Anatomy: reflexes of the eye Flashcards
what nerve is responsible for sensory innervation of the face
CNV - trigeminal
what part of the face does CNV1 sense and what is the nerve called
ophthalmic - upper eyelid, forehead, conjunctiva, tip and middle of nose
what part of the face does CNV2 sense and what is the nerve called
maxillary - skin of lower eyelid, skin over maxilla and the sides of the nose, upper lip
what part of the face does CNV3 sense and what is the nerve called
mandibular - skin over mandible, lower lip, side of fac
what type of outflow do sympathetic nerves have
thoracic lumbar (T1-L2)
where do sympathetic chains run with the vertebral column
parallel
where do sympathetic nerves for the head and neck exit the vertebral column and how do they travel
T1 - pass onto peri-artial plexus eg ICA and ECA
what type of outflow do parasymathetic nerves have
cranial sacral
what cranial nerves leave as parasympathetic
3,7,9,10
what 4 parasympathetic nerves are in head and neck
pterygopalatine, otic, submandibular and ciliary ganglion
what cranial nerve is the ciliary ganglion related to
CN III - oculomotor
describe the corneal blink reflex (briefly)
sensation on the cornea is relaye to the brain and causes the eyelid to blink
what sensory (afferent) pathway takes sensation to the brain in the corneal blink reflex
cornea –> CNV1 –> CNV –> pons –> central CNS connections between CNV and CNVIII
what motor (efferent) pathway causes blinking in the corneal blink reflex
AP conducted via CNVII causing the eyelid orbicularis oculi to blink (LPS then lifts it)
name 6 autonomic reflexes of the eye
wide eye fight or flight / papillary light reflex / accommodation reflex / lacrimation reflex / vestibulo-ocular reflex (keeps eyes focused in eye movement) / oculocardiac reflex (reflex bradycardia in response to pressure in the eye)
what effects does sympathetic innervation have on the eyes
opens eyes wider to get more light in, focuses on FAR objects, emotional lacrimation
what effects does parasympathetic innervation have on the eyes
less light into eye to protect retina, focuses on NEAR objects, reflex lacrimation (to wash out eye)
what muscles open the eye and what type of innervation do they have, why do eyes start to shut when we’re tired?
levatator palpebrae superioris has skeletal muscle (CN III) and sympathetic smooth muller’s muscle - when we get tires parasympathetic increases and sympathetic decreases which causes heavy eyelids
parasympathetics contrict the pupil in bright light, what is a cause of a non-physiological constricted pupil
horner’s syndrome
what can cause fixed pinpoint drugs
opiates eg heroin
what can cause fixed dilated/ blown pupils
trauma causing CNIII pathology
what is the sphincter pupillae and what does it do
encircles the pupil underneath the iris - when contracted by parasympathetics reduces light into eye and vice versa for sympathetics opening the eye
what is the afferent pupillary light reflex
shining a light in one eye is ipsilateral reflex of CNII in that eye bit the motor reflex is bilateral in CNIII which causes both pupils to constrict
where does light coming from the left hit the retinas of the eyes and vice versa
light from the left left nasal retina and right temporal retina - light from the right hits the left temporal retina and right nasal retina
where does light from the left optic nerve ‘come from’ vs left optic tract
left optic NERVE receives light in the LEFT eye - the left optic TRACT receives light from the left temporal retina and right nasal retina ie light that hits the left part of the eyes but is actually coming from the right
after the optic chiasm, describe the route light takes to get to the visual cortex
synapses in the thalamus at lateral GN –> optic radiations –> visual cortex in occipital lobe
what is the lens suspended by
ligaments (zonules) that attach to ciliary muscles
what is the natural state of the lens and state of the sphincter ciliary body
ciliary muscles are relaxed and so the lens is pulled flat by the zonules which helps you see FAR vision
what causes the ciliary muscles to contract and what effect does this have of the lens and vision
NEAR vision causes by parasympathetics causes the ciliary muscles to contract which loosens the zonules and causes the lens to become more spherical
what cranial nerve innervates the ciliary muscles and controls lens shape
CN III
what are basal tears
for corneal help, clean and nourish cornea, contain lysosomes
what are reflex tears
response to mechanic or chemical stimulation - afferent CNV1 and efferent CN VII
