Cranial Nerves - Cranial Nerves Olfactory Nerve (CNI)...

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Cranial Nerves Olfactory Nerve (CNI) Olfactory Nerve (CNI) Olfactory Nerve (CN I) The receptors cells for smell form a patch of epithelium of about 5cm 2 (olfactory mucosa) in the roof of the nasal cavity. It covers part of the superior nasal concha and septum. Olfactory receptor cells are neurons with a modified dendrite consisting of a swollen tip bearing 10-20 cilia called olfactory hairs . The hairs are immobile and have binding sites for odor molecules The basal end of the cell tapers to become an axon. These axons collect into small fascicles that leave the nasal cavity through pores ( cribriform foramina ) in the ethmoid bone Collectively, the fascicles are regarded as cranial nerve I (olfactory nerve) The olfactory cells ( OC ) are a form of bipolar neuron that serve as transducers of chemical sensations into neural signals. They are the only neurons in the body directly exposed to the external environment. Molecules with a "scent" bind to the surface of these cells and in so doing the modify the cell membrane's charge characteristics, sending a signal via a long axon back to the brain. The axons of these neurons are bundled together to form the olfactory nerve , which is then routed through the overlying bone of the nose (cribriform plate) into the olfactory lobe of the brain. There are other cell types present in olfactory epithelium. One is the conventional supporting cell ( SC ) which provides both physical and nutritive support for the neural elements; it's ciliated. The second is the so-called basal cell ( BC ) that appears to be a glial element. Olfactory cells have a life span of approximately 60 days They are continually replaced by the differentiation of the basal cells into new olfactory cells The axons of the bipolar olfactory cells are bundled together to form fascicles. These are collected and become the olfactory nerve (ON). In the image you see several such bundles, and also the place where they're collecting together and being channeled through the bone ( B ). The fibers have come from the region of olfactory epithelium ( OE ) at top left. After passing through the cribriform plate, they enter olfactory bulb where they synapse with neurons called mitral cells and tuft cells
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Granule cells receive signals from the cortex and are inhibitory to the mitral cells (causing adaptation) can change odor quality and significance under different conditions The axons from the mitral and tuft cells from bundles called the olfactory tract The tracts follow a pathway leading to the medial side of the temporal lobe Input goes to the amygdala and hypothalamus which triggers emotional and visceral responses. Olfactory signals differ from other sensory inputs in that they
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Cranial Nerves - Cranial Nerves Olfactory Nerve (CNI)...

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