The power point presentation on Sleep.pptx

Sleep is a naturally recurring state of rest characterized by reduced consciousness, decreased sensory activity, and inhibition of voluntary muscles. It is a vital physiological process essential for physical restoration, cognitive functioning, emotional regulation, and overall health. Sleep is not merely a passive state but involves active processes that support learning, memory consolidation, metabolic regulation, and tissue repair. Despite being a universal behavior across species, the mechanisms and functions of sleep are complex and multifaceted.

Sleep occurs in cycles, typically lasting 90–120 minutes, alternating between two main types: Rapid Eye Movement (REM) sleep and Non-Rapid Eye Movement (NREM) sleep. NREM sleep is further divided into three stages: N1 (light sleep), N2 (intermediate sleep), and N3 (deep or slow-wave sleep). NREM sleep is primarily restorative, supporting physical repair, immune function, and energy conservation. REM sleep is characterized by rapid eye movements, muscle atonia, vivid dreaming, and heightened brain activity resembling wakefulness. REM sleep plays a critical role in memory consolidation, emotional regulation, and cognitive processing.

Functions of sleep are diverse and essential. Physiologically, sleep aids in tissue growth and repair, hormonal regulation, immune system strengthening, and metabolic balance. Psychologically, sleep facilitates memory consolidation, learning, attention, problem-solving, and creativity. During sleep, experiences and knowledge acquired during wakefulness are processed and integrated into long-term memory. Sleep deprivation, either acute or chronic, impairs cognitive performance, mood, attention, decision-making, and overall health, increasing the risk of cardiovascular disease, diabetes, obesity, and mental health disorders.

Regulation of sleep involves two primary processes: the circadian rhythm and the homeostatic sleep drive. The circadian rhythm, governed by the suprachiasmatic nucleus (SCN) of the hypothalamus, aligns the sleep-wake cycle with environmental cues like light and darkness. The homeostatic drive reflects the body’s need for sleep, which increases the longer one stays awake and dissipates during sleep. Neurotransmitters and hormones such as melatonin, serotonin, gamma-aminobutyric acid (GABA), and adenosine play crucial roles in initiating and maintaining sleep, regulating transitions between different sleep stages, and ensuring overall sleep quality.

Sleep is influenced by age, lifestyle, health, and environmental factors. Newborns require 14–17 hours of sleep, adolescents 8–10 hours, and adults 7–9 hours. Sleep hygiene, including consistent sleep schedules, a dark and quiet environment, limited screen exposure, and relaxation techniques, can enhance sleep quality. Disorders such as insomnia, sleep apnea, narcolepsy, and restless leg syndrome disrupt normal sleep patterns and can have serious health consequences if untreated.

1. UNIT – III SLEEP

2. SYLLABUS Sleep: Rhythms of sleeping and waking, neural basis of biological clocks, Stages of sleep B rain mechanisms of REM sleep and dreaming P hysiological mechanisms of sleep and waking

3. SLEEP Sleep is a behaviour Characteristics of sleep The insistent urge of sleepiness (a motivation) forces us to seek out a quiet, warm, comfortable place; lie down; and remain there for several hours (a behavior) Because we remember very little about what happens while we sleep, we tend to think of sleep more as a change in consciousness than as a behavior

4. BRAIN WAVE MECHANISM

5. During wakefulness the EEG of a normal person shows two basic patterns of activity: alpha activity and beta activity Alpha activity consists of regular, medium-frequency waves of 8–12 Hz. The brain produces this activity when a person is resting quietly, not particularly aroused or excited and not engaged in strenuous mental activity Although alpha waves sometimes occur when a person’s eyes are open, they are much more prevalent when they are closed

6. The other type of waking EEG pattern, beta activity , consists of irregular, mostly low-amplitude waves of 13–30 Hz Beta activity shows desynchrony It reflects the fact that many different neural circuits in the brain are actively processing information Desynchronized activity occurs when a person is alert and attentive to events in the environment or is thinking actively.

7. STAGES OF SLEEP The first physiological description of sleep stages was published in 1957, and by 1968 Rechtschaffen and Kales had published a manual for a standardized sleep stage scoring method known as the R & K method In additional to wakefulness, the original scoring guidelines included four stages of non-REM sleep (stages 1–4) and one stage of REM sleep, composed of EEG waveforms of different frequencies and amplitudes Since the early 2000s, a revised scoring system has been proposed by the American Academy of Sleep Medicine ( AASM method ) The new system identifies stages of wakefulness (stage W), three stages of non-REM sleep (NREM 1, 2, and 3) and one REM sleep stage (stage R)

8. STAGES OF SLEEP

9. STAGE 1 Stage 1 sleep - marked by the presence of some theta activity (3.5–7.5 Hz), Indicates that the firing of neurons in the neocortex is becoming more synchronized This stage is actually a transition between sleep and wakefulness Eyelids slowly open and close and eyes roll upward and downward The sleeper may experience hypnic jerks , muscle contractions followed by relaxation - sudden, involuntary muscle contractions you may experience as you are falling asleep Many people experience these along with a falling sensation

10. STAGE 2 About 10 minutes later Sleep spindles are short bursts of waves of 12–14 Hz that occur between two and five times a minute during stages 1–3 of sleep. They appear to play a role in consolidation of memories K complexes are sudden, sharp waveforms, which are usually found only during stage 2 sleep. They spontaneously occur at the rate of approximately one per minute. Often can be triggered by noises—especially unexpected noises K complexes appear to be the forerunner of delta waves , which appear in the deepest levels of sleep The person is sleeping soundly now; but if awakened, she might report that she has not been asleep.

11. STAGE 3 About 15 minutes later the individual enters slow-wave sleep , signaled by the occurrence of high-amplitude delta activity (less than 3.5 Hz) Stage 3 is the deepest stage of sleep; only loud noises will cause a person to awaken, and when awakened, the person acts groggy and confused. If we wake the person up during slow-wave sleep and ask, “Were you dreaming?” she will most likely say, “No.” However, if we question him/her more carefully, she might report the presence of a thought, an image, or some emotion

12. REM Sleep About 90 minutes after the beginning of sleep , we notice an abrupt change in a number of physiological measures Eyes are rapidly moving back and forth beneath her closed eyelids. This peculiar stage of sleep is referred to as REM sleep (Rapid eye movement) There is a profound loss of muscle tone During REM sleep, a person might not react to most noises, but he or she is easily aroused by meaningful stimuli, such as the sound of his or her name. Also, when awakened from REM sleep, a person appears alert and attentive. The dreams of REM sleep tend to be narrative in form, with a storylike progression of events

13. REM Sleep During REM sleep we become paralyzed At the same time the brain is very active Cerebral blood flow and oxygen consumption are accelerated During most periods of REM sleep a male’s penis and a female’s clitoris will become at least partially erect, and a female’s vaginal secretions will increase (Schmidt and Schmidt, 2004) People can have dreams with sexual content. In males some dreams culminate in ejaculation—the so-called nocturnal emissions, or “wet dreams.” Females, too, experience orgasm during sleep.

14. During the rest of the night individual’s sleep alternates between periods of REM and non-REM sleep Each cycle is approximately 90 minutes long, containing a 20- to 30-minute bout of REM sleep Thus, an 8-hour sleep will contain four or five periods of REM sleep.

15. What happens when we sleep? - YouTube How Sleep Affects Your Brain (youtube.com)

16. BRAIN ACTIVITY DURING SLEEP

17. BRAIN ACTIVITY DURING SLEEP Researchers have found that the rate of cerebral blood flow in the human brain during REM sleep is High in the extra-striate cortex (visual association cortex) - reflects the visual hallucinations that occur during dreams. Low in the striate (primary) visual cortex - reflects the fact that the eyes are not receiving visual input Low in the prefrontal cortex (The prefrontal cortex is involved in making plans, keeping track of the organization of events in time, and distinguishing illusion from reality)

18. LUCID DREAMING Lucid dreaming: An awareness that they are dreaming and are not awake. Some researchers have hypothesized that activation of the normally inactive prefrontal cortex during REM could be involved in the experience of lucid dreaming. Lucid dreaming may also occur in non-REM sleep.

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20. FUNCTIONS OF SLOW WAVE SLEEP Human Brain = 2 % of the total body weight Energy required by brain = 20% of the body’s energy during quiet wakefulness C erebral metabolic rate & cerebral blood flow = decline during slow-wave sleep, falling to about 75 % of the waking level ( Buchsbaum et al., 1989; Maquet , 1995; Sakai et al., 1979)

21. R egions with highest levels of activity during waking = Highest levels of delta waves—and the lowest levels of metabolic activity— during slow-wave sleep T he presence of slow-wave activity in a particular region of the brain appears to indicate that that region is resting E vidence suggests that the brain needs to rest periodically to recover from adverse side effects of its waking activity

22. Free Radicals & Oxidative stress Siegel (2005): the waste products produced by the high metabolic rate associated with waking activity of the brain are free radicals ( chemicals that contain at least one unpaired electron) Free radicals are highly reactive oxidizing agents; they can bind with electrons from other molecules and damage the cells in which they are found, a process known as oxidative stress Prolonged sleep deprivation = increase in free radicals in the brains of rats = resulted in oxidative stress (Ramanathan et al., 2002) During slow-wave sleep the lowered rate of metabolism permits restorative mechanisms in the cells to destroy the free radicals and prevent their damaging effects.

23. WHAT ARE FREE RADICALS? And What Do They Do To Your Body? – YouTube Oxidative stress and antioxidants (youtube.com)

24. FUNCTIONS OF REM SLEEP Promotes brain development Facilitates learning Rebound phenomenon: If selective deprivation causes a deficiency in REM sleep, the deficiency is made up later, when uninterrupted sleep is permitted

25. BRAIN ACTIVITY DURING SLOW WAVE SLEEP Regional cerebral blood flow during slow-wave sleep is decreased throughout the brain compared to waking Some researchers have found localized increases in the visual and auditory cortexes, which are hypothesized to be the neural basis for the dream like imagery experienced during slow wave sleep Blood flow to the thalamus and cerebellum is decreased in slow-wave sleep

26. SLOW WAVE SLEEP AND EXERCISE Experiment on humans the relationship between sleep and exercise does not appear to be very strong no changes in slow-wave or REM sleep of healthy participants who spent six weeks resting in bed ( Ryback and Lewis, 1971) Effect of cog activity on slow wave sleep: Tasks that demand alertness and mental activity do increase glucose metabolism in the brain (Roland, 1984): most sig in frontal lobe

27. A few studies… Huber et al., (2004):motor learning task just before going to sleep During sleep the participants showed increased slow-wave activity in the region of the neocortex that became active while they were performing the task Horne and Minard (1985) : Exp.: increase mental activity without affecting physical activity and without causing stress : Participants taken to art exhibition, a shopping center , a museum, an amusement park, a zoo, and an interesting mansion T heir slow-wave sleep was increased After all that mental exercise, the brain appears to have needed more rest than usual.

28. Sleep & Learning Research with both humans and laboratory animals indicates that sleep does more than allow the brain to rest: It also aids in the consolidation of long-term memories (Marshall and Born, 2007) there are two major categories of long-term memory: declarative memory (also called explicit memory ) and nondeclarative memory (also called implicit memory ) Declarative memories : Memories of relationship b/w stimuli & event Non Declarative: gained through experience and practice that do not necessarily involve an attempt to “memorize” information; driving a car, catching a ball Mednick et al., (2003): Learning non-declarative visual discrimination task at 9AM-the ability to perform the task was tested 10 hours later, at 7:00 PM Some took a 90 Minute nap between the learning and testing: EEG: to see which had REM and n-REM The performance of participants who did not take a nap was worse, They engaged only in slow-wave sleep did about the same during testing as training the participants who engaged in REM sleep performed significantly better

29. Tucker et al., (2006): trained participants on two tasks: a declarative task (learning a list of paired words) and a nondeclarative task (learning to trace a pencil-and-paper design while looking at the paper in a mirror) S ome of the participants were permitted to take a nap lasting for about 1 hour EEGs were recorded, and they were awakened before they could engage in REM sleep T ested 6 hours after the original training N ap consisting of just slow-wave sleep increased the participants’ performance on the declarative task but had no effect on the performance of the nondeclarative task REM sleep facilitates consolidation of nondeclarative memories and slow-wave sleep facilitates consolidation of declarative memories

30. PHYSIOLOGICAL MECHANISMS OF SLEEP AND WAKING

31. NEURAL CONTROL OF SLEEP Benington et al., (1995) suggested that adenosine , a neuromodulator, might play a primary role in the control of sleep Astrocytes maintain a small stock of nutrients in the form of glycogen , an insoluble carbohydrate that is also stocked by the liver and the muscles. In times of increased brain activity, this glycogen is converted into fuel for neurons. Thus, prolonged wakefulness causes a decrease in the level of glycogen in the brain (Kong et al., 2002). A fall in the level of glycogen causes an increase in the level of extracellular adenosine , which has an inhibitory effect on neural activity. This accumulation of adenosine serves as a sleep-promoting substance.

32. During slow-wave sleep, neurons in the brain rest, and the astrocytes renew their stock of glycogen If wakefulness is prolonged, even more, adenosine accumulates, which inhibits neural activity and produces the cognitive and emotional effects that are seen during sleep deprivation. Caffeine blocks adenosine receptors to reduce sleepiness

33. Two body processes control sleeping and waking periods. These are called sleep/wake homeostasis and the circadian biological clock . With sleep/wake homeostasis, the longer you are awake, the greater your body senses the need to sleep.

34. Your body’s internal clock is controlled by an area of the brain called the SCN (suprachiasmatic nucleus). The SCN is located in the hypothalamus. The SCN is sensitive to signals of dark and light. The optic nerve in your eyes senses the morning light. Then the SCN triggers the release of cortisol and other hormones to help you wake up. But when darkness comes at night, the SCN sends messages to the pineal gland. This gland triggers the release of the chemical melatonin. Melatonin makes you feel sleepy and ready for bed.

35. NEURAL CONTROL OF AROUSAL

36. AROUSAL: The state of being awake and alert At least five different neurotransmitters play a role in some aspect of an individual’s level of arousal: Acetylcholine Norepinephrine Serotonin Histamine Orexin

37. ACETYLCHOLINE

38. ACETYLCHOLINE Two groups of acetylcholinergic neurons LOCATION : In the pons and one located in the basal forebrain When stimulated  cortical arousal and desynchrony  Wakefulness

39. NOREPINEPHRINE

40. Noradrenergic system is located in the locus coeruleus (LC), located in the pons Neurons of the locus coeruleus release norepinephrine throughout the neocortex, hippocampus, thalamus, cerebellar cortex, pons, and medulla RESEARCH: The firing rate of these neurons was high during wakefulness, low during slow wave sleep, and almost zero during REM sleep Stimulation of the neurons caused immediate waking, and that inhibition decreased wakefulness and increased slow-wave sleep.

41. SEROTONIN

42. Most of the brain’s serotonergic neurons are found in the Raphe nuclei , which are located in the regions of the reticular formation The axons of these neurons project to many parts of the brain, including the thalamus, hypothalamus, basal ganglia, hippocampus, and neocortex Stimulation of the raphe nuclei causes locomotion and cortical arousal (as measured by the EEG)

43. HISTAMINE

44. Histamine, a compound synthesized from histidine, an amino acid Antihistamines, which are used to treat allergies, can cause drowsiness. They do so by blocking histamine H2 receptors in the brain More modern antihistamines cannot cross the blood–brain barrier, so they do not cause drowsiness The cell bodies of histaminergic neurons are located in the tuberomammillary nucleus (TMN) of the hypothalamus The axons of these neurons project primarily to the cerebral cortex, thalamus, basal ganglia, basal forebrain, and other regions of the hypothalamus The projections to the cerebral cortex directly increase cortical activation and arousal

45. The activity of histaminergic neurons is high during waking but low during slow-wave sleep and REM sleep Injections of drugs that prevent the synthesis of histamine or block histamine H1 receptors decrease waking and increase sleep Although histamine clearly plays an important role in wakefulness and arousal, evidence suggests that control of wakefulness is shared with the other neurotransmitters

46. OREXIN

47. It is called hypocretin by some researchers and orexin by others The name “hypocretin” comes from the fact that the lateral hypothalamus contains the cell bodies of all of the neurons that secrete this peptide The name “orexin” comes from the role this peptide plays in the control of eating and metabolism Two laboratories independently discovered the peptide; hence it has two names The cause of narcolepsy is degeneration of orexinergic neurons in humans

48. The cell bodies of neurons that secrete orexin are located in the lateral hypothalamus The axons of these neurons project to almost every part of the brain involved in arousal and wakefulness, including the cerebral cortex, raphe nuclei, tuberomammillary nucleus, and acetylcholinergic neurons in the dorsal pons and basal forebrain (Sakurai, 2007) Orexin has an excitatory effect in all of these regions

49. Control of wakefulness is shared by all the neurotransmitters

50. Identify a latest research article/ case that discusses the role of neurotransmitters in sleep and wakefulness

51. NEURAL CONTROL OF SLEEP/ WAKE TRANSITIONS

52. R oles of homeostatic/allostatic/ circadian factors Homeostatic : follows the principles that regulate our eating and drinking Allostatic: refers to reactions to stressful events in the environment (danger, lack of water, and so on) that serve to override homeostatic control Circadian factors : time of day factors, tend to restrict our period of sleep to a particular portion of the day/night cycle.

53. Reaction to stressful environment, OVERRIDING HOMEOSTATIC CONTROL Role of neurotransmitters and harmones Role of Adenosine

54. CIRCADIAN RYTHM Our daily pattern of sleep and waking follows a 24-hour cycle Time of day factors, tend to restrict our period of sleep to a particular portion of the day/night cycle Some of these rhythms are passive responses to changes in illumination However, other rhythms are controlled by mechanisms within the organism—by “internal clocks”

55. Regular daily variation in the level of illumination (that is, sunlight and darkness) normally keeps the clock adjusted to 24 hours Light serves as a zeitgeber (German for “time giver”); it synchronizes the endogenous rhythm. we use artificial lights to delay our bedtime and window shades to extend our time for sleep.

56. Region of the brain_Control of sleep Preoptic area: anterior hypothalamus: When our preoptic neurons (sleep neurons) become active, they suppress the activity of our arousal neurons, and we fall asleep (Saper et al., 2005) Destruction: insomnia in Rats (Nauta,1990) Electrical stimulation: Drowsiness vlPreoptic Area: Majority of sleep neurons=damage=suppress sleep