Sleep and circadian rhythms Flashcards
What does REM stand for?
Rapid Eye Movement
What does electromyography (EMG) record?
Electrical activity of the muscles
What does electro-oculography (EOG) record?
Electrical activity of the eye muscles
What does electroencephalography (EEG) record?
- Electrical activity from large populations of neurons in the brain
- Ionic movement creates an electric field which is picked up by electrodes
What are advantages of electroencephalography? (4)
- Non-invasive
- Easy to administer
- Data easily gathered
- High temporal resolution (time)
What are disadvantages of electroencephalography (EEG)? (2)
- Low spatial resolution
- The further you are from the electric source the less detectable it is so only cortical activity is detectable
What are the main types of brain waves? (4)
- Beta
- Alpha
- Theta
- Delta
What are the 2 main stages of sleep?
- REM
- Non-REM
What are the features of non-REM sleep? (5)
- Decrease in neuronal firing
- Decrease in metabolic rate and brain temperature
- Decrease in heart rate and blood pressure due to less sympathetic nervous system outflow
- Increase in parasympathetic nervous system activity
- Muscle tone and reflexes intact
How many stages are there in non-REM sleep?
4
What is stage 1 of non-REM sleep?
Drowsiness
What happens during stage 1 of non-REM sleep? (3)
- Eyes move slowly and muscle activity slows
- Can experience sudden muscle contractions in response to a falling sensation
- EEG shows mostly theta waves
What is stage 2 of non-REM sleep?
Light sleep
What happens during stage 2 of non-REM sleep? (5)
- Eye movement stops
- Brain waves become slower with occasion bursts
- Body temperature drops
- Heart rate slows
- EEG shows K-complexes and sleep spindles
What is a sleep spindle?
Burst of high frequency activity in the brain on EEG
What is a K complex?
Low frequency large increases/decreases in brain activity on EEG
What is stage 3 of non-REM sleep?
- Deep sleep
- Transition between non-REM and REM sleep
What happens during stage 3 of non-REM sleep? (2)
- Very slow delta waves interspersed with smaller, faster waves
- Sleep walking, night terrors, sleep talking, bedwetting (parasomnia)
What is parasomnia?
Disruptive sleep behaviours such as sleep walking etc.
What is stage 4 of non-REM sleep?
Very deep sleep
What happens during stage 4 of non-REM sleep? (1)
Mostly delta brain waves
What happens if you wake someone up during stage 4 of non-REM sleep?
Disorientation for several minutes
What happens during stage 5 of sleep (REM)? (4)
- Eyes move rapidly from side to side
- EEG mimics activity when awake
- Activity of the motor cortex is blocked causing paralysis below neck
- The phase where we dream vividly
What is stage 5 of sleep?
REM
What are the features of REM sleep? (3)
- Increase in brain temperature and metabolic rate
- All skeletal muscles are paralysed
- Muscles controlling eye movement, middle ear ossicles and diaphragm remain active
What is the normal sleeping pattern of humans?
- Non-REM and REM alternate cyclically
- Non-REM section is non-linear
- One sleep cycle is from stage 1 of non-REM to end of REM
How long do we stay in non-REM before moving to first REM of the night?
70-80 minutes
How long do we spend in the first REM of the night?
8-10 minutes
How long is one sleep cycle (from stage 1 of non-REM to end of REM)?
90-110 minutes
How many sleep cycles do we go through per night?
4/5
How does the sleeping pattern change through the night?
- Decrease in duration of stages 3 and 4 of non-REM
- Increase in duration of REM
Which stage of sleep do young people spend the most time in?
Stage 2
What regulates sleep? (3)
- Diffuse modulatory neurotransmission system controls rhythmic behaviour in the thalamus
- Noradrenergic and 5-HT neurons in the brainstem
- Inhibition of motor neurons
What is a diffuse modulatory neurotransmission system?
Sparsely distributed neurons reduce the activity of surrounding neurons during sleep
What does a lesion in the brain stem cause?
Sleep/coma
What does stimulation of the brain stem cause?
Awakening
What happens in the brain during non-REM sleep?
- Decreased firing in the brain stem
- Increased firing in the thalamus (sleep spindles and delta rhythms)
What happens in the brain during REM sleep? (3)
Similar to awake brain but:
- No activity in the frontal lobe
- No activity in raphe nuclei and locus coeruleus
- Inhibition of motor neurons
What is the locus coeruleus?
Location of noradrenaline production in the brain
What are circadian rhythms?
Periodic patterns of behaviour when changing between sleeping and wakefulness within 24 hours
What happens to circadian rhythms when you remove environmental cues?
- Rhythm persists but shifts slightly
- Can adapt to external cues
Which area of the brain determines circadian rhythms?
Suprachiasmatic nucleus of the anterior hypothalamus
What does a lesion in the suprachiasmatic nucleus cause?
Decrease in circadian rhythm of sleep timing
How does the visual system influence circadian rhythms?
- Ganglion cells in the retina respond to light (different to photoreceptors)
- Send information to the suprachiasmatic nucleus
