reflexes of the eye Flashcards
what does the opthalmic nerve innervate in the face
- upper eyelid
- cornea
- conjunctiva
what does the maxillary nerve innervate in the face
- skin of the lower eyelid
- skin over the maxilla
what does the mandibular nerve innervate in the face
- skin over mandible and TMJ
- except angle of mandible
what are the autonomic reflexes of the eye
- wide eye opening of flight or fight
- pupillary light reflex
- accommodation reflex
- lacrimation reflex
what does the vestibulo-ocular reflex do
turns eyes in the opposite direction to a head movement
-stabilises gaze on an object during head movement
what is the oculocardiac reflex
reflex bradycardia in response to tension on extraocular muscles or pressure on eye
what are the sympathetic reflexes of the eye
- get more light into eyes
- open eyes wider
- focus on far objects
- emotional lacrimation
parasympathetic reflexes of the eye
- get less light into eyes
- focus on near objects
- reflex lacrimation (to wash away the stimulant foreign body and clean the cornea)
which muscle opens the eyes wider
levator palpebrae superioris
how does the pupil constrict
- parasympathetics constrict the pupil
- sphincter pupillae fibres encircle pupil
when does the pupil constrict
in bright light and rest&digest
how does the pupil dilate
- sympathetic innervation dilates the pupil
- dilator pupillae fibres are radially arranged
what is a non-physiologically enlarged pupil called
a mydriatic pupil
what is a non-physiologically constricted pupil called
miotic pupil
-horners syndrome for example
how many neurons are in the chain for the pupillary light reflex
4
what do the first neurons do in the pupillary light reflex
- retinal ganglion cells
- pass via ipsilateral optic nerve
- decussate in optic chiasm
- synapse in pretectal nucleus in midbrain
what do the second neurons do in the pupillary light reflex
-locates entirely within midbrain and connect pretectal nucleus to next synapse in Edinger-Westphal nucleus
what do the third neurons do in the pupillary light reflex
pass from EW nucleus, via CN III then its inferior division, to synapse in ciliary ganglion
what do the fourth neurons do in pupillary light reflex
course in short ciliary nerves to sphincter pupillae muscles
what does the ciliary muscle do in far vision
relaxes
-ligament tightens and lens flattens to focus on an object in the distance
what does the ciliary muscle do in near vision
contracts
-ligament relaxes and lens becomes spherical to focus on near objects
what is the lens accommodation reflex
focusing on near objects
function of basal tears
- corneal health
- clean/nourish and hydrate the avascular cornea
- contain lysozyme (hydrolyses bacterial cell walls)
what are reflex tears
extra tears in response to mechanical or chemical stimulation
