Ch. 8 Wakefulness and Sleep
REM sleep depends on both ___ and ___ activity for its onset and continuation
serotonin and acetylcholine stimulation of acetylcholine synapses quickly moves a sleeper into REM and serotonin interrupts or shortens REM sleep norepinephrine from the LC also blocks REM
Zeitgeber
Stimulus that is necessary for resetting the circadian rhythm. sunlight, tides, exercise, meals, arousal of any kind, temperature of environment, depression, irritability, and impaired job performance
phase-delay
What happens to our circadian rhythms when we travel west, as we stay awake late and awaken the next day already partly adjusted to the new schedule
PGO (pons-geniculate-occipital) waves
a distinctive pattern of high-amplitude electrical potentials associated with REM sleep. the waves are detected first in the pons, shortly after in the lateral geniculate nucleus of the thalamus, and then in the occipital cortex
sleep is a state that the brain actively produces, characterized by..
a moderate decrease in brain activity and a decreased response to stimuli
pontomesencephalon
a part of the midbrain that contributes to cortical arousal stimulation of the pontomesencephalon awakens a sleeping individual or increases alertness in someone already awake by releasing acetylcholine, glutamate, or dopamine
orexin
a peptide neurotransmitter released in a pathway from the lateral nucleus of the hypothalamus highly responsible for the ability to stay awake- stimulates acetylcholine-releasing cells in the forebrain and brain stem to increase wakefulness and arousal
free-running rhythm
a rhythm that occurs when no stimuli reset or alter it
locus coeruleus (LC)
a structure in the pons that emits impulses, releasing norepinephrine in response to meaningful events, especially those that produce emotional arousal. it is also important for storing information
reticular formation
a structure that extends from the medulla into the forebrain; controls motor areas of the spinal cord and selectively increases arousal and attention in various forebrain areas lesions through the reticular formation decrease arousal
night terrors
an abrupt, anxious awakening from NRM sleep, this disorder is more common in children than adults
stage 2 sleep
characterized by sleep spindles (12-14 Hz brain waves in bursts that last at least half a second) and K-complexes (a sharp brain wave followed by a smaller, positive wave, associated with temporary inhibition of neuronal firing)
prostaglandins
chemicals produced by the immune system that promote sleep by stimulating a cluster of neurons that inhibit the hypothalamic cells that increase arousal
recent studies have indicated that repeated adjustments of the circadian rhythm can
damage the hippocampus and cause memory loss
getting to sleep
decreasing the temperature of the brain and body core and decreasing stimulation are important steps in reducing arousal certain basal forebrain cells release GABA and promote sleepiness. the sleep-related basal forebrain cells get their input from the anterior and preoptic areas of the hypothalamus (areas important for temperature regulation)
animals generate endogenous 24 hour cycles of wakefulness and sleep. it also regulates the frequency of...
eating and drinking, body temperature, secretion of hormones, urination, and sensitivity to drugs
functions of sleep
energy conservation decrease in body temp of about 1-2 Celsius degrees in mammals decrease in muscle activity restoration of the brain and body proteins rebuilt in the brain energy supplies replenished memory consolidation performance on a newly learned task is often better the next day if adequate sleep is achieved during the night. Increased brain activity occurs in the area of the brain activated by a newly learned task while one is asleep. Patterns of activity in the hippocampus during learning were similar to those shown during sleep, suggesting that the brain replays its daily experiences during sleep the brain strengthens some synapses and weakens others during sleep sleep spindles increase in number after new learning, correlated with nonverbal IQ
alpha waves
have a frequency of about 8-12 brain waves per second; these waves are typical of a relaxed state of consciousness
caffeine
increases arousal by inhibiting adenosine
sleep talking
may occur during either REM or NREM sleep, it is common and harmless
brain death
no sign of brain activity and no response to any stimulus
minimally conscious state
one stage higher than a vegetative state marked by occasional brief periods of purposeful action and limited speech comprehension
the 3 categories of insomnia
onset insomnia: trouble falling asleep maintenance insomnia: waking up frequently during the night after falling asleep termination insomnia: waking up too early and cannot go back to sleep
in flies, the SCN regulates the circadian rhythms through the regulation of 2 genes, ___ and ___
period (per) and timeless (tim) early in the morning the concentration of both Per and Tim are low and they increase during the day in the evening protein concentrations are high and result in sleepiness. During the night the genes stop producing the proteins
Slow-wave sleep (SWS)
stages 3 and 4 sleep sleep occupied by slow, large amplitude brain waves
in a study using hamsters housed living under constant light...
the SCN (suprachiasmatic nucleus) in the right hemisphere got out of phase with the SCN in the left hemisphere causing 2 periods of wakefulness and 2 periods of sleep
non-REM (NREM) sleep
the stages of sleep other than REM
clinico-anatomical hypothesis
-places less emphasis on the pons, PGO waves, or even REM sleep -Suggests that dreams are similar to thinking, just under unusual circumstances
sexsomnia
A condition similar to sleepwalking, engaging in sexual behavior while asleep. Can pose a threat to romances and marriages.
jet lag
A disruption of our biological rhythms due to crossing time zones.
when Per and Tim levels are high, they interact with a protein called ___ to induce sleepiness
Clock
REM behavior disorder
Disorder where people move around vigorously during their REM periods apparently acting out their dreams. Likely due to the inability of the pons to inhibit spinal motor neurons.
.Either internal or external stimulation activates parts of the parietal, occipital, and temporal cortex;
No visual information overrides the stimulation and no criticism of the prefrontal cortex censors it, so it develops into hallucinatory perceptions. Similar to the activation synthesis hypothesis in that dreams begin with arousing stimuli that are generated within the brain. Stimulation is combined with recent memories and any information the brain is receiving from the senses. Since the brain is getting little information from the sense organs, images are generated without constraints or interference. Arousal can not lead to action as the primary motor cortex and the motor neurons of the spinal cord are suppressed. Activity in the prefrontal cortex is suppressed, which impairs working memory during dreaming. Activity is high in the hypothalamus and amygdala, which accounts for the emotional and motivational content of dreams
functions of REM sleep
Species with the most total sleep also have the highest percentage of REM sleep. Human infants spend more time in REM sleep and get more total sleep than adults. Adults who get the most sleep have the most REM sleep and adults who get the least sleep get the least amount of REM. REM sleep deprivation leads to increased attempts at REM sleep. REM sleep has been implicated in memory storage and as a way of getting oxygen to the corneas. During REM: The brain may discard useless connections. Learned motor skills may be consolidated.
Mechanisms of the circadian rhythms include the following:
The Suprachiasmatic nucleus genes that produce certain proteins melatonin levels
sleep cycle
When people fall asleep. they enter stage 1 followed by stages 2, 3, and 4, in that order About 60-90 min after going to sleep they cycle back from stage 4 through stages 3, 2. and then enter rapid eye movement (REM) sleep. After entering REM sleep, the sleep cycle sequence repeats with each complete cycle lasting 90 minutes. Early in the night, stages 3 and 4 predominate but toward morning stage 4 grows shorter and REM grows longer. REM sleep is associated with dreaming, but dreams can happen in non-REM sleep.
insomnia
a sleep disorder associated with inadequate sleep caused by a number of factors including noise, stress, pain medication can also be the result of disorders such as epilepsy, Parkinson's disease, depression, anxiety or other psychiatric conditions dependence on sleeping pills and shifts in the circadian rhythms biological rhythm abnormalities (ex: trying to sleep while body temp rises)
polysomnograph
a combination of EEG and eye-movement records
Narcolepsy
a disorder characterized by frequent unexpected periods of sleepiness during the day symtoms include: sudden attacks of sleepiness, occasional cataplexy sleep paralysis (inability to move while asleep), and hypnogogic hallucination (dream-like experiences occurring at the onset of sleep) each of the symptoms of narcolepsy is interpreted as REM sleep intruding into wakefulness a deficiency in orexin is the possible explanation for narcolepsy narcolepsy is currently treated with stimulant drugs such as pemoline or methylphenidate (Ritalin) to enhance dopamine and norepinephrine activity
rapid eye movement (REM) sleep
a period of sleep characterized by repeated eye movements and fast, low-voltage brain waves plus breathing and heart rates similar to stage 1 sleep paradoxical sleep is synonymous with REM sleep except that many animal species lack eye movments
stage 1 sleep
a stage of light sleep noted by the presence of irregular, jagged, low-voltage waves, brain activity starts to decrease
basal forebrain
an area just anterior and dorsal to the hypothalamus whose axons release acetylcholine and GABA; promotes wakefulness and sleep damage to the basal forebrain leads to decreased arousal by releasing histamine and orexin or hypocretin (neurotransmitters that increases wakefulness and arousal) antihistamine drugs produce drowsiness if they cross the blood-brain barrier oxrexin stimulates acetylcholine-releasing cells in the basal forebrain and brain
The SCS regulates the Pineal gland,
an endocrine gland located just posterior to the thalamus that releases the hormone melatonin
adenosine
an important inhibitor of the basal forebrain arousal system
endogenous circannual rhythm
an internal calendar which prepares a species for annual seasonal changes; self-generated rhythm that lasts about a year
coma
extended period of unconsciousness caused by head trauma, stroke, or disease characterized by low brain activity that remains fairly steady.- person shows little response to stimuli
melatonin
hormone that influences both circadian and circannual rhythms melatonin release usually starts 2-3 hours before bedtime melatonin stimulates receptors in the SCN to reset the biological clock melatonin taken in the afternoon can phase-advance the internal clock and can be used as a sleep aid
sleep apnea
inability to breathe during sleep for a prolonged period of time obesity is a common cause of this disorder, particularly in men it is possible cause of sudden infant death syndrome Consequences include: sleepiness during the day, impaired attention, depression, and sometimes heart problems. • Cognitive impairment may result from loss of neurons due to insufficient oxygen levels. • Causes include, genetics, hormones, old age, and deterioration of the brain mechanisms that control breathing and obesity
endogenous circadian rhythm
internal rhythms which last about a day (wakefulness and sleepiness). in humans; the circadian rythm has a self-generated duration of about 24.4 hours cycles can differ between people and lead to different patterns of wakefulness and alertness the purpose of the circadian rhythm is to keep our internal workings in phase with the outside world human circadian clock generates a rhythm slightly longer than 24 hours when it has no external cue to set it resetting our circadian rhythms is sometimes necessary changes as a function of age: sleep patterns from childhood to late adulthood
Suprachiasmatic nucleus (SCN)
nucleus located above the optic chiasm in the hypothalamus controls the rhythms for sleep and temperature. the neurons of the SCN generate impulses that follow a circadian rhythm SCN generates circadian rhythms in a genetically controlled, unlearned manner single cell extracted from the SCN and raised in tissue culture continues to produce action potential in a rhythmic pattern various cells communicate with each other to sharpen the circadian rhythm the cells respond directly to light and do not require any input from the rods or cones
vegetative state
person alternates between periods of sleep and moderate arousal but no awareness of surrounding
the ___ triggers the onset of REM sleep
pons the pons also relays messages to inhibit motor neurons in the spinal cord during REM sleep
electroencephalograph (EEG)
records gross electrical potentials in an area of the brain through electrodes attached to the scalp
periodic limb movement disorder
repeated involuntary movements of the legs and arms that can cause insomnia the limb movements occur mostly during NREM sleep this disorder is often treated with tranquilizers
The SCN is reset by the..
retinohypothalamic path that extends from the retina to the SCN the retinal ganglion cells that reset the SCN are different from the ganglion cells that contribute to vision and have their own photopigment called melanospin. these ganglion cells near the nose responds light directly without inputs from rods and cones
light travels directly from the retina to the SCN to reset the SCN via the
retinopothalamic path- a special population of ganglion cells that have their own photopigment called melanopsin
paradoxical sleep
sleep that is deep in some ways and light in others discovered in cats where the brain is very active but muscles are completely relaxed includes REM
activation-synthesis hypothesis
suggests dreams begin with spontaneous activity in the pons, which activates many parts of the cortex so the brain creates a story to make sense of all this activity random nerve cell firings + cortical interpretation of random firings the cortex synthesizes a story from the pattern of activation normal sensory information cannot compete with the self-generated stimulation and hallucinations result inout from the pons activates the amygdala giving the dream an emotional content because much of the prefrontal cortex is inactive during PGO waves, memory of dreams is weak; also explains sudden sense changes that occur in dreams
sleepwalking
usually occurs during stages 3 or 4 early in the night and is more common in children than adults
when Per and Tim levels are low, they result in
wakefulness light during the night inactivates the Tim protein and decreases sleepiness
phase advance
what happens to our circadian rhythms when we travel east, as we tend to sleep and awaken earlier than usual
