Answer:
The correct answer is ''action potentials from different sensory modalities are carried on different nerve tracts.''
Step-by-step explanation:
A nerve tract is a set of axons (bundles of nerve fibers) of the central nervous system that have the same origin and the same destination. Each of the main sensory types that we can experience, pain, touch, vision, sound, etc., is called sensation modality. Nerve fibers only transmit action potentials whatever the stimulus. The perceived modality will depend on the specific point in the central nervous system where the excited fiber ends, that is, the response indicates that each nerve bundle ends at a specific point in the central nervous system and the type of sensation experienced when a nerve fiber is stimulated is determined by the area of the nervous system to which this fiber leads. For example, if a fiber is stimulated for pain, the person perceives this sensation regardless of the type of stimulus that excites them. It can be electricity, overheating the fiber, crushing it, or activating the nerve ending for pain when tissue cells are injured. In all these cases, the person perceives pain. Similarly, if a tactile fiber is stimulated by electrical excitation of a touch receptor or by some other mechanism, the person perceives a sensation of touch because these fibers lead to specific areas of touch in the brain. In this same sense, the fibers from the ocular retina end in the visual areas of the brain, those from the ear end in the auditory areas and the thermal fibers in the areas for temperature. This specificity of nerve fibers to transmit nothing more than a sensation modality is called the principle of the marked line.