Sleep and circadian rhymths Flashcards
What behavioural changes occur during sleep?
Reduced motor activity
Reduced response to stimulation
Stereotypic postures (closed eyes)
Easily reversible
What structural changes occur during sleep?
Properties of neurons and gene expression levels
How are sleep muscle movements recorded?
Electromyography
How are sleep eye movements recorded?
Electro-oculography
How is sleep brain activity recorded?
Electroencephalography
How are the muscles activity during sleep recorded?
The electrodes are attached to a muscle
- When the muscle depolarises, the depolarisation is recorded
What is an electroencephalogram used to meaure?
The synchronous, electrical activity from large populations of neurones in the brain
What are some advantages of electroencephalogram?
- Non invasive
- Generates lots of data quickly
- High temporal resolution
What is the frequency of beta brain waves?
13-30 Hz
What is the frequency of Alpha brain waves?
8-13 Hz
What is the frequency of Theta brain waves?
4-8 Hz
What is the frequency of Delta brain waves?
0.5-4 Hz
Why is amplitude larger at a lower frequency?
Easier to have more synchronous neurons
Give an overview of non-rem sleep
- Neuronal activity decreases
- Metabolic rate and brain temp decreases
- Hr and Bp decrease
- Increase in pns activity
Why do heart rate and blood pressure decrease during non-rem sleep?
A decrease in the sympathetic nervous system activity
Describe sleep stage 1
Non REM
- Awakened easily
- Eyes move slowly, muscle activity decreases
- Sudden muscle contractions
What type of brain wave is seen during stage 1?
Alpha waves
Describe the EOG in stage 1
- Eyes show slow rolling movements
Describe the EMG in stage 1
Some muscular activity
Describe the EEG in stage 1
Characterised by low voltage activity of mixed frequencies
- Mainly theta waves
Describe stage 2 of sleep
Light sleep
- Eye movement stops-
- Brain waves become slower with an occasional burst of rapid brain waves
- Prep for deep sleep
- Body temp drops, hr slows
Describe the brain waves in stage 2 of sleep
Bursts of sinusoidal waves (sleep spindles)
- 12-14 Hz
- Biphasic waves (K complexes)
Describe stage 3 of sleep
Deep sleep
- Slow delta waves interspersed with smaller faster waves
- Sleepwalking, sleep talking, bedwetting
Describe the stage 3 brain waves
Delta waves 0.5-2Hz
Describe stage 4 of sleep
Very deep sleep
- Disorientation following waking
- Slow wave sleep
Describe stage 4 brain waves
Exclusively Delta waves
- 0.5-2 Hz
Describe sleep stage 5
REM sleep
- Closed eyes move rapidly from side to side
-Mimics wakefulness
- High brain activity
- All skeletal muscles are atonic-flaccid and paralysed
- Brain temp and metabolic rate rise
- Middle ear, eyes and diaphragm are active
Describe stage 5 brain waves
Similar to stage 1/awake
- Low voltage with mixed frequency
Describe the normal sleeping pattern in humans
REM and Non- REM are cyclical
- Non linear
- REM appears 8-10 times
What is the total time of a sleep cycle from stage 1 to REM?
90-110 mins
What happens to stage 3&4 as REM increases?
They decrease in duration
In young adults, which stage is the longest duration of sleep?
Stage 2 (50-60%)
How is sleep regulated?
- Diffuse modulatory neurotransmission system
- NE and 5-HT neurons in the brainstem
- Inhibition of motor neurons
- Diffuse modulatory system controls rhythmic behaviour in the Thalamus
What will lesion of the brainstem cause?
Sleep and coma
What causes awakening?
Stimulation of the brainstem
What precedes awakening?
Activation of neurons in the brainstem
What do delta rhythms show?
Activity in the thalamus
Where is there no activity during REM sleep?
In the frontal lobe
- In the raphe nuclei and locus coeruleus
How long is a circadian rhythm?
24hrs
What are circadian rhythms modulated by?
External timing cues (zeitgebers)
What is the major internal clock?
Suprachiasmatic nucleus
- In the anterior hypothalamus
What provide input on light to the suprachiasmatic nucleus?
Intrinsically photosensitive ganglion cells
