Final answer:
The dorsal column system, also known as the dorsal column-medial lemniscus pathway, consists of the fasciculus gracilis for the lower body and fasciculus cuneatus for the upper body. It transmits touch and proprioceptive information to the brain and is part of a sensory pathway that includes three successive neurons.
Step-by-step explanation:
The dorsal column system, also referred to as the dorsal column-medial lemniscus (DCML) pathway, is a key sensory pathway of the nervous system. It is composed of fasciculus gracilis and fasciculus cuneatus, which are tracts within the white matter of the spinal cord carrying sensory information. The fasciculus gracilis is the medial division containing fibers from sensory neurons in the lower body, while the fasciculus cuneatus is the lateral division composed of fibers from the upper body.
This system begins with a dorsal root ganglion neuron whose axon enters the dorsal root and ascends in the spinal cord. In the dorsal column, the axons are organized in a way that those from lower limb levels are positioned medially, while those from upper body levels are positioned laterally. The dorsal column system is mainly responsible for transmitting touch and proprioceptive senses to the brain.
Both the dorsal column system and the spinothalamic tract consist of three successive neurons that conduct sensory signals. However, while the DCML focuses on touch and proprioception, the spinothalamic tract is primarily involved in transmitting pain and temperature sensations.