Olfactory nerve
Olfactory nerve | |
---|---|
Smell | |
Identifiers | |
Latin | nervus olfactorius |
MeSH | D009832 |
NeuroNames | 32 |
TA98 | A14.2.01.004 A14.2.01.005 |
TA2 | 6181 |
FMA | 46787 |
Anatomical terms of neuroanatomy] |
Cranial nerves |
---|
|
The olfactory nerve, also known as the first cranial nerve, cranial nerve I, or simply CN I, is a
The
Structure
The specialized
The sense of
The olfactory nerve is the shortest of the twelve cranial nerves and, similar to the optic nerve, does not emanate from the brainstem.[2]
Function
The olfaction system works to ensure that people can successfully identify an extensive range of odorants and distinguish odors from one another.[4][5] Odorants interact with the olfactory receptor neurons (ORNs) at the periphery and transmit olfactory information to the central nervous system via axons at the basal surface.[4][5] These axons aggregate, forming the olfactory nerve.[4][5][6] Therefore, the olfactory nerve works to transduce sensory stimuli in the form of odorants and encode them into electrical signals, which are relayed to higher-order centers through synaptic transmission.[4][6]
Odor Transduction
Odorants bind to specific
ORN axons are responsible for relaying odorant information to CNS through action potentials.
Regeneration of Olfactory Nerves
ORNs directly interact with odorants inhaled into the olfactory epithelium which can also subject the ORNs to damage through continuous exposure to harmful substances such as
ORN Specificity
In the nasal passages, inhaled odorant molecules interact with receptor proteins on localized neuronal cilia of ORNs.[5][6] These dendritic extensions, cilia, express one type of protein receptor, although individual odorants can interact with multiple different receptor proteins.[5][6] As new ORNs mature, they have decreased expression levels of multiple olfactory receptor genes, contrasting with mature ORNs firm rule of one neuron—one expressed olfactory receptor gene.[4][6] Moreover, different odors activate specific ORNs in a molecular and spatial manner due to receptor specificity.[4] Some ORNs contain receptor proteins with high affinity for some odorants, with distinct odor selectivity to a specific chemical structure, while other receptor proteins are less selective.[4]
Clinical significance
Examination
Damage to this nerve leads to impairment or total loss of the sense of smell (anosmia). To simply test the function of the olfactory nerve, each nostril is tested with a pungent odor. If the odor is smelled, the olfactory nerve is likely functioning. On the other hand, the nerve is only one of several reasons that could explain if the odor is not smelled. There are olfactory testing packets in which strong odors are embedded into cards and the responses of the patient to each odor can be determined.[2]
Lesions
Lesions to the olfactory nerve can occur because of "blunt trauma", such as
Aging and smell
A decrease in the ability to smell is a normal consequence of human aging, and usually is more pronounced in men than in women. It is often unrecognized in patients except that they may note a decreased ability to taste (much of taste is actually based on reception of food odor). Some of this decrease results from repeated damage to the olfactory nerve receptors due likely to repeated upper respiratory infections. Patients with Alzheimer's disease almost always have an abnormal sense of smell when tested.[2]
Pathway to the brain
Some nanoparticles entering the nose are transported to the brain via olfactory nerve. This can be useful for nasal administration of medications.[8] It can be harmful when the particles are soot[9] or magnetite[10] in air pollution.[11]
In naegleriasis, "brain-eating" amoeba enter through the olfactory mucosa of the nasal tissues and follow the olfactory nerve fibers into the olfactory bulbs and then the brain.
Additional images
-
Olfactory nerve, deep dissection, inferior view
See also
References
- ^ Mcgraw Hill's Anatomy and Physiology Revealed
- ^ ISBN 978-1118492017.
- ISBN 978-1-61906-437-9.
- ^ ISBN 978-1-60535-380-7.
- ^ PMID 31194396. Retrieved 2023-12-07.
- ^ PMID 34209997.
- ^ PMID 35239810.
- PMID 30081536.
- .
- PMID 27601646.
- ^ Stevens AS (17 December 2014). "Nano air pollutants strike a blow to the brain". Science News for Students.
External links
- "Cranial Nerve I - Olfactory Nerve". Cranial Nerves. Yale School of Medicine. 22 March 1998. Archived from the original on 2016-03-03.