Anatomy & Physiology of the Visual System Flashcards
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Read the first 7 Anatomy & Physiology of the Visual System flashcards as text
The Edinger-Westphal nucleus provides parasympathetic innervation to which intraocular structures?
Answer: Sphincter pupillae and ciliary muscle
The Edinger-Westphal nucleus provides parasympathetic innervation via CN III to both the sphincter pupillae (pupil constriction) and the ciliary muscle (accommodation).
Which of the following correctly describes the action of the inferior oblique muscle in primary position?
Answer: Extorsion, elevation, and abduction
In primary position, the inferior oblique produces extorsion as its primary action, with secondary actions of elevation and abduction.
Panum's fusional area refers to which concept in binocular vision?
Answer: The region around the horopter within which objects are seen in single binocular vision
Panum's fusional area is the region around the horopter where objects with slight retinal image disparity are still fused into a single percept, forming the basis of stereopsis.
The optic nerve exits the eye through which structure and is surrounded by an extension of the meninges?
Answer: The lamina cribrosa of the sclera
The optic nerve exits through the lamina cribrosa, a sieve-like region of the sclera, and is surrounded by extensions of the dura, arachnoid, and pia mater.
Accommodation is primarily achieved by which change in the crystalline lens?
Answer: The lens becomes more convex due to ciliary muscle contraction and zonule relaxation
During accommodation, ciliary muscle contraction causes the zonular fibers to relax, allowing the inherently elastic lens to become more convex (increased curvature) and thus more powerful.
Which pathway mediates the consensual pupillary light reflex (contralateral pupil constriction)?
Answer: Commissural fibers connecting the two Edinger-Westphal nuclei via the posterior commissure
The consensual response occurs because pretectal nucleus fibers cross via the posterior commissure to reach the contralateral Edinger-Westphal nucleus, producing bilateral pupil constriction to unilateral light stimulation.
In the stereoscopic depth perception mechanism, crossed disparity signals indicate that an object is located where relative to the fixation point?
Answer: In front of the fixation plane (closer to the observer)
Crossed disparity occurs when an object's retinal images fall on temporal retina in each eye, indicating the object is closer (nearer) than the fixation plane.