Sleep Flashcards
What three techniques are used to monitor activity during sleep?
Electroencephalography (EEG) - evaluates electrical activity of brain. Electromyography (EMG) - electrical activity of muscle in response to stimulus. Electrooculography (EOG) - measuring the corneo-retinal standing potential that exists between front and back of human eye.
What is the behavioural criteria for sleep?
Stereotypic or species-specific posture. Minimal movement Reduced responsiveness to external stimuli. Reversible with stimulation - unlike coma, anaesthesia or death.
What are stages of sleep?
Stages 1 + 2 NREM Stages 3 + 4 NREM Stage 5 REM
Compare psychological measurements during stage 1 + 2
Light sleep
EEG theta waves (4-8Hz) - gradually more and more drowsy
EOG - no eye movements
EMG - reduced muscle activity from wake
Compare psychological measurements during stage 3 + 4
Very very deep sleep
EEG - delta activity <4Hz
EOG - minimal eye movement
EMG - continued relaxation of muscles
Compare psychological measurements during stage 5
REM sleep
EEG - brain shifts abruptly back to fast rhythm similar to awake state
EOG - rapid eye movement
EMG - muscle activity at its lowest - basically paralysed
How long is a sleep cycle?
1 to 1 and a half hours
When do we dream?
Usually during REM sleep however, it is not exclusive to REM
Heart rate also increases during REM sleep.
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
What controls consciousness?
Reticular activating system which is found in the brainstem
What projections does RAS have?
Network of neurons located in the brainstem
anterior projections to the hypothalamus, direct to cortex, posterior to thalamus
How does the reticular activating system control the activity of the cortex?
Or via indirect connections through the intralaminar nuclei of the thalamus
In layman’s terms what does RAS do?
Turns the lights on
Enables consciousness to happen and controls it
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 – excitatory, promotes wakefulness via orexin/hypocretin neurotransmitter
Ventrolateral Preoptic Nucleus (anterior hypothalamus) – promotes sleep
NOTE: they have an antagonistic relationship
Describe the circadian synchronisation of the sleep-wake cycle.
The suprachiasmatic nucleus is responsible for synchronising the sleep-wake cycle with falling light level, pathway that produces melatonin (makes you sleepy) . Stimulates pineal gland to produce melatonin. (ALSO HYPOTHALAMUS)
It receives an input from the retina (not from the usual photogenic cells) and as light level falls the suprachiasmatic nucleus becomes more active
Describe the effect of the suprachiasmatic nucleus on the nuclei within the hypothalamus.
Falling light level à increased activity of suprachiasmatic nucleus
This leads to activation of ventrolateral preoptic nucleus and inhibition of lateral hypothalamus so you become sleepier
What are the effects of sleep deprivation?
Psychiatric and neuro - Sleepiness, irritability, stress, mood fluctuations, depression, impulsivity, hallucinations
Neurological - Impaired attention, memory, executive function
Risk of errors and accidents
Neurodegeneration (?)
Somatic - Glucose intolerance, Reduced leptin/increased appetite, Impaired immunity, Increased risk of cardiovascular disease and cancer, Death
How is sleep regulated accurately?
After sleep loss - reduced latency of sleep onset
increased slow wave sleep (NREM)
Increase of deep sleep ( after selective REM deprivation )
Describe the brain activity of the limbic system compared to the frontal lobe in sleep.
Brain activity in the limbic system is higher than in the frontal lobe
This is because the content of dreams tends to be more emotional than in real life
What was the perception of the function of sleep and how were these theories/thoughts disporved?
Restoration and recovery - more active individuals don’t sleep more
Energy conservation - 10% drop in BMR but lying still is just as effective
Predator avoidance - but why is sleep so complex
Specific brain function - memory and consolidation THOUGHT TO BE A REAL PURPOSE
When are dreams easier to recall?
When they are in REM sleep but are not exclusive to REM
More emotional and sensationalised than real life.
What are the functions of dream?
- Safety valve for antisocial emotions
- Disposal of unwanted memories
- Memory consolidation
Sleep is important in memory consolidation. What is the difference in memory consolidation between NREM and REM sleep?
NREM – declarative = facts and events
REM – procedural = learning skills
