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The olfactory nerve, also known as the first cranial nerve, cranial nerve I, or simply CN I, is a cranial nerve that contains sensory nerve fibers relating to the sense of smell. The afferent nerve fibers of the olfactory receptor neurons transmit nerve impulses about odors to the central nervous system ( olfaction ).
The olfactory nerve zone is composed of preterminals and terminals of the olfactory nerve and is where the olfactory receptor cells make synapses on their targets. [2] The non-olfactory nerve zone is composed of the dendritic processes of intrinsic neurons and is where dendrodendritic interactions between intrinsic neurons occur.
The olfactory epithelium is a specialized epithelial tissue inside the nasal cavity that is involved in smell.In humans, it measures 5 cm 2 (0.78 sq in) [1] and lies on the roof of the nasal cavity about 7 cm (2.8 in) above and behind the nostrils. [2]
ORs activate ORNs that transduce the input signal into action potentials. In general, glomeruli receive input from ORs of one specific type and connect to the principal neurons of the OB, mitral and tufted cells (MT cells). Olfactory sensory neurons project axons to the brain within the olfactory nerve, (cranial nerve I).
The peripheral olfactory system consists mainly of the nostrils, ethmoid bone, nasal cavity, and the olfactory epithelium (layers of thin tissue covered in mucus that line the nasal cavity). The primary components of the layers of epithelial tissue are the mucous membranes, olfactory glands, olfactory neurons, and nerve fibers of the olfactory ...
The olfactory bulb is supported and protected by the cribriform plate of the ethmoid bone, which in mammals separates it from the olfactory epithelium, and which is perforated by olfactory nerve axons. The bulb is divided into two distinct structures: the main olfactory bulb and the accessory olfactory bulb.
The cell bodies of the ORNs are distributed among all three of the stratified layers of the olfactory epithelium. [4] Many tiny hair-like non-motile cilia protrude from the olfactory receptor cell's dendrites. The dendrites extend to the olfactory epithelial surface and each ends in a dendritic knob from which around 20 to 35 cilia protrude.
Mitral cells are a key part of the olfactory bulb microcircuit. Mitral cells receive input from at least four cell types: olfactory sensory neurons, periglomerular neurons, external tufted cells and granule cells. The synapses made by external tufted cells and olfactory sensory neurons are excitatory, whereas those of granule cells and ...