Problem 6 Sleep & Circadian rhythms Flashcards
Circadian rhythms
daily rhythms in behaviour
Zeitgeber
A stimulus (usually the light of dawn) that resets the biological clock that is responsible for circadian rhythms
Free running rhythm
Biological rhythm without external factors
suprachiasmatic nucleus (SCN)
A nucleus situated at the optic chiasm. It contains a biological clock that is responsible for organizing many of the body’s circadian rhythms
subparaventricular zone (SPZ)
A region dorsal to the SCN which is responsible for organizing cycles of sleep and waking
o they project to the dorsomedial nucleus of the hypothalamus (DMH) which in turn projects to several brain regions
Intercellular ticking
o The system involves at least seven genes and their proteins and two interlocking feedback loops
o When one of the proteins produced by the first loop reaches a sufficient level, it starts the second loop, which eventually inhibits the production of proteins in the first loop, and the cycle begins again. Thus, the intracellular ticking is regulated by the time it takes to produce and degrade a set of proteins
Melatonin
controls seasonal rhythms in mammals
Pineal gland
The pineal gland produces melatonin, a serotonin-derived hormone which modulates sleep patterns in both circadian and seasonal cycles
Stage 1
o Theta activity: 3.5-7.5 Hz which indicates that the firing of neurons in the neocortex is becoming more synchronized
o Transition between sleep and wakefulness
o From time to time the person will open and close their eyes and they will roll upwards and downwards
o Ca. 10 min
Stage 2
o Generally irregular EEG but contains periods of theta activity
o K complexes: are suddenly, sharp wave forms which are only found in Stage 2, ca. one per minute, are triggered by noises
o Ca. 15 minutes
Sleep spindles
short bursts of waves of 12–14 Hz that occur between two and five times a minute during stages 1–4 of sleep
K complexes
are suddenly, sharp wave forms which are only found in Stage 2, ca. one per minute, are triggered by noises
Stage 3+4/ slow-wave sleep
o Delta activity: less than 3.5 Hz occurs during the deepest stages of slow-wave sleep
o Slow-wave sleep: Non-REM sleep, characterized by synchronized EEG activity during its deeper stages, contains slow oscillation of less than 1 Hz
o Contains down state phase where the neurons show no activity and a up state phase where the neurons fire at high frequency
o Stage 3 ca. 20 min 20-50 % delta activity
o Stage 4 ca. 45 min is also the deepest stage of sleep more than 50 % delta activity
Slow-wave sleep
Non-REM sleep, characterized by synchronized EEG activity during its deeper stages, contains slow oscillation of less than 1 Hz
o Contains down state phase where the neurons show no activity and a up state phase where the neurons fire at high frequency
o Occur during the first half of the night
o associated with declarative memories
REM sleep
o EEG becomes desynchronized with some delta waves
o The eyes are moving rapidly
o Person becomes paralyzed during REM sleep
o Persons are not sensitive to stimuli despite it contains their name or it’s the sound of their alarm
o spinal and cranial motor neurons are strongly inhibited
o genital activity
o high blood flow in the visual association cortex but low in the primary visual cortex and the prefrontal cortex
o Associated with nondeclarative memories
o Only for some seconds
o Occurs mostly in the first Phase but only after the first repetition
