24 Questions
What is the primary visual cortex also known as?
Striate cortex
Which area is responsible for the recognition of objects and perception of color?
Visual Association Cortex (areas 18 and 19)
What causes pupils of both eyes to constrict when light is shone into one eye?
Direct light reflex
Which cranial nerve supplies the orbicularis oculi muscle to close the eyelids in the corneal reflex?
Cranial nerve III
Which muscles are involved in the conjugate horizontal gaze?
Medial recti and lateral rectus muscles
Which structure controls the automatic eye and head movements during reading and toward sources of visual stimuli?
Superior colliculi
What is the result of lesions past the optic chiasm?
Contralateral defects
Which condition results from the destruction of the macula?
Central scotoma
Which artery occlusion is more common leading to lesions of visual radiations?
Posterior cerebral artery occlusion
What causes cortical blindness?
Lesions of visual radiations
Which structure controls the medial recti muscles contracting, lens thickening, and pupils constricting during the accommodation reflex?
Frontal eye fields
What is responsible for sending fibers to parasympathetic nuclei (Edinger-Westphal nuclei) of cranial nerve III during direct and consensual light reflexes?
Olivary pretectal nucleus
What type of cells form the myelin sheaths of the optic nerve?
Oligodendrocytes
Where does the optic nerve leave the orbital cavity?
Through the optic canal
What is the point of contact called where fibers from the nasal half of each retina cross midline and enter the optic tract of the opposite side?
Optic Chiasm
Where do fibers from the temporal half of each retina, including the temporal half of macula, pass posteriorly?
Optic Tract of same side
Where do most fibers of the optic tract terminate by synapsing?
Lateral Geniculate Body
Which part of the thalamus consists of 6 layers of cells on which axons of the optic tract synapse?
Lateral Geniculate Body
What is the function of the pretectal area to which some fibers of the optic tract project?
Light reflex
Which structure do fibers from nasal (medial) half of each retina, including nasal half of macula, cross midline and enter?
Optic Tract of opposite side
Where are fibers from temporal (lateral) half of each retina, including temporal half of macula, located in relation to fibers from nasal half after crossing at the optic chiasm?
On opposite side in optic tract
What is the point where optic nerves from both sides unite to form a structure called?
Optic Chiasma
What is the Greek meaning of 'chiasma' in relation to its point of contact at the junction?
To mark with an X
What is comparable to a tract within the central nervous system due to its myelin sheaths formed from oligodendrocytes?
Optic Nerve
Study Notes
- Optic radiations: axons of neurons within lateral geniculate body pass through the geniculocalcarine tract and terminate in the visual cortex (area 17)
- Visual Cortex (area 17): primary visual cortex, also known as the striate cortex or Brodmann area 17, located upper and lower lips of calcarine sulcus on the medial surface of the occipital lobe
- Visual Association Cortex (areas 18 and 19): responsible for recognition of objects and perception of color
- Direct and Consensual Light Reflexes: light shone into one eye causes pupils of both eyes to constrict (direct light reflex) and the opposite pupil to constrict (consensual light reflex)
- Direct and Consensual Light Reflexes: afferent impulses travel through optic nerve, optic chiasm, optic tract, synapse on neurons in olivary pretectal nucleus, which sends fibers to parasympathetic nuclei (Edinger-Westphal nuclei) of cranial nerve III
- Accommodation Reflex: eyes adjust focus on an object by medial recti muscles contracting, lens thickens, and pupils constricting
- Corneal Reflex: blinking of eyelids in response to light touching the cornea or conjunctiva, impulses travel through ophthalmic nerve to sensory nucleus of trigeminal nerve, interneurons connect to motor nucleus of facial nerve, which supplies orbicularis oculi muscle to close eyelids
- Conjugate Horizontal Gaze: eyes move in conjugate (parallel) gaze to ensure images project to same spot on each retina, muscles used include lateral rectus and medial rectus muscles, controlled by frontal eye fields, abducens nucleus, and medial longitudinal fasciculus
- Visual Body Reflexes: automatic eye and head movements during reading and toward sources of visual stimuli, protected by the closing of eyes and raising of arms, controlled by superior colliculi, tectospinal and tectobulbar tracts, and anterior gray columns of spinal cord
- Clinical Correlates: destruction of macula causes central scotoma, lesions of optic nerve cause anopsia and loss of sensory limb of light reflex, compression of optic chiasm results in peripheral vision loss, lesions past chiasm cause contralateral defects, lesions of visual radiations are more common due to occlusion of posterior cerebral artery, combination of blindness with intact pupillary reflexes results in cortical blindness, causes of lesions include optic neuritis, central retinal artery occlusion, internal carotid artery aneurysm, pituitary tumor, craniopharyngioma, middle or posterior cerebral artery occlusion.
Test your knowledge of the optic pathway, visual reflexes, and the anatomy of the optic nerve with this quiz. Learn about the structure and function of the optic nerve as well as its role in visual processing.
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