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