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43 Cards in this Set
- Front
- Back
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How are the stages of sleep measured? |
Using an EEG, which records the average of electrical potentials of the cells and fibers in the brain areas nearest each electrode on the scalp. EEG monitors brain activity during sleep. |
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What is a polysomnograph? |
A combination of EEG (measuring brain activity) and eye-movement records. |
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What is stage 1 sleep? |
First stage in sleep cycle. The EEG is dominated by irregular, jagged, low-voltage waves. Less brain activity than relaxed awake, but higher than other sleep stages. |
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What is stage 2 sleep? |
Characterized by sleep spindles and K-complexes on EEG. |
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What are sleep spindles? How are they produced? |
12-14 Hz waves on EEG that last at least half a second during stage 2 sleep. They result from oscillating interactions between cells in the thalamus and cortex. |
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What are K-complexes? What are they associated with? |
A sharp EEG wave during stage 2 sleep. Associated with temporary inhibition of neuronal firing. |
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What are stage 3 & 4 of sleep otherwise known as? What is characteristic of these sleep stages? |
Slow-wave sleep (SWS). Heart rate, breathing and brain activity decrease. Slow, large amplitude waves on EEG become more common. The only difference between stage 3 and 4 is the prevalence of these slow waves. |
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What do large, slow waves on EEG indicate? |
A low level of sensory input, which allows for highly synchronized neuronal activity. |
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1. What does REM sleep stand for? 2. What is another name for it? 3. Why does it have this name? |
1. Rapid eye movement. 2. Paradoxical sleep 3. Because there is a high level of brain activity, but postural muscles of the body are the most relaxed. In some ways this sleep is light and in some ways it is the deep. |
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What is characteristic of REM sleep? |
The EEG shows irregular, low-voltage fast waves (indicate increased neuronal activity). Postural muscles are the most relaxed in this stage. Heart rate, blood pressure and breathing are more variable than in stages 2-4. There are also intermittent facial twitches and eye movements. |
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Describe the sequence of sleep throughout the night |
When you first fall asleep you start at stage 1 and slowly progress through stages 2, 3, 4 in order. After about an hour, you cycle back from stage 4, to 3, 2, and then to REM. This sequence repeats, each cycle lasting around 90min. |
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What sleep stage(s) predominate early in the night? What stage(s) predominates towards the morning? |
Early in the night: stages 3 and 4. Toward the morning: REM sleep. |
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What does the amount of REM sleep you get depend on? |
It depends on the time of day more than how long you have been asleep. If you go to sleep later than usual, you still increase your REM sleep about the same time that you would have ordinarily. |
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During which part of a night's sleep is REM most common? |
Toward the end of the night's sleep |
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How does a cut through the midbrain decrease arousal? (cause prolonged sleep) |
By damaging the reticular formation. |
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What is a part of the reticular formation that contributes to cortical arousal? What neurotransmitters does it release and to where? |
Pontomesencephalon. It releases acetycholine and glutamate in the forebrain. |
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What does stimulation of the pontomesencephalon do? |
It increases alertness or will wake up a sleeping person, shifting EEG from long, slow waves to short, high-frequency ones. |
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What is the locus coeruleus? What does it do? |
It is a small structure in the pons. It emits bursts of impulses (neurotransmitter: norepinephrine) during meaningful events. It increases the activity of the most active neurons and decreases activity of less active neurons. Results in enhanced memory and attention to important info. -Increases info storage during wakefulness; suppresses REM sleep |
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What does the hypothalamus do (in relation to arousal and attention)? |
Some parts of it release neurotransmitter histamine, which enhances arousal and alertness. Another part releases peptide neurotransmitter called orexin, which enhances wakefulness. Orexin is necessary to stay awake, not to wake up. |
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Where do axons releasing orexin extend from and to where? |
Extend from hypothalamus to the basal forebrain and many other areas. |
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What does the basal forebrain do (in relation to arousal and alertness)? |
Some axons from basal forebrain cells release acetylcholine which is excitory, which excites the thalamus; it increases and attention; shifts sleep from NREM to REM. Other axons release GABA, which is inhibitory, which inhibits thalamus and cortex. It interferes with the spread of info from one neuron to another. |
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Why do most anti-histamines make people drowsy? |
Because two paths from the hypothalamus - one to the basal forebrain and one to the pontomesencephalon - use histamine to increase arousal. Antihistamines that cross the blood-brain barrier block those synapses. |
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What would happen to the sleep-wake schedule of someone who lacked orexin? |
Someone without orexin would alternate between brief periods of waking and sleeping. |
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What happens to neurons in the thalamus during sleep? |
They become hyperpolarized, decreasing their readiness to respond to stimuli and decreasing the info they transmit to the cortex. When they do fire, they do so all together. |
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What do the dorsal raphe and pons secrete? What effect does it have? |
Secrete serotonin which interrupts REM sleep. |
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How can sleep be local within the brain? |
Because sleep depends on GABA-mediated inhibition, there might be more inhibition during sleep in one part of the brain compared to other ones. |
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Other than release serotonin, what does the pons do in relation to sleep? |
Cells in the pons (and medulla) send messages that inhibit spinal neurons that control the body's large muscles.
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What would happen to the sleep-wake schedule of someone who took a drug that blocked GABA? |
They would remain awake. |
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Someone who has just woke up sometimes speaks in a loose, unconnected, illogical way. How can this be explained? |
Close to waking up, a person is typically in REM sleep. Not all brain areas may wake up at the same time. While waking up, some parts of the brain may still be in a REM-like state. |
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What kind of waves are distinctive of REM sleep? Where do they appear and in what sequence? |
PGO waves (pons-geniculate-occipital waves), which are distinctive patterns of high-amplitude electrical potentials. Wave of activity are first detected in the pons, then lateral geniculate nucleus of the thalamus, and then in the occipital cortex. |
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What does REM sleep depend on? |
Relationship between neurotransmitters serotonin and acetylcholine. (Acetylcholine is important for REM sleep and serotonin interrupts it) |
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What are some causes of insomnia? |
Noise, uncomfortable temperatures, stress, pain, diet, medications. Conditions such as Parkinson's, epilepsy, brain tumors, depression and anxiety. |
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What happens to someone whose rhythm is phase-delayed? |
Have trouble doing to sleep. |
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What happens to someone whose rhythm is phase-advanced? |
Falls asleep easily but has difficulty staying asleep (wakes up early) |
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What is sleep apnea? What can it result in? What is it caused by? |
Impaired ability to breath while sleeping. It can result in sleepiness during the day, impaired attention, depression and sometimes heart problems. Caused by genetics, hormones, old-age deterioration of brain mechanisms that control breathing, obesity |
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1. What is narcolepsy? 2. What is it caused by? 3. What are the four main symptoms? |
1. A condition characterized by frequent periods of sleepiness during the day. 2. It is caused by a lack of hypothalamic cells that produce and release orexin (which is important for maintaining wakefulness) 3. 1) Attack of sleepiness during the day 2) Occasional cataplexy 3) Sleep paralysis 4) Hypnagogic hallucinations |
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What is cataplexy? |
Attack of muscle weakness while the person remains awake. Often triggered by strong emotions such as anger or excitement. |
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What is sleep paralysis? |
Inability to move while falling asleep or waking up |
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What are hypnogogic hallucinations? |
Dream-like experiences that the person has trouble distinguishing from reality |
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What are factors of a typical hypnagogic hallucination? |
Intruder - feeling of a presence, fear; originates in midbrain Incubus - breathing problems and chest pressure; motor neuron activity Unusual bodily experiences - out of body, flying, floating; right angular gyrus |
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What is periodic limb movement disorder? |
Repeated involuntary movement of the legs and sometimes arms during sleep. Occur mostly during NREM sleep. |
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What is REM behaviour disorder? |
Movement during REM sleep, apparently acting out dreams. Inadequate inhibitory transmission (GABA mostly) may be responsible for it. |
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What are night terrors? |
Experiences of intense anxiety from which a person awakes screaming in terror. Occur during NREM sleep and are more common in children. |
