Physiology, Psychology And Pathology Of Sleep Flashcards
What is sleep? (Key elements)
- A state of altered consciousness, not necessarily unconscious
- Increased threshold for sensory perception
- Active brain patterns: Brain waves are all present yet differ in amplitude and frequency
- Evolutionary ancient: Conserved across millions of evolutionary years
- Essential for restoration of immune, skeletal, nervous and muscular systems,
for maintenance of mood and cognitive function - Sleep is not well understood.
Role of the thalamus in sleep?
Thalamic-mediated synchronization mechanisms give rise to large-scale integration of information across cortical circuits
Brain Waves associated with different sleep stages?
Awake - Alpha
REM - Theta, Sawtooth
Non REM 1 - Theta
Non REM 2 - Spindle, K-complex
Non REM 3 - Delta
Non REM 4 - Delta
2 key characteristics of the Circadian Rhythm
- Self-sustained - without external time-giving cues
- Entrained - influenced by external time giving cues
‘Coordinator’ of the circadian rhythm?
Suprachiasmatic Nucleus (SCN)
–> lesion studies show importance
Light exposure as entrainment mechanism
lanopsin-containing retinal ganglion cells = circadian photoreceptors
- Project to SCN through direct + indirect pathways
- SCN signals to pineal gland to inhibit melatonin production
- Removal of light exposure –> removal of inhibition –> melatonin release
- Melatonin feeds back to SCN –> permits sleep drive
What is a Circadian Rhythm Sleep Disorder?
chronic, recurrent pattern of sleep/wake disturbance due to
a) dysfunction of internal CR
b) misalignment between internal circadian timing and externally imposed sleep-wake cycles
Examples of Circadian Rhythm Sleep Disorders
- Delayed Sleep Phase Disorder
- Non 24-hour Sleep Wake Disorder
- Advanced Sleep Phase Disorder
- Irregular Sleep Wake Rhythm Disorder
- Shift Work Disorder
- Chronic Jet Lag
Classification of Insomnia
- difficulty falling/remaining asleep
- at least 3/week for 3 months
- can be Primary or Secondary
- has high levels of mental health comorbidities
Sleep and Stress
-complex, dynamic relationship
-stress affects sleep regulation and vice versa
- “vicious cycle”
What is restless REM sleep?
REM sleep = only ‘time out’ from noradenaline –> locus coeruleus is silenced
restless REM = insufficient LC silencing
–> disrupts synaptic plasticity
What characterizes hyperarousal?
acute anxiety/distress
imbalances of noradrenaline, GABA, glutamate
What characterizes sleep reactivity?
- disrupted cortical networks
- dysregulation of autonomic nervous system and HPA axis
Non-pharmacological treatment of insomnia
CBT-I, paradox intervention, sleep hygiene, daytime activation, sleep restriction, relaxation training, stimulus control
What are hypnotics?
heterogenous group of substances with sedative/sleep-inducing effects
side effects include: amnesia, distortion of sleep architecture
Benzodiazepines/Non-benzodiazepines for insomnia
- activation of GABA-receptors
-ligand-gated ion channels open
–> influx of Cl- (cell becomes negative)
-BZD/Non-BZD bind to alpha-gamma/alpha unit of GABAa receptors
- induce conformation change
(depends on presence of GABA)
–> inhibitory effect on the nervous system
Melatonin Receptor Agonists for Insomnia
Melatonin = hormone produced in pineal gland under SCN supervision
- Melatonin Receptor Agonists activate Mt1 and Mt2 and simulate presence of melatonin
–> promote onset of sleep
Orexin Receptor Antagonists for Insomnia
Orexin: neuropeptide
–> binds to OR1X and OR2X receptors
–> opening of Ca2+ channels (influx)
-> promotes wakefulness and suppresses REM
(involved in narcolepsy)
Orexin Receptor Antagonists bind to OX1R/OX2R receptors and block Orexin from activating receptors –> promote sleep
