Sleep-Wake Pharmacology

Inactivity Theory

inactivity at night is an adaptation of survival function by keeping organisms ouut of harm’s way

• counter argument: it’s always safer to remain conscious in order to react to an emergency

Eenrgy Conservation Theory

primary fxn of sleep is to reduce energy demand and expenditure, especially at times when it’s least efficient

• metabolism decreases during sleep

Restorative Theory

sleep provides body an opportunity to repair + rejuvenate, major restorative fxns like muscle growth, tissue repair, protein synthesis, and growth hormone release are mostly/only during sleep

adenosine

byproduct of neuron activity that accumulates + remains high during wakefulness, cleared during sleep

Brain Plasticity Theory

synaptic connections increase throughout the day but space limitation keeps only valued synapses while discarding unnecessary ones

Emotional Discharge Theory

possibility that dreaming during REM sleep provides safe discharge of emotions + relief of stress

hypothalamus

controls sleep onset

hippocampus

memory center that is active during dreaming

amygdala

emotion center that is active during dreaming

thalamus

• prevents sensory signals from reaching cortex

• maintains cortical oscillations during sleep

• essential for sleep spindles

reticular formation

regulates transition between sleep and wake

pons

helps initiate REM sleep

reticular activating system (RAS)

set of interconnected nuclei located throughout the brainstem

• maintains behavioral arousal + consciousness

• determines level of alertness

• stimulation to RAS promotes wakefulness

• other regions inhibit RAS to induce sleep

ventrolateral preoptic nucleus

subregion at hypothalamus that promotes sleep by releasing GABA + galanin to inhibit RAS

suprachiasmatic nucleus

located in hypothalamus that controls circadian rhythm

sleep spindles

play an active role in inducing/maintaining/advancing NREM sleep towards deeper stages of sleep

beta waves

• 13-30 Hz

• irregular LOW amplitude, HIGH frequency

• present when very alert + attentive

alpha waves

• 8-13 Hz

• similar amplitude to beta waves but LOWER frequency

• mostly present in relaxed + effortless alertness

theta waves

• 4-8 Hz

• HIGHER amplitude but LOWER frequency than alpha waves

• occurs during early stages of sleep

• sudden increases in frequency = sleep spindles

• sudden increases in amplitude = K complexes

delta waves

• 0.5-4 Hz

• HIGHEST amplitude and LOWEST frequency

• mainly during deep sleep

arousal promoting neurotransmitters:

• 5-HT

• NE

• histamine

• orexin

• ACh

• DA

sleep promoting neurotransmitters:

• GABA

• galanin

• melatonin

• adenosine