Sleep Flashcards
What is the behavioural criteria for sleep?
o Stereotypic or species-specific POSTURE
o Minimal movement
o Reduced responsiveness to external stimuli
o Reversible via. stimulation
- unlike coma, anaesthesia or death
How can you monitor sleep?
3 different methods
EEG, EOG or EMG
ONENOTE!!
Outline Stages of Sleep?
Awake
Stage 1, 2, 3, 4 & 5
First 4 stages = Non-REM (NREM)
Last stage = REM
‘Awake’ stage of Sleep?
FAST brain activity in EEG (beta-rhythm)
o 30Hz
Reasonable amount of MUSCLE TONE
‘Stage 1 & 2’ of Sleep?
Light Sleep!
o EEG activity SLOWS as the person becomes drowsy
o Beta –> theta activity (4-8Hz)
o NO eye movements
o general muscle activity is REDUCED
‘Stage 3 &4’ of Sleep?
Deep Sleep!
o Theta –> delta activiy
- slowest rhythm at around 1Hz
o Minimal eye movement
o Continued relaxation of muscles
‘Stage 5’ of Sleep?
REM sleep
o Brain activity shifts back to a FAST RHYTHM
o REMs are seen
o Muscle activity is LOWEST - paralysed
EEG, EOG & EMG of the different stages of Sleep?
ONENOTE!!
Explain Sleep Cycles
Have multiple sleep cycles per night
o Each cycle lasts ~1-1.5hours
You tend to get
o MORE SLOW-WAVE sleep at the beginning of the night
o MORE REM sleep towards end of the might
HR and RR during sleep?
Both are SLOW during slow-wave sleep
Both are FASTER during REM sleep
What controls consciousness?
RAS
o starts in the brainstem and projects into
& influences the cerebral cortex
The effects of the RAS can be
o DIRECT
OR
o through intralaminar nuclei in the thalamus
What controls the RAS and explain it?
Two nuclei located in the hypothalamus (hence control the wake/sleep cycle)
o Lateral hypothalamus - EXCITATORY input
- ACTIVE during the day
o Ventrolateral Preoptic Nucleus - NEGATIVE EFFECT
- this PROMOTES SLEEP
There is an ANTAGONIST relationship between the nuclei
o activity of one, inhibits the other
What controls the Circadian Synchronisation of the Sleep/Wake Cycle?
Suprachiasmatic nucleus
- synchronises sleep with falling light level
How is the Circadian Synchronisation of the Sleep/Wake Cycle controlled?
Suprachiasmatic nucleus - synchronises sleep with falling light level
o receives input from the retina via. a special type of ganglionic cell (NOT RGCs)
o light level fall = activates the SN = activate more nuclei within the hypothalamus
o this inhibits the LH nucleus = stimulates the VLP nucleus
o also has direct effect on the RAS, resulting in reduction of traffic
Explain how else the SC nucleus controls the Circadian Synchronisation of the Sleep/Wake Cycle
Suprachiasmatic nucleus also has a projection to the PINEAL GLAND
o SC nucleus activates it
o secretes MELATONIN throughout the night
o this ADJUSTS the PHYSIOLOGICAL PROCESSES in the body to fit it with sleep
Effects of sleep deprivation?
o Sleepiness & irritability
o Performance decrements/increased risk of error
o Concentration & learning difficulties
o Glucose intolerance
o Reduced leptin - increased appetite
o Hallucinations - after LONG sleep deprivation
o Death - fatal familial insomnia
What happens after Sleep Loss to regulate it?
o Reduced latency to sleep onset
- if you lose a night’s sleep, you go to bed earlier the next day
o Increase of NREM (slow-wave sleep)
- so sleep for longer is sleep deprived
o Increase of REM sleep
- after specifically, selective REM sleep deprivation
What is the function of sleep?
o Restoration & recovery
- but active individuals do NOT sleep more
o Energy conservation
- 10% drop is BMR but to lying still is just as effective
o Predator avoidance
o Specific brain function
- memory, consolidation
Explain Dreams
Occur in REM and/or NREM sleep
- MORE frequently in REM sleep
- can be more easily recalled in REM sleep
- contents of dreams more emotional than ‘real-life’
How does brain activity differ in dreams?
Brain activity is
o HIGHER in limbic system
o LOWER is the frontal lobe
Limbic system = emotions
Frontal lobe = logical thought and informed decision-making
Function of dreams?
o Act as safety valve for antisocial emotions
o Sorting of memory
o Disposing of unwanted memories
o Memory consolidation
- NREM sleep = declarative memory (facts and events)
- REM sleep = procedural memory (learning skills)
Sleep disorders?
Insomnia & Nacrolepsy
Also Shift-work
Causes of Insomnia?
o Physiological
- e.g. sleep apnoea, chronic pain
o Brain dysfunction
- e.g. depression, fatal familial insomnia, night-work
High prevalence & most cases transient (comes and goes)
Treatment for Insomnia?
o Remove cause
o Hypnotics
- enhance inhibitory circuits in the brain (GABAergic circuits)
Narcolepsy?
Falling asleep repeatedly during the day
Disturbed sleep at night
Cataplexy (part of narcolepsy)?
Sudden onset muscle weakness
- that may be precipitated by excitement or emotion
- sometimes in just one part of the body
- can occur in most muscles –> fall over
- REM sleep = LOW muscle tone (dysfunction of control of REM sleep)
Causes of narcolepsy?
Orexin deficiency
o orexin is a neuropeptide which is the transmitter used by the lateral hypothalamus
- CAUSE could be genetic or autoimmune
- normally treatment is a strict regimen of sleeping routines
Shift-work?
Night-working causes physiological processes to become desynchronised
This can lead to
o sleep disorders
o fatigue
o increased risk of some conditions e.g. obesity, diabetes, cancer
