eye reflexes and vision stuff Flashcards
(11 cards)
whats the frontal eye field do
its in the brain in the frontal hemisphere. this is where we begin voluntary eye movements. eye field does contralateral control. movement is always siccadic
whats the occipital eye field do
involuntary tracking of an object. fixation and smooth pursuit for moving objects
what happens in the pupiliary light reflex
when we shine a light in one eye, we see that both eyes get smaller
what is the pupilliary light reflex good for and what does it need
it tests if the brainstem is intact, so can be done in coma patients as no higher function is needed for the test
how does pupillary light reflex work
So we begin by shining light into the eye . The information of light is carried by the optic nerve CN2 to the pre-tectal area where a synapse to an interneuron occurs. The interneuron then synapses to BOTH oculomotor nerves in the Edinger-Westphal nucleus. The oculomotor then goes out to the ciliary ganglion where synapse to interneuron occurs. The interneuron then goes to the pupillary constrictor muscles. So then when light is shone into one eye, both pupils will constrict.
what cranial nerves are involved in the pupillary light reflex
optic nerve carries light info into pretectal area where interneuron synapse. then the occulomotor carries the info out from the edinger-westphal to ciliary ganglion
what happens to lens when ciliary muscles contract and relax
The ciliary nucleus is a sphincter. So when the ciliary muscles are at rest, the suspensory ligaments are taut and thus pulling the lens to a flat shape. In this shape in far vision.
So when we need to do near accommodation we have the ciliary muscle contract. This makes the suspensory ligaments relax and thus the lens rounds up.
whats the pathway of the accomodation reflex
Sensory information of things moving closer is carried by the optic nerve CN2 to the lateral geniculate nucleus where a synapse to an interneuron occurs. The interneuron then sends the information to the occipital visual cortex. Information that the retinal vision is blurred. Then the info goes to the visual association area. Then another interneuron to the pre-tectal area. Then another interneuron to the Edinger-Westphal nucleus, where synapse to the oculomotor nerve. Oculomotor to the ciliary ganglion then interneuron to the ciliary muscles which then makes the ciliary muscles contract. And boom accommodation.
what nerves and ganglion are in the accomodation reflex
optic carries blurred info to lateral geniculate nucleus. then interneuron to occipital cortex. then interneuron to pretectal then interneuron to EW nucleus and then cranial nerve 3 to ciliary ganglion
why do we have the gaze centres and what are they
the PPRF is the horizontal gaze centres
the pre-tectal areas are the vertical gaze centres
we have these are there are no direct connections between the cortical initiation areas and the motor nuclei of the extra-occular muscles
if no direct connections between cranial initation areas how do we co-ordinate eye movements
we have the medial longitudinal fasciculus
