CO Anatomy & Physiology of the Visual System 1 — Questions and Answers
Question 1: Which extraocular muscle is responsible for primary abduction of the eye?
- Medial rectus
- Lateral rectus (Correct answer)
- Superior oblique
- Inferior oblique
Correct answer: Lateral rectus
The lateral rectus, innervated by cranial nerve VI (abducens), is the primary abductor of the eye.
Question 2: The visual pathway travels from the retina to the primary visual cortex located in which brain lobe?
- Frontal lobe
- Parietal lobe
- Temporal lobe
- Occipital lobe (Correct answer)
Correct answer: Occipital lobe
The primary visual cortex (V1/striate cortex) is located in the occipital lobe, specifically in the calcarine fissure.
Question 3: Which cranial nerve innervates the superior oblique muscle?
- CN III (Oculomotor)
- CN IV (Trochlear) (Correct answer)
- CN V (Trigeminal)
- CN VI (Abducens)
Correct answer: CN IV (Trochlear)
The trochlear nerve (CN IV) exclusively innervates the superior oblique muscle, making it the only cranial nerve to exit from the dorsal brainstem.
Question 4: At the optic chiasm, which fibers decussate (cross) to the opposite side?
- Temporal retinal fibers
- Nasal retinal fibers (Correct answer)
- All retinal fibers
- No fibers cross at the chiasm
Correct answer: Nasal retinal fibers
Nasal retinal fibers, which carry temporal visual field information, cross at the optic chiasm, while temporal retinal fibers remain ipsilateral.
Question 5: The fovea centralis contains predominantly which type of photoreceptors?
- Rods only
- Cones only (Correct answer)
- Equal numbers of rods and cones
- Ganglion cells only
Correct answer: Cones only
The fovea centralis is packed exclusively with cone photoreceptors, providing maximum visual acuity and color discrimination in bright light.
Question 6: The near reflex triad consists of accommodation, miosis, and which third component?
- Divergence
- Convergence (Correct answer)
- Cycloduction
- Abduction
Correct answer: Convergence
The near reflex triad comprises accommodation (lens focusing), miosis (pupil constriction), and convergence (inward turning of both eyes) for near viewing.
Question 7: Which layer of the retina contains the cell bodies of the photoreceptors?
- Ganglion cell layer
- Inner nuclear layer
- Outer nuclear layer (Correct answer)
- Retinal pigment epithelium
Correct answer: Outer nuclear layer
The outer nuclear layer contains the nuclei (cell bodies) of both rod and cone photoreceptors.
CO Anatomy & Physiology of the Visual System 1
Which extraocular muscle is responsible for primary abduction of the eye?