Answer
Fig.14:9
Signals in the cuneate fasciculus ascend to the cuneate nucleus in part (c), and signals in fasciculus gracilis ascend to the adjacent gracile nucleus in the medulla. Both set of fibers decussate together to the contralateral medial lemniscus in parts (b) and (c), and travel this route to the thalamus.
Work Step by Step
The gracile fasciculus extends throughout the spinal cord. The cuneate fasciculus starts at T6 and extends upwards --it is not found below T6. Axons of sensory neurons in the DRG enter the spinal cord. and ascend ipsilaterally to the gracile and cuneate nuclei in the medulla. Internal arcuate fibers from these nuclei decussate and ascend in the medial lemniscal pathway to the thalamus. Third order neurons ascend from the thalamus to the somatosensory cerebral cortex. The dorsal column pathways transmit impulses from touch, pressure, vibration, and proprioception receptors.
