Anatomy: Eye Autonomics Flashcards
describe the sensory innervation of CNV1
upper eyelid
cornea and conjunctiva
skin of root/bridge/tip of nose
name 2 branches of the CNV1 and their areas of innervation
what notch does the supraorbital nerve (CNV1) pass through
supraorbital foramen
describe the sensory innervation of CNV2 (maxillary nerve)
skin of lower eyelid
skin over maxilla
skin over ala of nose
skin/mucosa of upper lip
infraorbital nerve
what CNV2 is called after it enters the infraorbital foramen
describe the sensory innervation of CNV3 (mandibular nerve)
skin over mandible and TMJ
(apart from angle of mandible - C2, 3 spinal nerves)
what is the only branch of CNV that has motor innervation
mandibular branch - muscles of mastication
describe the corneal reflex
- involuntary blinking of eyelids, stimulated by tactile, thermal or painful stimulation of cornea
- CNV1 is the afferent branch - conducts APs from the cornea to the trigeminal ganglion, it then goes along CNV to pons
- there are central CNS connections between CNV and CNVII, which is the motor efferent branch
- causes contraction of orbicularis oculi
describe the route of sympathetic axons
originate from autonomic centres in the brain
pass down spinal cord and exit with T1-L2 nerves (thoracolumbar outflow)
travel so sympathetic chains and into all spinal nerves, and then splanchnic nerves to eventually supply organs
describe the presynaptic sympathetic axons from CNS
exit spinal cord in T1 spinal nerve and ascend within sympathetic trunk
synapse in superior cervical sympathetic ganglion
describe the postsynaptic sympathetic axons
enter internal and external carotid nerves and pass onto the surface of internal and external carotid arteries
they are carried to the organs of the head on the surface of the branches of these arteries
ophthalmic artery carries the sympathetic axons into the orbit
describe the parasympathetic outflow
all parasympathetic axons leave the CNS via cranial nerves III, VII, IX and X and via sacral spinal nerves (craniosacral outflow)
describe the course of CNIII in the cranial cavity
originates from the anterior aspect of the midbrain
passes through cavernous sinus
exits cranial cavity via superior orbital fissure and divides into superior and inferior branches
what does the superior branch of CNIII do
motor innervation to superior rectus and levator palpebrae superioris
what does the inferior branch of CNIII do
motor innervation to inferior rectus, medial rectus and inferior oblique
parasympathetic fibres to ciliary ganglion, which ultimately innervates sphincter papillae and ciliary muscles
where is the ciliary ganglion located
within the bony orbit
anteriorly to the superior orbital fissure, between the lateral rectus muscle and the optic nerve
describe the sympathetic innervation with ciliary ganglion
preganglionic sympathetic fibres relay in superior cervical ganglion
postganglionic fibres are carried by long ciliary nerves (and some short) from sympathetic plexus around ICA to supply dilator pupillae muscle
describe the parasympathetic innervation with ciliary ganglion
preganglionic fibres originate from Edinger-Westphal nucleus in midbrain and run with CNIII (inferior division) to relay in ciliary ganglion
postganglionic fibres are carried by short ciliary nerves to innervate ciliary muscles and sphincter pupillae muscles
what are pre-ganglionic fibres of ciliary ganglion associated with
inferior division of CNIII
which ciliary nerves form the first part of the corneal reflex
long ciliary nerves - sensory fibres from the surface of CNV1
what are some autonomic reflexes of the eye
maximal eyelid elevation/wide eye opening
pupillary dilation/constriction to adjust light entry
focussing lens far and near vision
lacrimation reflex tear production
vestibulo-ocular reflex
stabilizes gaze on an object during head movement by turning the eyes in the opposite direction of the head
involves connections between CN VIII and CNIII, IV and VI
oculocardiac reflex
reflex bradycardia in response to tension on extraocular muscles/pressure on eye
CNS connections betwen CNV1 and CNX
does sympathetic innervation cause one to focus on far or near objects
far
parasympathetic - near
reflex lacrimation arc
- afferent: CNV1 innervates the cornea
- efferent: lacrimal gland under parasympathetic CNVII innervation to produce lacrimal fluid
- function is to wash away stimulant foreign body and clean the cornea*
how are eyes opened really wide in fight/flight situations
LPS contains skeletal and smooth muscle
the LPS is innervated by CNIII (parasympathetic) and raises the eyelid
the superior tarsus is innervated by the sympathetic nervous system and so can act to open the eye even wider??
mydiatric agent
drug that induces dilation of the pupil
what is a non-physiologically enlarged pupil called
a mydiatric pupil
dilator pupillae fibres
dilator pupillae fibres are innervated by sympathetic nervous system - when stimulated contract and widen the pupil
the fibre originate around the external circumference of the iris (fixed) and insert around the internal circumference of the iris (mobile)
how are the dilator pupillae fibres arranged
radially
pupillary constriction
parasympathetics - the sphincter pupillae encircles the pupil around the internal circumference of the iris
stimulation by short ciliary nerve results in constriction of the pupil
what is a non-physiologically constricted pupil called
miotic pupil
what drugs can cause miosis
opiates
what is a fixed dilated (‘blown’) pupil often a sign of
CNIII pathology
pupillary light reflex - afferent and efferent nerves
special sensory (afferent) nerve is ipsilateral CNII
motor (efferent) nerve is bilateral CNIII
a direct light reflex occurs in the stimulated eye and a consensual light reflex occur in the non-stimualted eye
pupillary light reflex
4 neuron chains
1. retinal ganglion cells are stimulated and pass via ipsilateral CNII, cross optich chiasma and synapse in pretectal nucleus in the mid brain
2. neurons (bilateral) in midbrain connect pretectal nucleus to next synapse in Edinger-Westphal nucleus
3. neurons (bilateral) pass from EW nucleus via CNIII, inferior division and to synapse at ciliary ganglion
4. short ciliary nerves to sphincter pupillae muscles - constriction
Edinger- Westphal nucleus
location of cell bodies of parasympathetic axons of CNIII
where is the lens of the eye located
anteriorly between vitreous humour and pupil
shape is altered by ciliary body - changing it’s refractory power
suspensory ligament of the lens
connects the circumferences of lens and ciliary body
contraction of ciliary muscle
contracts in parasympathetics, allows near vision as the ligament relaxes and lens becomes more spherical to focus on closer objects
relaxation of ciliary muscle
ligament tightens and the lens flattens to allow focus on objects in the distance
accomodation reflex
response of the eye to looking at near objects:
- bilateral pupillary constriction (parasympathetic of sphincter pupillae)
- bilateral convergence of both eyes towards the midline (medial rectus)
- bilateral relaxation of the lens (spherical due to contraction of ciliary muscles)
- All innervated by CNIII*
importance of basal tears
important in corneal health as they clean and nourish and hydrate the avascular cornea
contain lysosome which is an enzyme that hydrolyses bacterial cell walls
reflex tears
extra tears in response to mechanical/chemical stimulation
- afferent limb is CNV1 from cornea/conjunctiva
- efferent limb is parasympathetic axons originating from CNVII
which foramen does CNVII pass through on the temporal bone
stylomastoid foramen
which nerve supplies the stapedius
CNVII
where does CNVII exit the cranial cavity
internal acoustic meatus
chorda tympani branch of CNVII
carries parasympathetic axons for submandibular and sublingual glands
nerve for sensory component of lacrimal gland
CNV1 (after V2)
what is Horner’s syndrome often a result of
impaired sympathetic innervation to the head and neck - sympathetic trunk may be compressed
CNIII palsy
eye is positioned down and out with ptosis
bitemporal hemianopia
homonymous hemianopia
