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An example of eye movement over a photograph over the span of just two seconds. Eye movement includes the voluntary or involuntary movement of the eyes. Eye movements are used by a number of organisms (e.g. primates, rodents, flies, birds, fish, cats, crabs, octopus) to fixate, inspect and track visual objects of interests.
The nerve also contains fibers that innervate the intrinsic eye muscles that enable pupillary constriction and accommodation (ability to focus on near objects as in reading). The oculomotor nerve is derived from the basal plate of the embryonic midbrain. Cranial nerves IV and VI also participate in control of eye movement. [1]
Sometimes: cranial accessory, spinal accessory. Mainly motor Cranial and Spinal Roots Located in the jugular foramen. Controls the sternocleidomastoid and trapezius muscles, and overlaps with functions of the vagus nerve (CN X). Symptoms of damage: inability to shrug, weak head movement. XII Hypoglossal: Mainly motor Medulla
The three nerves that control the extraocular muscles are the oculomotor, trochlear, and abducens nerves, which are the third, fourth, and sixth cranial nerves. the abducens nerve is responsible for abducting the eye, which it controls through contraction of the lateral rectus muscle.
Eye movements must be precise and fast. This is seen in scenarios like reading, where the reader must shift gaze constantly. Although under voluntary control, most eye movement is accomplished without conscious effort. Precisely how the integration between voluntary and involuntary control of the eye occurs is a subject of continuing research. [5]
Cranial nerves are the nerves that emerge directly from the brain (including the brainstem), of which there are conventionally considered twelve pairs. Cranial nerves relay information between the brain and parts of the body, primarily to and from regions of the head and neck , including the special senses of vision , taste , smell , and hearing .
Many voluntary movements rely on spinal lower motor neurons, which innervate skeletal muscle fibers and act as a link between upper motor neurons and muscles. [2] [3] Cranial nerve lower motor neurons also control some voluntary movements of the eyes, face and tongue, and contribute to chewing, swallowing and vocalization. [4]
Light from a single point of a distant object and light from a single point of a near object being brought to a focus. The accommodation reflex (or accommodation-convergence reflex) is a reflex action of the eye, in response to focusing on a near object, then looking at a distant object (and vice versa), comprising coordinated changes in vergence, lens shape (accommodation) and pupil size.