LONGITUDINAL CONDUCTION SYSTEMS SERVING SPINAL AND BRAIN-STEM COORDINATION

Abstract

Two distinguishable systems coordinate reflex activities along the entire sequence of spinal and brainstem segments. One system is sufficient within the spinal cord and is relatively direct, the propriospinal system. It is characterized by bilateral projections which frequently cross and recross the spinal cord. A second system involves projections going up to the medulla oblongata and returning downward again to influence spinal motoneurons. This indirect spino-bulbo-spinal system is cross-connected at the level of sensory input and within the medulla oblongata, but otherwise ascends and descends the spinal cord without decussation.