Anatomy
Summary
The first two cranial nerves are the olfactory nerve and the optic nerve. The olfactory nerve is involved with smell and the optic nerve with sight. The olfactory nerve, represented by cranial nerve I, originates from specialized sensory cells located in the roof of the nose. Central processes of these cells, also known as rootlets, connect to the olfactory bulb via perforations in the cribriform plate of the ethmoid bone. The olfactory bulb sends signals to the brain through the olfactory tract. A loss of function of this nerve results in anosmia, the inability to smell, and the possible misinterpretation of loss of smell as a loss of taste.
The optic nerve, or cranial nerve II, is responsible for sight and includes the afferent limb of the pupillary light reflex. This nerve collects sensory data from the eye and enters the skull through the optic canal in the sphenoid bone. Once inside the skull, the two optic nerves come together at the optic chiasm, where they cross and proceed as two optic tracts. The pathways then move towards the thalamus and eventually the visual cortex. Note that the ophthalmic artery, a branch of the internal carotid artery, also traverses the optic canal, supplying blood to the eye and surrounding structures.
Lesson Outline
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FAQs
The olfactory nerve, also known as cranial nerve I, is responsible for the sense of smell. Specialized olfactory receptor neurons located in the upper part of the nasal cavity transduce chemical signals (smell) into electrical signals. These electrical signals are then transmitted to the brain via the olfactory nerve, passing through the ethmoid bone.
The optic nerve, or cranial nerve II, is the nerve of sight. It transmits visual information from the retina of the eye to the brain via the optic nerve, which travels through the optic canal.
The optic chiasm is an X-shaped structure located at the base of the brain where the two optic nerves intersect. Each optic nerve transmits information from one eye, but at the optic chiasm, some fibers from each eye cross over to the other side.
Anosmia is the inability to perceive smell. However, it may be perceived as a loss of taste. Since the olfactory nerve is responsible for transmitting smell information to the brain, damage or impairment of this nerve can lead to anosmia.
