Functions of Sleep

• Restorative/recuperation is the replenishment of depleted resources used during the day.

• Information processing is important for consolidating memories, and memories are improved by sleep.

• Evolutionary theory/The adaptive hypothesis holds the premises that:

  • Animals that need more time to get food overall sleep less.

  • That when predators are removed, animals can hide and sleep more.

  • And that more vulnerable animals sleep little.

Polysomnography

• Studies that focus on sleep and sleep disorders.

• Takes measures of the following:

  • Heart rate.

  • Breathing.

  • Brain waves (With an EGG.).

  • Eye movements (With an EOG.)

  • Muscle activity (With an EMG.)

Circadian Rhythms

• Circadian rhythm is the name given to our biological clocks. It serves as a consistent cycle of our bodily activity as well as behaviors that occur during a twenty-four-hour period.

• The term “Circadian” means “about a day.”

• Circadian rhythms are physical, mental, and behavioral changes that follow a roughly 24-hour cycle and respond primarily to light and darkness in an organism's environment.

• Low points in the Circadian rhythms cycle are between 1-4 Pm and 2-4 Pm.

• Key ways we can upset our circadian rhythms include:

  • Shift work

  • Jet lag

  • Weekends

Suprachiasmatic Nucleus

• The suprachiasmatic Nucleus (SCN) is the area in the hypothalamus that is just above the optic chiasm.

  • The SCN regulates the pineal gland’s secretion of melatonin.

Pineal Gland

• The pineal gland plays an important role in the circadian rhythm as well as our sleep and wake cycles.

  • The pineal gland releases melatonin which affects sleep.

• Levels of melatonin change within a twenty-four-hour cycle.

• Melatonin both reduces jet lag and is used as a sleep aid.

Types of Sleep

• There are two types of sleep, which include REM and NREM.

• It was thought that there were four stages of NREM; however, sleep researcher no longer differentiates between stages three and four, so there is officially 3 stages of NREM.

Sequence of Stages

• The REM stage gets progressively longer during the night

• Deep NREM gets progressively shorter

• More deep NREM in the first half of the night

• More REM in the second part of the night

• Sleeping only 4 hours instead of the usual 7 results in losing more REM sleep

NREM: Non-Rem

• NREM sleep starts with Stage 1

• Stages 1 and 2 are considered light sleep or light NREM

• Stage 1 is so light that a person might not even realize they were asleep

• In Stage 1, a person can be easily awakened by their partner, but they may insist that they haven't been sleeping

• Stage 3 is considered deep sleep or deep NREM. Stage 3 is also known as delta sleep or slow wave sleep; It is very difficult to awaken a person in Stage 3.

NREM

• Bedwetting: frequently happens during deep sleep.

• Night terrors: prevalent among children.

• Sleepwalking: takes place during NREM as there is partial paralysis during REM, preventing walking.

Sleep Disorders

• Sleepwalking occurs during non-rapid eye movement (NREM) sleep.

• The person gets up and walks around during sleepwalking.

• The person is not acting out their dreams during sleepwalking.

• Sleepwalking can be dangerous as the person may walk out of a second-floor window.

• There is a controversial defense in crimes committed by sleepwalkers, also known as "Sleepy Murderers."

• A sleep-related eating disorder is a condition where a person eats while sleepwalking.

• Night Terrors

  • Happen during NREM sleep.

  • A person sits up in bed, looks terrified, and screams.

  • Usually, no memory of the experience in the morning.

• Nightmares

  • Happen during REM sleep.

  • A person may see frightening images and wake up.

  • Upon awakening, a person can describe the nightmare in great detail.

Rem

• REM stands for Rapid Eye Movement and is characterized by rapid eye movement.

• Approximately 20-25% of the night is spent in REM.

• A person goes into REM 4 or 5 times per night.

• The REM stage comes approximately every 90 minutes.

• The REM stage gets progressively longer throughout the night.

• REM is also called Paradoxical sleep because brain waves look like those of an awake person or a person in light sleep, but it is hard to awaken the person.

• REM is considered active sleep because bodily functions speed up.

REM: Partial Paralysis

• Fibers from the brain, including pons, descend and inhibit motor neurons during REM sleep, causing sleep paralysis.

• Jouvet, a researcher, cut fibers in cats during REM sleep.

• The cats "acted out" their dreams, indicating that the paralysis during REM is necessary to prevent physical movement during dreams.

• Sleepwalking does not occur during REM sleep because of partial paralysis.

REM & Dreams

• Dreaming mostly occurs during REM sleep.

• Non-REM sleep involves less vivid dreams that are more like thinking.

• Everyone dreams, but not everyone remembers their dreams.

• The amount of REM sleep decreases with age.

• REM sleep is important for neural development and memory consolidation.

• A night of sleep with REM deprivation leads to less retention of information.

• NREM sleep is also involved in memory.

• Dreams can incorporate external and internal stimuli.

• No sleep learning occurs, meaning you can't learn a language by playing tapes while asleep.

REM Rebound

• REM Rebound:

  • Increase in REM to make up for a deficit

  • Happens after REM deprivation

  • Recovery night allows for sleeping through the night

• Drugs that decrease REM can cause REM rebound:

  • Happens when discontinued

  • REM rebound can come in the form of nightmares.

Sleep Disorders: Insomnia

• Difficulty falling asleep and staying asleep.

• Stress and anxiety are major causes of insomnia.

• Depression can cause early morning awakening despite being able to fall asleep.

• Sleeping pills such as tranquilizers, barbiturates, and alcohol can induce insomnia.

Drug-Induced Insomnia

• Tranquilizers, Barbiturates, and Alcohol can interfere with REM and overall sleep quality.

• Over time, the body can build up a tolerance to these substances, leading to a decrease in sleep quality.

• When someone quits taking these substances, they may experience insomnia.

• Once they do fall asleep, they may experience REM rebound in the form of nightmares.

Sleep Deprivation: Microsleeps

• Microsleeps occur when a person has been sleep deprived.

• Microsleeps are fleeting, uncontrollable, brief episodes of sleep that last for seconds.

• Microsleeps are sometimes referred to as "zoning out."

• During microsleeps, the brainwaves resemble those of sleep.

• Microsleeps can be dangerous, especially when driving or operating heavy machinery.

Sleep Disorders: Apnea

• Sleep Apnea is a condition where a person stops breathing for minutes at a time, and this can happen many times during the night.

• Sleep Apnea increases the risk of heart attacks and other health problems.

• Anoxia, which is a lack of oxygen to the brain, can occur due to Sleep Apnea.

• Sleep Apnea is sometimes referred to as Sudden Adult Death Syndrome (SADS) because it can be dangerous to stop breathing many times per night.

• People with Sleep Apnea are often loud snorers.

• The treatment for Sleep Apnea is a CPAP machine.

Sleep Apnea Remedies

• Losing weight

• Stop smoking

• Reduce sleeping pill use

• Dental implants

• CPAP machine: Continuous positive airway pressure

Sleep Disorders: Narcolepsy

Narcolepsy Symptoms

• Sleep attacks & excessive daytime sleepiness triggered by emotions such as anger or laughter

• Cataplexy: temporary loss of muscle tone causing falls while awake

• Sleep paralysis: inability to move after waking up

• Hypnagogic hallucinations: upsetting hallucinations while falling asleep or waking up

Testing for Narcolepsy

• In a sleep lab, individuals with narcolepsy go straight into REM stage instead of going through NREM first.

Disorders: REM Sleep Behavior Disorder

• People with this disorder lack the normal muscle paralysis that occurs during REM sleep.

• As a result, they act out their dreams while sleeping.

• This disorder is more common in older males.

• It can be dangerous as there is a risk of physical injury to oneself or to the person sharing the bed.

Sleep Promoting Drugs

Benzodiazepines

• Benzodiazepines are GABA agonists that increase GABA.

• Diazepam (Valium) is a benzodiazepine.

• Benzodiazepines can be addictive and cause an overdose when combined with alcohol and opiates by suppressing breathing.

Z-Drugs

• Z-drugs are similar to benzodiazepines and also GABA agonists.

• Ambien is a Z-drug that can cause sleep disturbances like sleepwalking or sleep eating.

Sleep Hygiene

• Avoid full-spectrum light (phones, TV) before going to sleep

• Exercise is good for sleep, but not right before bedtime

• Avoid caffeine or other stimulants

• Establish a regular sleep schedule to regulate circadian rhythms

• Avoid eating before sleeping, especially spicy foods

• Get exposure to natural light in the morning to help with circadian rhythms

• Reduce stress.

Parts of the Brain

• Pons: pathways that cause partial paralysis during REM by inhibiting motor neurons

• Raphe Nucleus: main area of serotonergic pathways that promote sleep

• Serotonin is responsible for inducing sleep

• Tryptophan is a precursor to serotonin