Olfactory system

The olfactory system is the sensory system used for smelling (Olfaction). Most mammals and reptiles have a main olfactory system and an accessory olfactory system. The main olfactory system detects airborne substances, while the accessory system senses fluid-phase stimuli.

Structure

The main components of the olfactory system are:

• Olfactory epithelium: This is the tissue which covers the cribriform plate, the roof of the nasal cavity, and the upper part of the nasal septum. It contains the olfactory sensory neurons.
• Olfactory bulb: This is a structure of the vertebrate forebrain involved in olfaction.
• Olfactory nerve: Also known as cranial nerve I, this is the first of 12 cranial nerves. It relays sensory data to the brain, and it is responsible for the sense of smell.
• Olfactory cortex: This is a part of the cerebral cortex involved in olfaction.

Function

The olfactory system begins in the nasal cavity. To smell something, molecules from that item need to make it to your nose. Everything you smell, therefore, is giving off molecules -- whether it is bread in the bakery, onions, perfume, a piece of fruit or whatever. Those molecules are generally light, volatile (easy to evaporate) chemicals that float through the air into your nose. Once the molecules are in your nose, the process of smelling begins.

Clinical significance

Damage to the olfactory system can result in an inability to smell (anosmia), a distortion in the sense of smell (parosmia), or an enhanced sense of smell (hyperosmia). Conditions such as Alzheimer's disease and Parkinson's disease are often associated with olfactory system dysfunction.

See also

• Olfaction
• Anosmia
• Parosmia
• Hyperosmia
• Alzheimer's disease
• Parkinson's disease

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  Head Olfactory Nerve Labeled
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  Comprehensive List of Relevant Pathways for the Olfactory System
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  Action Potential Propagation Animation
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  Olfaction
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  Olfactory System
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  Vesalius' Olfactory Bulbs