SLEEP DISORDERS Flashcards
What are the functions of sleep?
Cognitive processing e.g. memory consolidation
Emotional regulation
Metabolic e.g. tissue repair, protein synthesis, hormone secretion, glucose relation, appetite control
Growth of nerve cells
Regulation of bp
Immune regulation
What are some problems with not getting enough sleep?
Psychiatric problems can be made worse
Increased risk of dementia
Increased rates of accidents, particularly RCTs
Reduced cognitive performance
Physical health problems e.g. T2 Diabetes, CVD, poor immune system, hypertension, stroke, kidney disease
Reduced fertility
Reduced QOL
How much sleep do we need as adults?
7-9 hours
(Once over 65 you only need 7-8 hours)
How is sleep studied?
Using a polysomnography
What does a polysomnography measure?
brain activity (EEG), eye movements (EOG), muscle activity or skeletal muscle activation (EMG), and heart rhythm (ECG)
Outline the structure of sleep?
Sleep begins with a short period of NREM stage 1 -> stage 2 -> stage 3 -> stage 4
Then it moves onto REM sleep
This cycle continues 4-6 times
The first NREM-REM cycle is 70-100 minutes and after this they are 90-120 minutes
How does the structure of the sleep cycle change as sleep progresses?
In normal adults, REM sleep increases as the night progresses and is longest in the last 1/3rd of the sleep episodes
As the sleep episode progresses, stager 2 begins to account for the majority of NREm and stages 3+4 may disappear altogether
What are the stages of sleep?
Awake
Drowsy/relaxed
Stage 1 sleep
Stage 2 sleep
Stage 3 sleep
Stage 4 sleep
REM sleep
What does drowsy/relaxed state look like on polysomnography?
Alpha waves
What does an awake state look like on polysomnography?
Beta waves (highest frequency, lowest amplitude EEG)
What does stage 1 state look like on polysomnography?
Theta waves (4-7Hz and some alpha waves)
What does stage 2 state look like on polysomnography?
Sleep spindles (sigma waves) and K complexes (negative sharp waves followed by positive slow waves)
What do stage 3 and 4 states look like on polysomnography?
Delta waves (lowest frequency, highest amplitude EEG)
What does REM sleep look like on polysomnography?
High (fast waves) and mixed frequency with low voltage
When does dreaming occur during sleep?
Dreams can happen during any stage of sleep, but the vivid ones that you remember tend to happen during REM sleep.
Why do we remember some dreams and not others?
It depend as when you wake
If you wake during the REM period you are likely to remember it
As we sleep, the REM portion of our sleep cycle becomes longer, and we’re more able to remember those dreams
When do we have the most energy-intensive sleep?
In REM sleep
Our heightened brain activity requires more glucose, leading to a higher metabolism
What proportion of the sleep period is spent in NREM:REM?
NREM is 75-80% of total time spent asleep
REM is 20-25%
How long is NREM stage 1 and what are its characteristics?
1-7 minutes
Easily interrupted by disruptive noise
How long is NREM stage 2 and what are its characteristics?
10-25 minutes and lengthens with every successful cycle, eventually constituting between 45-55% of a total sleep episode
Requires more intense stimuli than in stage 1 to awaken
The sleep spindles are important for memory consolidation; those who learn a new test have a significantly high density of sleep spindles
How long is NREM stage 3+4 and what are its characteristics?
Stage 3 lasts a few minutes and stage 4 lasts 20-40 in the first cycle
The arousal threshold is highest for all stages in stage 4
How is REM sleep characterised?
Desynchronised brain activity
Muscle atonia
Bursts of rapid eye movements
Why do we not act out our dreams?
Loss of muscle tone and reflexes prevents us from acting them out
Inhibition of motor neurons in the spinal cord and removal of brainstem excitatory inputs to motor neurones
Whats the 2 process model for sleep-wake regulation?
Process S promotes sleep and process C maintains wakefulness
What regulates process C?
Circadian system
What regulates process S?
Neurones in the preoptic area of the hypothalamus that inhibit neuronal communication and turn off the arousal systems during sleep
What is cicrcadium rhythm?
the 24-hour internal clock in our brain that regulates cycles of alertness and sleepiness by responding to light changes in our environment.
What do circadian rhythms control?
Sleep-wake cycle
Physical activity
Food consumption
Regulate body temp, HR, muscle tone and hormone secretion over the day
What regulates circadian rhythms?
Suprachiasmatic nucleus
What is the suprachiasmatic nucleus?
2 paired nuclei located in the anterior part of the hypothalamus
It received direct inputs from photoreceptor cells in retina along the retinohypothalamic tract.
Norepinephrine is released from SCN of hypothalamus
It regulates rhythmic secretion of melatonin from pineal gland
= sleep induction
When are melatonin levels highest?
At night
Associated with an increase in tiredness
How can melatonin production be inhibited?
Exposure to blue-wavelength light
(Avoid electronic devices before bedtime)
What areas of the brain are responsible for sleep?
Visual cortex
Motor cortex
Hippocampus
Amygdala and cingulate gyrus
Why is it suggested that dreaming may be necessary to recover from traumatic experiences?
Dreaming reduces the reactivity of the amygdala and helps restore functioning of the prefrontal cortex. This supports emotional regulation
It allows emotional content of memories to be processed and stored in autobiographic memory
How does sleep change across the lifespan?
In babies sleep is polyphasic
By age 4 sleep is biphasic
After that sleep is monophasic
At what point after being awak is our drive for sleep strong?
16 hours fo wakefulness
What causes the drive for sleep?
A build up of adenosine
Why does coffee keep us awake?
It’s an adenosine antagonist
What are the sleep hygiene advice?
• exposure to light in day and dark room at night
• Avoid screens before sleep and try relaxation techniques
• Try to avoid baths near bed time and avoid large meals
• Alcohol, drugs, stress can disturb homeostatic sleep drive
• Importance of regular bedtime and waking time
• Desireabilitu of bedtime in late evening
• Dont go to bed too early
• Avoiding napping (relieves adenosine based drive)
• Risks of shift work to sleep pattern
• Exercise during the day
• Eliminate stimulates e.g. alcohol, caffeine, nicotine
• Condition the brain by only use the bed for sleeping and sex
• Do not lie awake for longer than 15 minutes. Get yp and do another relaxing activity and then try sleeping later
What is the reticular activating system?
a complex bundle of nerves in the brain that’s responsible for regulating wakefulness and sleep-wake transitions
It’s found in the anterior-most segment of the brainstem and received input from spinal cord, sensory pathways, thalamus and cortex
What are the nuclei that make up the RAS?
locus coeruleus, raphe nuclei, posterior tuberomammillary hypothalamus, and pedunculopontine tegmentum
What neurotransmitters are used in RAS?
acetylcholine, serotonin, noradrenalin, dopamine, histamine, and hypocretin (orexin)
What types of medications can be used to promote sleep?
acetylcholine, serotonin, noradrenalin, dopamine, histamine, and hypocretin (orexin) antagonists
GABA, adenosine and melatonin agonists
What are the types of sleep disorders?
Insomnia
HYPERSOMNIA
Parasomnia
Circadian rhythm disorders
Sleep-related breathing disorders
Movement disorders
What is insomnia?
difficulty in getting to sleep, difficulty maintaining sleep, early wakening, or non-restorative sleep which occurs despite adequate opportunity for sleep and results in impaired daytime functioning.