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My question is about the neurological signals. In our body when a signal, for example a hearing signal from hair cells, is built, it goes through a lot of neurons and it passes a lot of synapses. I am wondering how it doesn't lose it's correct path and chooses the right way to auditory cortex? I mean what are the features of a neurological signal that shows it the correct way?

In other words, how can a neurological signal be created and sent through a chain of neurons to the brain, how can it 'know' when entering a synapse contacting multiple neurons which is the correct one for going through it?

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  • $\begingroup$ please, read this section on how to ask good questions and try asnwering: "Have you thoroughly searched for an answer before asking your question?" This is not only about searching through this site, but also googling $\endgroup$ – aaaaaa Jul 5 '15 at 11:42
  • $\begingroup$ @aaaaaa - I must say this question and related ones are understandable. E.g., folks in computer science tend to compare the nervous system with computer commands and don't understand why an isolated '1' (an action potential) enters up in the correct place without proper guiding info. $\endgroup$ – AliceD Jul 5 '15 at 13:41
  • $\begingroup$ i have problem of different kind with given question $\endgroup$ – aaaaaa Jul 5 '15 at 15:35
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Short answer
Neuronal signals neither choose where to go, nor do they carry routing flags of some sort to guide them. Instead, neuronal signals are guided by the hard wiring of the nervous system.

Background
Neuronal signals (action potentials) basically follow a one-way path. When they encounter a cross roads, action potentials are simply propagated to all of those alternatives. External effects of neurons, hormones or drugs may alter these signals, for example by inhibiting action potential formation or propagation.

To take the example of the auditory system (Fig. 1):

auditory system
Fig. 1. Auditory system. Source: New York University.

One can readily see that the signal from the hair cells are routed into the auditory nerve to the cochlear nucleus, from there to the colliculi in the brain stem and further up to the auditory cortex via the medial geniculate. Basically this is a one-way, straightforward route.

There is complexity in the system, however. For example, the fibers of the auditory nerve bifurcate on entering the cochlear nucleus and make synapses on a number of morphologically different types of neuron. Each of the latter sends its axon out of the cochlear nucleus with a distinctive projection pattern that gives rise to further divergence. Specifically, some cochlear nucleus neurons project directly to the inferior colliculus, whereas others project to various divisions of the superior olivary complex and nuclei of the lateral lemniscus, which in turn project to the inferior colliculus (Irvine, 1992).

But even in this complexity the divergence is basically generated by simple bifurcations. An action potential reaching such a junction by default simply gives rise to two parallel signals; there is no choice involved. Regulation is due to other neurons targeting these pathways.

Reference
- Irvine, The Mammalian Auditory Pathway: Neurophysiology Springer Handbook of Auditory Research (1992).

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  • $\begingroup$ Ok thank you. Now my quedtion is what are the features of a specific neurological signal? I mean for making a fake signal . $\endgroup$ – Pedram Jul 6 '15 at 20:34
  • $\begingroup$ @Pedram, I do not understand your follow up question and you should perhaps consider asking a new question. The answer comments should be reserved for clarifications only. $\endgroup$ – AliceD Jul 6 '15 at 20:45
  • $\begingroup$ I mean our ear collects sound and make signals and it goes to brain and we hear.Now I want to make a fake signal and the brain hear it I mean here the ear doesn't have any role and we give a stimulation to auditory nerve and it take it to the brain. $\endgroup$ – Pedram Jul 7 '15 at 16:50
  • $\begingroup$ @Pedram, I suggest asking a new question on this and carefully explain what you mean with a fake stimulus etc. Comments are not ideal for new questions. Thanks. $\endgroup$ – AliceD Jul 7 '15 at 21:28

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