Sleep

Learning objectives What are daily rhythms and how are they maintained? What is sleep? How do we characterize different phases of sleep? What is REM and NREM sleep? How does sleep change with age? What are the health effects of sleep (or lack of sleep) What is the difference between dyssomnias and parasomnias?

Rhythms Circannual rhythms hibernation, migration Fertility cycles monthly in humans Circadian Rhythm Daily

Circadian Rhythm Maintained by suprachiasmic nuclei (SCN) controls body temp, alertness inactive at night, allowing sleep Signals for the release of melatonin by pineal gland hormone that increases relaxation and sleepiness Resets due to light Mismatch between internal and external cues induces insomnia or sleepiness — jet lag

What is sleep? A state of unconsciousness or partial consciousness from which a person can be roused by stimulation (i.e. not a coma) Strongly influenced by circadian rhythms

Structure of sleep Non-rapid eye movement sleep (NREM) Rapid eye movement sleep (REM)

NREM sleep Stage 1 relaxed, half-awake state “nope, I wasn’t asleep” no movement — stimulates sleep admit to being asleep Stages 3 & 4 deep sleep Blood pressure drops, heart and respiration slow Most deep sleep in beginning of night

REM sleep Breathing and heart rate increase brain activity increases, dreaming REM sleep paralysis brain seems awake no muscle tone REM rebound effect more frequent REM after inadequate sleep We ‘file’ ideas and thoughts in long-term memory People lacking REM sleep can’t learn complex tasks

Structure of sleep REM increases throughout night “Deep sleep” most likely during first cycles

Irregular temperature cycling Sleep and age More deep sleep Irregular temperature cycling Less melatonin

Health effects of sleep Metabolism less sleep —> higher obesity rates alters glucose metabolism hormone imbalance ghrelin = increases appetite leptin = decreases appetite less REM (which burns calories) more cortisol (encourages food binges)

Health effects of sleep Safety Sleep deprivation —> drowsiness loss of 1 hour sleep at daylight savings time coincides with 20% increase in auto accidents the next day Heart Disease Immune function

Health effects of sleep Cancer Shift workers more likely to get breast and prostate cancer changes in hormones? immune system suppression? decreased melatonin? Mental health sleep complaints common in schizophrenic, bipolar, and depressive patients

Possible reasons why we need sleep Wound healing, growth, and restoration Immune system function decreases with lack of sleep More growth hormone at night Waste clearance in brain Brain development Filing memories into long-term memory Especially during REM sleep

How much sleep do we need? 8-9 hours for most people varies by individual Sleep deprivation less sleep than needed to feel ‘vibrant’ Sleep debt sleeping in on weekends usually NOT enough Signs of insufficient sleep: Daytime drowsiness falling asleep ‘as soon as you head hits pillow’

How to get a good night’s sleep Maintain a regular schedule Sleep in conducive environment (cool, quiet, comfortable) Avoid caffeine, nicotine, and alcohol Get exercise (but not too close to bedtime, > 3hrs) Manage stress Short naps only pull the plug (computers and lights keep you from falling asleep)

Sleep disorders Dyssomnias Parasomnias Difficulty falling asleep, staying asleep, or excessive sleepiness Insomnia Sleep apnea narcolepsy brain’s inability to control sleep-wake cycles Parasomnias physiological functioning or behavior during sleep Usually occur between wake and NREM sleep sleepwalking sleep-related eating disorder

Sleep aids Prescription Lunesta and Ambien Can be addictive side effects include cognitive distortion sleep driving sleep related binge eating should not be taken form more than 2 weeks Over-the-counter antihistamines promote drowsiness but the body develops tolerance