BM - Sleep Flashcards
What is sleep?
A physical state of:
- postural recumbency
- quiescence
- closed eyes
however 2 separate states of sleep have been identified (through using electrodes in the brain) - REM and non-REM
Sleep isn’t passive - intact very active.
What are the stages of sleep?
Relaxed, wakefulness Stage N1 Stage N2 Stage N3 REM
What is relaxed, wakefulness?
Alpha waves are present when one begins a state of relaxation, high frequency.
this is the cosy feeling in bed and is part of the sleep cycle.
What is stage N1?
Irregular, jagged, low amplitude waves, brain activity begins to decline, decreases in frequency
The brain is starting to slow down
What is stage N2?
Present elf sleep spindles and K-complexes
K complexes and sleep spindles provide vital function to humans
What is stage N3?
Low frequency (slow), high amplitude waves (delta waves, slow wave activity - SWA)
Frequency and amplitude have increased
What is REM stage?
Irregular, low-amplitude and his frequency (fast) waves; PGO waves; rolling eye movements; loss of muscle tone
REM - tells you about psychopathology, almost a mixture of being awake and being in stage 1 sleep. Just looking at brainwave activity cant actually tell if in REM or just a relaxed state so need to look at muscle tension. Should have no muscle tension during REM. REM behaviour disorder is the acting out of violent or aggressive acts during REM without any knowledge - would have muscle tension. Also might see RBD in Parkinsons and other neurodegenerative disorders. Think something to do with release of acetylcholine
What are the specifics of stage 2 sleep?
NREM takes up 75% of the whole night and REM takes up approximately 20-25%
Stage 2 takes up between 45-55% of the whole night.
Have to see a K complex and sleep spindle for someone to be defined as in stage 2 sleep.
Performs several important functions. This is when we review the information form our day and determine what we need to turn into memory later on. Memory filing system. Will get rid of the information that isn’t needed and can consolidate what you do need, and can be turned into long term memory.
See very long stage 2 sleep in fibromyalgia, chronic fatigue syndrome and chronic pain. This is showing the attempt/capacity of the neurological system to mask pain, trying to keep the organism asleep. If there is pain then will automatically evoke a k complex and sleep spindle, stopping focus on the pain and keeping asleep. Also masks anything from the sensory system eg gurgles from digesting food.
Also, when we have a transition in sleep a spindle and k complex will try and cover that distance so that we don’t actually wake up.
A normal healthy adult will wake up 5-6 times at night but wont be remembered because the k-complex and spindle will kick in to put back to sleep until the transition is over.
Don’t see stage 2 in children until they are about 2 years old. Don’t need stage 2 as a small child because don’t need to discard memories, everything needs to be consolidated because everything is new. Sleep stages in children are about 60 minutes alternating between REM and slow wave. Therefore there is no real need, unless the child is in pain, for stage 2 sleep.
What is the hyping jerk?
follows stage 1 and is the sign of transition into stage 2 sleep
this is using up the last bits of cortisol in order to sleep. cortisol keeps us unregulated which we don’t want, we want down regulation. the body tenses and released very quickly and resealed this cortisol - completely normal.
What happens in REM sleep?
Muscle tension non-existant
body paralysis
eye movements and respiratory system active
dream activity
What is the typical sleep sequence?
If prodded in stage 1 likely to say that you were awake because it’s a very light stage of sleep.
You will then have an incident, HYPNIC JERK, this is telling us that it is the transition to stage 2 sleep.
Then into stage 3 - slow wave sleep.
After slow wave sleep we go back up into stage 2 sleep. After another period of stage 2 we will enter into out first REM period.
That should take approximately 90 minutes. Slightly longer for the first sleep cycle and then about 90 minutes.
For the rest of the night we do concentric circles - 2,3,2,REM,2,3,2,REM etc
What happens during stage 3 sleep?
This is the only time the immune system is working at its full capacity. If deprived from this then you start to see physical illness. Release growth hormone during this time - growth in young and damage repair in adults. Immuno modulate during this time, produce hormones which will fix the body. Kill caricnoma cells during slow wave sleep. Also fix allergies during this time, body will prodcue immunomodulators to try and fight the allergen. Necrotics - hunt and eat up all the dead things in our bodies during this time. Immense ability to help the physical body during slow wave sleep.
Why do we go back into stage 2 following slow wave sleep?
This is assumed to be an evolutionary response - so that we can scan the environment for unusual noises. Make sure that it is safe to continue sleeping. After another period of stage 2 we will enter into our first REM period.
Does all dream activity take place in REM?
Not all dream activity takes place during REM. We also dream outside of RME but the dreams are slightly different. If dreaming in colour you are in REM, if in black and white not in REM. You should not hit REM for 90 minutes form falling asleep. This is important in psychopathology. If go into rem quicker than that it is likely that in the next 4-5 weeks you will develop major depressive disorder.
What is the distribution of REM across the night?
Over the night the first slow wave block will be about 25 minutes in duration. The first REM cycle will be about 5 minutes in duration. As the night progresses, slow wave sleep decreases and REM increases. By the end of the night likely to have 25mins of rem and less than 5 minutes of slow wave. Makes evolutionary sense as more important to protect the physical body than the mental body, and that is why slow wave first as need to protect and repair physical body first and then if all is well you can then protect the mental body too.
What are the brain mechanics in sleep 1?
Prefrontal cortex - inactive
- Memory (STM) - Attention - Perception
Limbic cortex - inactive NREM
- Autonomic function
Parietal cortex - less active REM
Frontal cortex - less active NREM
Prefrontal cortex should be inactive throughout the whole process of sleep - not needed any of its functions. No good for us to be creating new knowledge during sleep.
There is a particular issue called cortical arousal which may explain insomnia. This is believed to be because the prefrontal cortex hasn’t become completely inactive.
Limbic cortex should be inactive during nonREM and active during REM.
Parietal less active in REM - parietal cortex for spatial awareness, reasoning, unrational dreams doing weird things show that the parietal cortex is not active, we arent questioning dreams and being rational
Frontal cortex much less active during non REM but more active in REM - personality, emotions etc - shows why have emotions in dreams, still allowing the brian to process emotional information
What are the brain mechanisms in sleep II?
Thalamus - bridge between cortex and receptors
Thalamic reticular nucleus
- Excitatory neurons - glutamate - Inhibitory neurons - GABA --> inhibits arousal in brain centres
Thalamic pacemaker
Thalamic reticular nucleus is the draw bridge of the brain - can be up or down. If up, information travels through, if down, doesn’t pass through. Regulated through excitatory neurones (glutamate) or inhibitory neurones (GABA). Brings up drawbridge between cortex and receptors - this is the thalamic pacemaker.
What is the ascending reticular activating system (ARAS) - reticular formation?
A heterogeneous region of several brain areas that runs…
- Through brainstem from the medulla
- To the pons and midbrain
- And into the posterior hypothalamus
Second and third points control wakefulness/sleep
Experimental lesions in animals and clinical observations in patients with strokes/tumours produce hypersomnolence.
Electrical stimulation of this area causes aroused EEG and behavioural activation.
Confirms the reticular formation is necessary for wakefulness.
Monoaminergic – serotonin / histamine / noradrenalin – activity high in wake, reduced in NREM and absent in REM
Cholinergic – acetylcholine – highest in wake and REM and low / absent in NREM
Activation of both systems desynchronises EEG during wake and REM
Monoaminergic – serotonin / histamine / noradrenalin – activity high in wake, reduced in NREM and absent in REM
Cholinergic – acetylcholine – highest in wake and REM and low / absent in NREM
Activation of both systems desynchronises EEG during wake and REM
Neurons of the ARAS produce neurotransmitters
· gamma-aminobutyric acid (GABA)
Inhibitory effects on target neurons promotes sleep by reducing activity of wake-promoting neurons.
What are the neurotransmitters produced by the neutrons of the ARAS?
· Acetylcholine (Ach) · Norepinephrine (NE) · Dopamine (DA) · Serotonin (5-HT) · Histamine (HA) Orexin/hypocretin
What happens if there are lesions in any of the ARAS areas?
you start to create somulance/hypersomulance - excessive sleepiness. This is the mechanisms by which sleep is turned on or off - the ‘sleep switch’
What does Ach do in ARAS?
Keeps us paralysed - parasomnia in non-rem sleep if walking/eating/talking/sex then not producing enough Ach
What is NE doing in ARAS?
down regulating
What does DA do in ARAS?
also helps to keep us paralysed and from moving too much
What does 5-HT do?
high levels indicated in depression and other psychological disorders, in essence it regulates mood
What does HA do in ARAS?
is a wakefulness drug. stopping release of histamine makes you drowsy
what does orexin do in ARAS?
newest in sleep medicine. During the day if have a huge influx of orexin this is narcolepsy. That suggests to us that orexin puts you to sleep. Does this by inhibiting wakefulness, not a somnogenic. All of the new drugs for sleep in the future will be orexin based - now know it is more important to manage orexin than to manage any of other other elements, such as GABA
What does GABA do in ARAS?
reduces wakefulness promoting neurones, but there are some problems with GABA. Associated with dependence, the system likes GABA and so can get addicted and start wanting it. Benzodiazapines has addictive qualities because of this.
What are the sleep mechanisms in sleep III?
SCN - regulates circadian rhythm:
- melatonin
- BCT
- cortisol secretion
Circadian rhythm works on basis of cortisol secretion or melatonin. Can buy artifical melatonin from a lot of supermarkets in the US and australia, this is made of dried, ground cow brain. Because of SCM.
