Special Senses: Vision Flashcards
what nerve is the tactile sensory ending around the eye?
trigeminal, CN5
what nerve is the motor unit around they eye - orbicularis oculi?
CN7, facial
what cranial nerve does the majority of eye movement?
CN3
where is light focused?
fovea centralis
which species has a better fovea - diurnal or nocturnal?
diurnal
what neurons are in the retina?
bipolar cells
horizontal cells
amacrine cells
ganglion cell
which is rods and which is cones?
which is rods and which is cones?
which is rods and which is cones?
which is rods and which is cones?
which is rods and which is cones?
which is rods and which is cones?
the more light the ____ the response and the _____ transmitter is released
the more light the greater the response and the less transmitter is released
is light energy converting to chemical energy a graded potential?
yes
what does one bipolar neuron recieve convergent input from?
many rods
are rods or cones more sensitive to structural detail?
cones
what allows for cones to have high visual acuity?
one-to-one wiring
what is the trade off for cones being able to see high spatial discrimination?
requires ample light
which species is tetrachromatic? what does this mean?
avians - opsins absorb red, green, blue, and UV
where does the signal from the rods and cones go to?
bipolar and ganglion cells
what do horizontal and amacrine cells provide?
lateral transmission
what happens when light does not hit a certain part of the retina?
affected by adjacent portion that it did hit - increase contrast, directional sensitivity, color discrimination
which arrow is the direction of light vs the direction of visual processing?
red - direction of light
blue - direction of visual processing
what does lateral inhibition do?
increase contract and sharpness of visual response
when are excited ganglion cells inhibited?
if neighboring photoreceptors are also excited
what do horizontal cells do when ganglion cells are stimulated in a well-defined illuminated field?
send inhibitory signals to neighboring ganglion cells
map out the optic nerve to the occipital cortex
optic nerve -> optic chiasm ->nasal fiber to opposite side , temporal fiber to same side -> fibers go to thalamus -> synapse on lateral geniculate nucleus -> occipital cortex
In mammals ganglion cells project to the _______ and _______ visual cortex
In mammals ganglion cells project to the ipsilateral and contralateral visual cortex
An injury to the left hemisphere will affect perception in what visual field?
right
what are the 3 kinds of eye movement?
eye position
accommodation
regulation of pupil size
what is eye position
convergence of the two eyes to focus objects on the fovea
follow objects, fixate visual field
what is accommodation
adapt focal length to increase optic power by altering shape of lens
what is regulation of pupil size
constriction of pupil to reduce spherical aberration
what is this an example of?
convergence
what is this an example of?
divergence
what reflex tests eye following an object, fixate the visual field?
vestibulo-ocular reflex
what is stabismus
misalignment of eyes
when might double vision occur?
strabismus
object projected on different part of retina
A patients with left lateral displacement (Exotropia) could have a lesion where?
left oculomotor nucleus, CN3
what is esotropia
eye turned inward
what is the neural control of accomodation?
RGS pathway
retina -> optic nerve -> lateral geniculate nucleus -> visual cortex -> superior colliculus -> oculomotor nucleus -> parasympathetic motor efferent to ciliary muscle, CN3
what does ciliary muscle contraction do the lens?
relax tension, more curved, focus on nearby target
what is the diameter of the pupil regulated by?
ANS
what controls the iris sphincter muscle?
parasympathetics
what controls the iris dilator muscle?
sympathetics
what does the retino-geniculo-striate pathway do?
conscious visual perception
what is the retino-tectal pathway
provides pupillary reflexes and reflex orientation of eyes to visual targets
map out the retino-tectal pathway
ganglion cells -> pretectal nuclei -> edinger westphal nucleus -> oculomotor (CN3)
what is the retino-hypothalamic pathway?
provides for light to set up physiological rhythms in suprachiasmatic nucleus (SCN)
ex. short and long day breeders
map out the eye blink reflex - touch the cornea/eyelid
free nerve endings in cornea stimulate CN5 -> CN5 terminates in spinal trigeminal nucleus-> reticular formation interneurons send bilateral axons to facial nucleus -> CN7 send axons down the facial nerve to orbicularis oculi -> lower eyelids
map out the menace response - don’t touch cornea/eyelid
visual stimulus relayed on CN2 -> CN2 goes to occipital cortex via thalamus -> threat perceived -> motor neurons stimulate ipsilateral facial nerves in CN7 -> CN7 motor neurons excite orbicularis oculi -> lower eyelides
what can cerebral lesion result in with the menace reflex?
loss of menace reflex
what is a good test to asses damage to cortex?
menace response
what pathway does the pupillary light reflex go on?
retino-tectal pathway
map out the pupillary light reflex pathway
ganglion cells of retina project bilaterally to pretectal nucleus via CN2 -> pretectal nuclei project crossed and uncrossed fibers to edinger-westphal nucleus -> rise of preganglionic parasympathetic fibers -> exit brain via CN3 -> synapse with postganglionic parasympathetic neurons of ciliary ganglion -> sphincter muscle of iris excited
what is a direct response to the pupillary light reflex?
ipsilateral side respond to stimulus
what is consensual response to the pupillary light reflex?
contralateral side responds after ipsilateral stimulus
what is the deficit?
left CN2 deficit
what is the deficit?
left CN3 deficit
what caused the animal to be blind?
possible right cerebral hemisphere lesion
what is seen in horner’s syndrome?
-nicotating membrane ventromedial in conjunctival sac
-prolapsed nicotating membrane
what space is the nicotating membrane in?
enophthalmic state
what is horners syndrome?
damage to sympathetic NS to eye
what can damage sections 1,2,3 - horner’s syndrome
1 & 2 - infection, inflammation, injury, spinal compression
3 - middle or inner ear diease
what are the symptoms of horner’s syndrome?
miosis (small pupils)
ptosis (drooping of upper eyelid)
enopthalmus (sunken eyes)
prolapsed nicitating membrane
