PET 3323 Functional Anatomy and Physiology II
Sleep & Mental Function
Reflect the pattern of electrical activity (neuronal
firing) in cerebral post-synaptic neurons upon which
higher mental functions are based
 Each person has a unique brain wave pattern
(like a fingerprint)
Brain Waves
 Waves are grouped into 4 classes
» Frequency: expressed in units of Hertz (Hz)
(number of peaks in 1 second)
» Amplitude: reflects synchronization of many neurons,
not amount of electrical activity of individual neurons
Electroencephalogram (EEG): recording of brain waves as
they spread to the cerebral cortical areas
» Used to diagnose epilepsy, sleep disorders, and determine
occurrence of brain death
Voltage
Brain Waves
Types
Unique to individuals,
but can be grouped into
one of four categories
(based on frequency):
1) Beta: mentally alert
2) Alpha: awake, but
relaxed
3) Theta: deeply relaxed
(zoned out)
4) Delta: sleep
Electroencephalogram (EEG) &
Wakefulness
• Alpha waves - low amplitude, slow waves with a frequency of 8-13 Hz,
calm relaxed and awake state (regular and rhythmic).
• Beta waves - rhythmic but irregular waves with a frequency of 14-25
Hz, mentally alert and concentrating.
• Theta waves – higher amplitude and more irregular waves with a
frequency of 4-7 Hz. Can occur while awake (dozing off).
• Delta waves - highest amplitude waves with a frequency of 4 Hz or
less, occur during a deep sleep and when under anesthesia. Indicates
brain damage in awake adults.
Brain Waves
Brain wave monitoring shows status of brain
 Changes occur with:
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Age
Sensory stimuli
Brain disease
Chemical state of the body
⁎ Abnormalities indicate severe issues
» Delta in awake adults = brain damage
» Epilepsy
» Tumors
» Metabolic abnormalities
» Encephalopathy
» Seizures
Sleep
Types
1) Non-Rapid Eye Movement
(NREM) Sleep
 Further divided into 4
stages
2) Rapid Eye Movement (REM)
Sleep
 Takes ~90 min to get
into REM sleep
Sleep
NREM Stages
Stage 1: eyes closed, relaxed, lasts 1-7 min,
easily awakened
Stage 2: light sleep, dream fragments occur,
harder to awaken
 1st two stages occur w/in 30-45 min
Stage 3: moderately deep sleep, HR & body
temperature fall
Stage 4: deep sleep, body temperature &
HR low
 2nd two stages: slow-wave sleep
 Important for restoration
 Neural activity at basal levels
Sleep
REM
 Occurs every 90min
 Most dreaming occurs
 Body temporarily paralyzed
 HR & respiration increase, irregular
 Appearance of alpha waves at onset
 Short periods (5-10 min) initially,
gradually lengthen as time of sleep
progresses
 Important for processing day’s events
and emotional problems
REM Sleep
Deprivation
⁎ Confusion
⁎ Paranoia
⁎ Affective disorders
⁎ Memory consolidation
impairments
⁎ Decrease in motor
performance
⁎ Loss of balance
⁎ Decreased immune efficiency
Sleep
Putting NREM & REM Together
» Sleep begins with NREM and goes through 4
stages
» REM begins after ~ 90 min
» When REM hits it last for about 5-10 min and
then NREM begins again
» The next time REM begins it lasts longer
» Cycle occurs continuously through the night
with final REM sleep ranging between 20-50
min (our longest dreams occur just before we
awake)
Waking Up
 It’s hard to wake up in Stage 4 NREM sleep
» Thalamic neurons hyperpolarized during sleep
 Spontaneous neural arousal occurs in REM
 Easier to wake up if have regular sleep schedule
 Orexins: chemicals released from the
hypothalamus that wake us up
Physiological Effects of Sleep
» Reduced sympathetic activity (norepinephrine) and muscle tone
» Body temperature drops, energy loss decreases
» Increased growth hormone secretion
» Helps with maintenance of normal activity of the CNS
» Helps to maintain “balance” between the different parts of the CNS
» Skin and tissue repair
Physiological Effects of Sleep
Stanford University NCAA men and women
swim teams:
 Study design
 Maintain usual sleep-wake pattern for 2 wks
 Then, athletes extended sleep to 10hrs per day
 Athletic performance assessed after each swim practice
 Results
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0.51s decrease in 15m sprint
0.15s faster reaction off the blocks
0.10s faster turn time
5 more kicks than before
Sleep Patterns
With Age
 Infants normally sleep about 16
hrs with REM sleep accounting
for 50% of the time
 REM sleep declines until age 10
when it stabilizes at 25% of sleep
time
 Total sleep time decreases to
about 7hrs in young adults
 Stage 4 sleep declines steadily
throughout life…often
completely disappearing in those
over 60!
What Makes
Us Get Sleepy?
Adenosine levels in the basal forebrain rise as sleep
debt builds up
» Natural by-product of using up our internal energy stores
(ATP breakdown)
» Accumulates over course of day and during high periods of
nervous system ATP usage
» Inhibits neurons of the Reticular Activating System (RAS)
» Levels fall rapidly during the subsequent sleep period
How does Coffee increase wakefulness?
» Sleep is induced by accumulated adenosine
» Adenosine binds to adenosine receptors (A1R, A2R) to
activate these receptors
» A1R and A2R activation inhibit RAS neurons that participate
in arousal
» CAFFEINE blocks A1 and A2 receptors to prevent this
adenosine effect.
Sleep – Wake Control Centers
SCN: suprachiasmatic nucleus
Circadian Rhythm
• 24-hour “internal central clock”
• Regulates:
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Sleep-wake cycle
Hormone release
Hunger
Digestion
Heartrate
Blood Pressure
Neurological Function
• Circadian Disorders
• Exhaustion
• Poor quality sleep
• Mood disorders - depression
• Disorders may contribute to:
• Weight gain
• Cardiovascular disease
• Neurodegenerative diseases
Melatonin
• Produced by the pineal gland in the SCN in response to darkness
• Helps regulate the circadian rhythm
• Helps synchronize sleep-wake cycle with night and day
• Promotes quiet wakefulness in the evening
• Promotes drowsiness and deeper sleep at night
Melatonin Peaks at Night
Blue wavelength light depresses melatonin
Blue light increases alertness
Sleepiness
Mental Lapses
Reaction Time
Blue light alters brainwave activity
• Fewer Delta Waves than Green Light
• More Alpha Waves than Green Light
https://psych-neuro.com/2021/03/28/to-be-successful-as-a-society-we-need-to-go-to-sleep/comment-page-1/