The purpose of the optic chiasm is to ensure that visual signals go to both hemispheres of brain. The majority of neural signals are sent to the thalamus for processing and are then distributed into areas of the occipital lobe.
What does optic chiasm mean?
Listen to pronunciation. (OP-tik ky-A-zum) The place in the brain where some of the optic nerve fibers coming from one eye cross optic nerve fibers from the other eye. Also called optic chiasma.
What happens when the optic chiasm is damaged?
Damage to the retina or one of the optic nerves before it reaches the chiasm results in a loss of vision that is limited to the eye of origin. In contrast, damage in the region of the optic chiasm—or more centrally—results in specific types of deficits that involve the visual fields of both eyes (Figure 12.8).
What do the oculomotor nerves control?
The oculomotor nerve is the third cranial nerve (CN III). It allows movement of the eye muscles, constriction of the pupil, focusing the eyes and the position of the upper eyelid. Cranial nerve III works with other cranial nerves to control eye movements and support sensory functioning.
Where is the optic chiasm located quizlet?
The optic chiasm is located at the bottom of the brain immediately below the hypothalamus.
How many fibers of the optic nerve cross over at the optic chiasm?
At the chiasm, roughly 53% of the optic nerve fibers from each eye cross and pass through the contralateral optic tract. The other approximately 47% continue through the ipsilateral optic tract (Kupfer, Chumbley, & Downer, 1967).
Is your eyeball round?
The eye is round because it is inflated by the pressure from the fluid inside.
How does the optic chiasm contribute to human vision quizlet?
Vision is generated by photoreceptors in the retina, a layer of cells at the back of the eye. The information leaves the eye by way of the optic nerve, and there is a partial crossing of axons at the optic chiasm.
How does Bitemporal hemianopia occur?
Bitemporal hemianopsia most commonly occurs as a result of tumors located at the mid-optic chiasm. Since the adjacent structure is the pituitary gland, some common tumors causing compression are pituitary adenomas and craniopharyngiomas. Also, another relatively common neoplastic cause is meningiomas.
What effect would a lesion through the optic chiasm have on vision?
A lesion involving complete optic chiasm, which disrupts the axons from the nasal field of both eyes, causes loss of vision of the right half of the right visual field and the left half of the left visual field. This visual field defect is called as bitemporal hemianopia.
What happens to a person when the primary visual area is destroyed?
In the domain of vision, damage to the primary visual cortex, or V1, but not any other cortical region, abolishes visual awareness and leads to chronic blindness.
Which cells in the retina have axons that leave the retina?
Ganglion cell axons exit the retina through a circular region in its nasal part called the optic disk (or optic papilla), where they bundle together to form the optic nerve.
What happens when the oculomotor nerve is damaged?
Damage to any of these nerves or the muscle or muscles they innervate causes dysconjugate gaze, which results in characteristic patterns of diplopia (double vision). In addition, with oculomotor nerve damage, patients also lose their pupillary constriction to light as well as the elevation of their eyelid.
What role does the oculomotor nerve play in the parasympathetic nervous system?
The oculomotor nerve (the third cranial nerve; CN III) has three main motor functions: Innervation to the pupil and lens (autonomic, parasympathetic) Innervation to the upper eyelid (somatic) Innervation of the eye muscles that allow for visual tracking and gaze fixation (somatic)
Is the oculomotor nerve sensory or motor?
The trochlear, abducens, accessory, and hypoglossal nerves are only motor nerves; the trigeminal nerve is both sensory and motor; the oculomotor nerve is both motor and parasympathetic; the facial glossopharyngeal, and vagus nerves have sensory, motor, and parasympathetic components (Standring, 2008).
