Reflexes of the Orbital Region Flashcards
what are the 3 divisions of the trigeminal nerve (CNV)
V1- opthalmic
V2- maxillary
V2- mandibular
what does the ophthalmic nerve innervated (V1) (sensory)
upper eyelid
cornea
conjunctiva
skin of the root/bridge/tip of the nose
what does the maxillary nerve innervate (CNV2) (sensory)
skin of the lower eyelid
skin over maxilla
skin over the ala of the nose
skin/mucosa of upper lip
what does the mandibular nerve (cNV3) innervate (sensory)
skin over mandible and temporomandibular joint (apart from angle of the mandible)
what foramen does the ophthalmic nerve travel through
supraorbital fossa
what foramen does the maxillary nerve travel through
infraorbital fossa
What is the sensory component of the ‘blink reflex’
CNV1 - The ophthalmic nerve
what is the pathway of the action potential in the blink reflex
CNV1– trigeminal ganglion – along trigeminal nerve – to pons – to motor nerve (CNVII - facial)
what is the motor component of the blink reflex and what does it do
CNVII - facial nerve
causes the closure of the eyelid via the orbicularis oculi
at what level do sympathetic neurons leave the spinal cord
T1-L2
therefore thoracolumbar output as the sympathetic neurons follow T1-L2 nerves to get to the sympathetic chain
where do sympathetic axons go after the sympathetic chain
run out in all spinal nerves to the splanchnic nerves which take them to organs
what phrase describes the sympathetic nervous system
‘fight or flight’ segment of the autonomic nervous system
how do post synaptic sympathetic fibres make it from T1 up to the eye
synapse at the superior cervical sympathetic ganglion
travel up the internal and external carotids
pass onto the surface of the carotids
carried to organs of the head on the surface of the branches from the carotid artery
ophthalmic artery carries sympathetic axons into the orbit
where do parasympathetic axons leave the spinal cord
Via cranial nerves III. VII, IX and X as well as sacral spinal nerves
therefore known as cranialsacral outflow
what is phrase that describes the parasympathetic nervous system
‘rest and digest’ segment of the autonomic nervous system
what do the parasympathetic ganglia in the head supply
the eye
the lacrimal gland
the salivary glands
where does the occulomotor nerve connect with the CNS
between the midline and the pons
where does the oculomotor nerve exit the skull
superior orbital fissure
what does the oculomotor nerve provide somatic motor innervation to
Superior rectus medial rectus inferior rectus inferior oblique elevator palpebrae
what do the ciliary nerves innervate
supply autonomic axons to control the diameter of the iris and refractive shape of the lens
what are the long ciliary nerves
sympathetic
somatic sensory
first part of blink reflex
what are the short ciliary nerves
sympathetic and parasympathetic
what are the autonomic reflexes of the eye
- wide eye - maximal eyelid elevation
- pupillary dilation/constriction
- focussing lens for far and near vision
- Lacrimation reflex tear production
- vestibulo-ocular reflex (stabilises gaze during head movement)
- oculocardiac reflex (bradycardia in response to tension on the eye)
what are the functions of the sympathetic nervous system on the eye
- opening eyes wider
- gets more light into eyes (dilation)
- focuses on far objects
- emotional lacrimation
functions of the parasympathetic system on the eye
- lets less light into the eye (constriction)
- focuses eye on near objects
- Reflex lacrimation (wash away foreign bodies)
- allows orbularis oculi to work
how do sympathetic fibres travel to the elevator palpebrae
- superior cervical sympathetic ganglion
- internal carotid
- internal carotid plexus
- carried on ophthalmic artery
- carried on branches of ophthalmic artery
then opens eyes wider
do sympathetic/parasympathetic fibres dilate the pupil
sympathetic
what is a non-physiologically dilated pupil
mydriatic pupil
caused by mydriatic drug
in what direction are the DILATOR papillae fibres arranged
radially
do parasympathetics/sympathetics constrict the pupil
parasympathetics
what is a non-physiologically constricted pupil
mitotic pupil eg. component of horners syndrome
what is the sensory part of the pupillary light reflex
CN II optic nerve
what is the motor part of the pupillary light reflex
Oculomotor nerve CN III
what happens when one eye is stimulated by light
direct light reflex occurs in the stimulated eye
a consensual light reflex occurs in the non-stimulated eye
what is the first neurone in the pupillary light reflex chain
retinal ganglion cells
pass via optic nerve to optic chasm
synapse in the pretectal nucleus in the midbrain
what is the pathway of the second neurone in the pupillary light reflex chain
v small neurones in the midbrain which synapse in the Edinger Westphalia nucleus
what is the path of the third neurone in the pupillary light reflex chain
from the Edinger Westphalia nucleus via CNIII to synapse at the ciliary ganglion
what do the 4th neurones in the pupillary light reflex do
short ciliary nerves to the spinchter papillae muscles
what ligament connects to the lens and the ciliary body
suspensory ligament
what happens to the ciliary muscle when far vision is needed
it relaxes to flatten the lens to focus on objects in the distance
what happens to the ciliary muscle when near vision is needed
it contracts so the suspensory ligaments relax and the lens becomes spherical
what are basal tears
tears which clean/nourish and hydrate the avascular cornea
contain lysosome to kill bacteria
what are reflex tears
extra tears in response to mechanical stimuli or chemical stimulation
sensed by ophthalmic nerve
motor component - CNVII (facial)
what are emotional tears
happy, sad or frightened tears
what are the symptoms of horners syndrome
miosis (constriction)
ptosis (drooping of upper eyelid)
reduced sweating (anhydrosis)
Increased warmth and redness
what causes Horner’s syndrome
impaired sympathetic innervation to the head and neck
what are some causes of compression of the cervical parts of the sympathetic trunk
root of neck trauma carotid dissection internal jugular vein engorgement deep cervical node metastases pancoast tumour (lung apex)
