system
Given the following post, respond as if you're commenting on Reddit:
human
A question about nerves

Does every nerve ending have it's own dedicated pathway back to the brain, or are there some pathways that carry information from multiple nerve endings? If the latter is the case, how are the signals from different nerve endings distinguished from each other (I think 'multiplexed' would be the word in comp sci)? 

That is, will, say, a nerve in my pinky finger have its own 'wire' going back up to my brain, or will it share a 'wire' with nerves from another finger at some point?
gpt
No. It gets complicated. There are multiple kinds of touch receptor in your skin: receptors for fine touch, for pressure, for pain, for temperature, for vibration, and so on. These all are associated with a nerve fiber that travels through a nerve to the spinal cord. Some go up to the brainstem directly; others connect in the spinal cord itself to secondary neurons, which can connect with multiple peripheral nerves. Some secondary neurons gather together peripheral fibers of the same "modality" (temperature, pressure, etc), some gather together fibers from a specific area. This combined information is passed on up to the thalamus and then to the cortex via the spinothalamic tracts and dorsal columns. It's in the primary sensory cortex and the somatosensory association areas of the cortex that this complicated input gets integrated into something we think of as just a single sense.