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What is the Olfactory Nerve?

Mary McMahon
Updated May 17, 2024
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The olfactory nerve is a collection of nerve rootlets which extends from the olfactory bulb to the olfactory epithelium, the area of the nose which actually intercepts scents. The nerve cells in this part of the nose are chemosensitive, responding to chemical signals which are converted to electrical impulses which are carried up the olfactory nerve to the olfactory bulb. Once these impulses reach the microregion in the olfactory bulb which corresponds with the nerve cells which were stimulated, the signals are passed on to various areas in the brain, and the owner of the nose is allowed to perceive the smell.

Also known as the first cranial nerve, this nerve is the shortest of the cranial nerves. It is also the only cranial nerve, other than the optic nerve, which does not meet up with the brainstem. People have two olfactory nerves, one on each side of the face, and these nerves can be tested independently by plugging one side of the nose and exposing a patient to various odors. It helps to use a strong or pungent aroma for a stronger response.

This nerve is one of the most basic, reflecting the early origins of the olfactory system, which is one of the oldest sensory systems in most living organisms. It is also very vulnerable to damage, as it extends beyond the hard protection of the skull to the softer areas of the face, which means that it can be injured as a result of facial trauma. Someone with a broken nose, for example, may have an injured olfactory nerve as well.

Exposure to harsh chemicals, strong odors, and certain types of infections can also lead to olfactory nerve damage. Since patients may only damage one olfactory nerve at a time, they may not be immediately aware of the damage, attributing a diminished sense of smell to a stuffy nose or not even noticing the decreased sensitivity to odors. A doctor can diagnose olfactory nerve damage by exposing a patient to strong odors and monitoring the patient's reaction.

This nerve makes up an important part of the larger olfactory system, the system which allows organisms to intercept and perceive smells. The sensitivity of the olfactory system is largely determined by the size of the olfactory epithelium; the larger the epithelium, the more smells an organism can isolate, and the more precisely an organism can differentiate between different smells. Although humans may feel like they are living in a world of smell sometimes, they in fact have comparatively weak olfactory systems when compared to many other animals.

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Mary McMahon
By Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a WiseGeek researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Discussion Comments
By ShadowGenius — On Mar 04, 2011


Very good questions. First off, I would say that the human being is a completely unique creature, with a brain which is developed far beyond any other animal in terms of ability to distinguish, react to, and innovate based on, patterns in the world. As to how we get meanings for things in the first place, I would say that that is a result of societal understanding of things. It is also a result of the instinct we are endowed with at birth, instincts to make sense of the world in a previous context, kind of like a soul or a collective unconscious.

By BioNerd — On Mar 03, 2011


This is an interesting point, and I agree. The question I would have is this: how would we get meaning for things in the first place? Who determined these meanings? And also, why don't animals have the same degree of developed understanding as that which a human child is capable of?

By TrogJoe19 — On Mar 01, 2011


It is interesting to note that this process which you mentioned is how we determine meaning for everything. The way a child learns a language is by recognizing different contexts in which phrases and words are used to get something done. The way a child learns to perceive smell is also based on context. That is how we give meaning to every sense and way of communicating.

By JavaGhoul — On Feb 28, 2011

The way that the nose works is that certain stimuli are affected differently by different smells. When we first smell things at a young age, these smells are unique and we don't know how to interpret them. When we see the source of smell or recognize the place in which we sense that particular smell, we assign meaning to it based on context. Olfactory memory is one of the strongest memories, and that is why, when you smell something that you haven't smelled since you were a baby, you will have a flashback to the situation and the feelings you were experiencing as a child.

By anon79893 — On Apr 25, 2010

thanks for info but you should add more info about it, as in unique info.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a...

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