sleep cycle tell Flashcards
what stage is N1 in sleep
the shortest, last for around 8-10 minute
Stage N2,
either increasing in depth to N3 or moving up into REM or light sleep/waking.
what are physiological features of going into deeper sleep
-muscle tone reduces
- eye movement is low
- heart rate slows
- respiratory rate is held at normal
REM sleep
active brain state similar to waking, yet the body is inactive. REM sleep is metabolically demanding as the brain is active, heart and respiratory rate increase and there is increased eye movement, but atonia (lack of muscle tone) in the body.
EEG
investigating the changes occurring during sleep as all stages of the sleep-wake cycle have characteristic rhythms and patterns of activity that can be identified in the EEG
Brainstem reticular formation
control the normal daily patterns of the sleep wake cycle.
what is the reticular formation(RF) made up of?
mix of cells, nuclei and networks that lie within the brainstem and upper cervical regions of the spinal cord
3 things RF plays a role in?
control of arousal levels, or alertness, and consciousness.
what 2 tracts does the RF involve?
1.Ascending Reticular Activating System (ARAS)
2.Descending Reticulospinal tracts
Ascending Reticular Activating System (ARAS
these pathways are not well understood but are involved in arousal and alertness through activation of the higher cortical circuitry.
Descending Reticulospinal tracts
these pathways are involved the control of movement.
how does ARAS increase activity in the thalamus?
conceptual collection of fibres that increase activity in the thalamus and cortex when activated by the reticular formation.
what do the fibres activate in ARAS?
fibres activate the thalamus, and also the major transmitter pathways enabling activation of a large amount of cortex, which maintains a high level of arousal and attention. As a result ARAS is suggested to be involved in: arousal, motivation, integration, motor and autonomic control, reaching all regions of the brain
function of reticular nucleus
controls the activity in the other nuclei, permitting or stopping information flow through this region
what is the key nucleus involved in control of the arousal in the thalamus ?
reticular nucleus
what is another nucleus involved in the arousal system?
centromedian nucleus
what is the function of centromedian nucleus?
connects the basal ganglia and limbic regions with the reticular formation.
what do activation of the certain nuclei in the brainstem reticular formation and the reticular nuclei of the thalamus allow in arousal?
allows or supresses information flow to the thalamus (and the hypothalamus) and out to the cortex
what happens in the information if flow is reduced in the nuclei in the brainstem reticular formation and the reticular nuclei of the thalamus allow
there is nothing to process in the cortex and limbic system and the autonomic nervous system remains passive, so consciousness is reduced
what happens if the information is high in the
nuclei in the brainstem reticular formation and the reticular nuclei of the thalamus allow
what happens during waking
-brainstem activated
-histamine neurons activate cholinergic pathways activating thalamus -enables info from motor to sensory
what happens in result of brain activity after waking stage
-brain activity-levels of adenosine increase
-levels of adenosine by-product of energy(ATP) increase
what is adenosine?
inhibitory neuromodulator that binds to adenosine receptors (found across the brain), so increasing levels start to dampen cortical activity, acting as a driver for sleep initiation
glymphatic system removes sleep excess ,define this system?
inhibitory neuromodulator that binds to adenosine receptors (found across the brain), so increasing levels start to dampen cortical activity, acting as a driver for sleep initiation
what happens to the circadian centres in the hypothalamus?
activate GABAergic pathways which also dampen down neuronal activity and relax the muscles and this starts the process of falling asleep. The body begins to relax to relax and we start feeling drowsy
what do the GABAergic pathway
1.histamine-containing cells in the hypothalamic tuberomamillary bodies
2. in the brainstem reticular formation; and also inhibit the brainstem cholinergic pathways
what does the GABAergic pathway reduce the activity of?
thalamus, preventing information flow and creating a lower level of arousal.
why is muscle tone maintained?
inhibition does not affect the motor tracts which arise in the brainstem and cerebellum, but sensory information does not reach the cortex and consciousness, giving an ‘inactive mind in an active body.’
what is the slow wave sleep pattern recorded in a ECG ?
-thalamus has slow oscillations
-when sensory and motor pathway flow is inhibited -becomes dominant activity in the region
-slow rhythm passes along ascending tracts into the cortex and cells follow the activity pattern
in paradoxical(rem) sleep what happens to the GABA initiation?
decreases and begins to impact on the tonic activity controlling motor tone
in paradoxical(rem sleep) what 2 transmitter pathways does it start to inhibit and do they increase or decrease?
1.5HT
2.Noradrenaline
they decrease
in paradoxical(rem sleep) what levels do 5HT and noradrenaline control?
acetylcholine levels by dampening down cholinergic neuron activity
In paradoxical(rem sleep) what happens when the acetylcholine levels dampen the cholinergic neurone activity?
increases cholinergic input to the thalamus and triggers cortical activity, producing a state of an ‘active mind in an inactive body,’ paradoxical, or REM (rapid eye movement) sleep
insomnia
inability to fall asleep or remain asleep for sufficient time
what are the common causes of insomnia?
Lifestyle (learnt behaviour)
Circadian rhythm disruption (jet-lag/shift work)
Emotional Disturbances
Ageing
Children
short term treatment of insomnia?
over the counter hypnotics (sleep inducing drugs) such as antihistamine
treatment for insomnia in the clinic?
cognitive behavioural therapy if often recommended.
Parasomnias
disorders that occur around and during sleep
-occur during the later stages of N2 and N3, but a few disorders are associated with REM sleep.
what does Parasomnias include?
Somnambulism (sleep walking)
Night/sleep terrors
Sleep paralysis/Hallucinations
Nocturnal seizures
REM behavioural disorder (RBD)
Restless leg syndrome
Bruxism (teeth grinding)
what does RBD cause?
by incomplete/absent paralysis during REM – can ‘act out’ dreams, which can be terrifying for a person’s partner, family
Sleep apnoea
condition in which the sufferer experiences period of breathing cessation during sleep
in sleep apnoea what happens during the person stopping breathing in their sleep?
respiratory reflexes restart once the brain detects an increase in CO2 in the blood
what do the 2 types of forms of sleep apnoea mean?
Central - caused by problems within the brainstem respiratory circuitry
Obstructive - caused by structural compression of the airway
factors that cause obstructive sleep apnoea?
weight, hypertension, adenoid/tonsil size, presence of polyps (small cellular growths), smoking and drinking. Indicators often include, excessive snoring and tiredness during the day
how to manage risk factors of sleep apnoea
-weight and BP
or orthodontic intervention
-surgery to maintain airway patency
CPAP (Continuous positive airway pressure)
patient wears a mask which blows air into the airway to keep it open
what does sleep deprivation link to?
rebound REM sleep and loss of the deep stages of NREM sleep
