Sleep and consciousness Flashcards
What is consciousness?
Ability of an individual to react appropriately to stimuli in the outside world
How is consciousness clinically assessed?
Using Glasgow Coma Scale: max 15 points for being awake and alert
- tests eye opening, verbal response and motor response
- so better to ask how conscious is a person instead of is that person conscious= consciousness is not an all or nothing state but a continuum
What are the stages of consciousness?
- coma (with or without reflexes present)
- unconsciousness (unarousable, but maybe only temporarily by intense stimuli)
- sleep (arousable by normal stimuli)
- drowsy wakefulness (responding in non-reflex way)
- normal wakefulness (responding to spoken/written stimuli)
- high arousal (hyper alert and fast reactivity)
What are the categories of the Glasgow scale in terms of eye opening?
- spontaneous
- to sound
- to pressure
- none
What are the categories of the Glasgow scale in terms of verbal response?
- orientated
- confused
- words
- sounds
- none
What are the categories of the Glasgow scale in terms of motor response?
- obey commands
- localising
- normal flexion
- abnormal flexion
- extension
- none
What is an electroencephalograph
- measures brain arousal
- small voltages recorded from scalp electrodes
- average thousands of nerve cells so cannot be used to measure what individual neurons are doing
What are the uses of an EEG?
- best for detecting seizure activity
- picks activity from muscles in head
What is the normal appearance of an EEG?
- high frequency low amplitude signal
- desynchronised appearance as some neurons fire out of phase with others so cancel each other out
What is the appearance of an EEG in a seizure?
Synchronous firing
- slow wave appearance with higher amplitude
- more synchronous = less conscious
- consciousness = function of desynchronization
What does sleep produce on an EEG?
- cortical neuronal synchronisation
- large amplitude slow waves which can be confused with a seizure
(SLOW WAVE SLEEP)
What is the purpose of non-REM/slow wave sleep
Maintenance and Repair
Increased growth/maintenance of immune/nervous/skeletal and muscular systems
- GH secreted
- wound repair
What is the purpose of REM sleep?
- EEG more like normal wave sleep
- memory consolidation
- removing junk and defragment memories
- coping with life stresses
What is the role of antioxidants in sleep?
- High levels of reactive oxygen species generated in the mitochondria
- metabolic rates decrease in sleep
- melatonin released from pineal gland
Where is the pineal gland?
At posterior border of 3rd ventricle
- endocrine organ
What is melatonin?
Powerful free radical scavenger
- removes free radicals that have accumulated in waking
- prevents seizures by maintaining GABA function
- glycogen brain stores increase during sleep
What are the stages of sleep?
4 stages of normal/slow wave sleep
1 stage of paradoxical/REM sleep
- repeat in regular stages around 90 minute cycles
Where does control of sleep and wakefulness occur?
- in reticular formation of pons
- pontine centres modulated by hypothalamus which decides when we need more sleep
Which chemicals are sleep inhibitors?
Ghrelin
Glucose
Which chemicals are sleep inducers?
Leptin
Adenosine
Antihistamines
How are chemicals regulating sleep and wakefulness controlled?
- medial and ventrolateral preoptic nuclei in hypothalamus detect blood levels
- preoptic nuclei project to tuberomammillary nucleus which has histaminergic neurons which are active during waking and silent during sleeping
- preoptic nuclei may trigger sleep by inhibiting activity of TMN histaminergic neurons
What happens in diurnal rhythms?
Suprachiasmatic nucleus receives input from retina
- projects to TMN
- neurons of retina fire continuous during daylight
What is the cause of narcolepsy?
- loss of orexins due to autoimmune attack from T cell lymphocytes on orexin-containing neurons
- found in posterior hypothalamus
What do orexins stimulate the release of?
Acetylcholine
Noradrenaline
Serotonin
Dopamine
What is wakefulness maintained by?
Orexin
Histaminergic neurons
When does sleep onset occur?
When signals from preoptic nuclei and suprachiasmatic nucleus inhibit histamine and orexin neurons
- they stop excitatory transmission to reticular formation of pons
Where are the cell groups which maintain wakefulness found?
In reticular formation
What are the cell groups which maintain wakefulness?
- dopaminergic cells (in ventral tegmental area)
- cholinergic cells/acetylcholine (predunculopontine nucleus)
What is the role of the dopaminergic cells in the ventral tegmental area?
- at low level during sleep
- nigrostriatal dopamine system activates basal ganglia during waking so we can move fluently
- mesolimbic system activates limbic system
- mesocortical system activates cortical system
What do the cholinergic cells do?
- project to the thalamus
- cholinergic cells found in nucleus basalis that sends axons to all parts of cerebral cortex
- adjacent to accumbens nucleus
- activity increased in REM sleep and waking
How are dreams different than waking?
- we normally forget dreams (memory making parts switched off)
- lower motor neurons are paralysed (apart from respiratory and extraocular muscles)
What is the locus coeruleus?
The noradrenergic cells
What does the noradrenaline system do?
- during all forms of sleep neurons drop to low level
- control center for SNS
- projects to cerebral cortex and activates a form of central sympathetic system to activate alertness and attention for us to retrieve memory and use in dreams
What do serotonergic cells do during sleep?
Cells stop during REM sleep activity
What is the theory of the function of serotonergic cells during sleep?
Maintain connection between UML and LMN
- motor cortex active in sleep
- don’t move as believe that without firing of serotonin connection will not happen
- sleepwalking is thought to be failure of motor disconnection during REM
What is the role of amphetamine?
Prevent sleep by continually releasing dopamine/noradrenaline despite amine cell bodies in brainstem being inactive
What do SSRIs do to sleep?
Reduce duration of REM sleep
- serotonin ceases during sleep so if kept high might decrease efficiency of sleep
- also memory loss of REM used to consolidate memory
What is the role of antidepressants and sleep?
TCA - enhance sleep as block H1 receptors/noradrenaline reuptake
MOAs - reduce sleep as increase noradrenaline/dopamine/serotonin levels
How is insomnia treated?
- lifestyle changes
- CBT
- Antihistamines
- Benzodiazapines
- Zopiclone (increase release of GABA)
What is the cause of sleep apnea?
- motor disconnection during REM must specifically avoid respiratory system otherwise stop breathing
- muscles of throat relax too much obstructing airways
- can lead to sudden infant death syndrome
