Endogenous inputs to the respiratory system in wakefulness and sleep

Breathing differs in wakefulness and sleep because of the presence or absence of state-specific tonic inputs to the respiratory system. In non-rapid eye movement (NREM) sleep, tonic inputs that occur in wakefulness are lost. The source of the tonic inputs in wakefulness may be the serotonergic neurons of the raphe nuclei, the reticular activating system, or other central nervous system structures that participate in behavioral control of the respiratory system. In rapid eye movement (REM) sleep, there are both inhibitory and excitatory endogenous inputs to the respiratory system. Some respiratory muscles are hypotonic or atonic because of disfacilitation and/or active inhibition of their motoneurons. There are also endogenous excitatory inputs that affect brain stem respiratory neurons and respiratory muscles and that can account for the irregular, rapid breathing pattern characteristic of REM sleep.