Transcript sleep

Lecture 10 – Chapter 14
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
Polyphasic vs monophasic
Part time sleepers….
• unihemispheric
Dolphins sleep with only
one half of their brain
Breathing is a conscious
act…
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
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 (2 TO 3 WEEKS)
• 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
(REM/hypnagogic hallucinations)
- "sleep attacks" happen without
warning and can occur even after a
good night's rest
- normally last about 20 minutes
TX: Stimulants &
Antidepressants (tend to
suppress REM sleep)
- after waking up, the person feels
refreshed, only to feel sleepy again
a few hours later
So need more 5HT
- There is no known cause of this
chronic sleep disorder
Gene found in dogs…
Yanagisawa et al., (1998) University of Texas Southwestern Med
Cen discovered
orexin
dog chromosome 6
PLAYING DEAD? A narcolepsy symptom called cataplexy causes some dogs to
collapse when they get excited, as they have here during a tussle. The dogs have a
genetic defect that affects a brain hormone that's missing in people with the sleep
disorder.
Mignot/Stanford University