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Plan of olfactory neurons
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An also called an '''olfactory sensory neuron,''' is the primary
Transduction cell for
Olfaction in the
Olfactory System . Humans have about 40 million olfactory receptor neurons. In verebrates, olfactory receptor neurons reside on the
Olfactory Epithelium in the
Nasal Cavity . The cells are bipolar
Neuron s with a
Dendrite facing the interior space of the nasal cavity and an
Axon that travels along the
Olfactory Nerve to the
Olfactory Bulb .
Many tiny hair-like
Cilia protrude from the olfactory receptor cell's dendrite into the
Mucus covering the surface of the olfactory epithelium. These cillia contain
Olfactory Receptor s, a type of
G Protein-coupled Receptor . Each olfactory receptor cell contains only one type of olfactory receptor, but many separate olfactory receptor cells contain the same type of olfactory receptor. The axons of olfactory receptor cells of the same type converge to form
Glomeruli in the
Olfactory Bulb .
According to prevaling theory, olfactory receptors are activated by binding to structures on the odor molecule. The activation of the olfactory receptor activates the intracellular G-protein GOLF, which activates the enzyme
Adenylate Cyclase .
Cyclic AMP , produced by adenylate cyclase, binds to and opens
Ion Channel s in the
Cell Membrane , resulting in an influx of
Sodium and
Calcium ions into the cell. This influx of positive ions causes the neuron to depolarize, starting an electrical signal called an
Action Potential .
Individual olfactory receptor neurons die out and are replaced approximately every 40 days, so that there is a constant turnover of neurons in the olfactory epithelium. These cells are replaced by
Stem Cell s residing in the olfactory epithelium. Most neurons in other parts of the
Nervous System cannot be replaced, so research focusing on how stem cells differentiate into olfactory sensory neurons could lead to the use of these stem cells to replace damaged or degenerated neurons in the
Brain ,
Spinal Cord , or other parts of the nervous system.
In
Insect s, olfactory receptor neurons typically reside on the
Antenna . Much like in vertebrates, axons from the sensory neurons converge into glomeruli in the
Antennal Lobe .
''See also:''
Chemoreceptor ,
Sensory Receptor
