SCN)
• Shift work causes higher rates of cancer, type 2 diabetes, and cardiovascular issues

Suprachiasmatic Nucleus (SCN)

• SCN controls circadian rhythms of sleep and temperature
• The SCN is located above the optic chiasm, and is part of the hypothalamus
• Damage to the SCN can remove circadian rhythm, resulting in timing disruptions

Retinohypothalamic Pathway

• Retinohypothalamic pathway in mammals contains ipRGC in the retina, which projects to the SCN
• ipRGC is sensitive to overall average levels of light, being more active with light and less when dark
• Blind people are often more tired

Biochemistry

• Two types of genes generate the circadian rhythm, PER (proteins) and TIM (Timeless proteins)
• In mammals, retinal ganglion cells detect light and release glutamate in the SCN
• Glutamate promotes production of the PER protein

Melatonin

• The pineal gland produces melatonin
• Melatonin release changes the circadian and circannual rhythm
• Marine life can use melatonin
• Melatonin does not cause sleep, but it indicates light change

Sleep

• Sleep is an active state of brain production
• It is characterized by decreased brain activity and response to stimuli
• Sleep differs from coma, vegetative states, minimally conscious states, and brain death
• Electrical activity in the brain can classify levels of arousal and the states of sleep
• Electrical activity is recorded
• EEG is the recording of the neck and scalp
• EOG records lateral eye movements
• EMG measures respiration using the movement of the jaw and neck
• Humans cycle through 5 sleep stages every 90 minutes in order of 1, 2, 3, 4, 3, 2, REM

Sleep Stages

• Stage 1 is a brief light sleep stage of 10-30 minutes, that causes "falling" sensations, and irregular brain waves
• Stage 2 lasts about 20 minutes, marked by spindles, which are bursts of brain activity
• Stage 3 is brief, and is the transitioning stage to deeper sleep, characterized by large slow delta waves
• Stage 4 lasts for 30 minutes, has delta waves and is deep sleep
• REM lasts 10 minutes, and has similar function to being awake

REM Sleep

• REM sleep is associated with vivid dreams, learning, memory consolidation, and similar brain function to awake states
• NREM includes stages 1 through 4, involves lower-frequency brain waves, decreased pulse, occasional dreams, and is needed for biological restoration
• Stage 4 must be met before REM
• REM sleep recurs and periods become longer at night, with vivid, vibrant dreams
• It plays a role in learning and memory
• During paradoxical sleep the body is paralyzed but heart rate and breathing increase
• There is external calm (muscles), and internal arousal (heart rate)
• The pons and limbic system are active

Brain Function

• During REM sleep, brain activity increases in the pons and the limbic system which affects emotions, learning, and memory
• Brain activity decreases in the visual, motor, and prefrontal cortex areas like the occipital lobe
• PGO waves occur during the absence of visual stimuli, which can create a dream

Brain Regulation

• Sleep is regulated by serotonin and acetylcholine
• As serotonin increases, melatonin decreases
• Acetylcholine activity is associated with cortisol arousal/activation and can include Alzheimer's or sundowner syndrome, as well as potentially outrageous behavior, aggressive behavior, and are hard to control
• A heightened sense of anxiety before sleep can cause sleeping with one eye open when danger is sensed, as discovered in unilateral studies on iguanas

Unilateral Sleep

• Unilateral sleep is when one hemisphere falls asleep at a time, examples of animals that can do this include dolphins and marine mammals
• Two inner mallard ducks in a row can sleep with both eyes closed when they feel safe and have no predation risk
• Outer ducks sleep unilaterally and can turn 180 degrees so the other eye could sleep

Stages of Sleep

• The stages of sleep in a typical night is 123432REM
• It starts to shift to stage 2 to REM over longer intervals as the night progresses
• Humans need more sleep when they are younger and less sleep when they are older

Neural Systems

• Sleep is an active state, mediated by the forebrain system (SWS)
• Forebrain system is part of the brain that contributes to slow wave sleep
• The brainstem mediates wakefulness, which alerts the body it is time to wake up

Brain systems

• A pontine mediates REM sleep
• A Hypothalamic system controls all parts of the brain
• Slow wave sleep is promoted by the basal forebrain which releases GABA, creating inhibition that is essential to slowing down the CNS
• General anesthesia activates GABA receptors, accounting for the state caused by anesthesia
• Stimulating the SWS area makes animals sleepy
• If you damage SWS, you get insomnia and can't get to SWS
• Removing the basal forebrain still allows for the generation of delta slow wave sleep

Brain Regions

• The pontomesencephalon has acetylcholine and glutamate and contributes to cortical arousal
• It extends to the thalamus, hypothalamus, and basal forebrain, sending excitatory messages and causing a high level of arousal
• The pontomesencephalon tends to inhibit movements, but stimulate it, and more alertness and less movement may result
• Locus coeruleus is a key source of norepinephrine and remains dormant during sleep but provides norepinephrine upon waking, promoting REM sleep
• The hypothalamus uses histamine, so taking an antihistamine makes you drowsy and sleepy
• It promotes wakefulness and produces widespread excitatory effects throughout the brain and is also responsible for the immune response
• It sends axons to three other sleep centers and controls them
• The reticular formation drives wakefulness, stimulation can cause one to feel awake and alert
• Damaging the reticular formation causes a constant sleep state

Brain Regions

• The basal forebrain and reticular formation gives us the sleep-wake cycle in most species
• Pons create cortical arousal, inhibits movement in REM, causes muscle atonia and paralysis, and uses widespread projections to promote sleep
• Damaging the pons causes an animal to be up and moving during dreams

Need for Sleep

• Sleep is needed for evolutionary purposes
• Includes safety, energy conservation, and efficiency
• Sleep is needed for self maintenance
• Sleep is needed for body rejuvenation
• Sleep is needed to restore and repair brain tissue
• Sleep enhances synaptic connections, increasing neuronal growth, as well as memory consolidation

Sleep Disorders

• Sleep disorders stem from inadequate sleep, and can manifest with different patterns of sleep
• Sleep disorders can result from mental disorders or dependence on drugs, causing shifts in circadian rhythms

Sleep Deprivation

Examples of the effects of sleep loss

• Fatigue
• Impaired concentration
• Immune suppression
• Irritability
• Slowed performance
• More accidents (planes, autos, and trucks)

Insomnia and Narcolepsy

• Insomnia is characterized by persistent problems in falling or staying asleep
• Narcolepsy causes uncontrollable sleep attacks
• The individual will lapse directly into REM sleep, often at inopportune times
• Their muscles will become atonic and move into REM sleep
• Ritalin and hypocretin increase dopamine, and norepinephrine, which prevents transition from wakefulness to REM sleep

Breathing Disorders

• Sleep apnea is when one intermittently stops breathing during sleep
• There is frequently momentary awakenings
• Obstructive sleep apnea is the most common disorder
• Causes throat muscles to relax too much which closes the space to cause breathing difficulty
• It is treated using a CPAP which pushes air into one's system

Terrors and Disorders

• Night terrors usually occur in children between ages 4 and 12
• Night terrors are accompanied by a terror appearance and temperature changes
• All will grow out of it
• Individuals tend to remember least during SWS, they are running around, screaming, and their heart is accelerated
• REM behavioral disorder (RBD) shows onset after 50
• RBD is predictive of another type of disorder and is more common in men

Parkinson's and Dementia

• Individuals will develop either parkinson's or dementia
• Organized behavior will characterize an individual that is asleep
• They can be awakened and recall vividly what was happening in REM
• Damage begins in brainstem
• Parasomnia causes individuals to act out the dreams they are fully experiencing

Parasomnia

• Parasomnia has been used in court cases
• Individuals have harmed or killed their spouse and have no recollection
• In a Parasomnia state the brain tells the body to move and engage in activities

Dreams

• Dreams are images, emotions, and thoughts passing through a sleeping person's mind
• They can be emotional and consist of different thoughts
• Hallucinatory imagery is seeing things in the absence of visual stimuli
• The brain is active, generating a signal and interpreting it
• REM sleep causes vivid recall if awoken during

Biological Views

• Biological views on dreaming include the activation-synthesis and the clinico-anatomical hypothesis
• The activation-synthesis proposes which is seen in a Nova video, that the pons are connected to the cortex, and the story is created from the pattern of activation for what is sensed with a lack of movement

Dreaming in Brain

• REM sleep is an important event
• The pons sends widespread projections throughout the cortex
• Dreams are created from neuron activity starting in the pons
• Dreams begin with spontaneous activity in the pons that activates the cortex
• Then cortex then synthesizes a story to make sense of brain activity
• This brain activity is awareness
• Stimulation in the brainstem activates the cortex

Limbic System

• The limbic system provides stimulation in the brainstem
• The stimulation is related to our thoughts/awareness
• PGO waves occur during REM sleep
• Pons activate other areas, and PGO waves give us a sense of dreams, and can evoke visual imagery and visual memories

Sleep Models

• The clinico-anatomical hypothesis has less emphasis on pons, and believes dreams are similar to thinking
• Dreams are just more thinking that takes place under unusual conditions
• Dreams begin with arousing stimuli that are generated within the brain, consisting of what we know and can incorporate into experiences
• Activity happens in various parts of the cortex, like parietal, occipital, and temporal
• Images are created in this way without constraint, without sensory input and with repressed PFC, resulting in hallucinatory perceptions

General Knowledge

• In order to dream, PFC needs to do with goals and reality
• Yes, but it is rare because it requires damage to Temporaperietal junction
• Average time to fall asleep is about 15-20 Minutes
• The number of nightmares an adult has per year is, about 1 a month
• Typically have 3-5 Dreams a night, usually one for every sleep wake cycle
• If you are born blind you don't have visual input thus dreams
• Domesticated animals dream Alcohol and Marijuana can disrupt sleep patterns
• Sleep has vivid dreaming
• Only mammals dream
• Some people never remember dreams