Sleep and Arousal Flashcards
Consciousness or Arousal
The ability of an individual to react appropriately to stimuli in the outside world
Coma
Unarousable unresponsiveness
–> with or without reflexes present
Unconsciousness
Arousable
–> But perhaps only temporarily by intense stimuli
Sleep
Arousable by normal stimuli
Drowsy wakefulness
Responding in a non-reflex way
Normal wakefulness
Responding to spoken or written stimuli
High arousal
Hyper alert and fast reactivity
EEG
Electroencephalograph
Small voltages recorded from pairs of scalp electrodes
Envelope of the average activity of many hundreds or thousands of nerve cells
Detect seizure activity
Normal waking EEG
High frequency
Low amplitude
Desynchronised EEG
Individual neurones firing out of phase with each other
Normal
Slow waved EEG
Individual neurones firing in phase with each other
Abnormal
Consciousness + synchronisation
More synchronised the cortical neuronal activity, the less conscious
Sleep + synchronisation
Normal (slow wave) sleep produces cortical neuronal synchronisation + thus large amplitude (delta) slow waves
Non-REM sleep / Slow wave sleep (SWS)
Normal
Increased growth and maintenance of immune, nervous, skeletal and muscular systems
Growth hormone main secretion
Most growth of long bones
Wound repair + regrowth of injured tissue
Melatonin
Released from pineal gland during sleep
Powerful free radical scavenger
Removes/neutralises free radicals that have accumulated during waking
Maintains GABA function + prevents seizures
Glycogen stores in brain during sleep
Increase
Pineal gland location
Posterior border of 3rd ventricle
Where are key control centres that control sleep and wakefulness
Reticular formation of Pons
Hypothalamus
Decides when we need sleep
Then sends signal to pons to trigger sleep state
Ghrelin
Inhibitory action on sleep
Low blood glucose levels
Inhibitory action on sleep
Leptin
Increases sleepiness
High adenosine levels
Induce sleepiness
Medial + Ventrolateral preoptic nuclei
In Hypothalamus
BBB leaky
Receptors here detect blood levels of various molecules –> can promote or inhibit sleep
Preoptic nuclei Projections
Project to tuberomammillary nucleus
Contains histaminergic neurones
–> active during waking and silent during sleep
–> project to all areas of neocortex
Preoptic nuclei neurones can trigger sleep by inhibiting activity of TMN histaminergic neurones
Histamine
Monoamine
Histamine receptors- H1,2,3 etc
Diurnal sleep rhythm
Regulated by suprachiasmatic nucleus
Special photoreceptor cells in retina send axons to SCN - fire continuously in daylight
–> SCn integrates this to compute hours of daylight
Suprachiasmatic nucleus lesions
Destroy diurnal seep rhythm
Still sleep, but at irregular patterns
Narcolepsy
Abnormal sleep
Loss of orexin-containing neurones by autoimmune attack from T cell lymphocytes
Orexin
Peptides
Orexin neurone cell bodies found in posterior hypothalamus
–> innervate the brainstem monoamine cell bodies, especially locus coeruleus + raphe nuclei
Stimulate release of ACh, NA, 5HT and DA
2 hypothalamic systems involved in maintaining wakefulness
Histamine neurones of tuberomammillary nucleus
Orexin neurones of posterior thalamus
Sleep onset
Signals from preoptic nuclei and suprachiasmatic nucleus inhibit histamine and orexin neurones
Stops excitatory drive to monoamine neurones of reticular formation of pons and midbrain, which are necessary for cortical arousal
Dopaminergic cells
Ventral tegmental area
Cholinergic cells
Pedunculopontine nucleus
Noradrenergic cells
Locus coeruleus
Serotoninergic cells
Raphe nuclei
2 Cholinergic systems
Cholinergic cells in pedunculopontine nucleus project to thalamus
Cholinergic neurones in basal forebrain nucleus send cholinergic axons to all parts of cerebral cortex
Cholinergic neurones + Alzheimer’s
Cholinergic neurone systems damaged in Alzheimer’s
Majority of Alzheimer’s patients also have sleep disorders
Noradrenaline + serotonin neurones
Decrease activity during sleep
Noradrenaline system
Noradrenergic neurones drop to low activity in sleep
Alertness + attention
ACh system
ACh activity low during SW sleep
During REM sleep activity in cholinergic neurones increases near waking levels
ACh enables thalamus + cortex to operate in same way during normal alert waking and REM sleep
Serotonin system
REM- serotonin neurones completely stop + stay at 0
Maintain connection between UMN and LMN –> so if asleep, not maintained
REM sleep function
Memory consolidation- Long term memory
Removing junk + defragmenting memories
Coping with life’s stress
SSRIs
Serotonin release in brain ceases during REM sleep
Reduce duration of REM sleep
Increase sleep onset latency
Decrease in sleep efficiency
TCAs
Promote sleep
Exert prominent blockade of H1 receptors
MOAIs
Reduce sleep- increase NA, DA and 5HT levels
Insomnia treatment
Lifestyle changes CBT Antihistamines Benzodiazepines Zopiclone
Sleep Apnoea
Stop breathing when start dreaming
Muscles of throat relax too much, and obstruct airway
Build up of CO2
SIDS
Mainly happen when baby asleep
Respiratory system not woken by rise in CO2 caused by the apnoea because immaturity of system
