PSB 4006 - Chapter 8: Wakefulness and Sleep

body temperature patterns

- based on circadian rhythm - 2 hours after falling asleep, body temperature tends to be at its lowest; maintaining heat takes a lot of energy, so it is more efficient to do so - in the late afternoon, body temperature is its highest

mood patterns

- based on circadian rhythm - people tend to be most happy from wake to the late afternoon, and their mood decreases by nighttime.

stages of sleep

1, 2, 3, REM

what kind of sleep do antidepressants decrease?

REM, but it does not cause memory problems

Slow Wave Sleep

Stage 3 and Stage 4, characterized by: - slow, large amplitude waves - highly syncronized neuronal activity - heart rate, breathing rate, and brain activity slows

transplanted SCN tissue

a 1990 study on hamsters showed that when SCN tissue was transplanted, the receivers' rhythms, which were previously 24 hours, became the same as the donors' (20 hrs due to a mutation) after receiving the donor's SCN tissues. - significance: shows that rhythms come from the SCN itself

Jet lag

a disruption of circadian rhythms due to crossing time zones

astronaut circadian rhythm

astronauts in space recieved 40 minutes of light followed by 40 minutes of darkness, which made it difficult to sleep and cause reduced performance.

human circadian rhythms

can be slightly longer than a day (24-25 hrs)

Polysomnograph

device that measures sleep stages using a combination of EEG and eye-movement records

Brain death

no sign of brain activity and no response to any stimulus

study on a correlation betwen sleep time, study time, and performance

people learning swahilli in the morning performed worse than those that learned it slept right after

Periodic limb movement disorder

repeated involuntary movement of the limbs, which only occur during sleep

Stage 1 Sleep

sleep that has just begun and shows rapid, irregular, low voltage waves on EEGs. - brain activity is less than in relaxed wakefulness but has the most compared to other sleep stages. - alpha waves present

what is the purpose of the circadian rhythm?

to keep our internal workings in phase with the outside world

t/f: a single isolated SCN cell can maintain a circadian rhythm.

true

how does the suprachiasmatic nucleus control circadian rhythm?

various cells communicate with each other to create and sharpen the circadian rhythm.

K-complex

very high amplitude pattern of brain activity associated with stage 2 sleep that may occur in response to environmental stimuli. they may be associated with memory consolidation and staying asleep.

what neurotransmitters regulate REM sleep?

1.) acetylcholine (promotes wakefulness and moves person into REM sleep) 2.) serotonin, norepinephrine (interrupts REM sleep)

Sleep and the Inhibition of Brain Activity

1.) axons that release GABA (inhibitory NT) become more active during sleep, which interferes with the spread of information among neurons. 2.) when GABA binds to receptors of thalamic neurons, it opens ion channels, causing hyperpolarization. this decreases the neurons' readiness to respond to stimuli, which in turn decreases the total amount of information transmitted to the cortex. 2.) when neurons do fire, they do so in sync, which is represented as high amplitude waves that are characteristic of slow-wave sleep

how is energy conserved during sleep?

1.) body temperature drops 1-2 degrees C. 2.) muscle activity decreases 3.) increasing sleep duration during food shortages (hibernation)

genes and proteins involved in the circadian rhythm

1.) period: produces PER proteins 2.) timeless: produces TIM proteins

brain mechanisms of wakefulness and arousal

1.) reticular formation 2.) pontomesencephalon (acetylcholine, glutamate) 3.) pons (locus coeruleus) 4.) hypothalamus (orexin/hypocretin) 5.) basal forebrain (GABA, acetylcholine)

symptoms of narcolepsy

1.) sleep attacks & daytime sleepiness 2.) cataplexy (attacks of muscle weakness) 3.) sleep paralysis 4.) hypnagogic hallucinations

what are the main mechanisms of circadian rhythms?

1.) suprachiasmatic nucleus 2.) genes that produce certain proteins 3.) melatonin levels

PGO waves

a distinctive pattern of high-amplitude electrical potentials that occur first in the pons during REM sleep

Orexin (hypocretin)

a peptide NT produced by neurons whose cell bodies are located in the hypothalamus. they extend into other areas of the brain, especially the basal forebrain. - increases wakefulness and arousal. it keeps the person awake; it does not wake them up! - drugs that block this NT help people sleep

Hibernation

a period of inactivity that some animals experience in winter, which allows them to survive on stored energy - often come out of hibernations every few hours for a few hours - animals that hibernate have prolonged lives compared to those that do not

Narcolepsy

a sleep disorder characterized by uncontrollable sleep attacks, which is often emotionally triggered (negative or positive). - people with narcolepsy lack the hypothalamic cells that produce and release orexin

Zeitgeber

a stimulus that resets the circadian rhythm - temperature, light intensity, social interactions, etc.

what is a potential consequence of constant jet lag?

a study showed a correlation between constant jet lag and a smaller hippocampus, as well as memory impairments.

Optogenetics

a treatment that allows researchers to turn on activity in certain neurons using light (this was used in a study to inhibit orexin in mice). 1.) a specially manipulated virus inserts light-sensitive proteins into the membrane of the targeted neuron 2.) when the light is detected, sodium channels are opened and excite the neuron

Endogenous circadian rhythm (adolescents)

adolescents tend to be more active at night, and sleep later in the day and wake up later

NREM and REM cycles

after calling asleep, a person goes through a cycle of 4 stages a sleep, followed by REM sleep. in the later parts of sleep, REM sleep becomes more longer and common

Morning People and Evening People

because circadian rhythms differ, peoples productivity depends on their circadian rhythm; morning people wake up early and their productivity peaks early and decreases throughout the day. evening people are more productive later in the day, but all people generally are most productive in the late afternoon/evening.

circadian rhythms of blind individuals

blind people set their circadian rhythms by zeitgebers other than light (noise, meals, tempertature, etc.), but this is often insufficient to keep their biological blocks in line with external time. as a result, many blind individuals have circadian rhythms longer than 24 hours and experience sleep problems.

Pons

brain structure serves as a relays station for messages from the cerebellum to the rest of the brain. - it is located directly above the medulla and near the hindbrain

Sleep spindle

bursts of brain waves present in stage 2 sleep. its frequency ranges from 12 to 14 Hz and lasts for at least half a second.

how does the SCN regulate waking and sleeping?

by controlling activity levels in other areas of the brain, including the pineal gland

Endogenous circadian rhythm (children)

children (and adults) tend to be morning people; more active in the mornings, and sleep and wake up earlier

Vegetative state

condition in which a person alternates between wake and sleep. - stimuli can produce autonomic responses, the person shows no awareness of surroundings and no purposeful behavior. - can last months

hypnagogic hallucinations

dreamlike experiences during wakefulness, in which the person has trouble distinguishing from reality. this usually occurs right when a sleep attack is about to occur in narcoleptic individuals.

why are dreams often disorganized?

during sleep, GABA is released, which inhibits the frontal lobe and interferes with its ability to connect with and spread information to the rest of the brain

Brain Function in REM Sleep

during sleep, activity increases in the pons, triggering REM sleep. cells in the medulla and pons also send messages to the spinal cord to inhibit motor neurons of the body's large muscles, in order to prevent the person from acting out their dreams

study on sleep and memory involving the hippocampus

during sleep, activity patterns occurred in the hippocampus, which were similar to the patterns that occurred while learning it in wake. 1.) the amount of hippocampal activity that was correlated with an improvement in performance on those tasks

is it better to travel west or east (jet lag)?

east to west is best because it phase-delays circadian rhythms; it's easier to sleep later and wake up later than sleep earlier and wake up earlier (phase-advancing, cause by traveling east); west to east is a beast

Pineal gland

endocrine gland that secretes melatonin and is located posterior to the thalamus.

Acetylcholine

excitatory neurotransmitter that increases arousal, learning, and attention, and is released by axons from the basal forebrain. - it is released during wakefulness and REM sleep, but NOT slow-wave sleep - shifts sleep from NREM to REM

coma

extended period of unconsciousness, with limited reaction to stimuli

Hypothalamus

has a role in promoting wakefulness and arousal. it contains neurons that release histamine (increases arousal) and orexin (maintains wakefulness) throughout the brain

basal forebrain

has both excitatory and inhibitory cells. - excitatory: releases acetylcholine - inhibitory: releases GABA

Melatonin

hormone that increases sleepiness and is secreted a few hours before bedtime by the pineal gland.

Sleep Apnea

inability to breathe while sleeping; the person often has breathless moments where they will stop breathing, then gasp for air, which causes them to awaken. 1.) results in sleepiness during the day, and is associated with impaired attention 2.) neurons associated with alertness are often impaired in these individuals

what may be a possible reason adolescents tend to sleep and wake up later, whereas children and adults do not?

increased levels of sex hormones

how does the brain strengthen memory during sleep?

it prunes off weaker synapses, while strong connections are kept, which prevents overactivity in the brain

Functions of Sleep

its original function was most likely to conserve energy, as being awake all day would mean needing more energy and food. other functions: 1.) hormonal balance 2.) strengthens immune system 3.) hunger control 4.) tissue regeneration 5.) memory consolidation

study on mice & orexin

mice that lacked orexin would alternate between waking and sleeping. when their orexin-producing neurons were inhibited, they would quickly go into slow-wave sleep

Cataplexy

muscle weakness or sudden loss of muscle control, which is often a symptom of narcolepsy

neuronal activity during wakefulness and stage 1 sleep

neurons providing input to the cerebral cortex are out of phase with one another, causing rapid and choppy waves

Histamine

neurotransmitter released by neurons in the hypothalamus that produces excitatory effects. - antihistamine counteracts this NT, which is why a side effect of this drug is often drowsiness.

GABA

neurotransmitter released by the basal forebrain, which inhibits the thalamus and cortex. - decreases temperature, metabolic rate, and stimulation of neurons

Serotonin

neurotransmitter released by the dorsal raphe and pons, which interrupts REM sleep

study on sleep duration and memory

one group studied for 4 hours and slept for 8 hours, while the other studied for 9 hours and slept for 4. The group that slept more performed better, despite studying less.

Minimally conscious state

one stage higher than a vegetative state marked by occasional brief periods of purposeful action and some speech comprehension - can last months

Suprachiasmatic Nucleus (SCN)

part of the hypothalamus that provides the main control of the circadian rhythms pertaining to sleep and temperature through a genetically controlled, unlearned manner.

Pontomesencephalon

part of the reticular formation that contributes to cortical arousal. - its axons release acetylcholine and glutamate - axons extend into the thalamus, hypothalamus, and basal forebrain - its neurons receive input from many sensory systems and can also generate spontaneous activity of their own

study on sleep involving objects and sounds

people were shown 50 objects w/ sounds in various locations on a screen, napped after, then were tested on where they remembered each object to be. some objects' sounds were played during sleep, and memory for those objects were enhanced.

why is it hard for shift workers to adjust their circadian rhythms?

prolonged shift work periods often do not reset biological clocks, especially due to artificial lights and body temperatures. although bright lighting can help, their biological productivity and sleep schedules often cannot fully adjust to their work schedules due to the presence of other zeitgebers , such as sunlight during their sleep times.

PER and TIM

proteins that promote sleep and inactivity via feedback loops among neurons. 1.) light breaks down PER and TIM, so their levels are low in the morning. 2.) the less PER and TIM is present, the less inhibition of the mRNA that forms them occurs. throughout the day, thus, mRNA increases throughout the morning as PER and TIM decreases, causing PER and TIM to slowly be made and accumulate throughout the day. 3.) by nighttime, PER and TIM are at its peak and inhibiting mRNA. when morning comes, PER and TIM will break down, increasing mRNA.

Insomnia

recurring problems in falling or staying asleep, which can often be related to shifts in circadian rhythms; - the body normally sleeps when its temperature is declining. 1.) being phase delayed forces one to sleep when the body temperature is still high 3.) being phase advanced makes it so that temperature is too low when needing to be awake

neurocognitive theory

regards dreams as thinking that takes place under unusual conditions

dorsal raphe and pons

release serotonin and interrupts REM sleep.

Endogenous circadian rhythm

self-generated rhythm that lats about a day - temperature, sleeping, eating, mood, etc. - the sun and blue light have large affects on our circadian rhythms

Endogenous circannual rhythm

self-generated sense of time that lasts about a year - animal migration, storage of food for winter, hibernation

Stage 2 Sleep

sleep deeper than stage 1, characterized by a slower, more regular wave pattern, along with sleep spindles and K-complexes.

REM behavior disorder

sleep disorder in which the mechanism that blocks the movement of the voluntary muscles fails, causing vigorous movements during REM sleep when people act out their dreams. - people with this often have dreams about defending themselves - may be associated with a lack of secreted GABA, as mice who lacked it moved a lot more during sleep

Night terrors

sleep disruptions in which a person wakes up screaming, panicked, or confuse

Species Differences in Sleep

sleep habits are influenced by various characteristics of the species, such as: 1.) whether they are predator or prey; predators have the luxury of sleeping more than prey 2.) those that sleep less must eat more to stay awake, since doing so expends more energy (such as cattle)

Sleep and Memory

sleep plays an important role in enhancing learning and strengthening memory. - when sleeping the brain replays the day in fast motion to consolidate memories - why reviewing before sleep is a strategy to memorize things better

Paradoxical or REM Sleep

sleep that is deep in some ways, but light in others. - characterized by rapid eye movements, increased brain activity, and relaxation of postural muscles. - EEG waves are irregular, low-voltage, and fast - more variable heart rate, breathing rate, and blood pressure than stage 2-4

alpha waves

slow brain waves of a relaxed state, at a frequency of 8-12 per second

retinohypothalamic path

small branch of the optic nerve that conveys information about light to the SCN. when special ganglion cells (not rods/cones) respond to light, it can reset the SCN's circadian rhythm settings

Locus coeruleus

small structure in the pons that release norepinephrine and emits bursts of impulses in response to meaningful events, especially those that produce emotional arousal (such as a mother waking up from a baby crying). - it is usually inactive, especially during sleep - increases activity of the most active neurons, and decreases activity of the less active ones

non-REM (NREM) sleep

stages 1 through 4 of the sleep cycle, during which rapid eye movements and relaxation of large muscles do not occur

slow-wave sleep

stages 3 and 4 (non-REM sleep), characterized by synchronized EEG activity and slow, large-amplitude waves. - heart rate, breathing rate, and brain activity decreases.

what may be a function of REM sleep?

strengthening memories, as well as supplying oxygen to the corneas by causing them to move during sleep

Reticular formation

structure extending from the medulla into the forebrain, which plays a role in increasing wakefulness and arousal

which type of people are often happier: morning or night people?

studies have shown that morning people tend to be happier, because the most common work shift (9 am - 5 pm) falls in line with the time that they are able to be most productive.

Amounts of REM Sleep

the amount of time spent in REM sleep varies among species. - those that sleep more tend to spend more time in REM, such as birds and mammals

Sleep as a Local Phenomenon

the brain must actively put us to sleep, but sleep may sometimes only occur in only some parts of the brain ; all that needs to occur is the release of GABA in that region. - ex. dolphins only sleep with half their brain; are awake in motor cortex area, but asleep in others

activation-synthesis theory

theory that dreams reflect inputs from brain activation originating in the pons, which the forebrain then attempts to weave into a story; the brain is trying to make sense of distorted information

germany time difference

there's a 30 minute difference from when the sun rises in the east than from the west. a study found that the average midpoint between sleeping time and waking time was also a 30 minute difference between those that lived in the east vs the west.

Sleepwalking

walking or carrying out behaviors while asleep. - sleepwalkers are awake in motor cortex area, but asleep in others - often runs in families and is more common in children - often occurs during slow-wave sleep and when sleep deprived or stressed.

lucid dreaming

when a person dreaming becomes aware that he is asleep and dreaming, and is able to influence or control what happens

Shift Work

work that take place on a schedule outside the traditional 9 am - 5 pm day. - people with these schedules are more prone to suicide and health conditions