0
$\begingroup$

Recently, I have been learning about olfaction. To my surprise, I am having a heck of a time finding explicit information regarding which neurons' axons are comprising the olfactory nerve. I am aware that there are several cells types that are relevant in the olfactory bulb: mitral cells, olfactory sensory neurons, tufted cells, and many more. However, I have not been able to find any source that definitively states from which neuron type the projections that comprise the olfactory nerve arise from.

I keep seeing articles that seem to imply olfactory sensory neurons comprise the olfactory nerve, but this doesn't seem right to me. My understanding is that the projections that emanate from the olfactory bulb and terminate in the brain constitute the olfactory nerve. The only thing I can think of is that the "olfactory bulb" is actually being considered "part of the brain"...in which case, the olfactory sensory neurons are technically peripheral neurons.

If that is the case, what exactly are the olfactory bulbs? Are they part of the telencephalon? Are they an outgrowth similar to how the optic nerves are outgrowths of the telencephalon and therefore not "true nerves"?

Improve this question
$\endgroup$

1 Answer 1

Reset to default
2
$\begingroup$

Olfactory receptor neurons (ORNs) in the olfactory epithelium in the nasal cavity project to the olfactory bulb; this projection is Cranial Nerve 1 and it's more of a collection of fibers rather than a highly organized nerve.

Your surprise or confusion is probably based on this:

My understanding is that the projections that emanate from the olfactory bulb and terminate in the brain constitute the olfactory nerve

...which is false: the olfactory nerve is the step prior to the olfactory bulb. The olfactory bulb is part of the brain.

I'll add that I have seen poor diagrams of the brain that point to the olfactory bulb and label is as cranial nerve 1, which is false or at least misleading.

Improve this answer
$\endgroup$
2
  • $\begingroup$ what exactly is the olfactory bulb, then? It's certainly not a cortical structure. Is it classified as a subcortical, telencephalic-derived structure? $\endgroup$
    – S.C.
    Commented Mar 8, 2019 at 20:01
  • 1
    $\begingroup$ It's part of the forebrain, specifically the telencephalon. It's of course not neocortical, but much of the telencephalon is not, for example it includes the basal ganglia. $\endgroup$
    – Bryan Krause ♦
    Commented Mar 8, 2019 at 20:08

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .