Biological Rhythms a. types of biological rhythms b. neurohormones Sleep a. functions of sleep b....

Biological Rhythmsa. types of biological rhythmsb. neurohormones

Sleepa. functions of sleepb. measuring sleep

c. dreamingd. neural mechanismse. sleep disorders

Biological rhythms

1. Circannual

2. Infradian

3. Circadian (Latin: Circa = “around”, dian = “day”)

– Zeitgeber: “time giver”– Entrainment: alignment of rhythm with external cues

e.g., suprachiasmatic nucleus and sunlight

Biological Clocks

– Suprachiasmatic nucleus• A nucleus situated atop the optic chiasm responsible for

organizing circadian rhythms.

– Pineal gland• A gland attached to the dorsal tectum; produces melatonin and

plays a role in circadian and seasonal rhythms.

Suprachiasmatic Nucleus

– Part of hypothalamus– Damage disrupts rhythm.

Retinohypothalamic pathway

Pineal Gland

– Rene Decartes Treatise of man (1640)- “principal seat of the rational soul”

– releases melatonin (at night)– melatonin is derived from

serotonin

Functions of sleep

• Universal phenomenon among vertebrates.• Only warm-blooded vertebrates (mammals and birds) exhibit

REM sleep.• Essential to survival.• Improves memory.• Conserve energy resources.• Recuperate physically.

Sleep Deprivation

• Restorative effects of sleep appear to be more important for brain than rest of body.

• Deprivation does not appear to interfere with ability to perform physical exercise.

• Cognitive abilities can affected by sleep deprivation.• Brain rests during slow-wave sleep.• Mental activity during the day increases slow-wave

sleep at night.

Rebound phenomenon

• REM sleep increases after a period of REM sleep deprivation.

EEG

1. Frequency of the wave (n of peaks/unit time)– tells you about the number of cortical

neurons generating EPSPs

2. Amplitude of the wave (height of wave)– tells us about the n of EPSPs that occur at the same

point in time– n of neurons firing in synchrony

– Alpha activity• A smooth electrical activity of 8–12 Hz recorded from

the brain; associated with relaxation.

– Beta activity• Irregular electrical activity of 13–30 Hz recorded from

the brain; associated with arousal.

– Theta activity• EEG activity of 3.5-7.5 Hz that occurs intermittently during early stages of

slow-wave and REM sleep.

– Delta activity• Regular, synchronous electrical activity of less than

4 Hz recorded from the brain; occurs during deep sleep.

EEG Wave Types

– REM sleep• Desynchronized EEG activity during sleep; associated with

dreaming, rapid eye movements, and muscular paralysis.

– Non-REM sleep• All stages of sleep except REM sleep.

– Slow-wave sleep• Non-REM sleep, characterized by synchronized EEG activity

during deeper stages.

Stages of Sleep

Copyright © 2008 Pearson Allyn & Bacon Inc.

25

Characteristics of REM sleep

• low amplitude, high frequency desynchronous EEG• rapid eye movement (REM)• lower species show more REM sleep, as do human infants• narrative dreams • muscle atonia

– motor cortex active but descending motor pathways paralyzed

• penile erections and vaginal secretions• deepest stage?

– incorporate things into our dreams– more likely to spontaneously awaken

Sigmund Freud (1900) Interpretation of Dreams

water = birthflying = sexual arousalknifes, swords = castration anxietymud = fecescave, hallway = mother

– Freud• Repressed memories and expression of libido.

– Activation synthesis theory• Sensory experiences are fabricated by the cortex as a means

of interpreting signals from the PGO activity.

– Continual activation theory• Encoding of short term procedural memories into long-term

memories.

Dream theories

Sleep is not a passive process

Cerveau isole • mesencephalon transection• continuous sleep

Encephale isole• brainstem transection• permanent insomnia

Sleep/Waking “Flip-Flop”

vlPOA= ventrolateral preoptic areaACh = acetylcholineNE = norepinephrine5-HT = serotonin

Ventrolateral Preoptic Area

GABA neurons• Activation promotes sleep.• Destruction results in total insomnia.

Locus Coeruleus

Norepinephrine neurons• Located in the pons near the rostral end of the floor of the

fourth ventricle.• Involved in arousal and vigilance. • Decreased activity during sleep (both slow-wave and REM)

Locus coeruleus

– Acetylcholine• Cholinergic neurons located in the pons and basal forebrain produce

activation and cortical desynchrony.

– Serotonin (5-HT)• Appears to play a role in activating behavior.

– Histamine• Neurotransmitter that increases wakefulness and arousal; found in

tuberomammillary nucleus of hypothalamus, just rostral to mammillary bodies.

– Hypocretin (orexin)• A peptide produced by neurons whose cell bodies are located in the

hypothalamus and project to arousal mechanisms; destruction causes narcolepsy.

Neural control of REM sleep

– PGO wave (pontine, geniculate, occipital):• Bursts of phasic electrical activity originating in the pons,

followed by activity in the lateral geniculate nucleus and visual cortex.

– Peribrachial area• The region in the pons; contains acetylcholinergic neurons

involved in the initiation of REM sleep.

IC = inferior colliculusPPT = pedunculopontine tegmental n.LDT = lateral dorsal tegmentum

Peribrachial area

Sleep Disorders– Insomnia

• Affect approximately 25% of the population• No single definition of insomnia• May be a symptom of physical ailment.

– Sleep apnea• Cessation of breathing while sleeping. • Can be mediated centrally or locally (obstructive). • May play a role in sudden infant death syndrome.

– Narcolepsy• Disorder characterized by periods of irresistible sleep, attacks

of cataplexy, sleep paralysis, and hypnagogic hallucinations.• Treat with stimulant medications.

– Cataplexy• Paralysis during waking.

– Sleep paralysis• Paralysis just before a person falls asleep.

– Hypnagogic hallucination• Vivid dreams that occur just before a person falls asleep;

accompanied by sleep paralysis.

– Nocturnal enuresis• Bedwetting

– Somnambulism• Sleepwalking

– Pavor nocturnus• Night terrors

Insomnia vs. Sleep Deprivation• 27-year-old clinical psychologist on internship• Gets up at 6:30 AM• Works and mothers all day• Goes to bed about midnight• She gets about 6.5 hr sleep per night

Insomnia vs. Sleep Deprivation• 58-year-old woman, who is married and whose

husband has retired• Gets up at 8:30 AM• Goes to church, reads, plays bridge• Goes to bed about 10:00 PM

-sleeps until 1:30 AM

-is “up and down” rest of night

-finally gets out of bed around 8:30 AM

• She gets about 6.5 hr sleep per night

Insomnia vs. Sleep Deprivation• Insomnia assumes adequate opportunity to sleep.

• Sleep Deprivation

-adequate ability to sleep

-inadequate opportunity

-generally sleepy, at risk for accidents

• Insomnia

-inadequate ability to sleep

-adequate opportunity

-generally not sleepy, though may report fatigue

Definitions of Insomnia • Difficulty falling asleep• Difficulty maintaining sleep• Waking up too early• Nonrestorative or poor-quality sleep• May have daytime impact

Insomniaprimary cause - sleep medications

- develop tolerance; REM rebound- we are poor estimators of how much sleep we get.

treatments- Medications in short term- CBT in long term

• 8-10 wks to change poor habits and beliefs• sleep restriction, stimulus control, relaxation

techniques, and education.• unfortunately, takes time and few practitioners

Medications• Use of hypnotics increased 60% from 2000 to

2006, at a cost of $45 billion per year.

FDA-Approved Medications• Benzodiazepines

– estazolam (Prosom)– flurazepam (Dalmane)– quazepam (Doral)– temazepam (Restoril)– triazolam (Halcion)

• Benzodiazepine Agonists – eszopiclone (Lunesta)– zaleplon (Sonata)– zolpidem (Ambien)

• Melatonin Agonists – ramelteon (Rozerem)

Biological Rhythms a. types of biological rhythms b. neurohormones Sleep a. functions of sleep b....

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