sleep
Subcortical regions: Basal forebrain
Sends axons that release acetylcholine to the cerebral cortex - Key part of the brains system for arousal, wakefulness, and attention (along with reticular formation in pons)
endogenous circadian rhythms
all animals produce, internal mechanisms that operate on an approximately 24 hour cycle
Human circadian clock generates
a rhythm slightly longer than 24 hours when it has no external cue to set it
retinohypothalamic path comes from
a special population of ganglion cells
Sleep is useful for conserving energy while
an animal is inactive. Body temperature drops and metabolism slows down. - The brain is inactive and uses less energy.
REM behavior disorder is
associated with vigorous movement during REM sleep - Usually associated with acting out dreams - Occurs mostly in the elderly and in older men with brain diseases such as Parkinson's - Associated with damage to the pons (inhibit the spinal neurons that control large muscle movements)
Sleepwalkers are
awake in one part of the brain and asleep in others
Melatonin feeds
back to reset the biological clock through its effects on receptors in the SCN
Melatonin secretion usually
begins two to three hours before bedtime
Cycles can differ
between people and lead to different patterns of wakefulness and alertness
the superchiasmatic nucleus generates
circadian rhythms in a genetically controlled, unlearned manner
REM is strongly associated with
dreaming, but people also report dreaming in other stages of sleep
Circadian rhythms are
entrained by light.
Night terrors
experiences of intense anxiety from which a person awakens screaming in terror - Usually occurs in NREM sleep
pontomesencephalon axons
extend to the hypothalamus, thalamus, and basal forebrain, which release acetylcholine and glutamate
people who engage in shift work often
fail to adjust completely - Night-shift workers tend to have more accidents than day-shift workers • Most traffic accidents are at 2 am
causes of sleep apnea
genetics, hormones, old age, and deterioration of the brain mechanisms that control breathing and obesity
During REM sleep:Activity increases
in the pons (triggers on set of REM sleep) • limbic system (emotional systems), • parietal cortex (sensory), • temporal cortex (language, audition)
During REM sleep:Activity decreases
in the primary visual cortex, • motor cortex, • dorsolateral prefrontal cortex
orexin
is a peptide neurotransmitter released in a pathway from the hypothalamus - Stimulates acetylcholine-releasing cells in the basal forebrain to stimulate neurons responsible for wakefulness and arousal
Primary treatment of narcolepsy
is with stimulant drugs (i.e., Ritalin), which increase wakefulness by enhancing dopamine and norepinephrine activity
When the pons remains in REM and other brain areas wake up
it causes the inability to move
Narcolepsy Caused by
lack of hypothalamic cells that produce and release orexin
REM sleep is predominant
later in the night - Length increases as the night progresses
damage to the superchiasmatic nucleus
less consistent body rhythms • no longer synchronized to environmental patterns of light and dark
The suprachiasmatic nucleus
main control center of the circadian rhythms of sleep and temperature - Located above the optic chiasm
Growth hormones are
secreted during sleep and wound healing is increased. - Without sleep, rats lose body weight and develop skin lesions
The pineal gland
secretes melatonin, a hormone that increases sleepiness
Cells in the pons
send messages to the spinal cord, which inhibits motor neurons that control the body's large muscles Prevents motor movement during REM sleep
Dependence on sleeping pills or alcohol
shifts in the circadian rhythms can also result in insomnia
Insomnia
sleep disorder associated with inadequate sleep - Caused by a number of factors, including noise, stress, pain, diet, and medication - Can also be the result of disorders such as epilepsy, Parkinson's disease, depression, anxiety or other conditions
Narcolepsy
sleep disorder characterized by frequent periods of sleepiness - Gradual or sudden attack of sleepiness - Occasional cataplexy: muscle weakness triggered by strong emotions - Sleep paralysis: inability to move while falling asleep or waking up - Hypnagogic hallucinations: dreamlike experiences
Sleep apnea
sleep disorder characterized by the inability to breathe while sleeping for a prolonged period of time
Stage 3 and 4
sleep predominate early in the night - Length of stage decreases as the night progresses
consequences of sleep apnea
sleepiness during the day, impaired attention, depression, and sometimes heart problems
locus coeruleus
small structure in the pons whose axons release
endogenous circannual rhythms
some animals generate, internal mechanisms that operate on an annual or yearly cycle • Example: birds migratory patterns; animals storing food for the winter
The brain strengthens
some synapses and weakens others during sleep
Resetting our circadian rhythms
sometimes necessary
When one falls asleep, they progress through
stages 1, 2, 3, and 4 in sequential order • After about an hour, the person begins to cycle back through the stages from stage 4 to stages 3 and 2 and than REM • The sequence repeats with each cycle lasting approximately 90 minutes
Special ganglion cells
that have their own photopigment called melanopsin - The cells respond directly to light and do not require any input from the rods or cones
PER and TIM proteins increase
the activity of certain kinds of neurons in the SCN that regulate sleep and waking
Adenosine
the final breakdown product of ATP - energy, Adenosine high = resources are low, cell should rest - Common adenosine receptor antagonist
The SCN indirectly projects to the pineal gland. • This inhibits
the hormone, melatonin. - Under low light, melatonin production is disinhibited. - This makes melatonin levels increase. - This makes us sleepy at night.
Periodic limb movement disorder is
the repeated involuntary movement of the legs and sometimes the arms while sleeping - Legs kick once every 20 to 30 seconds for periods of minutes to hours - Usually occurs during NREM sleep - Tranquilizers can help in some cases
norepinephrine
to arouse various areas of the cortex and increase wakefulness - Usually dormant while asleep
The purpose of the circadian rhythm is
to keep our internal workings in phase with the outside world
Maurice (1998) suggests the function of REM is simply
to shake the eyeballs back and forth to provide sufficient oxygen to the corneas
The suprachiasmatic nucleus regulates
waking and sleeping by controlling activity levels in other areas of the brain - The SCN regulates the pineal gland, an endocrine gland located posterior to the thalamus
The clock also helps you know
when to stay awake and when to fall asleep
- Hamsters with a destroyed SCN no longer experience circadian rhythms but
you can restore the rhythm with transplanted brain tissue
Traveling east
"phase-advances" our circadian rhythms • harder to adjust • Sleep earlier and wake up earlier
Traveling west
"phase-delays" our circadian rhythms • easier to adjust • Stay awake later, sleep later
Sleep also plays an important role in enhancing learning and strengthening memory
- Increased performance on a newly learned task
The development of rhythms
Change as a function of age • Young infants sleep up to 18 hours a day - 3-4 hour stretches with little circadian rhythm. • This is a period of rapid brain development • Example: sleep patterns from childhood to late adulthood
•Sleep is a state that the brain actively produces
Characterized by a moderate decrease in brain activity and decreased response to stimuli
Functions of the inhibitory neurotransmitter GABA are also important for:
Decreasing the temperature and metabolic rate - Decreasing the stimulation of neurons
Zeitgeber:
German meaning "time giver"; refers to the stimulus that resets the circadian rhythm - Examples: sunlight, tides, exercise, meals, depression irritability
Cells of the basal forebrain release the
Inhibition provided by GABA is essential for sleep
first stage of sleep
Light NREM sleep. Stage 1 - The EEG is dominated by irregular, jagged, and low voltage waves - Brain activity begins to decline
retinohypothalamic path
Light resets the SCN via a small branch of the optic nerve. Travels directly from the retina to the SCN
Neurotransmitter production can't keep up with continuous activity.
Monoamine neurotransmitters (5HT, DA, NE, His) are depleted. - They are essential for wakefulness, mood, and attention. - This explains some of the effects of sleep deprivation.
Two types of genes are responsible for generating the circadian rhythm
Period: produce proteins called PER - Timeless: produce proteins called TIM
pontomesencephalon
Produce excitatory effects to widespread areas of the cortex - Stimulation of the awakens sleeping individuals and increases alertness in those already awake
3rd stage of sleep
REM (dreaming or paradoxical) sleep. -EEG waves are irregular, low - voltage, and fast - Postural muscles of the body are more relaxed than other stages - Rapid eye movement sleep (REM) are periods characterized by rapid eye movements during sleep
2nd stage of sleep
Sleep spindles: 12 - to 14 -Hz waves during a burst that lasts at least half a second - K -complex: a sharp high - amplitude negative wave followed by a smaller, slower positive wave
Low neural activity gives neurons a chance to rebuild.
Structural proteins can be replaced and repaired. - Glycogen is returned to the energy stores of the brain.
Patterns of activity in the hippocampus during learning were similar to those shown during sleep
Suggests that the brain replays its daily experiences during sleep
Circadian Rhythms
The 24-hour biological cycles found in humans and many other species.
during REM
The brain may discard useless connections - Learned motor skills may be consolidated
Light activates these photoreceptors in the retina. (special ganglion cells)
These respond much more slowly to light. - They respond to long periods of light but not brief bursts.
Pineal gland releases
melatonin
jetlag stems from
mismatch of the internal circadian clock and external time
Melatonin taken in the afternoon can
phase-advance the internal clock and can be used as a sleep aid
The SCN indirectly projects to the
pineal gland.
The original function of sleep was to
probably conserve energy
antihistamines
produce sleepiness
"histamine"
produce widespread excitatory effects throughout the brain
Destroying the SCN
removes the circadian rhythm.
Narcolepsy seems to
run in families although no gene has been identified
Sleepwalking
runs in families, mostly occurs in young children, and occurs mostly in stage 3 or 4 sleep - Not associated with dreaming - It is not dangerous to wake a sleepwalker