Wakefulness and Sleep Flashcards
Name some internal mechanism that operate on a 24 hour cycle.
Sleep, frequency of eating and drinking, body temperature, secretion of hormones, urination and sensitivity to drugs.
Explain circannual rhythms.
Internal mechanisms that operate on an annual or yearly cycle, like birds migratory patterns, or animals storing food for the winter.
What is the purpose of the circadian rhythm?
To keep our internal workings in phase with the outside world.
Explain the concept of zeitgeber.
Meaning time-giver, referring to the stimulus that resets the circadian rhythm.
Give some examples of zeitgeber.
Sunlight, tides, exercise, meals, and temperature of the environment.
Give three examples of the effect of using something other than sunlight as a zeitgeber.
Depression, irritability, and impaired job performance.
What is jet lag?
The disruption of the circadian rhythms due to crossing time zones.
Travelling west phase-____ our circadian rhythms.
Delays.
Travelling east phase-____ our circadian rhythms.
Advances.
How do people adjust best to night work?
If they sleep in a very dark room during the day and work under bright lights.
Give three mechanisms of the circadian rhythms.
The suprachiasmatic nucleus, genes that produce certain proteins, and melatonin levels.
What is the suprachiasmatic nucleus?
The main control centre of the circadian rhythms of sleep and temperature.
Where is the suprachiasmatic nucleus (SCN) located?
Above the optic chiasm and part of the hypothalamus.
What does damage to the SCN result in?
Less consistent body rhythms that are no longer synchronised to environmental pattern of light and dark.
How is the SCN reset?
Via a small branch of the optic nerve called the retinohypothalamic path, travelling directly from the retina to the SCN.
What does the retinohypothalamic path consist of?
Specialised ganglion cells that respond directly to light and require no input from rods or cones.
Name the two genes that are responsible for generating the circadian rhythm.
Period and timeless.
What proteins do period genes produce?
PER
What proteins do timeless genes produce?
TIM
What do mutations of the PER gene result in?
Odd circadian rhythms or decreased alertness if deprived of a good night’s sleep.
What do PER and TIM proteins increase the activity of?
Certain neurons in the SCN that regulate sleep and waking.
What does the SCN regulate?
The pineal gland.
Where is the pineal gland located?
Posterior to the thalamus.
What does the pineal gland secrete?
Melatonin.
What is sleep?
A state that the brain actively produces, characterised by a moderate decrease in brain activity and decreased response to stimuli.
Name some states that sleep differs from.
Coma, vegetative state, minimally conscious state, and brain death.
Explain stage 1 sleep.
Alpha waves are present when one begins a state of relaxation, brain activity begins to decline, and the EEG is dominated by irregular, jagged, and low voltage waves.
What waves are present in stage 2 sleep?
Sleep spindles and K-complex.
Describe a sleep spindle.
12-14 Hz waves during a burst that lasts at least half a second.
Describe a K-complex.
A sharp wave associated with temporary inhibition or neuronal firing.
What do stage 3 and 4 sleep constitute?
Slow wave sleep.
What occurs in stage 3 and 4 sleep? (4)
Slowing of heart rate, breathing rate and brain activity, as well as highly synchronised neuronal activity.
What do EEG readings show during stage 3 and 4 sleep?
Slow, large amplitude waves.
Give another name for REM sleep.
Paradoxical.
Explain deep sleep.
Postural muscles of the body are more relaxed than other stages.
Explain light sleep.
EEG waves are irregular, low-voltage and fast.
What does NREM refer to?
Stages other than REM sleep.
How long does it take fore a person to cycle back trough the stages of sleep?
An hour.
What is the sequence of sleep stages when a person cycles back through them?
4, 3, 2, REM.
How long does each complete sleep cycle last?
90 minutes.
What is the reticular formation?
Part of the midbrain that extends from the medulla to the forebrain.
What is the reticular formation responsible for?
Arousal.
What is the pontomesencephalon?
Part of the midbrain that contributes to cortical arousal.
Where do the pontomescencephalon’s axons extend? (3)
The hypothalamus, thalamus and basal ganglia.
What do the pontomescencephalon’s axons produce?
Acetylcholine and glutamate, which produce excitatory effects in widespread areas of the cortex.
What is the locus coeruleus?
A small structure in the pons whose axons release norepinephrine.
What does the locus coeruleus increase?
Wakefulness.
When is the locus coeruleus dormant?
When asleep.
What does the hypothalamus produce that enables anti-histamines to cause sleepiness?
Histamines, that produce widespread excitatory effects through the brain.
What does orexin do?
Enhances wakefulness, and is important for staying awake.
What is acetylcholine?
An excitatory neurotransmitter the increases arousal.
When is acetylcholine released?
During REM and wakefulness.
What is GABA?
An inhibitory neurotransmitter.
How many neurons rely on GABA in the SCN?
20’000
Explain lucid dreaming.
Dreaming but being aware of being asleep and dreaming.
How do sleepwalkers exist?
They are awake in one part of the brain and asleep in others.
What causes an inability to move upon waking?
The pons remaining in REM while the rest of the brain is awake.
Where does activity increase in the brain during REM? (2)
In the pons and limbic system.
Where does activity decrease in the brain during REM? (3)
In the primary visual cortex, the motor cortex, and the dorsolateral prefrontal cortex.
Explain PGO waves.
High-amplitude electrical potentials that pass through the pons, lateral geniculate and occipital lobe.
What is each PGO waves synchronised with?
An eye movement in REM.
Name some factors causing sleep disorders.
Noise, stress, pain, diet and medication.
Name some disorders causing sleep disturbance.
Epilepsy, Parkinson’s, depression, anxiety, and more.
Dependence on what two things an result in insomnia?
Sleeping pills or alcohol.
Describe sleep apnea.
A sleep disorder characterised by the inability to breathe while sleeping.
What are the consequences of sleep apnea? (4)
Sleepiness during the day, impaired attention, depression and sometimes heart problems.
Name some causes of sleep apnea.
Genetics, hormones, old age, obesity, and deterioration of the brain mechanisms that control breathing.
Describe narcolepsy.
A sleep disorder characterised by frequent periods of sleepiness.
Explain occasional cataplexy.
Muscle weakness triggered by strong emotions.
Describe sleep paralysis.
Inability to move while falling asleep or waking up.
What are hypnagogic hallucinations?
Dreamlike experiences.
What is periodic limb movement disorder?
The repeated involuntary movement of the legs and sometimes the arms while sleeping.
How often does leg movement occur in periodic limb movement disorder?
Once every 20-30 seconds for minutes to hours.
When does periodic limb movement generally occur?
During NREM.
What is REM behaviour disorder?
Associated with vigorous movement during REM sleep, usually associated with acting out dreams.
What may be responsible for REM behaviour disorder?
Inadequate GABA and other inhibitory neurotransmitters.
What are night terrors?
Experiences of intense anxiety from which a person awakens screaming in terror.
When do night terrors occur?
NREM sleep.
When does sleepwalking occur?
Stage 3 or 4 sleep.
What is sleepwalking not associated with?
Dreaming.
Name some functions of sleep.
Resting muscles, decreasing metabolism, performing cellular maintenance in neurons, reorganising synapses, strengthening memories, and conserving energy.
What happens to body temperature during hibernation?
It decreases until it is only slightly above that of the environment.
What happens to heart rate and brain activity during hibernation?
They drop to almost nothing.
What are the effects of hibernation on neurons? (2)
The cell bodies shrink, and dendrites lose branches.
What do animals sleep habits depend on? (3)
Whether they are predatory or prey, how many hours they spend each day devoted to looking for food, and safety from predators while they sleep.
How does sleep affect memory?
It enhances learning an strengthens memory.
What suggests that the brain replays its daily experiences during sleep?
Patterns of activity in the hippocampus during learning are similar to those shown in sleep.
What happens to synapses during sleep?
The brain strengthens some and weakens others.
How much of our lives do we spend asleep?
1/3.
How much of our lives do we spend in REM?
1/5.
In what animals is REM most common?
Birds and mammals.
What is percentage of REM sleep positively correlated with?
Total amount of sleep in most animals.
What did Maurice believe REM’s function was?
To provide sufficient oxygen to the corneas.
Name two things that may occur during REM.
The brain may discard useless connections, and learned motor skills may be consolidated.
Name the two biological theories of dreaming.
Activation-synthesis hypothesis, and the clinical-anatomical hypothesis.
Explain the activation-synthesis hypothesis.
Dreams begin with spontaneous activity in the pons, which activates many parts of the cortex, which then synthesises a story from the pattern of activation.
Explain the clinical-anatomical hypothesis.
Suggests that dreams are similar to thinking, and begin as arousing stimuli within the brain, which is combined with recent memories and information from the senses.
What accounts for the emotional and motivations content of dreams?
Activity in the hypothalamus and amygdala.
What account for visual-spatial perception in dreams?
The inferior parietal cortex.
What creates the hallucinatory perceptions?
Lack of sensory input from V1 and no criticism from the prefrontal cortex.
Explain endogenous circannual rhythm.
A rhythm generated by an animal that prepares them for seasonal changes.
How much does body temperature fluctuate over the course of a day.
From 36.7 during the night to 37.2 during the afternoon.
What is critical for resetting the circadian rhythm?
Light.
What is an important zeitgeber for marine animals?
The tides.
What is an ineffective zeitgeber?
Social stimuli.
How many blind people report sleep problems?
Over half.
A disruption of circadian rhythms due to crossing time zones is known as:
Jet lag.
Which artificial light is best for resetting the circadian rhythm?
Short-wavelength bluish light.
What is the main driver of rhythms for sleep and body temperature?
The suprachiasmatic nucleus (SCN).
What is the suprachiasmatic nucleus a part of?
The hypothalamus.
What alters the SCN’s rhythm?
The retinohypothalamic path.
What photopigment do ganglion cells in the retinohypothalamic path use?
Melanopsin.
The SCN regulates waking and sleeping by controlling activity in the:
Pineal gland.
Where is the pineal gland located?
Posterior to the thalamus.
What hormone does the pineal gland release?
Melatonin.
What does melatonin influence?
Circadian and circannual rhythms.
During the day, when does melatonin secretion increase?
Roughly two to three hours before bedtime.
Explain coma.
An extended period of unconsciousness caused by head trauma, stroke or disease.
What is coma characterised by?
A low level of brain activity and little or no response to stimuli.
Explain vegetative state.
The person alternates between periods of sleep and moderate arousal, but shows no awareness of surroundings and no purposeful behaviour.
What does painful stimuli result in during vegetative state?
The autonomic responses of increased heart rate, breathing and sweating.
Explain a minimally conscious state.
One stage higher than vegetative state, with occasional, brief periods of purposeful actions and a limited amount of speech comprehension.
Explain brain death.
A condition with no sign of brain activity and no response to any stimulus.
What is a polysomnograph?
A combination of EEG and eye-movement records.
What does an EEG show during stage 1 sleep?
Irregular, jagged, low-voltage waves.
What are characteristic of stage 2 sleep?
K-complexes and sleep spindles.
What do sleep spindles consist of?
Consists of 12-14Hz waves during a burst that lasts at least half a second.
What do sleep spindles result from?
Oscillating interactions between cells in the thalamus and the cortex.
What is a K-complex?
A sharp wave associated with temporary inhibition of neuronal firing.
What occurs during stage 3 and 4 sleep?
Decreases in heart rate, breathing rate, and brain activity.
Which waves become more common in stage 3 and 4 sleep?
Slow, large-amplitude waves.
Explain slow-wave sleep (SWS).
A combination of stage 3 and 4 sleep.
What do slow waves indicate?
Neuronal activity is highly synchronised.
Who named paradoxical sleep?
Jouvet.
Who named rapid eye movement (REM) sleep?
Kleitman and Aserinsky.
What does paradoxical sleep refer to?
REM sleep in nonhuman species that lack eye movements.
What does the EEG show during REM sleep?
Irregular, low-voltage fast waves that indicate increased neuronal activity.
What is the reticular formation?
A structure that extends from the medulla into the forebrain.
What is the pontomesencephalon?
A part of the reticular formation that contributes to cortical arousal.
What does the pontomesencephalon do?
Maintains arousal during wakefulness and increases it in response to new or challenging tasks.
What is the locus coerulus?
A small structure in the pons, which is usually inactive, especially during sleep.
What does the locus coerulus do?
Emits burst of impulses in response to meaningful events that produce emotional arousal.
How does the locus coerulus enhance memory and attention?
It releases norepinephrine throughout the cortex, increasing the activity of the most activity neurons, and decreasing the activity of less neurons.
What is histamine?
An excitatory neurotransmitter which enhances arousal and alertness throughout the brain.
Which brain areas release orexin/hypocretin?
The lateral and posterior nuclei of the hypothalamus.
What is orexin?
A peptide neurotransmitter necessary for staying awake.
When is acetylcholine released?
During wakefulness and REM sleep, but not during slow-wave sleep.
Where is the basal forebrain located?
Just anterior and dorsal to the hypothalamus.
What happens to neurons in the thalamus during sleep?
They become hyperpolarised, decreasing their readiness to respond to stimuli and decreasing the information they transmit to the cortex, and when they do fire, it is often in synchronous bursts.
Which neurotransmitters does the pontomesencephalon release?
Acetylcholine and glutamate.
What effects do acetylcholine and glutamate have?
They increase cortical arousal.
Which neurotransmitter does the locus coerulus release?
Norepinephrine.
Which neurotransmitter does the basal forebrain’s excitatory cells release?
Acetylcholine.
Which neurotransmitter does the basal forebrain’s inhibitory cells release?
GABA.
Which neurotransmitters does the hypothalamus release?
Orexin and histamine.
Which neurotransmitter does the dorsal raphe and pons release?
Serotonin.
What are the effects of serotonin?
Interrupts REM sleep.
What are the effects of orexin?
Maintains wakefulness.
What are the effects of histamine?
Increases arousal.
What are the effects of GABA?
Inhibits thalamus and cortex.
What are the effects of acetylcholine?
Excites the thalamus and cortex, increasing learning and attention, and shifts sleep from NREM to REM.
Which brain areas are awake during sleepwalking?
The motor cortex and other areas.
Which brain areas inhibit the movement of large muscles?
The pons and medulla.
Where does activity increase during REM?
The pons, parietal and temporal cortex, and limbic system.
Where does activity decrease during REM?
The primary visual cortex, the motor cortex and the dorsolateral prefrontal cortex.
What does PGO stand for?
Pons-geniculate-occipital.
What are PGO waves associated with?
REM sleep.
What are PGO waves?
High-amplitude electrical potentials.
Which neurotransmitters does REM sleep depend on?
Acetylcholine and serotonin.
Which neurotransmitters interrupt REM sleep?
Norepinephrine and serotonin.
Name some causes of insomnia.
Noise, uncomfortable temperatures, stress, pain, diet, medications, epilepsy, Parkinson’s, brain tumours, depression, anxiety, and neurological or psychiatric conditions.
What can frequent use of sleeping pills cause?
Insomnia, as frequent use causes dependence and an inability to sleep without the pills.
Explain sleep apnea.
Impaired ability to breathe while sleeping.
What are the effects of sleep apnea on the brain?
Deficiencies in learning, reasoning, attention and impulse control.
What are some causes of sleep apnea?
Genetics, hormones, obesity and old-age deteriorations of the brain mechanisms that regulate breathing.
Explain narcolepsy.
A condition characterised by frequent periods of sleepiness during the day.
Name the four main symptoms of narcolepsy.
Attacks of sleepiness during the day, occasional cataplexy, sleep paralysis, and hypnagogic hallucinations.
Explain occasional cataplexy.
An attack of muscle weakness while the person remains awake.
How can cataplexy be triggered?
Strong emotions.
Explain sleep paralysis.
An inability to move while falling asleep or waking up.
What are hypnagogic hallucinations?
Dreamlike experiences that the person has trouble distinguishing from reality, often occurring at the onset o sleep.
What neurotranmitter causes narcolepsy?
Orexin.
What cells do people with narcolepsy lack?
The hypothalmic cells that produce and release orexin.
What is periodic limb movement disorder?
A sleep disorder characterised by repeated involuntary movement of the legs and sometimes arms during sleep.
What age people does periodic limb movement disorder usually affect?
Middle-aged and old people.
Explain REM behaviour disorder.
People move around vigorously during REM sleep, and may act out their dreams.
What may be responsible for REM behaviour disorder?
Inadequate inhibitory transmission.
What are night terrors?
Experiences of intense anxiety from which a person awakes screaming in terror
Name some additional sleep difficulties that sleepwalkers may experience.
Chronic snoring, disordered sleep breathing, bed-wetting, and night terrors.
At what time during the night is sleepwalking most common?
During slow-wave sleep early in the night and is not usually accompanied by dreaming.
What are some of the functions of sleep?
Resting our muscles, decreasing metabolism, reorganise synapses, strengthen memories, and perform cellular maintenance of neurons.
What is sleep’s original function?
To save energy.
What happens to body temperature during sleep?
It decreases to just above that of the environment.
What happens to dendrites during and after hibernation?
They lose nearly 1/4 of their branches, but later replace them as body temperature increases.
How does sleep affect memory?
It improves it, and it helps people to reanalyse their memories.
What happens to the hippocampus during sleep?
Patterns that occur during sleep resembled those that occurred during learning, except that they were more rapid during sleep.
What evidence suggests that the brain replays its daily experiences during sleep?
Hippocampal activity during sleep.
What information does the brain replay during sleep?
Less common experiences more than common ones, and the brain replays its experience backwards just as often as forwards.
What do sleep spindles correlate with?
Learning, as they increase in number after new learning.
How much time do humans spend in REM?
1/5 of their lives.
How many hours does the average person spend in REM yearly?
600 hours.
What does depriving people of NREM sleep cause?
Impaired verbal learning,
What does depriving people of REM sleep cause?
Impaired consolidation of learned motor skills.
What did Maurice believe about REM sleep?
It purpose is to shake the eyes back and forth to get sufficient oxygen to the eyes.
What evidence support’s Maurice’s theory?
Corneas get their oxygen directly from the surrounding air, and deteriorate slightly overnight, though they do get some oxygen from the fluid behind them, but without movement it becomes stagnant.
What evidence contradicts Maurice’s theory?
Many people take antidepressants that restrict REM sleep, and are not known to suffer damage to the cornea.
What are dreams, according to the activation-synthesis hypothesis?
A dream represents the brain’s effort to make sense of sparse and distorted information - spontaneous activity in the pons via PGO waves, which the cortex organises this input and others into a story.
What supports the activation-synthesis theory?
Sensory stimuli is occasionally incorporated into dreams.
Name some criticisms of activation-synthesis theory.
The predictions are vague - why don’t we always dream of falling, flying or being unable to move if those are the external sensations the body recognises.
Explain the clinico-anatomical hypothesis.
Dreams begin with arousing stimuli that are generated within the brain combined with recent memories and any information the brain is receiving from the senses.
What does the clinico-anatomical hypothesis regard dreams as?
Thinking under unusual conditions.
Name the conditions of the clinico-anatomical hypothesis.
The brain gets little information from the sense organs so the primary visual and auditory areas of the cortex have lower than usual levels of activity, meaning that other brain areas are free to generate images without constraint.
What does suppression of the primary motor cortex and motor neurons lead to?
Arousal cannot lead to action.
What does suppression of the prefrontal cortex result in?
We forget most dreams after we awaken, as the prefrontal cortex is important for working memory, or memory of recent events.
During dreaming, where is activity high? (2)
The inferior parietal cortex, an area important for visuospatial perception, hypothalamus, amygdala, and areas of the visual cortex outside V1.
What does damage to the inferior parietal cortex result in?
Problems binding body sensations with vision, and no dreams.
What is the visual cortex important for in dreams?
The visual imagery that accompanies most dreams.
What is the basic mechanism behind the clinco-anatomical hypothesis?
Internal or external stimuli activates parts of the parietal, occipital and temporal cortex, which develops into a hallucinatory perception with no input from V1 to override it.
