Sleep - structures + chemicals involved
- Created by: Joanna
- Created on: 04-12-13 17:08
Structures
Outputs from SCN:
- subparaventricular zone (SPZ)
- dorsomedial nuclues of the hypothalamus (DMH)
Multistage pathway connecting SCN
ascending arousal system
via SPZ + DMH regul8s circadian rhythms of sleep + other bhvrs.
Reticular activating system (RAS) / Reticular form
RAS
- column of brain tissue extends from spinal cord to midbrain
- pass thru brainstem
- small clusters of neurones + fine branching network of fibres
- high r8 of firing its cholinergic fibres when awake + REM
- small r8 of RAS during NREM
- when RAS cells activ8d, EEG shows alpha type waves
Locus Coeruleus
- part of the pons
- involved w/ increasing animal's sensitivity to its environment
- increased activity of noradrenergic neuroes :associ8ed w/ wakefulness
- decreased activity involved w/ onset of REM sleep
Raphe Nucleus
- part of the medulla + pons
- important role in wakefulness
- blocks activity of neurones active in REM sleep
- serotonin - plays a role in triggering sleep
- serotonin influence neurones of preoptic nucleus
Preoptic nucleus + SCN
SCN - circadian patterns
destroying scn - disrupts the sleep wake cycle
implicated in insomnia
preoptic nucleus - close to the SCN + receives direct input from retinal fibers - input from eyes
light activating areas in retinal fibres - influential in sleep-wake cycle
Cholinergic mesopontine nuclei
- projects to the thalamus
- cholinergic mesopontine nuclei produces acetylcholine
- reduces activity of thalamic reticular nucleus - sleep system
- activ8s thalamocortical neurons involved in wakefulness
Chemicals involved in sleep
Nucleus involved in wakefulness:
- Mesopontine nuclei - acetylcholine - active neurones
- Locus Coeruleus - noradrenaline - active neurones
- Raphe nuclei - serotonin - active neurones
NREM sleep
- Mesopontine nuclei - acetylcholine - inactive neurones
- Locus Coeruleus - noradrenaline - less active neurones
- Raphe nuclei - serotonin - inactive neurones
REM sleep - on
- Mesopontine nuclei - acetylcholine - PGO waves
- Locus Coeruleus - noradrenaline - inactive neurones
- Raphe nuclei - serotonin - inactive neurones
REM sleep - off
- Locus Coeruleus - noradrenaline - less active neurones
REM sleep structures / areas
Primary visual cortex:
- conscious visual signals when awake
Extrastriate visual areas:
- - decode complex visual scenes
- - significantly more active during REM sleep
Prefrontal cortex:
- thought + judgement
Limbic system
- - active in REM
- - amygdala [emotion]
- - hippocampus [memory]
Anterior cingulate gyrus
- attention + motivation
- active during REM sleep
The pons
- active during REM
- REM sleep triggered by certain nuclei in the pons
Electrical brain potentials - levels of arousal +
Electroencephalography [EEG] - electrical activity in brain
Electro-oculography [EOG] - eye movements
Electromyography [EMG] - records muscle activity
Types of sleep
Slow-wave sleep [SWS]
- 4 stages
- characterized by slow-wave EEG activity
Rapid-eye-movement sleep [REM]
- small amplitude
- fast EEG waves
- no postural tension
- rapid eye movements
Brain waves:- low to high frequency
Delta waves up to 4Hz
- frontally in adults
- posterior in children
- adults slow wave sleep
- 3-4 SWS stage
Theta waves 4-7Hz
- drowsiness in older children + adults
- 1-2 SWS stage
Alpha waves 8-12Hz
- posterior regions of head, both sides
- higher in amplitude on dominant side
- central sites c3-c4 @ rest
- closing eyes by relaxation
- 1 SWS stage
Brain waves:- low to high frequency 2
Beta waves 12-30Hz
- both sides
- symmetrical distribution
- most evident frontally
Gamma waves 26-100Hz
- certain cognitive / motor functions
Pontogeniculooccipital [PGO]waves
- pons/geniculate [auditory/occipital vision]
- spiky waves during REM sleep
Human sleep - diff stages
Pattern of activity in awake
dominated by waves of fast freq + low amplitude : 15-20 Hz
beta activity / desynchronised EEG
alpha rhythm - during relaxation
regular oscillation
8 - 12 Hz
Stages of slow-wave sleep
Stage 1 sleep
- events of irregular freq + smaller amplitude / vertex spikes / sharp waves
- heart r8 slows, muscle tension reduces, eyes move about
- lasts several mins
Stage 2 sleep
- defined by waves of 12-14 hz - occur in burts = sleep spindles
- K complexes appear - sharp -ve EEG potentials
Stage 3 sleep
- continued sleep spindles as in stage 2
- appearance of large amplitude , slow waves = delta waves
- delta waves - once / second
Stage 4 sleep
- Delta waves - present about half the time
REM SLEEP follows:
- active EEG w/ small amplitude, high freq waves like an awake person
- muscles = relaxed = paradoxical sleep
Adult sleep
Typical night
- sleep time ranges : 7-8 hrs
- 45-50% = stage 2 sleep
- 20% = REM sleep
- Cycles last 90-110 mins
- cycles early in night = more stage 3 + 4 SWS
- later cycles = REM sleep
Dreams and nightmares
Vivid dreams during REM sleep
- visual imagery
- sense that dreamer is in the scene
Nightmares:
- frightening dreams
- awaken the sleeper from REM sleep
Night terrors:
- sudden arousals from stage 3/4 SWS
- fear + autonomic activity
Sleep patterns change across the life span
Mammals sleep more during infancy > adulthood
Infant sleep:
- shorter sleep cycles
- more REM sleep
- 50% - provide essential stimulation to the developing nervous system
Aging people - total time asleep = declines + # of awakenings increases
- Most dramatic decline = loss of time spent in stages 3 + 4
- age 60 : only 1/2 as much time spent at age 20 by age 90 stages 3 + 4 = disappeared
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