Chapter 8 Flashcards
Endogenous Circannual Rhythms
ANd
endogenous circadian rhythms
Some animals generate endogenous circannual
rhythms, internal mechanisms that operate on an
annual or yearly cycle
– Example: birds migratory patterns; animals storing food
for the winter
All animals produce endogenous circadian rhythms, internal mechanisms that operate on an approximately 24-hour cycle – Sleep cycle – Frequency of eating and drinking – Body temperature – Secretion of hormones – Urination – Sensitivity to drugs
notes from lecture:
effected by external cues
environmental change can have major impact on animals migratory patterns
book: your urge to sleep depends partly on the time of day , not just how many hours you’ve been awake.
The Daily Activity of a Squirrel Kept in Total Darkness
Book:
Represents the activity of a flying squirrel kept in total darkness for 25 days
Each horizontal line represent one 24-hour day
A thickening of the line represent a period of activity by the animal
Even in this unchanging environment , the animal produce a regular rhthym of activity and sleep.
Waking period starts earlier each day than the last
Sleep period starts earlier each day than the last
check diagram 5
Daily Pattern of Body Temperature
slide 6
human body temp at 37 degrees normally
it will fluctuate over the course of the day from a low of 36.7 at night to almost 37.2 in the afternoon
Daily Pattern of Positive Moods
slide 7
Setting and Resetting the Biological Clock
Purpose of it ?
How long is the clock ?
The purpose of the circadian rhythm is to keep our
internal workings in phase with the outside world
• The 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
Zeitgeber:
means what in german ?
German meaning “time giver”; refers to the
stimulus that resets the circadian rhythm
– Examples: sunlight, tides, exercise, meals, arousal of
any kind, meals, temperature of environment, and so on. – Depression, irritability, and impaired job performance are
effects of using something other than sunlight as a
zeitgeber
Difference in Sun Time Between East and West Germany
half an hour difference between the east and west
so, the sun in the east rise 30 min before the west
everyone in germany are on the same clock time
People at the eastern edge has a sleep midpoint about 30 min earlier than those at the west .
This correspond to the rising of the sun
Jet Lag
Refers to the disruption of the circadian rhythms due to
crossing time zones
– Stems from a mismatch of the internal circadian clock
and external time – Sleepiness during the day, sleeplessness at night, and
impaired concentration
• Traveling west “phase-delays” our circadian rhythms
• Traveling east “phase-advances” our circadian rhythms
Is it more difficult to fly east or west ?
why ?
More Difficult Flying East
Book:
Going west, we stayed awake later at night and then awaken late the next morning , already partly adjusted to the new schedule. Called phase delay our circadian rythms .
East : phase advance , to sleep earlier and to wake up earlier.
Shift Work
Sleep duration depends on when one goes to sleep
• Working at night does not reliably change the circadian
rhythm
– Even after long periods of working at night, people can
still feel groggy, sleep poorly during the day, and body temperature peaks while sleeping instead of while working
• People adjust best to night work if they sleep in a very
dark room during the day and work under very bright
lights at night
Morning People and Evening People
Cycles can differ between people and lead to different
patterns of wakefulness and alertness • Change as a function of age
– Young children are morning people
– Adolescents are often night people • As an adult, it partially depends upon genetics
book:
circadian rhythm differs among ppl
morning ppl: awaken early, quickly become productive and become less alert as the day progresses
night owl: warm up slowly, reaching their peak in the afternoon , or evening. They tolerate staying up all night better than morning ppl .5
Age and Gender Differences in Circadian Rhythms
slide 15
Notes from ppw:
Midpoint is lower for women than it is for men
This is the case until the 60s
13 hours for men , which they would normally sleep for
Mechanisms of the Biological Clock
Mechanisms of the circadian rhythms
– The suprachiasmatic nucleus (SCN)
– Genes that produce certain proteins
– Melatonin levels
the Suprachiasmatic Nucleus (SCN)
The main control center of the circadian rhythms of
sleep and temperature
– Located above the optic chiasm and part of the
hypothalamus
• Damage to the SCN results in less consistent body
rhythms that are no longer synchronized to
environmental patterns of light and dark
Supra = above the optic chiasm
The Suprachiasmatic Nucleus (SCN) and the Circadian Rhythm
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 Suprachiasmatic Nucleus (SCN) and the Retinohypothalamic Path
Light resets the SCN via a small branch of the optic
nerve called the retinohypothalamic path
– Travels directly from the retina to the SCN
• The retinohypothalamic path comes from a special
population of ganglion cells that have their own
photopigment called melanopsin
– The cells respond directly to light and do not require any
input from the rods or cones
Notes from class:
If you keep your eyes away from light, you can trick your brain
blind ppl have medications that we give to them in order to reset your SCN
The Biochemistry of the Circadian Rhythm
what are the 2 genes for generating the circadian rythm
Two types of genes are responsible for generating the
circadian rhythm
– Period: produce proteins called PER
– Timeless: produce proteins called TIM
• PER and TIM proteins increase the activity of certain
kinds of neurons in the SCN that regulate sleep and
waking
– Mutations in the PER gene result in odd circadian
rhythms or decreased alertness if deprived of a good night’s sleep
Interaction of MRNA with PER and TIM Proteins
check diagram on slide 23
Melatonin
The SCN regulates waking and sleeping by controlling
activity levels in other areas of the brain
• The SCN regulates the pineal gland, an endocrine
gland located posterior to the thalamus
• The pineal gland secretes melatonin, a hormone that
increases sleepiness
Melatonin secretion usually begins two to three hours
before bedtime
• Melatonin feeds back to reset the biological clock
through its effects on receptors in the SCN
• Melatonin taken in the afternoon can phase-advance
the internal clock and can be used as a sleep aid
Sleep
Sleep is a state that the brain actively produces
– Characterized by a moderate decrease in brain activity
and decreased response to stimuli
• Sleep differs from the following states:
– Coma, vegetative state, minimally conscious state, and
brain death
Relaxation and Stage 1 Sleep
Alpha waves are present when one begins a state of
relaxation
• Stage 1 sleep is when sleep has just begun
– The EEG is dominated by irregular, jagged, and low
voltage waves – Brain activity begins to decline
Stage 2 Sl eep
Stage 2 sleep is characterized by the presence of:
– Sleep spindles: 12- to 14-Hz waves during a burst that
lasts at least half a second – K-complex: a sharp wave associated with temporary
inhibition of neuronal firing
Slow Wave Sleep—Stage 3 and Stage 4
Stage 3 and stage 4 together constitute slow wave
sleep (SWS) and is characterized by:
– EEG recording of slow, large amplitude wave
– Slowing of heart rate, breathing rate, and brain activity
– Highly synchronized neuronal activity
Paradoxical or REM Sleep
Rapid eye movement sleep (REM) describes periods characterized by rapid eye movements during sleep – Also know as paradoxical sleep: deep sleep in some
ways, but light sleep in other ways
• EEG waves are irregular, low-voltage, and fast • Postural muscles of the body are more relaxed than
other stages
Polysomnograph Records
check slide 36
NREM and REM Cycles
Stages other than REM are referred to as non-REM
sleep (NREM) • When people fall asleep, they progress through stages
1, 2, 3, and 4 in sequential order
– After about an hour, the person begins to cycle back
through the stages from stage 4 to stages 3 and 2 and then REM
– The sequence repeats with each cycle lasting
approximately 90 minutes
Stages 3 and 4 sleep predominate early in the night
– Length of stage decreases as the night progresses • REM sleep is predominant later at night
– Length increases as the night progresses • REM is strongly associated with dreaming, but people
also report dreaming in other stages of sleep
Typical Sequences of Sleep Stages
check slide 39
Brain Mechanisms of Wakefulness and Arousal—The Reticular Formation
Various brain mechanisms are associated with
wakefulness and arousal
• The reticular formation is a part of the midbrain that
extends from the medulla to the forebrain and is
responsible for arousal
The Pontomesencephalon
The pontomesencephalon, a part of the reticular
formation in the midbrain, contributes to cortical arousal
– Axons extend to the hypothalamus, thalamus, and basal
forebrain, which release acetylcholine, glutamate, or dopamine
– Produce excitatory effects to widespread areas of the
cortex – Stimulation of the pontomesencephalon awakens
sleeping individuals and increases alertness in those
already awake
The Locus Coeruleus
The locus coeruleus is a small structure in the pons
whose axons release norepinephrine to arouse various
areas of the cortex and increase wakefulness
– Usually dormant while asleep
The Hypothalamus
The hypothalamus contains neurons that release
“histamine” to produce widespread excitatory effects
throughout the brain
– Antihistamines produce sleepiness
Orexin
The lateral and posterior nuclei of the hypothalamus
releases orexin
– Orexin is a peptide neurotransmitter and is sometimes
also called hypocretin – Needed to stay awake rather than wake up – Orexin is released by cells into the basal forebrain to
stimulate neurons responsible for wakefulness and
arousal – The basal forebrain is an area just anterior and dorsal to
the hypothalamus
GABA and Acetylcholine
Cells of the basal forebrain release the inhibitory
neurotransmitter GABA
– Inhibition provided by GABA is essential for sleep • Other axons from the basal forebrain release
acetylcholine, which is excitatory and increases arousal
Brain Mechanisms of Sleeping and Waking
slide 46
Functions of the inhibitory neurotransmitter GABA are
also important for:
Decreasing the temperature and metabolic rate
– Decreasing the stimulation of neurons
Sleep as a Local Phenomenon
Sleepwalker, lucid dreams
Sleep can be localized within the brain
– Sleepwalkers: awake in one part of the brain and asleep
in others – Lucid dreaming: dreaming but aware of being asleep and
dreaming – The pons remaining in REM while other brain areas
wake up: causes the inability to move
During REM sleep:
Activity increases in the pons and the limbic system
– Activity decreases in the primary visual cortex, the motor
cortex, and the dorsolateral prefrontal cortex
REM sleep is also associated with a distinctive pattern
of high-amplitude electrical potentials known as PGO
waves
– Waves of neural activity are detected first in the pons,
then in the lateral geniculate of the hypothalamus, and then the occipital cortex
• REM deprivation results in a high density of PGO
waves during uninterrupted sleep
How does it inhibit movement during REM sleep ?
• Cells in the pons send messages to the spinal cord,
which inhibits motor neurons that control the body’s
large muscles
– Prevents motor movement during REM sleep
REM is regulated by which NT
REM is also regulated by serotonin and acetylcholine
– Drugs that stimulate acetylcholine receptors quickly
move people to REM – Serotonin interrupts REM
PGO Waves and REM Sleep
sldie 53
Insomnia:
A sleep disorder associated with inadequate
sleep
– Caused by a number of factors, including noise, stress,
pain, diet, and medication
– Can also be the result of disorders such as epilepsy,
Parkinson’s disease, depression, anxiety or other
conditions
– Dependence on sleeping pills or alcohol and shifts in the
circadian rhythms can also result in insomnia
Sleep Disorders as a Result of Phase Delay
slide 55
Sl eep Apnea
A sleep disorder characterized by the inability to
breathe while sleeping for a prolonged period of time
– Consequences: sleepiness during the day, impaired
attention, depression, and sometimes heart problems
– Causes: genetics, hormones, old age, obesity and
deterioration of the brain mechanisms that control
breathing
– Effects: cognitive impairment may result
Narcolepsy (
A sleep disorder characterized by frequent periods of
sleepiness
– Attacks of sleepiness during the day
– Gradual or sudden attack of sleepiness
– Occasional cataplexy: muscle weakness triggered by
strong emotions
– Sleep paralysis: inability to move while falling asleep or
waking up
– Hypnagogic hallucinations: dreamlike experiences
Seems to run in families, although no gene has been
identified • Caused by lack of hypothalamic cells that produce and
release orexin • Primary treatment is with stimulant drugs (i.e., Ritalin),
which increase wakefulness by enhancing dopamine
and norepinephrine activity
Periodic Limb Movement Disorder
The repeated involuntary movement of the legs and
sometimes the arms while sleeping
– Legs kick once every 20–30 seconds for periods of
minutes to hours
– Usually occurs during NREM sleep
REM Behavior Disorder
Associated with vigorous movement during REM sleep
– Usually associated with acting out dreams
• Research suggest that inadequate GABA and other
inhibitory neurotransmitters may be responsible
Night Terrors and Sleepwalking
Night terrors are experiences of intense anxiety from
which a person awakens screaming in terror
– Usually occurs in NREM sleep
• “Sleepwalking” runs in families, mostly occurs in young
children, and occurs mostly in stage 3 or 4 sleep
– Not associated with dreaming
It is not dangerous to wake a sleepwalker
• A condition similar to sleepwalking is sexsomnia:
engaging in sexual behavior while asleep
• Can pose a threat to romances and marriages
Why Sleep? Why REM? Why Dreams?
We’ve evolved mechanisms to force us to sleep • Inhibitory processes in our brains force us to become
less aroused and less alert, and thus to sleep
Functions of Sleep
Some of the many functions of sleep include:
– Resting muscles
– Decreasing metabolism
– Performing cellular maintenance in neurons
– Reorganizing synapses
– Strengthening memories
Sleep and Energy Conservation
The original function of sleep was probably to conserve
energy
• Conservation of energy is accomplished via:
– Decrease in body temperature of about 1–2 Celsius
degrees in mammals
– Decrease in muscle activity
Hibernation is Analogous to Sleep
Decrease in body temperature to only slightly above
that of the environment
• Heart rate and brain activity drop to almost nothing
• Neuron cell bodies shrink, and dendrites lose almost a
fourth of their branches
– Replaced later when body temperature increases
Some Facts About Hibernation
Bear “hibernation” is not as extreme as that of smaller
hibernators such as bats and ground squirrels
• Hibernating animals come out of hibernation for a few
hours every few days
• Hibernation retards the aging process
• Hibernation is also a period of relative invulnerability to
infection and trauma
Species Differences in Sleep
Animals sleep habits and are influenced by particular
aspects of their life, including:
– Whether they are predator or prey
– How many hours they spend each day devoted to
looking for food
– Safety from predators while they sleep
§ Examples: sleep patterns of dolphins, migratory birds, and
swifts
check slide 70
Sleep and Memory
Sleep also plays an important role in enhancing
learning and strengthening memory
– 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
– Suggests 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
Amounts of REM Sleep
human
cat
Humans spend one-third of their life asleep; about one-
fifth is spent in REM
• Species vary in amount of sleep time spent in REM
– Cats spend up to 16 hours a day sleeping with lots of
that time in REM sleep
– Percentage of REM sleep is positively correlated with the
total amount of sleep in most animals
– Among humans, those who get the most sleep have the
highest percentage of REM
Functions of REM Sleep
Research is inconclusive regarding the exact functions
of REM
• During REM:
– The brain may discard useless connections
– Learned motor skills may be consolidated • Maurice (1998) suggests the function of REM is simply
to shake the eyeballs back and forth to provide
sufficient oxygen to the corneas
slide 75 - diagram
blind ppl
Book :
Some do their circadian rhythm by noise , temp, meals and activity,
Some ppl are not too sensitive to these stimuli
so, produce free running circadian rhythm (no stimulation reset or alerts it) that are a little longer than 24 hours
