Chronobiology Flashcards
Part of the brain regulating REM
-Pons
Stage 1 sleep
- Light sleep or NREM
- High frequency, low voltage theta waves
Stage 0 sleep
- Drousy
- Alpha waves
- Beta waves (when more excited)
Stage 2 sleep
-Start to see K complexes and sleep spindles
Stage 3 sleep
-Start to see delta waves
Stage 4 sleep
- Delta waves are greater than 50%
- Parasympathetic control
- Lowered vital signs
- Restorative, deepest sleep
REM
- Sawtooth waves
- Desynchronized, paradoxical, activated
- Low voltage, high frequency with random fast sawtooth waves
- Paralysis occurs
- Dreams occur
- Eyes move and erections occur
- Sympathetic tone dominates
- Likely controlled by LDT/PPT ACh firing
- Atonia: GABA and glycine released into spinal motor neuron tracts
Reticular formation
-Main system that keeps you awake
6 transmitters that keep you awake
- ACh
- Glutamine
- Norepi
- Dopamine
- Histamine
- Serotonin
ACh
- Role in wakefulness and REM
- Comes from basal forebrain and the laterodorsal and pendunculopontine nuclei
- LDT and PPT projection to thalamus is most robustly involved in wakefulness
- BF can also lower sleepyness through projection of GABA
- Pushes you into REM sleep
Norepinephrine
- Role in wakefulness
- Produced by locus coeruleus
- Optimizes attention and task performance
- Excessive firing can cause insomnia and anxiety at night
- Inhibited by A1 and A2 receptors in a feedback loop (can use BP medications to lessen anxiety and nightmares!)
Histamine
- Role in wakefulness
- Produced by tuberomammilary nucleus in posterior hypothalamus
- H1 receptors=wakefulness
- H3 autoreceptors inhibit HA activity so antagonizing H3 receptors promotes wakefulness
Serotonin (5HT)
- Generally promotes wakefulness and inhibits REM but there are 15 different receptors that contribute different effects
- Produced in dorsal raphe nucleus
- May push from deep sleep to light sleep
Dopamine
- Role in wakefulness
- Produced in substantia nigra (movement), ventral tegmental area (reward)
- Ventral periaqueductal gray in pons fires during wakefulness
- Motivational arousal as opposed to task oriented alertness
Orexin/hypocretin
- Not part of RAS
- Excitaroy neuropeptides
- Make in lateral hypothalamus
- Wakefulness regulators
- “back up generator”
- Innervate other wakefulness areas
- Fire only when awake
- Sustain wakefulness
Thalamus
- Uses glutamateric neurons to facilitate cortical arousal and GABAergic neurons to dampen ascending arousal pathways when sleep is needed
- Sleep spindles likely to originate here–during REM thalamic neurons are hyperpolarized
- REM and wakefulness–ACh input to those same neurons
Suprachiasmatic nucleus
-Governs the 24 hour sleep-wake clock
Ventrolateral and median preoptic areas
- Of the lateral hypothalamus
- OFF switch
- Uses GABA and galanin to shut down the wakefulness apparatus
- Fire rigorously during NREM
- MNPO: fires when drifting into sleep
- VLPO: fires while asleep
Melanin concentrating hormone
-MCH parallels orexin innervations but dampen other arousal center conversely
GABA and Galanin
-Push you into sleep and into deeper sleep
What pushes from REM to lighter sleep?
-Norepi, dopa, serotonin
Adenosine homeostasis
- Increases while awake during metabolism (ATP breakdown)
- Inhibitory feedback to wakefulness centers and stimulates the VLPO sleep center so sleep occurs
- Caffeine can counter
Cytokines interleukin-1B, tumor necrosis factor alpha
- Promote sleep–somnogens
- Increase in the evening
- Derived from brain parenchyma
Prostaglandin D2
- Promotes NREM sleep–somnogen
- Synthesized in meninges
Homeostatic drive
- Sleep drive increases the longer one stays awake–adenosine builds up
- During sleep adenosine converts back to ATP
Circadian clock
-Lack of light via optic nerves signals suprachiasmatic nuclei of hypothalamus to allow melatonin release from the pineal gland
Melatonin
- May drive 24 hour circadian rhythm
- MT1 receptor stimulation dampens ARAS
- MT2 receptor stimulation keeps SCN tuned to 24 hr clock
Clock genes
- CRY
- CLOCK
- BMAL1
- PER1
- Fluctuate on a 24 hr basis
- Can work in counterphases
Zeitgebers
- Gene & environment interactions
- Light, temp, food, exercise, socialization, melatonin, caffeine
Brain activity decrease in sleep deprivation
- Anterior cingulate gyrus
- Prefrontal cortex
- Thalamus
Likely cause of narcolepsy
-Bad orexin system
Central apnea
- Brain stem forgets to make you breath
- Wear a monitor that wakes you up
Obstructive apnea
-Due to weight gain, age, atrophy
Leg movements
- Nocturnal myoclonus
- Restless legs–creeping sensations, conscious movement
- Treat both with D2 receptor agonists
Sleep terror disorder
- Unlike nightmares, person has no memory
- 1st third of night
- NREM (stage 3 or 4)
Bruxism
- Teeth grinding
- Stage 2 usually
Somniloquy
-Sleeptalking
Somnambulism
-Sleep walking
REM sleep behavior disorder
- Loss atonia during REM
- Act out dreams
- D2 agonists treat
