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

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Presentation on theme: "10 Biological Rhythms and Sleep. 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus."— Presentation transcript:

1 10 Biological Rhythms and Sleep

2 10 Biological Rhythms and Sleep: Part I Biological Rhythms Many Animals Show Daily Rhythms in Activity The Hypothalamus Houses an Endogenous Circadian Clock

3 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

4 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

5 10 Many Animals Show Daily Rhythms in Activity Diurnalactive during the light Nocturnalactive during the dark Circadian rhythms are generated by an endogenous (internal) clock

6 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

7 Figure 10.2 How Activity Rhythms Are Measured (Part 1)

8 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

9 Figure 10.2 How Activity Rhythms Are Measured (Part 2)

10 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

11 Figure 10.3 The Effects of Lesions in the SCN

12 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

13 Figure 10.5 Brain Transplants Prove That the SCN Contains a Clock

14 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

15 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

16 Figure 10.6 Components of a Circadian System

17 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

18 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)

19 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

20 Figure 10.7 A Molecular Clock in Flies and Mice

21 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 mutantsseverely arrhythmic

22 Figure 10.8 When the Endogenous Clock Goes Kaput

23 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

24 Figure 10.9 Humans Free-Run Too

25 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

26 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

27 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

28 Figure Electrophysiological Correlates of Sleep and Waking

29 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

30 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

31 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

32 10 Human Sleep Exhibits Different Stages Late stage 3 sleep o Delta waves are present about half the time

33 10 Human Sleep Exhibits Different Stages REM sleep follows SWS Active EEG with small-amplitude, high-frequency waves, like an awake person Muscles are relaxedcalled paradoxical sleep

34 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

35 Figure A Typical Night of Sleep in a Young Adult

36 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

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

38 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

39 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

40 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 timethe other remains awake

41 Figure Sleep in Marine Mammals

42 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 sleep50%, which may provide essential stimulation to the developing nervous system

43 Figure The Trouble with Babies

44 Figure Human Sleep Patterns Change with Age

45 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

46 Figure The Typical Pattern of Sleep in an Elderly Person

47 10 Manipulating Sleep Reveals an Underlying Structure Effects of sleep deprivationthe partial or total prevention of sleep: Increased irritability Difficulty in concentrating Episodes of disorientation Effects can vary with age and other factors

48 Figure I Need Sleep!

49 10 Manipulating Sleep Reveals an Underlying Structure Sleep recovery is the process of sleeping more than normally, after a period of deprivation Night 1stage 3 sleep is increased, but stage 2 is decreased Night 2most recovery of REM sleep, which is more intense than normal with more rapid eye movements

50 Figure Sleep Recovery after 11 Days Awake

51 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 inheritedin midlife people stop sleeping and die 7–24 months after onset of the insomnia

52 10 What Are the Biological Functions of Sleep? Four functions of sleep: Energy conservation Niche adaptation Body restoration Memory consolidation

53 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

54 10 What Are the Biological Functions of Sleep? Sleep helps animals avoid predatorsanimals 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

55 Figure Sleep Helps Animals to Adapt an Ecological Niche

56 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

57 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

58 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

59 Figure A Nonsleeper

60 10 At Least Four Interacting Neural Systems Underlie Sleep Sleep is an active state mediated by: A forebrain systemdisplays SWS A brainstem systemactivates the forebrain A pontine systemtriggers REM sleep A hypothalamic systemaffects the other three

61 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

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

63 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 REMthus, the forebrain alone can generate SWS

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

65 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

66 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

67 Figure Brain Mechanisms Underlying Sleep

68 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

69 Figure Acting Out a Dream

70 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 cataplexya sudden loss of muscle tone, leading to collapse

71 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

72 Figure Canine Narcolepsy

73 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

74 Figure Neural Degeneration in Humans with Narcolepsy

75 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

76 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

77 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 Parkinsons disease This suggests damage in the brain motor systems

78 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

79 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 dont signal properly Sleep apnea may be accompanied by snoring Sleep state misperception occurs when people report insomnia even when they were asleep

80 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

81 Photo, p. 297 Back to Sleep

82 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


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