Wk 31 - Sleep disorders 1 Flashcards
What is sleep characterised by?
- Red in sensory activity + voluntary body movement
- Red/absent awareness of surroundings
- Altered state of consciousness
What is sleep controlled by?
- Circadian rhythms
- Hormones
- Env factors
What are the EEG patterns during wakefulness?
- a activity (8-12 Hz): relaxed state
- b activity (13-30 Hz): aroused state
What are the 4 frequency ranges of waves distinguished in an EEG trace?
- Beta: 13-15 to 60 Hz + amplitude of 30uV
- Alpha: 8-12Hz + amplitude of 30-50uV
- Theta: 3-4 to 7-8Hz + amplitude of 50-100uV
- Delta: 0.5 to 3 or 4Hz + amplitude 100 to 200uV
Waking state
- Eyes open
- B activity
Stage 1 non-rem sleep
- Transition from being awake to falling asleep
- Rapid B waves (13-30Hz + 30uV) replaced by slower a waves (18-12Hz + 30-50uV)
Stage 2 non-rem sleep
- Light sleep
- Irregular EEG. freq. dec + amplitude inc: Period of 0 activity + occasional sleep spindles (12-14Hz, 20-100uV) + K complex (0.5-0.7 Hz, >100 uV)
- Sleep spindles occur 2-5x a min
- K complex only found during stage 2
- 45-55% of total sleep time
Stage 3 non-rem sleep
- Passage to deep sleep
- High amplitudes (<3.5 Hz + 100-150 uV)
- Contains 20-50% theta activity
- Sleep spindles + k complexes less often
- Lasts 10mins during 1st sleep cycle
Stage 4 non-rem sleep
- Deepest stage
- EEG waves dominated by theta waves
- Neuronal activity at lowest
- 50% theta activity
- Brains temp at lowest
- BR, HR + BP red
- Muscle still have tonus
- Lasts 35-40 mins during 1st sleep cycle
- 15-20% ot total sleep
What happens when you wake someone up from sleep stage 4?
Person is groggy + confused
What happens during REM sleep?
- Rapid eye movement
- Presence of b activity (13-30Hz)
- Person easily aroused + when woken alert + attentive
- Dreams occur
- 25% of sleep cycle
- Pons + medulla sends signals to relax muscles essential for posture + limb movement
How long does a sleep cycle last + how often does it occur?
- 4-5 times
- 90-110 minutes
- 1st cycle = short REM + long deep sleep, as night progresses, REM inc
Human sleep propensity is regulated by what?
- Circadian process - promotes alertness during day + sleep at night
- Homeostatic process - drive sleep propensity in dependence on degree of sleep loss
What is sleep-wake homeostasis?
- Keeps track of need for sleep
- Evident in: night shift worker, jet lag, during wakefulness adenosine conc inc
What has the greatest influence on sleep?
Light
What is the circadian clock?
- Regulates sleep
- Located: suprachiasmatic nucleus
- Light synchronizes internal biological clock to env cycle
What is the suprachiasmatic nucleus?
- Circadian pacemaker
- Stimulate pineal gland to prod + release melatonin when light dec
- Inc melatonin, inc sleepiness
What is the pineal gland?
- Endocrine gland located near centre of brain btw 2 cerebral hemispheres
- Prod melatonin
What functions is the pineal gland involved in?
- Secretion of melatonin
- Regulate endocrine functions
- Conversion of NS signals to endocrine signals
- Causes sleepiness
- Influences sexual development + immune system function
- Antioxidant activity
What is the pituitary gland + what does is release?
- Pea-sized gland in hypothalamus
- GH, TSH, FSH, LH, prolactin, ACTH, ADH + oxytocin
Which hormones show significant interaction with sleep-wakefulness patterns?
- Growth hormone: released early in night
- Sleep stims prolactin secretion peaks middle of night
- TSH: peak prior sleep onset
- TSH secretion inhibited by sleep + stim by sleep deprivation
- Hypothalamic-pituitary-adrenal axis: inactive at nocturnal sleep onset
- Cortisol: inhibited during sleep onset
- Adrenocorticotropic hormone + cortisol rise at end of sleep
Give examples of neurotransmitters + peptides that play a role in sleep
- 5 HT from dorsal + medial raphe
- ACh from PPT + LDT of pons
- DA from PAG
- NA from locus coeruleus
- Histamine from tuberomammillary nucleus
- Adenosine from basal forebrain nuclei
Outline the mechanism of the melanin concentrating hormone and orexin from the LHA during sleep
- MCH neurones release GABA
- GABA promotes sleep
- MCH + orexin have antagonistic relationship
- Orexin active during wake periods
- MCH more active during sleep