Transcript sleep
SLEEP •Circadian •Humans spend 1/3 of life sleeping (well over 175,000 hrs) •typically 8 hours/day…so - 3/day = extra 21 hrs/week 10,952 hrs/decade!!! SLEEP •Amount of sleep changes with age – younger ages sleep more Why DO WE SLEEP? Do we need sleep? Repair & Rest 1965 – Randy Gardner Science fair project…break world record of No sleep (260 hrs) 264 hr 12 min = 11 days!!! “mind over matter” First night: 15 hrs Next night: 9 hrs too bad randy, Mrs. Maureen Weston (1977) 18 days!!!! Rocking chair marathon Sleep deprivation (3 to 4 hrs) Humans 1. Increase in sleepiness 2. Mood test 3. Perform poorly on test of vigilance (ex: tones) 2 to 3 days (continuous sleep deprivation) “Microsleeps” (2 to 3 sec long) 1. Eye lids droop 2. Less responsive to stimuli 3. Still standing Performance on complex cognitive tasks????? Performance in motor tests??????? Animals….different story….Death • Stop grooming • Loss ability to regulate temperature •Metabolic rate increases…eat…but never enough loss weight - Is sleep a passive? NO! Many changes in our body during sleep Sleep is a Behavior! How do we measure this? 1. EEG (electrical activity) 2. Biochemically (NT) 3. Neuroanatomically (brain structures) 1929, a German psychiatrist: Hans Berger, Found the it was possible to record the feeble electric currents generated on the brain, without opening the skull, and to depict them graphically onto a strip of paper. Berger named this new form of recording as the electroencephalogram (EEG, for short) First EEG recorded by Hans Berger, circa 1928. EEG (electroencephalograph) records electrical activity of the brain via electrodes attached to the scalp •Gross measurement of neuronal activity takes an average of the whole population of cells in the area under the electrode •Output of the electrodes are amplified and recorded EEGs tell you whether a person is asleep, awake or excited EEG lingo: Measurement of Brain Waves Amplitude: index of voltage = larger the voltage the higher the amplitude (Height) Frequency: index of waves across time, cycles per second (hertz, Hz) (how often they occur) 2 Basic EEG Patterns: 1. Desynchronized: neurons in the brain firing at many different times produces EEG patterns of low amplitude & high frequency (wakefulness) 2 Basic EEG Patterns: 2. Synchronized: neurons are firing at the same time – produces well defined waves of low frequency high amplitude (characteristic of deep sleep) EMG: Electromyogram - Leg EOG: Electroculogram - Eye muscle There are two divisions of sleep 1. non-rapid eye movement (NREM) 2. rapid eye movement (REM) Non-Rapid Eye Movement Sleep About 80% of adult sleep is NREM sleep. NREM sleep is divided into four stages: •Stage 1—the drowsy transition from waking to sleeping •Stage 2—intermediate sleep, when arousal is more difficult •Stage 3—the beginning of "deep," or slow-wave, sleep •Stage 4—the deepest sleep, when there is little contact with external sensations During NREM: breathing, heart rates, body temperature, blood pressure decrease. Stage EEG Rate (Frequency) EEG Size (Amplitude) Awake 8-25 Hz Low 1 6-8 Hz Low 2 4-7 Hz Occasional "sleep spindles" Occasional "K" complexes Medium 3 1-3 Hz High 4 Less than 2 Hz High REM More than 10 Hz Low Resting quietly Eyes closed Arousal & awake Transition btw wakefulness & sleep Short burst of waves 2 to 5 tx a min 1-4 (aging) Only here – pre to delta Sleeping soundly – but report Not asleep at all! “Saw Tooth” REM sleep resembles stage 1 Note that as sleep progresses from awake to sleep, brain activity becomes more synchronized (low frequency hi amplitude) * somnambolism 90 minutes to our first bout of REM – average of 5 cycles – REM lasts 10-20 min then we fall back to stage 2 and so on… REM SLEEP PGO spiking : Pontine-Geniculate-Occipital Triggers the onset of REM 1. Waves of neural activity first in the pons 2. Then in the lateral geniculate 3. Then in the occipital cortex - Wave is synchronized with eye movement - At this time Pons is also sending inhibitory messages to the spinal cord motor neurons Neurochemistry: Pons releases ACh stimulate LGN (inject carbachol=Ach agonist=REM) Locus Coeruleus: Noradrenergic neurons: destroy this area you get NO REM but SWS (stage 3 & 4) Raphe Nucleus: Serontonergic neurons: destroy this area you get NO SLEEP = insomnia…agonist=increase in SWS Narcolepsy (hypersomnia): - sleeping disorder (1 of 2000) characterized by periods of irresistible sleepiness - "sleep attacks" happen without warning and can occur even after a good night's rest - normally last about 20 minutes TX: Antidepressants Antidepressants tend to suppress REM sleep So need more 5HT Gene found in dogs - after waking up, the person feels refreshed, only to feel sleepy again a few hours later - There is no known cause of this chronic sleep disorder Sleep apnea (Muscle atonia) Apnea is a Greek word meaning "want of breath” disorder characterized by periods of time when the sleeper stops breathing (apnea) or experiences a sharp reduction in breathing (hypopnea) These periods normally last between 10 and 30 seconds, but can last longer males, overweight & elderly (SIDs) The person wakes up shortly and falls back asleep, usually not knowing there had been any interruption in sleep at all. These "apneic events" can occur as many as 20 or 30 times an hour.