Visual System Flashcards
Lecture 1 Exam 3
What are retinofugal projections?
Axons that leave the retina of the eye
What is the main target of retinofugal projections?
LGN of thalamus–up to 20% of optic nerve/tract axons have other brain targets
Are Nasal hemitetinal fibers decussating or non decussating
decussating
Are Temporal hemiretina fibers decussating or non decussating
non-decussating
What is the inner limits of our vision based on
our noses
_____ zone (field) is area seen by both eyes
binocular
_____ zone (field) is area seen by just one eye
monocular
Right visiaul field represented by ____ visual cortex
left
The right visiual field falls on the temporal hemiretina of the ____ eye and is registered in that visual cortex
left
The right visual field falls on the nasal hemiretina of the right eye and is registered in the ____ visual cortex
left
Left side of the brain sees the ____ half of the world
right
horses have a (larger/smaller) binocular vision zone
smaller due to their elongated noses
What is the function of the main retinofugal projects that go from the retina to the LGN of thalamus?
conscious vision, movement, and object recognition, etc.
Layers 3-6 are responsible for seeing what
colors and detail
Layers 1 and 2 of the LGN are responsible for seeing what
patterns and motion
T/F visual information from each eye is kept separate in the LGN
True
LGN we have visual information from both eyes, but they aren’t really mixing–there is no _______ vision yet
Binocular
What layers of the LGN are contralateral inputs
1
4
6
What layers of the LGN are ipsilateral inputs
2
3
5
Right LGN sees the ____ side of the world
left
Left LGN sees the ____ side of the world
right
From the LGN where do the retinofugal fibers go?
V1
What are the 3 subcortical targets of the optic tract
-pre Tectum
-superior colliculus
-Suprachiasmatic nucleus of the hypothalamus
What does the pretectum control
pupillary light reflex
What does the superior colliculus control
gaze shifting/eye movements
What does the Suprachiasmatic nucleus of the the hypothalamus control
circadian rhythms
Would a lesion of the LGN, optic radiation or visual cortex have any effect on the projections of the subcortical targets
NO, these fibers split from the optic tract prior to the Thalamus
What does the pupillary reflex allow the eye to do?
Adjust amount of light reaching retina
protect photoreceptors from bright light
_________ of the midbrain mediates the pupillary light reflex
Pre tectum
To keep vision consisten, what must occur during the pupillary light reflex?
consensual changes to pupil
Do some optic tract axons not synapse in LGN, but pass by to synapse in pretectum of midbrain
YES
Pretectum neurons synapse bilaterally onto _______ nucleus
edinger westphal
From the Edinger-Westphal nucleus where are upper motor neurons sent
to the ciliary ganglion outside the eye as part of CN lll
What do the cilliary ganglion lower motor neurons tell the muscles in the pupil to do with pupillary light reflex
constrict
T/F many muscles controlling the eyes are under voluntary control but often do not require conscious though, are somewhat automated
True
What do conjugate movements involve
activating opposite muscles of L and R eyes to movement towards same point in space
What do vergence movements move
central axis of each eye towards (convergence) or away from each other (divergence)
Where is the suprachiasmatic nucleus SCN
in hypothalamus
What does the SCN generate
24h circadian rhythms for the body via hormones and neurotransmitters
What does our circadian rhythm require
light
What visual functions only need to detect the presence of light
pupillary light response
photosensitivity for setting circadian rhythms
T/F rats with genetic pathologies that lack rods and cones still show circadian rhythm…but removing the eye disrupts circadian function
true
Do photo-sensitive retinal ganglion cells require inputs from receptors
not always
SCN gets input from the
intrinsically photo-sensitive retinal ganglion cells
How are intrinsically photo-sensitive RGCs distributed
evenly over the retina
Where do the intrinsically photo-sensitive retinal ganglion cells exit at
optic nerve head with other RGC axons to make up the optic nerve
Where do you peel away optic nerve to target hypothalamus
peel away from optic nerve around the point of chiasm (decussation)
