Swetha Rao Sleep

Why is sleep important? We sleep for nearly 1/3 of our lives Concentration, Memory, and Coordination Sleep Loss = Alcohol Lack of sleep can increase risk of diabetes, cardiovascular disease and heart attacks, stroke, depression, high blood pressure, obesity, and infections Sleep Disorders affect up to 70 million people

Slow Wave Sleep First hour or so brain waves slow down relaxation of the muscles and the eyes Heart rate, blood pressure, and body temperature all fall If awakened, most people recall only fragmented thoughts, not an active dream

REM Sleep Rapid Eye Movement Next half hour or so, neocortical EEG waves become similar to waking Atonia: paralysis of the body’s muscles (only the muscles that allow breathing and control eye movements remain active) Active dreaming Heart rate, blood pressure, and body temperature become much more variable Men often have erections First REM period usually lasts 10 to 15 minutes.

Stages of Sleep

Insomnia Initially or partway awakening Short-acting sedatives and sedating antidepressant drugs suppress deeper stages of slow wave sleep

Obstructive Sleep Apnea Deeper sleep = Airway muscles collapse and close airway Can’t enter deeper stages of slow wave sleep High blood pressure, increased risk of heart attack, increased risk of automobile accidents, Treatments to reduce airway collapse: lose weight, avoid alcohol and sedating drugs, avoid sleeping on back Devices that induce continuous positive airway pressure

Muscles fail to become paralyzed Periodic Limb Movements Intermittent jerks of legs and arms as entering slow wave sleep REM Behavioral Disorder Muscles fail to become paralyzed Act out dreams Common in Parkinson’s patients Treated with: benzodiazepine (clonazepam)

Narcolepsy Switching mechanisms don’t work properly Loss of nerve cells in the lateral hypothalamus which contains the neurotransmitter orexin Narcoleptic Dog: http://www.youtube.com/watch?v=X0h2nle WTwI

Sudden Sleep Attacks during the day Hypnagogic Hallucination: Enter REM sleep and dreaming state while still partially awake Cataplexy: Attacks of paralysis triggered by emotional experience

Sleep Regulation: AWAKE Acetylcholine and Monoamines (norepinephrine, serotonin, dopamine, and histamine)

REM sleep: Cholinergic nerve cells send signals to activate the thalamus EEG similar to wakefulness Monoamine pathway is quiet Perceived as a dream

Waking Up Two groups of nerve cells in hypothalamus Ventrolateral preoptic nucleus: GABA and galanin When they fire, they turn off arousal system and cause sleep Damage = irreversible insomnia Neurotransmitter orexin: Excitatory signal to monoamine neurons Orexin levels in patients with narcolepsy are abnormally low

Need for Sleep: Homeostasis Body’s need to seek a natural equilibrium Adenosine (chemical) increases in the brain during prolonged wakefulness levels modulate homeostasis Caffeine acts as an adenosine blocker

Circadian Timing System Suprachiasmatic nucleus: group of nerve cells in hypothalamus that acts as a master clock Cells express clock proteins which go through biochemical cycle of 24 hrs Receives input from retina so can be reset by light

Suprachiasmatic nucleus Subparaventricular nucleus Dorsomedial nucleus of hypothalamas Ventrolateral proptic nucleus (orexin) Regulate sleep and arousal