Chapter 14: Biological Rhythms, Sleep and Dreaming Flashcards
circadian rhythm
natural rhythms of 24 hours
what can influence circadian rhythms?
light and dark cycle
short rhythms
pacemaker cells in heart
long rhythms
seasonal cycles
free running
maintaining a circadian rhythm without external cues
phase shift
shift of activity due to a shift in a synchronizing stimulus
entrainment
process of this shift
zeitgeber
means time giver
- external cue used to synchronize activity (light)`
suprachiasmatic nucleus (SCN)
small region of hypothalamus that sets circadian rhythm
what do vertebrates have that entrain the circadian rhythm?
photoreceptors outside the eye
what in mammals provide this information to the SCN?
cells in eyes
retinal ganglion cells send axons to retinohypothalamic pathway, then split off at optic chiasm to directly synapse to SCN
what do retinal ganglion cells contain?
melanopsin
process of information getting to SCN
- light projects to the eye
- cones and rods provide form vision
- entrainment pathway consists of retinal ganglion cells containing melanopsin that project to the SCN through retinohypothalamic tract
- goes from SCN to thalamus to form vision which then sets the circadian rhythm
Circadian Rhythm Clock
- Two proteins, Clock and Cycle, bind together to form dimer
- Clock/Cycle dimer binds to DNA, enhancing the transcription of the genes for Period (Per) and Cryptochrome (Cry)
- Per and Cry bind together as a complex that inhibits the activity of the Clock/Cycle dimer, slowing transcription of the per and cry genes, and therefore slowing production of the Per and Cry proteins
- The Per/Cry proteins eventually break down or are modified so they no longer inhibit Clock/Cycle, allowing the process to start again. This cycle of gene transcription, protein interactions, and inhibition of gene expression takes about 24 hours to complete
- Retinal ganglion cells detect light with melanopsin, and their axons in the retinohypothalamic tract release glutamate onto neurons in the SCN. The glutamate stimulation leads to increased transcription of the per gene, synchronizing the molecular clock to the day-night cycle.
what causes night owls vs morning people?
different alleles of Clock or Per gene
ultradian rhythms
period shorter than circadian rhythm, usually several minutes or hours
- example: basic rest activity cycle (90 mins)
infradian rhythms
period longer than circadian rhythm, longer than a day
example: menstrual cycle
circannual rhythms
about a year
- light can affect these rhythms but do not depend on SCN
what is the most prominent circadian rhythm?
sleep/wake cycle (25 hours)
how to investigate sleep?
EEG, EMG, EOG
how long are cycles during sleep?
90-110 minutes
Rapid Eye Movement Sleep (REM)
vivid dreams, often built around stories where dreamer is present
what occurs during REM sleep?
eyes move rapidly, breathing and heart rate are uneven
EEG suggest awake brain, but muscles are relaxed and limp
Non-REM (NREM)
more about thoughts and thinking
stage 1 of NREM
8-12 Hz (alpha rhythm)
as drowsiness sets in, time spent in alpha rhythm decreases
vertex spikes: sharp wave EEG pattern
what occurs during stage 1 of NREM?
experience sensations of falling and jerk into wakefulness called “hypnic jerks”
stage 2 NREM
12-14hz (sleep spindles)
- occur periodically
K complexes: sharp negative EEG potentials
what occurs during stage 1 and 2 NREM?
people awakened in stage 1 or 2 deny having been asleep
stage 3 NREM
1hz (delta waves)
also called slow wave sleep
delta waves
large amplitude, but very slow
widespread synchronized activity across cortex
what occurs during stage 3 NREM?
night terrors: sudden arousal with intense fear and activation of autonomic system, feel a crushing on chest
what is REM sleep present in?
only birds and mammals
describe infants sleep cycles
they sleep more but have shorter sleep cycles
- have high percentage of REM sleep
what happens to sleep as you age?
less sleep is needed and there are more awakenings at night
what happens to elderly during stage 3 sleep?
there is a decline and it may be related to cognitive decline
elderly sleep cycles
fall asleep easily but cannot stay asleep
what does sleep deprivation lead to in rats?
increased metabolic rate, weight loss and after 19 days, death
what was the death caused by in the rats?
bacterial infection, which is normally fought off by immune system but lack of sleep prevented that
fatal familial insomnia
genetic defect, stop sleeping mid-age, die within 7-24 months
four functions of sleep
- energy conservation
- niche adaptation
- body restoration
- memory consolidation
energy conservation
reduced body temperature, slower respiration, slower heart rate –> reduced metabolic activity
niche adaptation
sleep enforces this adaptation to a particular ecological niche
body restoration
sleep helps restore body materials and functions
what does prolonged sleep deprivation lead to?
weakened immune system
what can increase risk of cancer?
working overnight and sleeping during the day
true or false: exercise causes people to sleep longer
false
memory consolidation
sleep promotes memory consolidation
what type of sleep is important for procedural memories?
NREM
neural systems and sleep
- forebrain system
- brainstem system
- pontine system
- hypothalamic system
forebrain system
displays slow wave sleep by itself
what causes sleepiness?
basal forebrain stimulations
what happens within the basal forebrain?
neural circuits activate GABA-ergic neurons that send their axons to the tubermammillary nucleus in the hypothalamus where the stimulation of GABA-A promotes sleep
brainstem system
activates forebrain into wakefulness
reticular formation
collection of cells throughout brainstem that project to variety of structures
what awakens mammals rapidly?
electrical stimulation of reticular formation
pontine system
triggers REM sleep
what specifically triggers REM sleep?
small group of cells in pons, ventral to locus coeruleus
where else do these pon cells travel?
they project to motoneurons and stop them which prevents them from reaching threshold and producing an action potential»_space; making muscles flacid
hypothalamic system
affects other three systems to determine sleep/wake
how was the connection between hypothalamic system and sleep discovered?
narcolepsy
narcolepsy
disorder that involves frequent, intense episodes of sleep that last from 5-30 minutes and can occur anytime during usual waking hours
what type of sleep do people with narcolepsy enter?
they enter REM sleep immediately upon falling asleep
cataplexy
sudden loss of muscle tone, leading to collapsing of body without loss of conciousness
what do narcoleptics suffer from?
cataplexy
treatment for narcolepsy
modafinil
why does cataplexy occur in narcoleptics?
continued activity in pontine system that inhibits motoneurons
what leads to narcolepsy?
loss of hypocretin neurons (located in hypothalamus)
where do hypocretin neurons project?
basal forebrain, reticular formation and locus coeruleus
and tuberomammillary nucleus in hypothalamus
most common sleep disorders in children
night terrors and sleep enuresis
sleep enuresis
bed wetting that occurs during slow wave sleep
treatment for sleep enuresis
drugs that decrease stage 3 sleep or antidiuretic
sommanbulism
sleepwalking that occurs during slow wave sleep
REM behavior disorder
person is physically acting out a dream
when does REM behavior disorder begin and who is it more common in?
begins around 50 and more common in males
what does onset of REM behavior disorder followed by?
parkinsons or dementia
sleep onset insomnia
difficultly falling asleep caused by situational factors
sleep maintenance insomnia
difficulty staying asleep
what is sleep maintenance insomnia caused by?
sleep apnea: respiration becomes unreliable and person may stop breathing for a minute
what does sleep apnea do?
kill neurons and lead to cardiovascular problems
treatments for insomnia
barbiturates, benzodiazepines, benzo mimics
problems with drugs used for insomnia
lose effectiveness over time, do not provide normal sleep and drowsiness during the day
best treatment for insomnia
visit a sleep clinic or work with sleep disorder expert to practice good sleep hygiene
sudden infant death syndrome
abnormalities in serotonin system in brainstem that regulate respiration
