Chapter 9 Wakefulness and Sleep Flashcards
Activation-synthesis hypothesis
idea that a dream represents the brain’s effort to make sense of sparse and distorted information
Alpha waves
a steady series of brain waves at a frequency of 8 to 12 per second that are characteristic of relaxation
Basal forebrain
area anterior and dorsal to the hypothalamus; includes cell clusters that promote wakefulness and sleep
Brain death
condition with no sign of brain activity and no response to any stimulus
Clinico-anatomical hypothesis
idea that considers dreams as a type of thinking that occurs under unusual conditions
Coma
an extended period of unconsciousness with a low level of brain activity
Endogenous circadian rhythm
self-generated rhythm that lasts about a day. See also Circadian rhythms
Endogenous circannual rhythm
self-generated rhythm that lasts about a year
Insomnia
inadequate sleep
Jet lag
a disruption of circadian rhythms due to crossing time zones
K-complex
a sharp brain wave associated with temporary inhibition of neuronal firing
Limbic system
interlinked structures that form a border around the brainstem
Locus coeruleus
a small structure in the pons that emits bursts of impulses in response to meaningful events, especially those that produce emotional arousal
Minimally conscious state
condition of decreased brain activity with occasional, brief periods of purposeful actions and limited speech comprehension
Narcolepsy
a condition characterized by frequent periods of sleepiness during the day
Night terrors
experiences of intense anxiety from which a person awakens screaming in terror; more severe than a nightmare
Non-REM (NREM) sleep
stages of sleep other than REM
Orexin (hypocretin)
neurotransmitter that increases wakefulness and arousal
Pineal gland
an endocrine gland located just posterior to the thalamus that releases the hormone melatonin
Polysomnograph
a combination of EEG and eyemovement records
Pons
hindbrain structure that lies anterior and ventral to the medulla
Pontomesencephalon
part of the reticular formation that contributes to cortical arousal
Rapid eye movement (REM) sleep
sleep stage with rapid eye movements, high brain activity, and relaxation of the large muscles
REM behavior disorder
a condition in which people move around vigorously during REM sleep
Sleep apnea
impaired ability to breathe while sleeping
Sleep spindle
12 to 14 Hz brain waves in bursts that last at least half a second
Slow-wave sleep (SWS)
stages 3 and 4 of sleep, which are occupied by slow, large-amplitude brain waves
Suprachiasmatic nucleus (SCN)
part of the hypothalamus; provides the main control of the circadian rhythms for sleep and body temperature
Vegetative state
condition in which someone has decreased brain activity and alternates between wakefulness and sleep but shows only limited responsiveness, such as increased heart rate in response to a painful stimulus
Zeitgeber
stimulus that resets the circadian rhythm
Paradoxical sleep
sleep that is deep in some ways and light in others
Periodic limb movement disorder
a sleep disorder characterized by repeated involuntary movement of the legs and sometimes the arms
PGO waves
a distinctive pattern of high-amplitude electrical potentials that occur first in the pons, then in the lateral geniculate, and then in the occipital cortex
What do we know about the factors that initiate migration in birds?
change in light or dark pattern of the day.
What are endogenous circannual rhythms? Circadian?
endogenous-generated from within
cicannual-about a year
circadian-about a day
How consistent are circadian rhythms within individuals in a given environment? Between individuals?
circadian within a given environment-24 hours cycle
between individuals-different - some are morning people and others are evening.
how can circadian rhythms be demonstrated experimentally? What are some bodily and behavioural changes that occur in circadian rhythms?
mood changes-happier in am/mid afternoon, decline after
- hormonal fluctuations
- body temp
- eating
What is a Zeitgeber? What is the most effective Zeitgeber for land animals? For many marine animals?
Stimulus that resets your circadian rhythm.
light for land animals
tides for marine animals
How easily can humans adapt to a new cycle length? What are limits of adaptation?
not very adaptable
we like close to 24hr
is it easier to cross time zones going east or west?
going west is easier
going west we stay awake later nat night then awake later the next morning
harder to awaken early
What is the best way to rest the biological clock when working night shift
sleep in a very dark room during the day and work under very bright light at night.
What sorts of attempted interference with the biological clock were not effective?
blind/ deaf animals generate circadian rhythms but do slowly drift out of phase with the external world.
-circaidian rhythm remains surprisingly steady despite food//water deprivation, X-rays, tranquilizers, alcohol, anaesthesia, lack of oxygen, most kinds of brain damage or removal of endocrine organs.
What structures is the source of the circadian rhythms? What is its relationship tot he visual system?
part of the hypothalamus, called the suprachiasmatic nucleus (SCN) gets its name from its location just above the optic chasm
it provides the main control of the circadian rhythms. for sleep and body temp
What is the evidence that the suprachiasmatic nucleus (SCN) generates rhythms itself?
after damage to the “SCN” suprachiasmatic nucleus the body’s rhythms become erratic
-if the SCN neurons are detached from rest of brain or removed from the body and maintained in tissue culture they continue to produce a circadian rhythm of action potential
What happened when SCN tissue from hamsters with a mutant gene for 20 hour rhythm were transplanted into normal hamsters
the normal hamsters circadian rhythm became 20 hrs
What two genes, discovered in Drosophila (fruit flies), govern circadian rhythms? How do they work? How common is this mechanism in other animals?
period and timeless genes which produce preteens PER and TIM [ ] of these preteens fluctuate/oscillates over a day based on feedback interactions among several sets of neurons.
Proteins low then gradually increase during the day-reach high at night.
From what Pathway does the SCN get its input from the visual system? Are blind mice and mole rats able to use light to reset their SCN? By what non-retinal path may light influence circadian rhythms in people?
yes blind mice and mole rats are able to se their rhythms with light.
-retinohypothalamic path to the SCN comes from a special population of retinal ganglion cells that have their own photopigment called malanopsin unlike the ones found in rods and cones.
What is melatonin? From which gland is it secreted? When does increased secretion of melatonin occur?
SCN regulates waking and sleeping by controlling activity levels in other brain areas including the pineal gland -an endocrine gland just posterior to the thalamus.
Describe the usual behavioural correlate of alpha waves. What is their frequency?
Alpha waves are characteristic of relaxation to of all wakefulness frequency of 8-12 per second.
Describe the EEG in stage 1 sleep?
EEG dominated by irregular, jagged, low-voltage waves
-overall brain activity is less than in relaxed wakefulness but higher than other sleep stages
What are the EEG characteristics of stage 2 sleep?
sleep spindles and K-complexes consists of 12-14 Hz waves during a burst that lasts at least a half sec (result from oscillating interaction between cells of thalamus and cortex)
K complexes are sharp waves associated with temp inhibition of neuronal firing.
Which stages of sleep are classed as slow-wave sleep (SWS)
stage 3 and 4 together is slow wave sleep
highly synchronized by stage 4 sensory input from cerebral cortex is greatly reduced and a few remaining sources of input can synchronize many cells.
Why is REM sleep sometimes call paradoxical sleep? What are its characteristics?
very similar one is REM in humans paradoxical in animals
- rapid eye movement
- EEG shows irregular low voltage fast waves and indicates increased neuronal activity
- postural muscles more relaxed.
What is the typical duration of the sleep cycle? During which part of he night is REM predominant? During which part are stages 3 and 4 SWS predominant?
90 mins- stage 1=>stage 4=> REM then cycle back from 4 to 2 to REM
later into night/ morning REM predominates-
Early in nigh stages 3 and 4 predominate.
How good is the correlation between REM and dreaming?
not conclusive
What is the result of a cut through the midbrain on sled and waking cycles? Was this result due simply to loss of sensory input or to damage to a particular brain structure?
- animal enters a prolonged stat of sleep for the next few days
- even after weeks of recovery the wakeful periods are brief
- the cut isolated the brain from sensory stimuli that come up from the medulla and spinal cord
- but if each individual tract that enters the medulla and spinal cord the animal still has period of wakefulness
Describe the input, output and interconnections of pontomesencephalon. What is its relation to the reticular formation?
pontomescencephalon-one part of the reticulin formation that contributes to the cortical arousal
input-receives input from many sensory systems and generate spontaneous active of their own.
axons extend into the forebrain releasing acetylcholine and glutamate which exit cells in the hypothalamus, thalamus and basal forebrain
Give the location, neurotransmitter, and a major function for the locus coeruleus
a small structure in the pons
usually inactive, esp. during sleep but emits bursts of imposes in response to meaningful events esp those that produce emotional arousal.
anything that stimulates the locus coreleus strengthens storage of recent memories
What is the major neurotransmitter released by neurons in the basal forebrain that contribute to arousal?
acetylcholine
What is the neurotransmitter of the two paths from the hypothalamus that stimulate arousal? What is the implication of this for allergy treatments?
histamine-active during arousal and alertness
Orexin-maintains wakefulness
people get drowsy after taking antihistamines cause they block the histamine transmitter
What is a good indicator of how fast a person will get to sleep? explain this finding
GABA responsible for sleep
inhibits synaptic activity
What neurotransmitter is released by neurons of the basal forebrain that promotes sleep? What is a major sours of input to those neurons? How is that source released to body temp?
GABA
During sleep body temp and metabolic rate decreases slightly as does the neurons
Brain function in REM sleep.
What are PGO waves? Where are the recorded? What happens to PGO waves after a period of REM deprivation?
PGO waves-pons-geniculate-occipital
waves of neural acidity first in the ons, shortly afterward in the lateral geniculate nucleus of the thalamus and then into the occipital cortex
PGO waves increase greatly after REM deprivation during sleep stages 2-4 and even wakefulness
Which neurotransmitter is important for REM onset? For interruption or shortening of REM? What is one effect of the drug carbachol?
Stimulates acetylcholine receptors=> moves sleeper into REM sleep
acetylcholine
serotonin and norepinephrine interrupt REM sleep
List and describe the characteristics of the three categories of insomnia. what circadian rhythm disorders may cause each category?
insomnia-inadequate sleep
Phase-delayed rhythm-trouble falling asleep
Phase-advanced rhythm-falls asleep easily but awakens early
other causes-noise, comfortable temp stress pain
What are the pharmacological effects of most tranquilizers that are used as sleeping pills? How may sleeping pills contribute to insomnia>
They help people fall asleep but repeated use causes depended and they can’t sleep
Describe the symptoms of sleep apnea. What is one cause of sleep apnea
impaired ability to breathe while sleeping.
they have breathless periods of a minute or so from which they awaken gasping for breath
they have multiple brain areas that appear to have lost neurons
Genetics
What four symptoms are commonly associated with narcolepsy? What is the limey cause of narcolepsy?
cause lack of OREXIN
a condition characterized by frequent periods of sleepiness during the day
-gradual/ sudden attacks of sleepiness during the day
-occ cataplexy- an attack of muscle weakness while person remains awake
sleep paralysis and lastly hypnagogic hallucinations
Define cataplexy. What tends to trigger it? Define hypnagogic hallucinations.
An attack of muscle weakness while person remains awake.
often triggered by strong emotions such as anger or great excitement
Describe the symptoms of periodic limb movement disorder
characterized by repeated involuntary movement of the legs and sometime of the arms
some people mostly middle-aged and older, the legs kick once every 20-30 secs for mins/ hours mostly during NREM sleep
What are the symptoms and possible cause of REM behaviour disorder?
most people, the major postural muscles are relaxed and inactive during REM sleep
But people with REM behaviour disorder remove around vigorously during their REM periods-apparedntly action gout their dreams
They frequently dream about defending themselves and may punch , kick and leap about
Most common in older people especially oder meant with brain disorders such as Parkinsons.
How do night terrors differ from nightmares? During which type of sleep are night terrors most common?
night terrors more intense than a nightmare
they are experiences of intense anziet from which a person awakens creaming in terror
nightmare is just a bad dream
night terrors occur during NREM sleep and more common in children than adults
During which states does sleep taking occur? Sleepwalking ?
sleepwalking during stages 3 or 4 sleep earl int eh night and is usually not accompanied by dreaming
Describe the repair and restoration theory of sleep.
During sleep we rest our muscles, decrease metabolism rebuild preteens in the brain, reorganize synapses and strengthen memories
What are some effects of sleep deprivation in humans? In rats
trouble concentrating and become more vulnerable to illness. esp. mental illness
even one night of sleeplessness activated the immune system with more prolonged sleep deprivation people report dizziness, tremors, and hallucinations
Describe the evolutionary throe of the need for sleep. What evidence supports it?
Evolutionary-save energy druign “inefficient” times
What is the relationship between percentage of time in REM and total sleep time?
avg person spends about 1/2
of his/her life asleep and about one fifth of sleep in REM totalling about 600hrs of REM sleep per year
What kinds of behaviour changes occur if people are selectively deprived of REM sleep
impairs consolidation of learned motor skills
Describe the apparent relationship between learning and paradoxical sleep. For what kind of learning does paradoxical sleep seem to be most important? Deos NREM also contribute to strengthening of memories
sleep enhances memories
learn something then take a nap or go to sleep memory often improves beyond what it was before sleep
How may REM contribute to oxygen supply for the cornea?
shaking of eyes lead to increased oxygen to the corneas of the eyes
State the activation-synthesis hypothesis. What evidence supports this hypothesis? How widely accepted its ti?
a dream represent the brain efforts to make sense of sparse and distorted information. Dreams begin with periodic burst of spontaneous acidity in the ons (the PGO waves previously described that activate parts of the cortex but not others
Dreaming about falling-cause body senses we are prone and also dreaming that you can’t move-postural muscles are virtually paralyzed
not widely accepted
Summarize the basic ideas of clinic-anatomical hypothesis
like activation-synthesis hypothesis the is theory emphasizes that dreams begin with arousing stimuli combined with recent memories and any infer the brain receives from the senses
but emphasis is less on the PONS; PGO waves or REM sleep
It regards dreams as thinking taking place under unusual circumstances
What three cortical areas are suppressed during dreams? What would the effect of these suppressions?
little info
sense organs, the primary vusal and auditory areas of the cortex so there brain areas are free to generate images without constraints or interference.
Also the primary motor cortex is suppressed as are the motor neurons of the spinal cord so arousal cannot lead to action
activity is suppressed in the prefrontal cortex, which is impt for working memory therefore we forget most dreams when we wake up
What two cortical areas are active during dreams?What would they contribute to dreams?
- activity is hight in the inferior (lower) part of the parietal cortex an area impt for visuospatial perception
- Fairly high activity also in area s of the visual cortex outside VI areas impt for visual imagery and activity increase in hypothalamus, amygdala and other ares impt for emotions and motivations.
