Chapter 9- Wakefulness and Sleep Flashcards
True or False?The body generates its own rhythm of wakefulness and sleep?
True
What is an Endogenous circannual rhythm?
A Rhythm that prepares an animal for season changes.
Ex. Animals storing food for the winter or migratory birds
What do Endogenous circannual rhythm operate on?
internal mechanisms on a yearly patterns
What is an Endogenous circadian rhythm?
Rhythms that last about a day.
True or False? Endogenous circadian rhythm only controls our wakefulness and sleep patters?
False. It also regulates the functions of eating, drinking, body temperature, secretion of hormones, urination and sensitivity to drugs
True or false? Every human has the exact same ECR cycle?
False. Cycles can differ between people and lead to different patterns of alertness
The human circadian clock generates a rhythm slightly..
longer than 24 hours
True or False. Sometimes the ECR needs to be reset?
True.
What is a Free-running rhythm?
a rhythm that occurs when no stimuli reset or alter it
What is a Zeitgeber?
The stimulus that resets the circadian rhythm “ time giver” . Light is the dominant one for land animals, others can include exercise, noise, meals, temperature of environment
What are some symptoms of using something other than sunlight as a zeitgeber?
Depression, irritability and impaired job performance
Circadian rhythms in blind people..
Still generate, just more slowly
What is jet lag?
A disruption of circadian rhythms due to crossing time zones. It is caused when there is a mismatch between our internal circadian clock and external time
When we travel east to west it results in…
Phase Delay, gaining time..it’s easier for us to adjust to
When we travel west to east it results in…
Phase advance, losing time
What happens to circadian rhythms when there is no environmental cue indicating the time of day?
They remain consistent
What is the Suprachiasmatic Nucleus ( SCN)?
Part of the hypothalamus; provides the main control of the circadian rhythms for sleep and body temperature .
Generates rhythms in genetically controlled, unlearned manner. Various cells communicate with each other to sharpen the circadian rhythm
Where is the SCN located?
above the optic chiasm
Damage to the SCN results in…
less consistent body rhythms that are no longer synchronized to environmental patterns of light and dark
A Mutation in one gene causes hamsters’ SCN to…
produce 20-hour instead of 24- hour rhythm
What resets the SCN?
Light from the retina
What is the retinohypothalamic path?
A small branch of the optic nerve that extends directly from the retina to the SCN
True or False? Most of input from the retinohypothalamic path does not come from normal retinal receptors?
True.
For all mammals, retinohypothalamic path to SCN comes from a special population of…
Retinal ganglion cells
They respond directly to light, not rods or cones , the overall average of the light that changes from one level to another
They are located mainly near the nose, and respond to light slowly and turn off slowly when light ceases
What is Melanopsin?
the name of the photopigment that cells have
True or False? The SCN regulates waking and sleeping by controlling activity levels in other brain areas?
True, including the pineal gland - an endocrine gland that is located behind the thalamus that releases melatonin
What are the two genes that generate circadian rhythms?
Period ( Per) and Timeless (tim)
How do Per and Tim interact with the body to generate rhythms?
The proteins start in small amounts in the morning and then increase during the day, reaching high levels by evening, interact with a protein called Clock which induces sleepiness.
High level feeds back to the genes to shut them down. Genes are dormant at night. Cycle starts again in the morning.
What happens when there is a pulse of light during the night ?
Inactivates Tim protein and resets biological clock, decreasing sleepiness
Mutations of the Period gene in humans …
Results in odd circadian rhythms or decreases alertness if sleep deprived
True or False? Melatonin influences both circadian and circannual rhythms
True. Secretion starts to increase about 2 or 3 hours before bedtimes, feeds back to reset the biological clock though its effects on receptors in the SCN
When should you take a melatonin pill?
In the afternoon so it can phase-advance your internal clock
Sleep is…
a state that the brain actively produces. It is characterized by a moderate decrease in brain activity and decreased response to stimuli
A Coma is….
extended period of unconsciousness with low brain activity that remains fairly steady with little response to stimuli
A Vegetative state is ….
Person alternates between periods of sleep and moderate arousal, there is some automatic arousal to painful stimuli, but not purposeful activity or response to speech
A Minimally conscious state…
One state higher than vegetative, marked by an occasionally brief periods of purposeful actions and limited speech comprehension
Brain death is…
No sign of brain activity and no response to any stimulus
What is an Electroencephalograph?
An EEG,- records average of the electrical potentials of the cells and fibers in the brain areas nearest each electrode on the scalp
It has allowed researchers to discover that there are various stages of sleep and to compare brain activity at different times during sleep
What is a Polysomnograph?
a combinations of EEG and eye-movement records
What are the stages of sleep?
Alpha Waves- relaxation
Stage 1 Sleep- Irregular, jagged, low-voltage waves, brain activity begins to decline
Stage 2 Sleep- characterized by sleep spindles ( 12-14 hz waves during a burst that’s at least half a second) and K-complexes ( sharp ,high amplitude negative wave followed by a smaller, positive wave)
Stage 3 & 4- heart rate, breathing and brain activity decrease, slow, large amplitude waves become more common SWS, indicates that neuronal activity is highly synchronized
By stage 4- more than half the record includes large waves of a t least .5 sec. duration
What are Alpha Waves?
have a frequency of 8-12 per sec, present when one begins a state of relaxation
In what order do the stages of sleep occur?
1,2,3,4,3,2, REM . Lengths of stages decrease as the night progresses , REM increases
What is REM sleep?
Rapid eye movement sleep, low voltage, fast waves that indicate increased neuronal activity, but postural muscles of the body are more relaxes than in other stages. It combines deep sleep and light sleep.
Is REM synonymous with dreaming?
It is associated with dreaming but you can dream in other stages
A cut through the midbrain separating forebrain and part of midbrain from all the lower structures results in…
decreasing arousal by damaging reticular formation, the part of the midbrain that extends from the medulla to the forebrain and is responsible for arousal. It has neurons with axons ascending into brain and other neurons with axons descending into spinal cord
What is the pontomesencephalon?
Part of reticular formation that contributes to cortical arousal, has axons that extend to the hypothalamus, thalamus, and basal forebrain that releases acetylcholine and glutamate
Maintains arousal during wakefulness and increases it in response to new or challenging tasks
Stimulation of one area awakens sleeping individual or increases alertness in one already awake
What is the Locus Coeruleus?
A small structure in the pons that emits bursts of impulses in response to meaningful events, especially those that produce emotional arousal, usually dormant while asleep
Axons release norepinephrine ( adrenaline) ( both a neurotransmitter and a hormone) widely throughout the cortex
Anything that stimulates this area strengthens storage of recent memories and increases wakefulness
Hypothalamus has several axon pathways that influence arousal…
one pathway release histamine which produces excitatory effects throughout the brain
antihistamine drugs produce sleepiness
What is Orexin or Hypoctretin?
a neuropeptide ( transmitter) released by pathway from hypothalamus- axons releasing Orexin extend to basal forebrain and other areas and stimulate neurons responsible for wakefulness . Acetylcholine.
Highly responsible for the ability to stay awake
Other pathways from lateral hypothalamus regulate cells in….
Basal forebrain. These cells provide axons that extend throughout thalamus and cerebral cortex- some release acetylcholine ( excitation)
- GABA- important for sleep- inhibitory
Decreases body temperature and metabolic rate, also stimulation of neurons
What is the brain’s main inhibitory transmitter?
GABA, it is release to damper brain activity even though neurons are still firing
True or False? Sleep can be local within the brain?
True. Dolphins and other mammals can do it, and lucid dreaming is another example.
What causes sleep paralysis?
During REM, cells in the ponds send messages that inhibit motor neurons that control large muscles
What happens during REM sleep to our body systems?
- activity increases in pons and limbic system
- activity decreases in primary visual cortex, motor cortex, and dorsolateral prefrontal cortex, but increases in parts of parietal and temporal cortex
What are PGO waves?
High amplitude electrical potentials.
What happens if there is REM deprivation?
PGO waves begin to emerge during stages 2-4 and even during wakefulness ( often associated with strange behaviors)
- results in a greater density of PGO waves during uninterrupted sleep
- waves of neural activity are detected first in the pons, then lateral geniculate of the hypothalamus, then in the occipital cortex
What relationship between neurotransmitters does REM depend on?
Serotonin and Acetylcholine
Drugs that stimulate Acetylcholine make us quick to fall into REM. Serotonin interrupts REM
What is Insomnia?
The best gauge of insomnia is how one feels the next day
What can cause Insomnia?
stress, noise, diet, medicine, uncomfortable temperatures, epilepsy, Parkinson’s, brain tumors, depression, anxiety and some cases relate to shifts in circadian rhythms
Rhythm is phase delayed, have trouble falling asleep at the usual time
Rhythm is phase advanced- falls asleep easily but awakens early
What is Sleep Apnea?
Impaired ability to breathe while sleeping
People with sleep apnea have multiple brain areas that have lost neurons, consequently showing deficiency of learning, reasoning, attention and impulse control
causes hypoxia, a lack of oxygen in the brain
What is Narcolepsy?
Condition characterized by frequent periods of sleepiness during the day with four main symptoms:
1) Gradual or sudden attacks of sleepiness during the day
2) Occasional cataplexy ( attack of muscle weakness while person remains awake)
3) Sleep Paralysis- inability to move while falling asleep or waking up
4) Hypnagogic hallucinations- dreamlike experiences
What causes Narcolepsy?
Related to neurotransmitter Orexin - lack of cells in hypothalamus that release it
Primary tx? Stimulant drugs, increase dopamine and norepinephrine activity
What is Periodic limb movement disorder?
Characterized by repeated involuntary movement of the legs and sometimes arms, legs kick every 20-30 seconds for minutes or hours
occurs mostly during NREM sleep
tranquilizers can help in some cases
What is REM behavior disorder?
People with this disorder move around vigorously during REM periods, acting out their dreams.
Occurs mostly in older people, esp. older men with brain diseases
Probable cause is damage to cells in pons ( no longer inhibits the motor neurons that control large muscles)
What are night terrors?
experiences of intense anxiety from which a person awakes screaming in terror. Occur during NREM and are more common in children than adults
What is sleepwalking?
- runs in families and occurs mostly in children
- more common when people are sleep deprived or after they take alcohol or various other drugs or medications
- most common during stage 3 or 4 sleep early in night and usually not accompanied by dreaming ( does not occur during REM)
Why do we sleep?
Energy Conservation, restoration of the brain and body, memory consolidation
How is sleep analogous to hibernation?
it conserves energy
How can sleep improve memory?
If people learn something and then go to sleep ( or even take a nap) their memory usually improves to greater than it was before going to sleep .
Mice deprived of sleep for even 4 hours show impairments in their ability to alter synaptic activity
True or false? During sleep the brain strengthens some connections while weakening others?
True. Sleep also helps people reanalyze their memories. Patterns of activity in the hippocampus during learning were similar to those shown during sleep
How does sleep enhance memory?
Electrical activity patterns observed during learning were observed again, except faster, during sleep.
Amount of activity in those areas during sleep correlated highly with improvements in skill seen the next day.
It also weeds out the less successful connections
What happens to sleep spindles during stage 2 sleep?
They increase in number after new learning: correlated with nonverbal IQ
How much of sleep is spent in REM?
About 20%. Humans spend 1/3 of their life asleep and 1/5 of that in REM.
Species with the most total sleep hours also have highest percentage of REM sleep
What kind of learning is associated with NREM?
Verbal
What happens if you deprive people of sleep during second half of night ( mostly REM)?
Impaired consolidation of learned motor skills
What is the Activation- Synthesis Hypothesis?
A dream represents the brain’s effort to make sense of sparse and distorted information, begins with periodic bursts of spontaneous activity in the pons (PGO waves), which activates many parts of the cortex
Cortex combines this haphazard input with whatever other activity was already occurring and does its best to synthesize story that makes sense…sometimes ends up in bizarre dreams
What is the Clinico-Anatomical Hypothesis?
- derived from clinical studies of brain-damaged patients
- similar to the activation synthesis hypothesis in that dreams begin with arousing stimuli, but places less emphasis on the pons, PGO waves or REM
- Regards dreams as thinking that takes place under unusual conditions
- Primary visual and auditory cortex have lower than usual activity- other brain areas are free to generate images without constraints or interference
- primary motor cortex and motor neurons of spinal cord are suppressed- arousal cannot lead to action
- activity is suppressed in prefrontal cortex
Consequence- we forget most dreams and also lose track of what has been happening within a dream, sudden changes are common
