Sleep, Part I: Understanding Sleep Stages
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Questions and Answers

What is the primary characteristic of pyramidal cells in the cortex?

  • The cell body has a unique spiral structure.
  • Their apical dendrites are positioned closest to the skull. (correct)
  • They are specialized for processing pain stimuli.
  • They have multiple axons projecting outwards.

    • What is the frequency range of the alpha rhythm observed in EEG readings?

  • 14-20 Hz
  • 21-30 Hz
  • 8-13 Hz (correct)
  • 4-7 Hz

    • Which of the following describes the wave patterns observed during REM sleep as noted from EEG readings?

  • They show distinct, synchronized waves.
  • They appear random and inconsistent. (correct)
  • They exhibit high amplitude consistent waves.
  • They reflect delta wave patterns.

    • When a person is wide awake with their eyes open, what type of EEG rhythm is primarily observed?

    <p>Beta rhythm</p> Signup and view all the answers

    Which of the following factors does NOT affect the measurements recorded by EEGs?

    <p>The emotional state of the individual</p> Signup and view all the answers

    What primarily characterizes the different stages of sleep?

    <p>Specific patterns of brain waves detected using EEG</p> Signup and view all the answers

    Which sleep disorder is characterized by sudden episodes of falling asleep during the day?

    <p>Narcolepsy</p> Signup and view all the answers

    What physiological function does melatonin primarily regulate?

    <p>Sleep-wake cycles in relation to environmental light</p> Signup and view all the answers

    What external condition can disrupt the architecture of sleep?

    <p>High ambient noise levels</p> Signup and view all the answers

    Which stage of sleep is often most critical for cognitive performance?

    <p>Stage III/IV (N3)</p> Signup and view all the answers

    What tool is commonly used to measure various physiological parameters during sleep?

    <p>Polysomnography</p> Signup and view all the answers

    Which of the following is NOT typically associated with sleep apnea?

    <p>Experiencing night terrors</p> Signup and view all the answers

    Which of the following describes restless leg syndrome?

    <p>Uncomfortable sensations leading to an urge to move the legs</p> Signup and view all the answers

    What is the primary role of the VLPO in sleep regulation?

    <p>Inhibiting the arousal systems</p> Signup and view all the answers

    Which neurotransmitter is primarily responsible for keeping REM sleep active?

    <p>Acetylcholine</p> Signup and view all the answers

    What occurs during the absence of light that triggers melatonin production?

    <p>Activation of the sympathetic nervous system</p> Signup and view all the answers

    How does MCH affect sleep during REM states?

    <p>Inhibits the monaminergic arousal system</p> Signup and view all the answers

    What is the relationship between REM-on and REM-off neurons?

    <p>REM-on neurons inhibit REM-off neurons</p> Signup and view all the answers

    Which of the following best describes the 'flip-flop switch' mechanism in sleep?

    <p>An exclusive state of awake or asleep with no in-between</p> Signup and view all the answers

    What triggers the synthesis of melatonin in the pineal gland?

    <p>Catecholamine stimulation</p> Signup and view all the answers

    Which system's activity does the VLPO inhibit to maintain sleep?

    <p>Monaminergic arousal system</p> Signup and view all the answers

    What is the role of serotonin in melatonin secretion?

    <p>It is synthesized in the presence of catecholamines.</p> Signup and view all the answers

    What effect does orexin have in sleep regulation?

    <p>Enhances wakefulness and arousal</p> Signup and view all the answers

    What is a commonly associated factor with narcolepsy that leads to the loss of orexinergic neurons?

    <p>Genetic predisposition related to HLA DQB1*06:02</p> Signup and view all the answers

    Which treatment approach is most effective for managing symptoms of narcolepsy?

    <p>Antidepressants that enhance noradrenergic and serotonergic tone</p> Signup and view all the answers

    What symptoms characterize Restless Legs Syndrome (RLS)?

    <p>Unpleasant sensations triggering a compulsion to move the legs</p> Signup and view all the answers

    How does Periodic Limb Movement Disorder (PLMD) primarily manifest?

    <p>Large movements of the legs during sleep</p> Signup and view all the answers

    Which aspect of dopamine signaling is hypothesized to contribute to Restless Legs Syndrome?

    <p>Excessive dopamine activity in the morning and inadequate at night</p> Signup and view all the answers

    What is the leading hypothesis regarding the relationship between iron deficiency and RLS?

    <p>Iron deficiency is linked to symptoms but not found in peripheral tests</p> Signup and view all the answers

    Which neurotransmitter is primarily targeted by dopamine agonists in the treatment of RLS?

    <p>Dopamine</p> Signup and view all the answers

    Which area of the brain is critically involved in the pathogenesis of RLS due to its role in dopaminergic signaling?

    <p>Substantia nigra</p> Signup and view all the answers

    What common physiological cycle's disruption is associated with RLS-related discomfort?

    <p>Circadian rhythm of dopamine release</p> Signup and view all the answers

    What is the predominant clinical consequence of movement disorders linked to issues with the basal ganglia?

    <p>Involuntary movements impacting motor control</p> Signup and view all the answers

    What role do MT-2 receptors play in melatonin function?

    <p>Increase the amount of time spent sleeping</p> Signup and view all the answers

    Which physiological rhythm is NOT primarily regulated by melatonin secretion?

    <p>Heat production</p> Signup and view all the answers

    What characteristic is common in individuals with narcolepsy?

    <p>Irresistible napping several times a day</p> Signup and view all the answers

    Which statement about cataplexy is true?

    <p>It can be triggered by strong emotional responses</p> Signup and view all the answers

    What is the homeostatic drive for sleep thought to be influenced by?

    <p>Increase in extracellular adenosine</p> Signup and view all the answers

    Which neurotransmitter system is primarily involved in promoting wakefulness?

    <p>Monaminergic</p> Signup and view all the answers

    What is a likely cause of sleep paralysis?

    <p>Rapid switching between sleep states</p> Signup and view all the answers

    Which disorder often presents with hypnagogic hallucinations?

    <p>Narcolepsy</p> Signup and view all the answers

    Allostasis is best described as the:

    <p>Body's adaptation response to stressors</p> Signup and view all the answers

    Which statement is true regarding sleep quality in individuals with narcolepsy?

    <p>They enter REM sleep quickly, often disrupting their sleep cycles.</p> Signup and view all the answers

    What is the function of caffeine in relation to adenosine receptors?

    <p>Inhibits adenosine receptor activity</p> Signup and view all the answers

    Which factor is least likely to affect sleep quality during stress?

    <p>Melatonin secretion</p> Signup and view all the answers

    Which of the following statements about excessive daytime sleepiness is accurate?

    <p>It can lead to automatic behavior during daytime sleep attacks.</p> Signup and view all the answers

    What characteristic is primarily observed in the beta rhythm when a person is fully awake?

    <p>13-30 Hz frequency with low amplitude</p> Signup and view all the answers

    What happens to the EEG wave patterns when a person transitions from an awake state to synchronized sleep?

    <p>Regular patterns/waveforms become discernible</p> Signup and view all the answers

    Which component of the pyramidal cell is mainly involved in receiving synaptic inputs?

    <p>The apical dendrites located closest to the skull</p> Signup and view all the answers

    What distinguishes the alpha rhythm observed in EEG readings?

    <p>A frequency range of 8-13 Hz with medium amplitude</p> Signup and view all the answers

    In terms of EEG measurements, what does the size of waves indicate?

    <p>The intensity of electrical activity in the cortex</p> Signup and view all the answers

    What EEG pattern is typically seen during Stage 2 sleep?

    <p>K-complexes and sleep spindles</p> Signup and view all the answers

    Which characteristic does Stage 3 sleep exhibit?

    <p>High-amplitude delta waves</p> Signup and view all the answers

    Which sleep stage is often referred to as the transition from wakefulness to sleep?

    <p>Stage 1 sleep</p> Signup and view all the answers

    How does the EEG pattern change as attention is focused on a task?

    <p>Beta rhythm appears and alpha rhythm decreases</p> Signup and view all the answers

    What is a key feature of REM sleep as identified by polysomnography?

    <p>Flat-line EMG activity with eye movements</p> Signup and view all the answers

    Which characteristic is true about theta rhythms?

    <p>They can appear during both sleep and awake states</p> Signup and view all the answers

    What distinguishes N3 sleep from other sleep stages?

    <p>Little to no eye movement with large amplitude waves</p> Signup and view all the answers

    What phenomenon characterizes the transition between wakefulness and sleep as recorded by the EEG?

    <p>Low-frequency theta rhythm</p> Signup and view all the answers

    What is noted about the EMG activity during N2 sleep?

    <p>Limited to no eye movement and some muscle activity</p> Signup and view all the answers

    What is the frequency range of delta waves observed in N3 sleep?

    <p>0.5-4 Hz</p> Signup and view all the answers

    Which of the following factors is essential to consider when diagnosing obstructive sleep apnea (OSA)?

    <p>Reported sleep history from an observer</p> Signup and view all the answers

    What is considered the gold standard for diagnosing obstructive sleep apnea?

    <p>Polysomnogram (PSG)</p> Signup and view all the answers

    What characterizes the waves observed during N3 sleep?

    <p>Delta waves resulting from thalamic-cortical activity</p> Signup and view all the answers

    Which symptom is least likely to be associated with sleep terrors in children?

    <p>Complete memory of the event</p> Signup and view all the answers

    What tool is often used in home sleep tests to monitor breathing patterns?

    <p>Pulse oximeter</p> Signup and view all the answers

    During which stage of sleep does the majority of REM sleep occur?

    <p>Near the end of the sleep session</p> Signup and view all the answers

    How does the sleep architecture change with age?

    <p>Fewer and shorter periods of N3 sleep with more awakenings</p> Signup and view all the answers

    Which of the following is a common characteristic of REM sleep behavior disorder?

    <p>Violent dream enactment</p> Signup and view all the answers

    What is a common finding in the oropharyngeal exam when suspecting obstructive sleep apnea?

    <p>Enlargement of the tonsils</p> Signup and view all the answers

    What is a distinctive feature of sleep during the N2 stage?

    <p>Low muscle activity with sleep spindles</p> Signup and view all the answers

    What neurological mechanism is responsible for paralysis during REM sleep?

    <p>Inhibition of alpha motor neurons by GABA</p> Signup and view all the answers

    During which stage of sleep do sleepwalking episodes typically occur?

    <p>N3 sleep</p> Signup and view all the answers

    Which sleep stage serves as a transitional phase where individuals may appear awake but lacking short-term memory?

    <p>N1 sleep</p> Signup and view all the answers

    Which of the following forms of testing is known for a high rate of false negatives when diagnosing OSA?

    <p>Home sleep tests</p> Signup and view all the answers

    What differentiates the electrical activity during REM sleep compared to other sleep stages?

    <p>Activity in cortical association areas without synchronization</p> Signup and view all the answers

    What is the typical duration of sleep cycles for a young adult?

    <p>90-110 minutes per cycle</p> Signup and view all the answers

    What phenomenon frequently occurs during the transition from N1 to N2 sleep stages?

    <p>Quick transitions with light sleep</p> Signup and view all the answers

    What is the primary neurotransmitter used by spinal inhibitory neurons that leads to paralysis in REM sleep?

    <p>GABA</p> Signup and view all the answers

    What is the primary characteristic of Type I narcolepsy?

    <p>Frequent REM sleep during daytime naps</p> Signup and view all the answers

    Which of the following factors is commonly associated with Restless Legs Syndrome?

    <p>Iron deficiency in the brain</p> Signup and view all the answers

    What is a potential cause of the symptoms experienced in Restless Legs Syndrome?

    <p>Inadequate dopaminergic activity at night</p> Signup and view all the answers

    What treatment methodology is often employed for managing symptoms of Periodic Limb Movement Disorder?

    <p>Stimulant medications to enhance dopamine activity</p> Signup and view all the answers

    How does narcolepsy typically result in the loss of orexinergic neurons?

    <p>Autoimmune response triggered by infections</p> Signup and view all the answers

    Which neurotransmitter is primarily influenced during the treatment of narcolepsy with antidepressants?

    <p>Serotonin</p> Signup and view all the answers

    Which structure in the brain is notably involved in the pathogenesis of Restless Legs Syndrome due to its role in dopaminergic signaling?

    <p>Substantia nigra</p> Signup and view all the answers

    What characteristic of dopamine release is suggested to be altered in individuals suffering from Restless Legs Syndrome?

    <p>Exaggerated circadian rhythm with low levels at night</p> Signup and view all the answers

    What common symptom do both Restless Legs Syndrome and Periodic Limb Movement Disorder share?

    <p>Compulsion to move during rest or sleep</p> Signup and view all the answers

    What is the primary conclusion researchers have drawn about the relationship between iron and dopamine in Restless Legs Syndrome?

    <p>Iron deficiency may impair dopamine metabolism</p> Signup and view all the answers

    Study Notes

    Sleep, Part I

    • Sleep is crucial for overall health, with disruption increasing risks of stroke, hypertension, and coronary artery disease.
    • Sleep deprivation degrades cognitive performance, with deeper sleep stages (N3) playing a critical role.
    • Polysomnography measures sleep stages through EEG, EMG, and EOG recordings.
    • EEG measures brain activity, reflecting potential differences between pyramidal cell dendrites and cell body, specifically the large dendrites closer to the scalp.
    • EEG rhythms (frequency and amplitude) are used to characterize different brain states, including alpha and beta rhythms in wakefulness, and synchronized sleep patterns in various sleep stages.
    • The ventrolateral preoptic nucleus (VLPO) plays a key role in sleep induction by inhibiting arousal systems and orexin release from the lateral hypothalamus.
    • The sleep-inducing and arousal systems in the brain operate as a "flip-flop switch", with one system typically dominating the other.
    • The monoaminergic arousal system is inhibited during REM sleep by MCH release from the lateral hypothalamus.
    • REM sleep is characterized by rapid eye movements, muscle atonia, increased brain activity, and vivid dreams.
    • The pineal gland produces melatonin, a hormone indirectly stimulated by darkness, that plays a role in entraining circadian rhythms.
    • Melatonin synthesis is regulated by catecholamines, primarily norepinephrine, released from the sympathetic nervous system.
    • Melatonin influences circadian rhythms, impacting cortisol, TSH, body temperature, and heart rate variability.
    • The suprachiasmatic nucleus (SCN) acts as a circadian pacemaker, with its internal rhythm entrained by light stimuli through the retinohypothalamic pathway.
    • Melatonin receptors (particularly MT-2) also contribute to SCN entrainment.
    • Homeostatic drive for sleep is characterized by increasing sleepiness with prolonged wakefulness, possibly due to adenosine accumulation.
    • Allostatic stress disrupts sleep by overly activating the monaminergic arousal system.
    • Narcolepsy, characterized by excessive daytime sleepiness and intrusion of REM sleep characteristics into wakefulness, affects approximately 1 in 2000 people.
    • Cataplexy, a defining symptom of narcolepsy, is characterized by sudden muscle weakness without loss of consciousness, often triggered by emotional responses.
    • Narcolepsy is often associated with a loss of orexinergic neurons, frequently caused by an autoimmune response, with a strong association with HLA DQB1*06:02.
    • Treatments for narcolepsy primarily involve antidepressants, stimulants, and agents influencing the availability of dopamine.
    • Restless legs syndrome (RLS) is marked by an irresistible urge to move the legs, particularly at rest, leading to sleep disturbance.
    • Periodic limb movement disorder (PLMD) involves involuntary leg movements during sleep.
    • Both RLS and PLMD are often associated with iron deficiency, particularly in the brain.
    • Disrupted dopaminergic signaling in the basal ganglia and substantia nigra, especially affecting iron transport and metabolism, is implicated in RLS and PLMD.
    • Obstructive sleep apnea (OSA) involves intermittent airway obstruction during sleep, leading to disrupted breathing and decreased blood oxygen levels.

    Pyramidal Cells & EEG

    • The pyramidal cell is a prevalent cell in the cortex and it's large dendrites are closest to the skull.
    • EEGs measure two major things in the underlying cortex: frequency and size of waves.
    • Waves in an awake state are typically irregular.
    • Alpha rhythm is characterized by medium amplitude waves with a frequency of 8-13 Hz and occurs when eyes are closed and mind is wandering.
    • Beta rhythm is characterized by low amplitude waves with a frequency of 13-30 Hz and occurs when eyes are open and the individual is awake.
    • Beta Rhythm can also be seen when focusing on a thought.
    • The transition from alpha to beta rhythm is known as alpha block, arousal, or the alerting response.
    • Sleeping stages have regular patterns of waves and the EEG will show larger amplitude waves than seen during the awake state.

    Sleep Stages

    • Sleep stages are defined by Polysomnography (PSG).
    • Stage 1 (N1) sleep is characterized by theta rhythm (4-7 Hz), slow rolling eye movements, and limited muscle activity.
    • Stage 2 (N2) sleep is characterized by theta rhythm with K complexes and Sleep spindles.
    • Stage 3 & 4 (N3) sleep is characterized by delta waves, large amplitude waves with frequencies of 0.5-4 Hz, and minimal eye movements
    • REM (R) sleep is characterized by bursts of rapid eye movements, minimal muscle activity, low amplitude and high frequency waves resembling theta rhythm in N1.
    • Those in REM sleep are often paralyzed due to the activation of spinal inhibitory neurons that use GABA as a neurotransmitter.

    Sleep Architecture & Disorders

    • Sleep architecture refers to the pattern of sleep stages throughout the night.
    • Young adults and children usually experience more deep sleep (N3) early in the sleep cycle.
    • Most REM sleep occurs near the end of a sleep session.
    • Elderly subjects have much fewer and shorter periods of N3 sleep and more frequent awakenings.
    • Narcolepsy tends to be associated with the autoimmune destruction of orexinergic neurons and includes features that are similar to REM sleep.
    • It is treated with antidepressants that increase noradrenergic or serotonergic tone, and stimulants such as methylphenidate or modafinil that increase dopamine levels.
    • Restless legs syndrome (RLS) is characterized by an unpleasant, irritable compulsion to move the legs that is triggered by rest or drowsiness.
    • Periodic limb movement disorder (PLMD) is characterized by movements typically in the legs that occur during sleep.
    • Both RLS and PLMD seem to be caused by iron deficiency in the brain and abnormalities in dopaminergic signaling.
    • Obstructive sleep apnea (OSA) is often found in those with hypertension and other heart conditions.
    • The gold standard for OSA diagnosis is polysomnography but home sleep tests may be used for screening.

    Parasomnias

    • Parasomnias are abnormal behaviors or experiences that occur during sleep.
    • Sleepwalking occurs during N3 and most commonly in children and adolescents.
    • Sleep terrors, which are nightmares, also occur mainly during N3 sleep, and tend to be more common in children.
    • REM sleep behavior disorder occurs during REM sleep, and is characterized by violent movements.
    • It is more common in older adults and is correlated with neurodegenerative disorders.

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