Also known as the optic nerve. This nerve connects the eye to the brain and carries the impulses formed by the back layer of the eye (retina) to the brain, which interprets them as images.
The cranial nerves emerge from or enter the skull (the cranium), as opposed to the spinal nerves which emerge from the vertebral column. There are twelve cranial nerves.
In terms of its embryonic development, the optic nerve is a part of the central nervous system (CNS) rather than a peripheral nerve.
The word “optic” comes from the Greek “optikos”, pertaining to sight.
Aside from the optic nerve, the eye has a number of other components. These include the cornea, iris, pupil, lens, retina, macula, and vitreous.
The cornea is the clear front layer of the eye that transmits and focuses light into the eye.
The iris is the colored part of the eye that helps regulate the amount of light that enters the eye.
The pupil is the dark circle in the center of the iris that determines how much light is let into the eye.
The lens is the transparent structure inside the eye that focuses light rays onto the retina.
The retina is the nerve layer that lines the back of the eye, senses light, and creates impulses that go through the optic nerve to the brain.
The macula is a small area in the retina that contains special light-sensitive cells and allows us to see fine details clearly.
The vitreous humor is a clear, jelly-like substance that fills the middle of the eye.
In sum, the optic nerve is uniquely a part of both the eye and the brain. It is embryologically the brain’s envoy to the eye and functionally the eye’s envoy to the brain.
- Nerve, seventh cranial
The seventh cranial nerve is the facial nerve, a mixed nerve that has fibers both going out and coming in (both efferent and afferent fibers). It supplies the muscles of facial expression. The cranial nerves emerge from or enter the skull (the cranium), as opposed to the spinal nerves which emerge from the vertebral column. […]
- Nerve, sixth cranial
to supply a muscle called the lateral rectus muscle that moves the eye outward. Paralysis of the abducens nerve causes inward turning of the eye (internal strabismus) leading to double vision. All 12 cranial nerves, the abducens nerve included, emerge from or enter the skull (the cranium), as opposed to the spinal nerves which emerge […]
- Nerve, spinal
One of the nerves that originates in the spinal cord. There are 31 pairs of spinal nerves. They consist of the 8 cervical nerves, 12 thoracic nerves, 5 lumbar nerves, 5 sacral nerves, and 1 coccygeal nerve.
- Nerve, tenth cranial
The tenth cranial nerve, and one of the most important, is the vagus nerve. All twelve of the cranial nerves, the vagus nerve included, emerge from or enter the skull (the cranium), as opposed to the spinal nerves which emerge from the vertebral column. The vagus nerve originates in the medulla oblongata, a part of […]
- Nerve, third cranial
The upper eyelid muscle which raises the eyelid; The extraocular muscle which moves the eye inward; and The pupillary muscle which constricts the pupil. Paralysis of the oculomotor nerve results in drooping eyelid (ptosis), deviation of the eyeball outward (and therefore double vision) and a dilated (wide-open) pupil.