Biological Rhythms and Sleep Flashcards
biological rhythms
regular fluctuations in any living process
any biological process (including behaviour) that repeats itself at regular intervals
manifest at all levels of biological organization and extend across a wide frequency spectrum
ie/ hormone levels, body temperature and drug sensitivity - change over the course of the day in a repeating pattern
circadian rhythms
circa meaning lasts about a day 24 hrs
ultradian
less than 24 hours
infradian
less than 24 hours
repeats less than once a day
ie/ menstrual cycles
diurnal
active during the day
nocturnal
active at night
crepuscular
anything true of dawn/ dusk
free-running rhythms
removing light and dark
lost reaosn to tell rhythm to start or stop
rhythm runs out of phase
like a clock going slower, starting later and later everyday
in a dimly lit room - still displays biological clock.
in a constant light/ dark environment - not exactly 24 hours - varies a few mins
maintaining own personal cycle, in absense of external cues, bit more than 24 hrs long
every animal has its own clock differing from one another
endogenous clock
keeping time for animals is difficult without a watch to look at
in constant conditions they will still run at approximentally the same time each day
phase shift
resetting the clock by an external cue
entrainment
process of phase shifting, shifting a rhythm
synchronizing biological clock to a stimulus
zeitgeber
time giver; primary one in the sun (light)
entrains circardian rhythm
any cue an animal uses to sync its activity with the environment
ecological significance
awake and active to find food or away hiding from a predator
anticipation of events in an environment
evolutionary opportunity
can physically and behaviourally prepare before an event
the brains clock
normally synched to light and dark
after lesion animals were more active when the lights were out
continuously in dim light, behaviour was random, lesions eliminated the endogenous rhythm
SCN suprachiasmatic nucleus
what they landed on for the source of the brains clock
large lesions in the hypothalamus had an effect - eliminate various rhythms
above optic chiasm
shows rhythmic metabolic activity
rhythms in slices and in cell cultures
retinohypothalamic tract
carries info about light to the hypothalamus - veering out of the optic chiasm to synapse directly within SCN
some amphibians have a third eye - pineal gland is sensitive to light (has photoreceptors) helping circadian rhythm
in mammals severing optic nerve eliminates rhythm
direct projection of retinal ganglion cells to SCN via optic nerve = RHT
ganglion cells here contain specialized photopigment melanopsin
melanopsin
makes cells sensitive to light
if you are blind still get entrained through light because this in mice
- typically absent in blind humans
- have free running system
melatonin
pineal gland secretes at night
informs brain about day length
molecular foundations of the brain’s clock
- two proteins clock and cycle, bind together to form a dimer
- the clock/cycle dimer binds to DNA, enhancing the transcription of the genes for Period (Per) and Crypyochrome (Cry)
- Per and Cry bind together as a complex that inhibits the activity of the clock/cycle dimer, showing transcription of the per and cry genes, and therefore slowing production of the Per and cry proteins
- the Per and Cry proteins eventually break down, releasing clock/cycle from inhibition and allowing the cycle to start over again. the rates of gene transcription, protein complex formation, and protein degration result in a cycle that takes about 24 hours to complete
- retinal ganglion cells detect light with melanopsin and their axons in the retinohypothalamic tract release glutamate stimulation leads to increased transcription of the per gene, synchronizing (entraining) the molecular clock to the day-night cycle
circannual rhythms
seasonal cycles
for winter survival and coordinated reproduction as antipredator strategy
type 1 seasonal rhythm
endogenous/exogenous control
due to photoperiodism (melatonin duration), lesions to the SCN prevens these cycles
tract day length
type 2 seasonal rhythms
true endogenous control
SCN lesions do not affect these cycles, indicationg that there must be secondary pacemakers/ oscillators
ie/ hiberation in ground squirrels
EMG in sleep
electrode on scalp
brain potentials allow for describing levels of arousal states of sleep
eye movements and muscle tensions are also monitered in sleep
stage 1 sleep
slowing of HR
relaxation of muscles
eyes may roll slowly under eyelids
8-12 Hz
alpha rhythm - rhythm where you relax and close your eyes - time spent here decreases as drowsiness sets in
EEG has smaller amplitude and irregular frequency
stage 2 sleep
sleep spindles - characteristic of 12-14 hz where a person is said to be in stage 2 sleep. occurs in periodic bursts
K-complexes - a sharp negative EEG potential
stage 3 SWS
defined by a large amplitude and slow delta waves
delta waves - slowest type of EEG about 1/sec
- more prominent as night progresses
brief return to stage two
synchronization of cortical neuron activity
pituatary releases growth hormone - prominent in early night
REM sleep
paradoxal sleep
small amplitude
high frrequency
in many ways a pattern of an awkae person
eyes darting rapidly under the lids
irregular breathing and pulse rate
experience vivid dreams
20 percent of total sleep
muscles show atonia
muscles relax
cant be in REM when sitting in class
unresponsive
flaccid muscle state
brainstem inhibiting motor neurons
atonia
complete absense of muscle tone
desynchronized EEG
beta activity; comprising a mix of many high frequencies with low amplitude
brief awakening
happens right after REM
Dreaming
most dreams occur REM sleep - lots of visual imagery, sense that you are there, experiencing the senses
70-90 percent of subject report dreaming in REM - tho it can occur in other stages
nightmares
REM
long frightening dreams that awaken the dreamer
night terrors
sudden arousal from stages 3-4 SWS
intense fear automatic activation, doesn’t recall a vivid dream
medication can make them more frequent
common in children during early sleep
non- REM dreams
more the thinking type
more problem, distinct difference between REM
babies circadian rhythms
circadian patterns of sleep evident at 16 weeks in babies - but sleep length is shorter than that of adults
potentially has to do with immaturity in brain
shorter in premies
babies spend a lot of time in REM, premies even more
- maturation of consolidation of memories
activate REM sleep is muscle twitches, smiles, grimaces
provides stimulation that is essential to maturation of the nervous system
sleep in the elderly
changes, but more slowly than in early development
stages 3 decline decline in old age - 1/2 the time as they did
eliminated by age 90
may relate to diminished cognitive abilities - characterized with dementia
inability to maintain sleep once acheived
loss of growth hormone?
Loss of SWS
impairs memory process
total amount of sleep declines
number of awakenings increases
lack of sleep and insomnia is common (associated with physical and cognitive impairments)
hard time staying asleep
effects of sleep deprivation
sleepiness!
bizarre behaviour - hallucinations in some subjects deprived of approximately 8.5 days
irritability, difficulty concentrating, disorientation
cognitive deficits on spatial tasks
reduced volume of temporal lobe
depends on age and personality factors
total sleep deprivation in mammals leads to death - due to hypothermia and immune system dysfunction
mental function impaired
sleep more to catch up
4-6 hours for 2 weeks show changes in attention, reaction time - compared to 8 hours
sleep recovery
performance on some tests were impaired, showed no signs of insanity
stage 3 increased at expense of stage 2, but never “catches up” to the sleep deficit
REM increases in intensity and recovers by night 2
sleeping more than normal after a period of sleep deprivation
fatal familia
an inherited disease that causes people in middle age to stop sleeping
after a few months results in death
energy conservation
energy consumption is reduced during sleep- lowered muscle tension, lowered heart rate, reduced blood pressure, reduced body temperature, slowed respiration
smaller animals with hight metabolic rates should sleep more - larger animals have lower metabolic rates and sleep less
caloric savings in humans for 8 hours of sleep vs. quiet inactivity is about 120 cals (10 percent)
predation avoidance
environmental opportunities - for what time you are awake at - species better at different parts of the day ie/ to get food; avoiding predators
sleep during the night may help reduce predation rates
also allows for foraging during daylight-temporal niche
REM sleep is easy to wake up from; brain waves also resemble ‘awake’ brain - may be periodic awakenings to check what is going on
important to conform to you ecological niche; what you are well adapted to
body restoration
rebuild proteins used up during the day
supported by sleep rebound
increased metabolic demands due to high energy use during the day does not increase our length of sleep
but not sleeping interferes with the immune systems and eventually leads to death (in rodents)
sleep deprivation makes us more susceptable to pain the next day
less than 5hrs a day more likely to develop diabetes
people sleeping less or more than 8 hours more likely to die
work at night, sleep in the day, more likely to develop cancer
sleep cleans out the brain - glia controlling CSF are faster at night (collecting and disposing toxins)
consilodation of memory
why waste memory space on a dream
replaying days activities and consolidating from these experiences
can’t learn new skills in our sleep - just helps us rememeber what we learned before we went to sleep
what are the 4 important neural system in sleep
forebrain, brainstem, pontine, hypothalamic
forebrain region
displays SWS by itself
generate SWS
brainstem region
activates forebrain region into wakefulness
pontine region
triggers REM
hypothalamic region
regulates the other 3 systems to determine sleep or wakefulness
the basal forebrain
neurons become active during SWS onset
actively imposes SWS on the brain
inhibited by noradrenergic stimulation
uses GABA to suppress tuberomammillary nucleus in hypothalamus; shuts down activity
Reticular formation in brainstem
wakes up cortex
axons spread dispersly; project to entire forebrain
electrical stimulation of reticular formation rapidy wakes animals up
lesions in the RF produce persistent sleep
activating system
the pons
triggers REM sleep - area near locus coeruleus
lesions eliminate REM sleep
some neurons here only seem to be active during REM sleep
electrical stimultion can induce REM sleep
causes atonia - though the inhibatory NT GABA causes IPSP to prevent APs - for motor neurosn
flaccid muscles
narcolepsy
frequent, uncontrollect and intense attacks of sleep brought on by emotional experience
can occur at any time usually during awaken hours
can last mins to hours
involves loss of muscle tone (cataplexy) and instant REM bouts
enter REM within a few mins
exhibit a normal sleep schedule at night
orexin is crucial
where does the hypothalamus project to, to release orexin
pons
basal forebrain
reticular formation
tuberomamillary nucleus
cataplex
sudden loss of muscle tone, leading to colapse of the body without loss of consciousness
can be triggered by intense emotional stimuli
orexin
neuropeptide made in hypothalamus that is involved in switching between sleep states
Somnambulism
sleep walking
more common in children
amnesia for experience
occur in stages 3 and 4
occasionally seen in murder and rape cases
REM behaviour disorder
organized sleep walking; fighting a Foe, eating a meal, acting like an animal
may be acting out a dream
more common in men
follwed by parkinsons and dementia
sleep enuresis
bed wetting
associated with SWS
insomnia
inability to fall asleep, 15-30 percent adults
more prevalent in females, smokes, alcoholic and caffeine users
multiple causes - medical conditions, first night effect, shift work
sleep onset and sleep maintanence
sleep apnea
sleep onset insomnia
difficulty falling asleep
sleep maintenence insomia
drugs seem to cause
sleep apnea
breathing ceases
blood levels of oxygen drop
arises from progressive relaxation, changes in pacemaker
sleep-state misperception
not even sleeping when EEG showed signs of sleep
sleeping without knowing it
