Sleep Flashcards
What 3 techniques are used to monitor activity during sleep?
Electroencephalography (EEG) (brain)
Electromyography (EMG) (jaw)
Electrooculography (EOG) (eyes)
Describe the EEG and EMG activity in wakefulness.
EEG: fast brain rhythm – beta waves (~30 Hz)
EMG: reasonable amount of muscle tone because you are maintaining posture + ready for action
Describe the EEG, EMG and EOG activity in non-REM sleep.
Stage 1+2 Light sleep EEG: theta (4-8 Hz) waves – gradually becoming more + more drowsy EOG: NO eye movements EMG: muscle activity reduced considerably Stage 3+4 Very deep sleep EEG: Delta activity (< 4 Hz) EOG: minimal eye movement EMG: continued relaxation of muscles
Describe the EEG, EMG and EOG activity in REM sleep.
EEG: brain shifts abruptly back to fast rhythm (similar to wakefulness)
EOG: rapid eye movement
EMG: muscle activity at its lowest, subject is basically paralysed
How long is a normal sleep cycle?
90 minutes
Compare the relative amounts of NREM and REM sleep in a sleep cycle at the start of a night’s sleep and at the end.
Start of the night: more NREM sleep
End of the night: more REM sleep
Describe how heart rate and respiratory rate change during sleep.
SLOW during NREM
FAST during REM sleep
Which system is responsible for maintaining consciousness?
Reticular activating system
How does the reticular activating system control the activity of the cortex?
Either via direct connections
Or via indirect connections through the intralaminar nuclei of the thalamus
What are the two important nuclei in the hypothalamus that are responsible for influencing the reticular activating system and, hence, regulating the sleep-wake cycle?
Lateral Hypothalamus: promotes wakefulness
Ventrolateral Preoptic Nucleus: promotes sleep
(antagonistic relationship)
Describe the circadian synchronisation of the sleep-wake cycle.
Suprachiasmatic nucleus is responsible for synchronising the sleep-wake cycle with falling light level
Receives an input from the retina (not the usual photogenic cells) + as light level falls the suprachiasmatic nucleus becomes more active
Describe the effect of falling light level on the suprachiasmatic nucleus on the nuclei within the hypothalamus.
increased activity of suprachiasmatic nucleus
Leads to activation of ventrolateral preoptic nucleus + inhibition of lateral hypothalamus so you become sleepier
What other important projection does the suprachiasmatic nucleus have and what is the importance of this projection?
Projection to the pineal gland
Increase in suprachiasmatic nucleus activity leads to activation of pineal gland so it releases melatonin
Melatonin adjusts physiological processes in the body that fit with sleep
What are 7 psychiatric consequences of sleep deprivation?
Sleepiness irritability Stress Mood fluctuations Depression Impulsivity Hallucinations
Describe 3 ways in which sleep is regulated after sleep deprivation.
Reduced latency of sleep onset (fall asleep faster)
Increased NREM sleep (sleep for longer)
Increased REM sleep (after selective REM sleep deprivation)
During what stages of sleep can you dream?
Both NREM + REM but tend to dream more + are able to recall dreams better during REM sleep
Describe the brain activity of the limbic system compared to the frontal lobe in sleep.
Brain activity in limbic system is higher than in the frontal lobe
Because content of dreams tends to be more emotional than real life
Sleep is important in memory consolidation. What is the difference in memory consolidation between NREM and REM sleep?
NREM: declarative = facts + events
REM: procedural = learning skills
State some causes of insomnia that are physiological or due to brain dysfunction.
Physiological: sleep apnoea, chronic pain
Brain Dysfunction: depression, fatal familial insomnia, night shifts
Hypnotics can be used to treat insomnia. How do they work?
Enhance inhibitory (GABAergic) circuits in the brain
What is narcolepsy?
Falling asleep repeatedly during the day + disturbed sleep during the night
What is cataplexy?
Sudden loss of voluntary muscle tone often triggered by strong emotions
Explain narcolepsy with regards to the sleep cycle.
It tends to be due to a dysfunction of control of REM sleep
Patients go straight to REM sleep without going through NREM sleep so become paralysed
What is narcolepsy caused by?
Orexin deficiency
Orexin is a neuropeptide, which is the NT in the lateral hypothalamus
Orexin deficiency could be AI or genetic
Manage with tight control of sleep
What are the potential consequences of working night shifts?
Physiological processes could become desynchronised
This can lead to sleep disorders, fatigue + increased risk of some conditions such as obesity, diabetes and cancer
What is thought to be an important neurotransmitter in the reticular activating cycle?
Orexin
What are 3 neurological consequences of sleep deprivation?
Impaired attention, memory + executive function
Risk of error/ accidents
Neurodegeneration
What are 4 somatic consequences of sleep deprivation?
Impaired immunity
Glucose intolerance– risk of diabetes
Reduced leptin/ increased appetite
Death
What are the 3 suggested functions of dreams?
Safety valve for antisocial emotions
Disposal of unwanted memories
Memory consolidation
List 3 treatment options for insomnia
Sleep hygiene
Hypnotics
Sleep CBT
List 5 common causes of secondary poor quality overnight sleep
Obstructive sleep apnoea Restless legs syndrome Nocturnal pain e.g. Arthritis Medication Anxiety
List 3 primary causes of poor quality overnight sleep
Narcolepsy
Idiopathic hypersommolence
Post-traumatic brain injury
