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10 Biological Rhythms and Sleep

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Page 1: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10Biological Rhythms

and Sleep

Page 2: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 Biological Rhythms and Sleep: Part I

Biological Rhythms• Many Animals Show Daily Rhythms in

Activity• The Hypothalamus Houses an

Endogenous Circadian Clock

Page 3: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 Biological Rhythms and Sleep: Part II

Sleeping and Waking• Human Sleep Exhibits Different Stages• Our Sleep Patterns Change across the

Life Span• Manipulating Sleep Reveals an Underlying

Structure• What are the Biological Functions of

Sleep?• At Least Four Interacting Neural Systems

Underlie Sleep• Sleep Disorders Can Be Serious, Even

Life-Threatening

Page 4: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 Many Animals Show Daily Rhythms in Activity

Biological rhythms are regular fluctuations in a living process• Circadian rhythms have a rhythm of

about 24 hours• Ultradian rhythms such as bouts of

activity, feeding, and hormone release repeat more than once a day

• Infradian rhythms such as body weight and reproductive cycles repeat less than once a day

Page 5: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 Many Animals Show Daily Rhythms in Activity

Diurnal—active during the light

Nocturnal—active during the dark

Circadian rhythms are generated by an endogenous (internal) clock

Page 6: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 Many Animals Show Daily Rhythms in Activity

A free-running animal is maintaining its own cycle with no external cues, such as light

The period, or time between successive cycles, may not be exactly 24 hours

Page 7: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

Figure 10.2 How Activity Rhythms Are Measured (Part 1)

Page 8: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 Many Animals Show Daily Rhythms in Activity

A phase shift is the shift in activity in response to a synchronizing stimulus, such as light or food

Entrainment is the process of shifting the rhythm

The cue that an animal uses to synchronize with the environment is called a zeitgeber or “time-giver”

Page 9: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

Figure 10.2 How Activity Rhythms Are Measured (Part 2)

Page 10: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 The Hypothalamus Houses an Endogenous Circadian Clock

The biological clock is located in the suprachiasmatic nucleus (SCN)—above the optic chiasm in the hypothalamus

Studies in SCN-lesioned animals showed disrupted circadian rhythms

Isolated SCN cells maintain electrical activity synchronized to the previous light cycle

Page 11: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

Figure 10.3 The Effects of Lesions in the SCN

Page 12: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 The Hypothalamus Houses an Endogenous Circadian Clock

Transplant studies proved that the SCN produces a circadian rhythm

Hamsters with SCN lesions received a SCN tissue transplant from hamsters with a very short period, ~20 hours

Circadian rhythms were restored but matched the shorter period of the donor

Page 13: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

Figure 10.5 Brain Transplants Prove That the SCN Contains a Clock

Page 14: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 The Hypothalamus Houses an Endogenous Circadian Clock

Circadian rhythms entrain to light-dark cycles using different pathways, some outside of the eye

The pineal gland in amphibians and birds is sensitive to light

Melatonin is secreted to inform the brain about light

Page 15: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 The Hypothalamus Houses an Endogenous Circadian Clock

In mammals, light information goes from the eye to the SCN via the retinohypothalamic pathway

Some retinal ganglion cells project to the SCN

Most contain melanopsin, a special photopigment, that makes them sensitive to light

Page 16: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

Figure 10.6 Components of a Circadian System

Page 17: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 The Hypothalamus Houses an Endogenous Circadian Clock

Molecular studies in Drosophila using mutations of the period gene helped to understand the circadian clock in mammals

SCN cells in mammals make two proteins:

• Clock

• Cycle

Page 18: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 The Hypothalamus Houses an Endogenous Circadian Clock

Clock and Cycle proteins bind together to form a dimer

The Clock/Cycle dimer promotes transcription of two genes:

• Period (per)

• Cryptochrome (cry)

Page 19: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 The Hypothalamus Houses an Endogenous Circadian Clock

Per and Cry proteins bind to each other and also to Tau

The Per/Cry/Tau protein complex enters the nucleus and inhibits the transcription of per and cry

No new proteins are made until the first set degrades

The cycle repeats ~every 24 hours

Page 20: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

Figure 10.7 A Molecular Clock in Flies and Mice

Page 21: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 The Hypothalamus Houses an Endogenous Circadian Clock

Gene mutations show how important the clock is to behavior in constant conditions:

• In tau mutations the period is shorter than normal

• Double Clock mutants—severely arrhythmic

Page 22: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

Figure 10.8 When the Endogenous Clock Goes Kaput

Page 23: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 The Hypothalamus Houses an Endogenous Circadian Clock

Sleep is synchronized to external events, including light and dark

Stimuli like lights, food, jobs, and alarm clocks entrain us to be awake or to sleep

In the absence of cues, humans have a free-running period of approximately 25 hours

Page 24: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

Figure 10.9 Humans Free-Run Too

Page 25: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 Human Sleep Exhibits Different Stages

Electrical brain potentials can be used to classify levels of arousal and states of sleep

Electroencephalography (EEG) records electrical activity in the brain

Page 26: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 Human Sleep Exhibits Different Stages

Two distinct classes of sleep:

• Slow-wave sleep (SWS) can be divided into four stages and is characterized by slow-wave EEG activity

• Rapid-eye-movement sleep (REM) is characterized by small amplitude, fast-EEG waves, no postural tension, and rapid eye movements

Page 27: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 Human Sleep Exhibits Different Stages

The pattern of activity in an awake person contains many frequencies:

• Dominated by waves of fast frequency and low amplitude (15 to 20 Hz)

• Known as beta activity or desynchronized EEG

Alpha rhythm occurs in relaxation, a regular oscillation of 8 to 12 Hz

Page 28: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

Figure 10.10 Electrophysiological Correlates of Sleep and Waking

Page 29: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 Human Sleep Exhibits Different Stages

Four stages of slow-wave sleep:

• Stage 1 sleep

o Shows events of irregular frequency and smaller amplitude, as well as vertex spikes, or sharp waves

o Heart rate slows, muscle tension reduces, eyes move about

o Lasts several minutes

Page 30: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 Human Sleep Exhibits Different Stages

• Stage 2 sleep

o Defined by waves of 12 to 14 Hz that occur in bursts, called sleep spindles

o K-complexes appear–sharp negative EEG potentials

Page 31: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 Human Sleep Exhibits Different Stages

• Early stage 3 sleep

o Continued sleep spindles as in stage 2

o Defined by the appearance of large-amplitude, very slow waves called delta waves

o Delta waves occur about once per second

Page 32: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 Human Sleep Exhibits Different Stages

• Late stage 3 sleep

o Delta waves are present about half the time

Page 33: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 Human Sleep Exhibits Different Stages

REM sleep follows SWS

• Active EEG with small-amplitude, high-frequency waves, like an awake person

• Muscles are relaxed—called paradoxical sleep

Page 34: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 Human Sleep Exhibits Different Stages

In a typical night of young adult sleep:

• Sleep time ranges from 7–8 hours

• 45–50% is stage 2 sleep, 20% is REM sleep

• Cycles last 90–110 minutes, but cycles early in the night have more stage 3 SWS, and later cycles have more REM sleep

Page 35: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

Figure 10.11 A Typical Night of Sleep in a Young Adult

Page 36: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 Human Sleep Exhibits Different Stages

At puberty, most people shift their circadian rhythm of sleep so that they get up later in the day

However, most high schools require adolescents to arrive even earlier

Later starts improved attendance and enrollment, and reduced depression and in-class sleeping

Page 37: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

Figure 10.12 How I Hate to Get Out of Bed in the Morning!

Page 38: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 Human Sleep Exhibits Different Stages

Vivid dreams occur during REM sleep, characterized by:

• Visual imagery

• Sense that the dreamer is “there”

Nightmares are frightening dreams that awaken the sleeper from REM sleep

Night terrors are sudden arousals from stage 3 SWS, marked by fear and autonomic activity

Page 39: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 Human Sleep Exhibits Different Stages

REM sleep evolved in some vertebrates:

• Nearly all mammals display both REM and SWS

• Birds also display both REM and SWS sleep

Page 40: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 Human Sleep Exhibits Different Stages

Dolphins do not show REM sleep, perhaps because relaxed muscles are incompatible with the need to come to the surface to breathe

In dolphins and birds, only one brain hemisphere enters SWS at a time—the other remains awake

Page 41: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

Figure 10.14 Sleep in Marine Mammals

Page 42: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 Our Sleep Patterns Change across the Life Span

Mammals sleep more during infancy than in adulthood

Infant sleep is characterized by:

• Shorter sleep cycles

• More REM sleep—50%, which may provide essential stimulation to the developing nervous system

Page 43: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

Figure 10.15 The Trouble with Babies

Page 44: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

Figure 10.16 Human Sleep Patterns Change with Age

Page 45: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 Our Sleep Patterns Change across the Life Span

As people age, total time asleep declines, and times awakened increase

The biggest loss is time spent in stage 3:

• At age 60, only half as much time is spent as at age 20

• By age 90, stage 3 has disappeared

Page 46: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

Figure 10.17 The Typical Pattern of Sleep in an Elderly Person

Page 47: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 Manipulating Sleep Reveals an Underlying Structure

Effects of sleep deprivation—the partial or total prevention of sleep:

• Increased irritability

• Difficulty in concentrating

• Episodes of disorientation

Effects can vary with age and other factors

Page 48: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

Figure 10.18 I Need Sleep!

Page 49: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 Manipulating Sleep Reveals an Underlying Structure

Sleep recovery is the process of sleeping more than normally, after a period of deprivation

• Night 1—stage 3 sleep is increased, but stage 2 is decreased

• Night 2—most recovery of REM sleep, which is more intense than normal with more rapid eye movements

Page 50: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

Figure 10.19 Sleep Recovery after 11 Days Awake

Page 51: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 Manipulating Sleep Reveals an Underlying Structure

Sleep deprivation can be fatal

• Total sleep deprivation compromises the immune system and leads to death

• The disease fatal familial insomnia is inherited—in midlife people stop sleeping and die 7–24 months after onset of the insomnia

Page 52: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 What Are the Biological Functions of Sleep?

Four functions of sleep:

• Energy conservation

• Niche adaptation

• Body restoration

• Memory consolidation

Page 53: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

14 What Are the Biological Functions of Sleep?

One role of sleep is to conserve energy

• Muscular tension, heart rate, blood pressure, temperature, and rate of respiration are reduced

Page 54: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 What Are the Biological Functions of Sleep?

Sleep helps animals avoid predators—animals sleep during the part of the day when they are most vulnerable

The ecological niche for each species is the unique assortment of opportunities and challenges in its environment

Page 55: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

Figure 10.20 Sleep Helps Animals to Adapt an Ecological Niche

Page 56: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 What Are the Biological Functions of Sleep?

Sleep restores the body by replenishing metabolic requirements, such as proteins

Most growth hormone is only released during SWS

Proper sleep is essential for immune function

Page 57: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 What Are the Biological Functions of Sleep?

Sleep may aid memory consolidation:

• Sleep during the interval between learning and recall may reduce interfering stimuli

• Memory typically decays and sleep may slow this down

• Or sleep, especially REM, may actively contribute through processes that consolidate the learned material

Page 58: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 What Are the Biological Functions of Sleep?

A challenge to sleep theories is the existence of a few people who hardly sleep at all yet are normal and healthy

Whatever the function of sleep, these people fill it with a brief nap

Page 59: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

Figure 10.21 A Nonsleeper

Page 60: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 At Least Four Interacting Neural Systems Underlie Sleep

Sleep is an active state mediated by:

• A forebrain system—displays SWS

• A brainstem system—activates the forebrain

• A pontine system—triggers REM sleep

• A hypothalamic system—affects the other three

Page 61: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 At Least Four Interacting Neural Systems Underlie Sleep

Transection experiments showed that different sleep systems originate in different parts of the brain

• The isolated brain is made by an incision between the medulla and the spinal cord

o Animals showed signs of sleep and wakefulness, proving that the networks reside in the brain

Page 62: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

Figure 10.22 Transecting the Brain at Different Levels (Part 2)

Page 63: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 At Least Four Interacting Neural Systems Underlie Sleep

• An isolated forebrain is made by an incision in the midbrain

o The electrical activity in the forebrain showed constant SWS, but not REM—thus, the forebrain alone can generate SWS

Page 64: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

Figure 10.22 Transecting the Brain at Different Levels (Part 3)

Page 65: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 At Least Four Interacting Neural Systems Underlie Sleep

The constant SWS activity in the forebrain is generated by the basal forebrain, a ventral region

Neurons in this region become active at sleep onset and release GABA

• GABA activates receptors in the nearby tuberomamillary nucleus

• GABA receptors are also stimulated by general anesthetics to produce slow waves resembling SWS

Page 66: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 At Least Four Interacting Neural Systems Underlie Sleep

The reticular formation is able to activate the cortex

• Electrical stimulation of this area will wake up sleeping animals

• Lesions of this area promote sleep

The forebrain and reticular formation seem to guide the brain between SWS and wakefulness

Page 67: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

Figure 10.23 Brain Mechanisms Underlying Sleep

Page 68: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 At Least Four Interacting Neural Systems Underlie Sleep

An area of the pons, near the locus coeruleus, is responsible for REM sleep

Some neurons in this region are only active during REM sleep

They inhibit motoneurons to keep them from firing, disabling the motor system during REM sleep

Page 69: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

Figure 10.24 Acting Out a Dream

Page 70: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 At Least Four Interacting Neural Systems Underlie Sleep

The study of narcolepsy revealed the hypothalamic sleep center.

Narcolepsy sufferers:

• Have frequent sleep attacks and excessive daytime sleepiness

• Do not go through SWS before REM sleep

• May show cataplexy—a sudden loss of muscle tone, leading to collapse

Page 71: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

14 At Least Four Interacting Neural Systems Underlie Sleep

Narcoleptic dogs have a mutant gene for a hypocretin receptor

• Hypocretin normally prevents the transition from wakefulness directly into REM sleep

• Interfering with hypocretin signaling leads to narcolepsy

Page 72: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

Figure 10.25 Canine Narcolepsy

Page 73: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 At Least Four Interacting Neural Systems Underlie Sleep

Hypocretin neurons in the hypothalamus project to other sleep system centers: the basal forebrain, the reticular formation, and the locus coeruleus

Axons also go to the tuberomamillary nucleus, whose inhibition induces SWS

The hypothalamus seems to contain a hypocretin sleep that controls wakefulness, SWS sleep, or REM sleep

Page 74: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

Figure 10.26 Neural Degeneration in Humans with Narcolepsy

Page 75: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 At Least Four Interacting Neural Systems Underlie Sleep

Sleep paralysis is the brief inability to move just before falling asleep, or just after waking up

It may be caused by the pontine center continuing to signal for muscle relaxation, even when awake

Page 76: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 Sleep Disorders Can Be Serious, Even Life-Threatening

Sleep disorders in children:

• Night terrors and sleep enuresis (bed-wetting) are associated with SWS

• Somnambulism (sleepwalking) occurs during stage 3 SWS, and may persist into adulthood

Page 77: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

14 Sleep Disorders Can Be Serious, Even Life-Threatening

REM behavior disorder (RBD) is characterized by organized behavior, from an asleep person

• It usually begins after age 50 and may be followed by beginning symptoms of Parkinson’s disease

• This suggests damage in the brain motor systems

Page 78: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 Sleep Disorders Can Be Serious, Even Life-Threatening

Sleep-onset insomnia is a difficulty in falling asleep, and can be caused by situational factors, such as shift work or jet lag

Sleep-maintenance insomnia is a difficulty in staying asleep and may be caused by drugs or neurological factors

Page 79: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 Sleep Disorders Can Be Serious, Even Life-Threatening

In sleep apnea, breathing may stop or slow down when muscles in the chest and diaphragm relax too much or respiratory neurons in the brain stem don’t signal properly

• Sleep apnea may be accompanied by snoring

Sleep state misperception occurs when people report insomnia even when they were asleep

Page 80: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 Sleep Disorders Can Be Serious, Even Life-Threatening

Sudden infant death syndrome (SIDS) is sleep apnea resulting from immature respiratory pacemaker systems or arousal mechanisms

Putting babies to sleep on their backs can prevent suffocation due to apnea

Page 81: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

Photo, p. 297 Back to Sleep

Page 82: 10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus

10 Sleep Disorders Can Be Serious, Even Life-Threatening

Most sleeping pills bind to GABA receptors throughout the brain.

Continued use of sleeping pills:

• Makes them ineffective

• Produces marked changes in sleep patterns that persist even when not taking the drug

• Can lead to drowsiness and memory gaps