Reflexes of the Eye Flashcards
what is the corneal reflex
a blink, when something touches the cornea/sclera
what is the function of the corneal reflex
to protect the eye from foreign objects or pathogens entering
describe which nerves are involved in the sensory(afferent) limb of the corneal reflex
action potentials conducted from the cornea via CN V1 branches, to trigeminal ganglion , then along CN V to the pons
describe which nerves are involved in the motor(efferent) limb of the corneal reflex
action potentials conducted via CN VII, to eyelid part of the orbicularis oculi
describe the function/action of the vestibulo-ocular reflex
turns eye in the opposite direction to a head movement, stabilises gaze on an object during head movement
what nerves connections are involved in the vestibulo-ocular reflex
CNS connections between CN VIII and CN III, IV and VI
describe the function/action of the oculocardiac reflex
reflex bradycardia in response to tension on extraocular muscles or pressure on eye
what nerve connections are involved in the oculocardiac reflex
CNS connections between CN V1 and CN X
what muscle is involved in the wide eye opening reflex of the eye, and is it para or sympathetic innervation
levator palpebrae superioris, sympathetic innervation
what muscles are involved in the pupillary constriction reflex, and is it para or sympathetic innervation
sphincter pupillae fibres, innervated by parasympathetic in bright light and “rest and digest”
what muscles are involved in the pupillary dilation reflex, and is it para or sympathetic innervation
dilator pupillae fibres, innervated by sympathetic
describe the muscles of the iris
sphincter pupillae fibres circulate around pupil on interior iris
dilator pupillae fibres radially arranged around external circumference of iris
what is a mydriatic pupil and a miotic pupil
mydriatic pupil = non-physiologically enlarged pupil
mitotic pupil = non-physiologically constricted pupil
what are the sensory(afferent) and motor(efferent) limbs of the pupillary light reflex
sensory = ipsilateral CN II motor = bilateral via CN III
what connects the ciliary body and the circumference of the lens
the suspensory ligament of lens
describe what the ciliary body is, and what reflex it is responsible for
muscular and vascular, smooth muscle like a sphincter around circumference of the lens
lens accommodation reflex
describe the lens accommodation reflex when the ciliary body relaxes
no parasympathetics, ligament tightens + lens flattens to focus on an object in the distance
relaxes in “far vision”
describe the lens accommodation reflex when the ciliary body contracts
parasympathetic, ligament relaxes + lens becomes spherical to focus on near objects
contracts in “near vision”
what 3 components are assessed clinically for lens accommodation reflex
bilateral pupillary constriction(sphincter pupillae), bilateral convergence of both eyes towards midline(medial rectus), bilateral relaxation of the lens(ciliary muscles)
what are reflex tears(lacrimation) in response to
extra response to mechanical or chemical stimulation
what are the afferent and efferent limbs of lacrimation reflex
afferent = CN V1 from cornea/conjunctiva efferent = parasympathetic axons from CN VII
