Final answer:
The phrase pertains to lateralization in the neurological system, illustrating different ascending pathways such as dorsal column (ipsilateral) and spinothalamic (contralateral).
Step-by-step explanation:
The phrase 'Closing on ipsilateral side, Opening on contralateral side' refers to the concept of lateralization in neurology and specifically relates to various neural pathways that coordinate body movements and sensations. For instance, in a hemisection of the spinal cord, the dorsal column pathway, which carries fine touch and proprioceptive sensations, ascends ipsilaterally, meaning on the same side of the body where the sensation originated. Conversely, the spinothalamic pathway decussates, or crosses over, immediately upon entering the spinal cord and ascends contralaterally, thereby reaching the opposite side of the brain relative to the source of the sensation. This arrangement allows the brain to integrate diverse sensory inputs and coordinate motor outputs effectively.