Ocular: Visual Pathways (scott) Flashcards
Rods are specialized for __________ light and __________ detection
Dim
Motion
Cones are specialized for __________ vision.
Color (day-time vision)
Where are cone photoreceptors most populated?
In the macula
The fovea only contains ___________.
Cones
The signal from photoreceptors are passed onto what cells?
Retinal interneurons - bipolar cells, amacrine cells, horizontal cells
Bipolar cells receive inputs from ____________ and project to ___________ cells.
Photoreceptors and project to ganglion cells
Horizontal cells are located between which two layers?
Receptor cell layer and the bipolar cell layer
Amacrine cells are located between the ___________ layer and the __________ layer and modulate the activity there.
Bipolar cell layer and the ganglion cell layer
How do retinal ganglion cells send their output signal and to where?
Send output via axons that form the optic nerve to communicate with the brain
Papillomacular Bundle is defined as:
Axons of the retinal ganglion cells coursing from the macula towards the optic disc
What side of the optic disc does the papillomacular bundle enter into?
Temporal side of the optic disc
Where are macular fibers situated within the retrobulbar optic nerve?
Centrally
When do optic nerve fibers become myelinated?
After they exit the eye
90% of the optic nerve fibers synapse where?
LGN
10% of optic nerve fibers will project to the ____________ nucleus.
Suprachiasmatic nucleus
Where is the optic chiasm located in relation to the 3rd ventricle?
Floor of 3rd ventricle
At what structure/area does the visual information from right and left eyes cross to the contralateral side of the visual system?
Optic chiasm
Posterior to the optic chiasm, the visual pathway continues on each side as an ____________.
Optic tract
The nasal retinal fibers will cross at the _________.
Chiasm
How do temporal retinal fibers course?
Remain Ipsilateral and do not cross over
How can a pituitary adenoma impact visual fields?
Compress optic chiasm and cause bitemporal hemianopia
An early stage pituitary adenoma will first compress the _____________ retinal fibers and manifest as a ______________________________.
First compress the inferonasal retinal fibers crossing in the chiasm
Manifest as a bitemporal superior quadrantanopia
How might an aneurysm of the internal carotid artery impact visual fields?
By compressing temporal fibers of the optic chiasm, it is displaced and compressed against the contralateral ICA, which in turn compresses the temporal fibers on that same side and results in a rare binasal hemianopia
Do afferent pupillomotor reflex fibers leave the optic tract before reaching the LGN?
Yes
Where do afferent pupillomotor reflex fibers synapse?
Pretectal nucleus of the midbrain
Each optic tract contains fibers from where?
Temporal retina of ipsilateral eye
Nasal retinal fibers of the contralateral eye
Temporal retinal fibers are carrying visual information regarding the __________ visual field.
Nasal visual field
Nasal retinal fibers are carrying visual information regarding the ______________.
Temporal visual field
Transection of the right optic tract would result in what deficit?
Left hemianopia
The LGN is located in the _______ thalamus.
Lateral
Visual information from the optic tracts is then relayed to their respective __________.
LGN
LGN is a _______ layered structure.
6
The axons exiting the LGN are known as the _______________.
Optic radiations
Some of the inferior fibers of the optic radiation will loop into the __________ lobe on their way to __________ and are collectively known as ______________.
Temporal lobe on their way to the occipital lobe and are collectively known as Meyer’s loop
Damage to the inferior optic radiations will produce what visual field deficit/pattern?
Superior quadrantopic field (Pie in the Sky pattern)
Fibers from the superior optic radiations will loop into __________ lobe on their way to __________ and are collectively known as ______________.
Parietal lobe on their way to the occipital lobe and are collectively known as Baums’ Loop
Damage to the superior optic radiations will produce what visual field deficit?
Inferior quadrantopic field (Pie on the Floor pattern)
The primary visual cortex is also known as _______ and ______________.
V1 and Brodmann area 17
The primary visual cortex is located predominantly on the medial surface of the _________________.
Occipital lobe
Calcarine fissure divides the visual cortex into an _________ and ______________ gyrus.
Upper (cuneus gyrus) and lower (lingual gyrus)
The striate cortex is involved in ____________ vision.
Binocular
Where do the superior optic radiations terminate in the striate cortex?
Superior to the calcarine fissure (cuneus gyrus)
Where do the Inferior optic radiations terminate in the striate cortex?
Below the calcarine fissure (lingual gyrus)
Damage to the superior optic radiations causes ____________________.
Contralateral lower quadrantanopia
Damage to the inferior optic radiations causes _____________________.
Contralateral upper quadrantanopia
The visual cortex must send visual information to which higher visual association areas?
Area 18 (parastriate cortex) and area 19 (peristriate cortex)
Visual association areas in one hemisphere are interconnected to the same areas in the contralateral hemisphere via ______________.
Inter-hemispheric commisural pathway in the posterior corpus callosum
Visual information is ultimately analyzed in the dominant __________ lobe.
Parietal
Most often times, Lesions of the left angular gyrus of the parietal lobe will result in _______________.
Faulty integration of visual information despite intact primary visual pathways
The Oculomotor nucleus will give rise to lower motor neurons supplying _____________.
EOMs (specifically Levator palpebrae superioris, superior rectus, inferior rectus, medial rectus, inferior oblique)
Edinger-Westphal nucleus gives rise to preganglionic parasympathetic neurons to supply the ___________ and ____________.
Sphincter pupillae and ciliary muscles
Trochlear nucleus gives rise to lower motor neurons supplying the ____________.
Superior Oblique muscle
Abducent nucleus gives rise to lower motor neurons supplying the __________.
Lateral rectus muscle
Accommodative pathway: Area 19 (visual association cortex) receives visual feedback from area ____________.
17 (primary visual cortex)
Describe the accommodative pathway?
- Area 19 (Visual Association Cortex) receives feedback from Area 17 (Primary Visual Cortex)
- Association detects blur & projects to PTN
- Pretectal projects bilaterally to EW
- Preganglionic fibers travel on CN3 & synapse in ciliary ganglion
- Postganglionic fibers go to sphincter muscle to constrict pupil & to ciliary muscle to thicken the lens
- CN3 carries out convergence of the eyes via MR
Accommodative triad
Accommodation, constriction, convergence
Pupillary Light Reflex Pathway
- Optic tract fibers directly project to pretectal nucleus
- Pretectal nucleus projects to EW nucleus bilaterally
- Preganglionic fibers from EW nucleus synapse in the ciliary ganglion
- Postganglionic fibers project to sphincter pupillae muscle to constrict the pupil
Consensual reflex of the pupil
Stimulation of one eye causes reflex in both eyes
Pupillary Dilation Pathway
Posterior hypothalamus projects to cells in the intermediolateral cell column of the spinal cord at the upper thoracic levels C8-T2
Preganglionic fibers synapse onto Postganglionic neurons in the superior cervical ganglion
Postganglionic fibers from the internal carotid nerve plexus and follow the internal carotid artery and its branches
Postganglionic fibers supply dilator pupillae muscles via the long ciliary nerve
A lesion of the superior optic radiations in the right parietal lobe will result in what visual field defect?
Left inferior quadrantanopia
A right inferior quadrantanopia suggests a lesion where in the visual pathway?
Superior optic radiation (Baum’s loop) in the left parietal lobe
