I am having a really hard time trying to understand what cranial nerve nuclei are. I have been reading/watching videos and I keep hearing, "that is where the cranial nerves make connection with the brainstem." Also, I keep hearing that some cranial nerves may have multiple nuclei and some nuclei may have multiple nerve synapsing there; however, this information doesn't really help me understand what they are. Are they a processing center? If so, doesn't information get processed in the cortex? So the main question is: What is a cranial nerve nucleus and what is it's function? What does it mean by "where nerves make connections"? I am attaching the image which I've been studying. You may refer to that when answering this question.enter image description here


1 Answer 1


Nerves (including cranial nerves) are constituted of neurons, and other supporting cells and structures (e.g. myelin sheath and extracellular protein matrix). Neurons are highly specialized cells that have a particular cellular anatomy:
enter image description here

As you can see, the cell body (or soma) contains the nucleus, and projects it's axon towards other structures in the body, sometimes more than a meter away! Cranial nerves (like other nerves) are a collection of the axons, not the cell bodies themselves. The cell bodies reside together, in the brainstem, forming what we call nuclei. So that's simply what they are.

  • $\begingroup$ That makes more sense now. I was overthinking a "nucleus". But the reason I was doing that was because of the picture I posted. How would interpret those colored columns and relate them back to this? I am thinking that those colored columns represent different types of nuclei? If so, how do you explain their size? $\endgroup$
    – Singh
    Mar 25, 2016 at 1:13
  • 1
    $\begingroup$ @JagmeetSingh The colored columns represent the nuclei themselves. The larger they are, the larger the number of cell bodies and the bigger the nerve they project. For example, the sensory part of the CN V (Trigeminal, in blue) innervates the skin of the whole face, whereas CN VI (Abducens, in yellow) innervates one single extra-ocular muscle (the lateral rectus). So you can imagine why the trigeminal sensory nucleus is much larger than the abducens nucleus. $\endgroup$
    – Maljam
    Mar 25, 2016 at 1:20
  • $\begingroup$ A cranial nerve nucleus is not the nucleus of a nerve cell (neuron). As Wikipedia says, a cranial nerve nucleus is a collection of neurons in the brain stem. $\endgroup$
    – mgkrebbs
    Mar 25, 2016 at 6:25
  • $\begingroup$ @mgkrebbs That contradicts what Maljam said. Do you know where information (sensory or motor) goes after it synapses at the nuclei and via what medium? Am I even thinking in the right direction? If so, I am slowly starting to understand CN nuclei, even though the long colored columns still confuse me. $\endgroup$
    – Singh
    Mar 25, 2016 at 6:50
  • $\begingroup$ The neurons of a CNN connect cranial nerves to the brainstem. Information flows both ways: sensory neurons within a CNN conduct info from the associated cranial nerve into the brainstem, and motor neurons in the same CNN conduct info in the reverse direction into the same cranial nerve. $\endgroup$
    – mgkrebbs
    Mar 25, 2016 at 7:14

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