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32 Cards in this Set
- Front
- Back
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Two physiological components of Consciousness |
Arousal - wakefulness Awareness |
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EEG |
Brain produces electrical activity Can put electrode on surface of brain See slow wavy signal - local field potential - its the sum of many neurons Every brain region has a different characteristics of wave firing |
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EEG spikes |
Are action potentials |
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PET |
Binding of certain neurotransmitters to their receptors Details of brain activity rather than structure FDG often used in studies of brain metabolism to see which areas of brain are most active during a task |
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Cerebral Metabolism varies with... |
states of consciousness |
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Excessive sleepiness associated with lesions of |
posterior hypothalamus/rostral midbrain |
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Excessive wakefulness associated with |
lesion of anterior hypothalamus, preoptic area |
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VLPO neurons |
The VLPO - ventro lateral preoptic region -preoptic area and adjacent anterior hypothalamus - contains sleep active cells decrease activity of wake promoting neurons in the hypothalamus and brainstem via release of GABA and galanin |
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Importance of EEG in sleep |
Informs about frequency and amplitude of electrical brain activity associated with sleep |
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Stage 1 of sleep |
Hyponogogic - first fall asleep transition from alpha waves to theta waves (lower frequency) Sudden twitches and hypnic jerks or positive myoclonus |
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Stage 2 of sleep |
Sleep spindle is characteristic of stage two. Person is asleep. muscular activity decreases, conscious awareness to external environment dissappears Occupies 45-55% of total sleep in adults |
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Stage 3 and 4 sleep |
Deep/Slow wave sleep - delta waves Sleep disorders affect this stage This stage is when parasomnias as night terrors, bedwetting, sleepwalking, and sleep-talking occur |
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REM sleep |
Accounts for 20-25% of sleep EEG looks similar to awake, low voltage high frequency Lucid dreaming Sleep induced descending muscular atonia: disconnection of muscles from brain, muscles most relaxed -prevents you from acting out your dreams Most difficult stage to wake someone from |
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Length of Stage 4 vs REM sleep in the 90 minute sleep cycle |
Stage 4 sleep decreases and duration of REM sleep increases |
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Effects of sleep deprivation |
Fatigue and subsequent death impaired concentration emotional irritability depressed immune system greater overall vulnerability |
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Study that shows REM sleep is important for memory storage |
Ability to memorize phone numbers tested in subjects with normal sleep, REM-deprived sleep, and stage 3 and 4 deprived sleep. Those with REM-deprived sleep did the poorest |
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Narcolepsy |
Sudden onset of sleep Go immediately into REM Often report hallucinations |
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What part of the brain is critical in maintaining wakefulness |
Reticular formation in brain stem Loose connection of neurons extending from caudal medulla through core of midbrain wakefulness is particularly dependent on the rostral half (mid brain reticular formation MRF) Does not require external stimuli to maintain an awake state Most reticular neurons contain excitatory AA Glutamate |
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Arousal states are determined by.... |
An interaction among the brainstem, hypothalamus, thalamus & basal forebrain ascending projections: stimulate cortical activation characterized by high frequency low amplitude fast activity descending projections: modulate muscle tonus and activity |
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How are arousal systems dampened? |
Active inhibition by thalamo cortical systems to produce sleep |
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Arousal Pathway |
Reticular formation project to: intralaminar nuclei of thalamus >> cortex relay neurons throughout thalamus nucleus reticularis (regulates the thalamic gate) |
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Pontomesencephalic cholingergic neurons |
Include: Pedunculopontine (PPT) & lateral dorsal tegmental nuclei (LDT located in dorsal mid brain and pons Actively discharge during wakefulness and REM sleep no activity during non rem sleep |
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Locus coeruleus noradrenergic neuons |
Synthesize NE Located in the mid to rostral pons near floor of 4th ventricle project throughout brain Maximal discharge during wakefulness and stops firing during REM (some in NREM) -enhances activation and increases arousal particularly in times of increased stress |
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Ventral Mesencephalic Dopaminergic neurons |
In substantia nigra pars compacta & ventral tegmental area (VTA) << important for arousal Project to dorsal and ventral striatum, BF and cortex May be important in maintaining alertness particularly in association with situations involving positive reward |
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Raphe Serotonergic Neurons |
Located bilaterally in the midline of the brainstem Project to much of the CNS Discharge across sleep wake cycle same as LC (Maximal during wakefulness, stops during REM) Increased 5-HT levels are associated with a relaxed or satiated waking state |
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What thalamic nuclei send projections to the cortx involved in the arousal system? |
Midline, medial and intralaminar nuclei Excitatory thalamocortical projections are associated with cortical activation (through glutamate release) during wakefulness and REM sleep |
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Firing pattern of intralaminar cells, and what does it do? |
Fire in a natural pattern of 40 cycles per sec (40 Hz) Source of rhythmicity that is detected at the surface of the cortex |
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Main neurons in the hypothalamus |
Histamine orexin |
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Posterior Hypothalamus |
Neurons with maximal rate of discharge during wakefulness, decreased discharge during slow wave sleep Involved in activation of sympathetic nervous system and hypothalamic pituitary axis during arousal |
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Histaminergic neurons |
Histamine - tuberomammilary nucleus -project diffusely throughout CNS -wake activating -important in promoting wakefulness during exposure to novel environments/situation which require higher behavior arousal + initially after waking |
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Orexigenic neurons |
Located in lateral and posterior hypothalamus project throughout CNS Excitatory projections to other arousal systems Levels are highest at the end of the day There is a lack of ORX signaling in 90% of pts with narcolepsy |
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Basal Forebrain and Arousal |
Cholinergic neurons that receive input from all of brainstem and hypothalamic arousal systems Most active during wakefulness and REM sleep |
