Sleep and conciousness Flashcards
Define conciousness
Ability of a person to react to stimulus in the outside world
Define coma
Unarousable response
What is high arousal
Hyper alert and fast reactivity
What does EEG stand for
Electroencephalograph
What does EEG measure
Average activity of the neurones NOT activity of individual neurones
What are the EEGs best used for
Detection of seizures
How do neurones fire during a seizure
Large groups of neurones all fire at the same time producing large amplitude waves
What is the normal amplitude/ frequency of neurones in the brain
High frequency
Low amplitude
Is desynchronisation or synchronisation normal in terms of neurones firing
Desynchronisation is normal
How do synchronised waves appear on an EEG
High amplitude, slow wave
The more synchronised the cortical neuronal activity…
The less consious the individual
What is conciousness a function of
Desynchronisation
What can be seen on an EEG during normal, slow wave sleep
Cortical neuronal synchronisation Large amplitude (delta) slow waves
What happens during slow wave sleep
- Increased growth and maintenance of immune, nervous, skeletal and muscular symptoms
- Growth hormone secretion
- Wound repair and regrowth of injured tissue
- Expansion of channels between neurones
- CSF influx
How do glycogen stores change during sleep
They grow
What is the result of the high levels of aerobic metabolism that occurs during waking
Accumulation of free radical reactive species
Is metabolic rate higher or lower during sleep
Lower
Where is melatonin released from
Pineal gland
What are the functions of melatonin
Powerful free radical scavenger
Maintains GABA functions
Prevents seizures
What brain structure appears to control sleep and wakefullness
Reticular formation of pons
Where do pontine neurones project
Diffusely to the cerebral cortex
Signals from which brain structure modulate the pontine centres
Hypothalamus
Function of hypothalamus in terms of sleep/wake cycle
Decides when we need sleep and sends signal to the pons
2 main stimuli for sleep
Chemicals in the blood
Diurnal rhythms
Around which structures in the blood brain barrier leaky
Medial and ventrolateral preoptic nucleus
Receptors in which nuclei detect blood levels of molecules of sleep
Medial and ventrolateral preoptic nucleus
Name 2 chemicals that inhibit sleep
Ghrelin
Glucose
Name 2 chemicals that induce sleep
Adenosine
Leptin
Caffiene is an antagonist to what molecule
Adenosine
Where does the preoptic nucleus project and what neurones are contains on this structure
Projects to the tuberomamillary nucleus which contains histaminergic neurones
Are the histaminergic neurones on tuberomamillary nucleus active during waking or sleep
Waking
Where do the histamingeric neurones on the tuberomamillary nucleus project to
All areas of the neocortex
How does the preoptic nucleus trigger sleep
Inhibiting activity of tuberomamillary activity
Effect of antihistamine on sleep
Cause drowsiness
The retina projects to which nucleus to regulate diurnal rhythm of sleep
Suprachiasmatic nucleus
Where does the suprachiasmatic nucleus project
Tuberomamillary nucleus
How does the suprachiasmatic nucleus ‘know’ the hours of the day
Photoreceptor cells in the retina sends axons to SCN which fire continuously into daylight
Integrates into hours of day by SCN
Briefly state the pathogenesis of narcolepsy
Autoimmune attack on orexin containing neurones by T cells
Loss of orexin peptides
Where are orexin cell bodies found
Posterior hypothalamus
What do orexins stimulate release of? Effect of this
Ach Noradrenaline 5-HT Dopamine Maintains wakefullness
When is sleep induced
When signals from the preoptic nuclei and suprachiasmatic nucleus inhibit histamine and orexin release
What is the effect of inhibiting histamine and orexin release
Stops excitatory drive to the monoamine neurones of the reticular formation of pons and midbrain
What cells groups are found in the locus coeruleus
Noradrenergic cells
What cell groups are found in the raphe nucleus
Serotoninergic cells
What cell groups are found in the ventral tegmental area
Dopaminergic cells
What cell groups are found in the pedunculopontine nucleus
Cholinergic
What results from a lesion in the reticular formation of pons and midbrain
Coma
Where do cholinergic peduncular nuclei neurones project to
Thalamus
As well as pedunculopontine, where are cholinergic neurones found
Basal forebrain nucleus adjacent to accumbens
Where do the cholinergic neurones found on basal forebrain project to
Accumbens nucleus
How do Ach levels change during REM sleep
Rise to near waking levels
When does Ach activate thalamus and cortex
During waking and dreaming
How do noradrenergic levels change during sleep
They drop
What is the control centre for the sympathetic nervous system during sleep
Locus coeruleus
Function of noradrenergic system in sleep and waking
Activates alertness and attention
Function of serotonergic system in sleep
Maintains connection between upper and lower motor neurones
Are dopamine levels high or low during sleep
Low
What does the nigrostriatal dopamine system activate
Basal ganglia
What do mesolimbic and mesocortical systems activate
Frontal cortex and limbic system
Purposes of REM
Removing junk memories
Stress management
Memory consolidation
Why do SSRIs intefere with sleep
Serotonin levels should be low during sleep, but SSRI make serotonin levels high 24 hours a day
As REM is associated with memory, consolidation, affects memory
How do tricyclic antidepressant affect sleep
Induce sleep by blocking histamine receptors
