Chapter 09: Wakefulness & Sleep

Rhythms of Wakefulness & Sleep

Endogenous Cycles Endogenous Circannual Rhythm Internal calendar which prepares a species for annual seasonal changes Endogenous Circadian Rhythm Internal rhythm lasting about a day In humans the circadian rhythm is about 24.2 hours

Endogenous Circannual Rhythm

Internal calendar which prepares a species for annual seasonal changes

Endogenous Circadian Rhythm

Internal rhythm lasting about a day

In humans the circadian rhythm is about 24.2 hours

Mechanisms of the Biological Clock Suprachiasmatic Nucleus Above the optic chiasm in the hypothalamus Controls rhythms through the regulation of 2 genes: period & timeless Code for proteins Per & Tim which are low & increase during the day but increase in the evening causing sleepiness Melatonin A hormone released by the pineal gland, mainly at night, increasing sleepiness Stimulates receptors in the SCN to reset the biological clock

Suprachiasmatic Nucleus

Above the optic chiasm in the hypothalamus

Controls rhythms through the regulation of 2 genes: period & timeless

Code for proteins Per & Tim which are low & increase during the day but increase in the evening causing sleepiness

Melatonin

A hormone released by the pineal gland, mainly at night, increasing sleepiness

Stimulates receptors in the SCN to reset the biological clock

Stages of Sleep Stage 1 Stage 2 Stages 3 & 4 Light sleep with slowed brain wave patterns & the presence of irregular, jagged low-voltage waves Sleep spindles & K-complexes Slow-wave sleep Comprised of slow, large amplitude waves

Paradoxical or REM Sleep REM Sleep Characterized by repeated eye movements, fast low-voltage brain waves with & breathing & heart rates similar to Stage 1 sleep N-REM Sleep The stages of sleep other than REM Cycling Through the Stages Upon falling asleep you enter Stage 1 Cycle through Stages 2, 3 & 4 After 60 to 90 minutes you cycle back through 4 through 2 and enter REM sleep After entering REM sleep, the sleep cycle sequence repeats with each cycle lasting 90 minutes REM sleep is associated with dreams but dreams can occur in n-REM sleep

REM Sleep

Characterized by repeated eye movements, fast low-voltage brain waves with & breathing & heart rates similar to Stage 1 sleep

N-REM Sleep

The stages of sleep other than REM

Cycling Through the Stages

Upon falling asleep you enter Stage 1

Cycle through Stages 2, 3 & 4

After 60 to 90 minutes you cycle back through 4 through 2 and enter REM sleep

After entering REM sleep, the sleep cycle sequence repeats with each cycle lasting 90 minutes

REM sleep is associated with dreams but dreams can occur in n-REM sleep

Wakefulness & Arousal in the Brain Reticular Formation Extends from Medulla into Forebrain Lesions decrease arousal Pontomesencephalon Part of the Reticular Formation contributing to cortical arousal Stimulation awakens sleeping or increases alertness in one awake Locus Coerulus In the pons, emits impulses releasing norepinephrine in response to meaningful events Important for storing information Basal Forebrain Release acetylcholine Damage decreases arousal, impairs learning & attention & increases time spent in n-REM sleep

Reticular Formation

Extends from Medulla into Forebrain

Lesions decrease arousal

Pontomesencephalon

Part of the Reticular Formation contributing to cortical arousal

Stimulation awakens sleeping or increases alertness in one awake

Locus Coerulus

In the pons, emits impulses releasing norepinephrine in response to meaningful events

Important for storing information

Basal Forebrain

Release acetylcholine

Damage decreases arousal, impairs learning & attention & increases time spent in n-REM sleep

Abnormalities of Sleep Insomnia Problems falling or remaining asleep 3 categories of insomnia: Onset Insomnia – trouble falling asleep Maintenance Insomnia – waking up frequently during the night after falling asleep Termination Insomnia – waking up too early & cannot go back to sleep May be due to biological rhythm abnormalities or the use of sleeping pills

Insomnia

Problems falling or remaining asleep

3 categories of insomnia:

Onset Insomnia – trouble falling asleep

Maintenance Insomnia – waking up frequently during the night after falling asleep

Termination Insomnia – waking up too early & cannot go back to sleep

May be due to biological rhythm abnormalities or the use of sleeping pills

Abnormalities of Sleep Sleep Apnea The inability to breathe during sleep Common cause is obesity Possible cause of SIDS Obstructive Apnea is most common type & related to snoring Central Apnea is related to a CNS problem & is inherited

Sleep Apnea

The inability to breathe during sleep

Common cause is obesity

Possible cause of SIDS

Obstructive Apnea is most common type & related to snoring

Central Apnea is related to a CNS problem & is inherited

Abnormalities of Sleep Narcolepsy Frequent, unexpected periods of sleepiness during the day Symptoms: gradual or sudden attacks of sleepiness, cataplexy, sleep paralysis & hypnogogic hallucination Symptoms interpreted as REM sleep intruding into wakefulness Overactive acetylcholine synapses & deficiency of orexin are 2 possible explanations Treatments: stimulants (pemoline or methylphenidate

Narcolepsy

Frequent, unexpected periods of sleepiness during the day

Symptoms: gradual or sudden attacks of sleepiness, cataplexy, sleep paralysis & hypnogogic hallucination

Symptoms interpreted as REM sleep intruding into wakefulness

Overactive acetylcholine synapses & deficiency of orexin are 2 possible explanations

Treatments: stimulants (pemoline or methylphenidate

Abnormalities of Sleep Periodic Limb Movement Disorder Involuntary movements of the legs that can cause insomnia Occurs during nREM sleep Treatment: Tranquilizers REM Behavior Disorder Vigorous movement during REM sleep apparently acting out the dreams Probably due to the inability of the pons to inhibit spinal motor neurons

Periodic Limb Movement Disorder

Involuntary movements of the legs that can cause insomnia

Occurs during nREM sleep

Treatment: Tranquilizers

REM Behavior Disorder

Vigorous movement during REM sleep apparently acting out the dreams

Probably due to the inability of the pons to inhibit spinal motor neurons

Abnormalities of Sleep Night Terrors Abrupt, anxious awakening from a nREM sleep More common in children than in adults Sleep Talking Can occur in REM or nREM sleep Harmless Sleep Walking Usually in Steges 3 or 4 sleep Early in the night More common in children

Night Terrors

Abrupt, anxious awakening from a nREM sleep

More common in children than in adults

Sleep Talking

Can occur in REM or nREM sleep

Harmless

Sleep Walking

Usually in Steges 3 or 4 sleep

Early in the night

More common in children

The Functions of Sleep Repair & Restoration Theory of Sleep The body, especially the brain, requires sleep to repair itself after the exertion of the day Evolutionary Theory of Sleep Sleep is to save energy when we would otherwise be energy inefficient, such as at night

Repair & Restoration Theory of Sleep

The body, especially the brain, requires sleep to repair itself after the exertion of the day

Evolutionary Theory of Sleep

Sleep is to save energy when we would otherwise be energy inefficient, such as at night

The Functions of REM Sleep Amount of REM Sleep The Amount of REM sleep is associated with the total amount of sleep you get Deprivation of REM Sleep Deprivation of REM sleep leads to increased attempts at REM sleep REM Sleep & Memory REM sleep is implicated in memory storage & as a way of getting oxygen to the corneas of the eyes

Amount of REM Sleep

The Amount of REM sleep is associated with the total amount of sleep you get

Deprivation of REM Sleep

Deprivation of REM sleep leads to increased attempts at REM sleep

REM Sleep & Memory

REM sleep is implicated in memory storage & as a way of getting oxygen to the corneas of the eyes

Biological Perspectives on Dreaming Activation-Synthesis Hypothesis During sleep, many brain regions become activated, so the brain creates a story to make sense of the activity Clinico-Anatomical Hypothesis Either internal or external stimulation activates parts of the parietal, occipital, & temporal cortex No visual information overrides the stimulation & no criticism of the prefrontal cortex censures it, so it develops into hallucinatory perceptions

Activation-Synthesis Hypothesis

During sleep, many brain regions become activated, so the brain creates a story to make sense of the activity

Clinico-Anatomical Hypothesis

Either internal or external stimulation activates parts of the parietal, occipital, & temporal cortex

No visual information overrides the stimulation & no criticism of the prefrontal cortex censures it, so it develops into hallucinatory perceptions