Endogenous Endogenous CyclesCycles

Endogenous Endogenous Circannual RhythmCircannual RhythmInternal calendar which Internal calendar which prepares a species for prepares a species for annual seasonal changesannual seasonal changes

Endogenous Circadian Endogenous Circadian RhythmRhythmInternal rhythm lasting Internal rhythm lasting about a dayabout a day

In humans the circadian In humans the circadian rhythm is about 24.2 hoursrhythm is about 24.2 hours

Mechanisms of the Biological Mechanisms of the Biological ClockClock

Suprachiasmatic Suprachiasmatic NucleusNucleusAbove the optic chiasm in the hypothalamusControls rhythms through the regulation of 2 genes: period & timelessCode for proteins Per & Tim which are low & increase during the day but increase in the evening causing sleepiness

MelatoninMelatoninA hormone released by the pineal gland, mainly at night, increasing sleepinessStimulates receptors in the SCN to reset the biological clock

Paradoxical or Paradoxical or REM SleepREM Sleep

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

N-REM SleepN-REM SleepThe stages of sleep other than REM

Cycling Through the Cycling Through the StagesStagesUpon falling asleep you enter Stage 1Cycle through Stages 2, 3 & 4After 60 to 90 minutes you cycle back through 4 through 2 and enter REM sleepAfter entering REM sleep, the sleep cycle sequence repeats with each cycle lasting 90 minutesREM sleep is associated with dreams but dreams can occur in n-REM sleep

Wakefulness & Arousal Wakefulness & Arousal in the Brainin the Brain

Reticular FormationExtends from Medulla into ForebrainLesions decrease arousal

PontomesencephalonPart of the Reticular Formation contributing to cortical arousalStimulation awakens sleeping or increases alertness in one awake

Locus CoerulusIn the pons, emits impulses releasing norepinephrine in response to meaningful eventsImportant for storing information

Basal ForebrainRelease acetylcholineDamage decreases arousal, impairs learning & attention & increases time spent in n-REM sleep

Abnormalities of Abnormalities of SleepSleep

InsomniaInsomniaProblems falling or Problems falling or remaining asleepremaining asleep3 categories of insomnia:3 categories of insomnia:

Onset Insomnia – Onset Insomnia – trouble falling asleeptrouble falling asleep

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

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

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

Abnormalities of Abnormalities of SleepSleep

Sleep ApneaSleep ApneaThe inability to breathe during sleepCommon cause is obesityPossible cause of SIDSObstructive Apnea is most common type & related to snoringCentral Apnea is related to a CNS problem & is inherited

Abnormalities of Abnormalities of SleepSleep

NarcolepsyNarcolepsyFrequent, unexpected periods of Frequent, unexpected periods of sleepiness during the daysleepiness during the day

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

Symptoms interpreted as REM sleep Symptoms interpreted as REM sleep intruding into wakefulnessintruding into wakefulness

Overactive acetylcholine synapses & Overactive acetylcholine synapses & deficiency of deficiency of orexinorexin are 2 possible are 2 possible explanationsexplanations

Treatments: Treatments: stimulants (pemoline or stimulants (pemoline or methylphenidatemethylphenidate

Abnormalities of Abnormalities of SleepSleep

Periodic Limb Movement DisorderInvoluntary movements of Involuntary movements of the legs that can cause the legs that can cause insomniainsomniaOccurs during nREM sleepOccurs during nREM sleepTreatment: TranquilizersTreatment: Tranquilizers

REM Behavior DisorderVigorous movement during Vigorous movement during REM sleep apparently acting REM sleep apparently acting out the dreamsout the dreamsProbably due to the inability Probably due to the inability of the pons to inhibit spinal of the pons to inhibit spinal motor neuronsmotor neurons

Abnormalities of Abnormalities of SleepSleep

Night TerrorsNight TerrorsAbrupt, anxious awakening from a nREM sleep

More common in children than in adults

Sleep TalkingSleep TalkingCan occur in REM or nREM sleep

Harmless

Sleep WalkingSleep WalkingUsually in Steges 3 or 4 sleep

Early in the night

More common in children

The Functions of The Functions of SleepSleep

Repair & Restoration Theory of Repair & Restoration Theory of SleepSleepThe body, especially the brain, The body, especially the brain, requires sleep to repair itself after the requires sleep to repair itself after the exertion of the dayexertion of the day

Evolutionary Theory of SleepEvolutionary Theory of SleepSleep is to save energy when we would Sleep is to save energy when we would otherwise be energy inefficient, such otherwise be energy inefficient, such as at nightas at night

The Functions of The Functions of REM SleepREM Sleep

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

Deprivation of REM SleepDeprivation of REM SleepDeprivation of REM sleep leads to increased attempts at Deprivation of REM sleep leads to increased attempts at REM sleepREM sleep

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

Biological Perspectives on Biological Perspectives on DreamingDreaming

Activation-Synthesis Activation-Synthesis HypothesisHypothesisDuring sleep, many brain regions become activated, so the During sleep, many brain regions become activated, so the brain creates a story to make sense of the activitybrain creates a story to make sense of the activity

Clinico-Anatomical HypothesisClinico-Anatomical HypothesisEither internal or external stimulation activates parts of the Either internal or external stimulation activates parts of the parietal, occipital, & temporal cortexparietal, occipital, & temporal cortex

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