Nerves & Pupils Flashcards
Which of preganglionic vs. postganglionic neurons in the ANS is usually myelinated?
preganglionic (first motor neuron)
What type of ANS innervation dilates the pupil?
Sympathetic
What type of ANS innervation constricts the pupil?
Parasympathetic
What type of ANS innervation allows accommodation to occur?
Parasympathetic (some inhibitory sympathetic)
What type of ANS innervation allows Muller’s muscle to open eyelids wide?
Sympathetic
Which levels of the spinal cord have sympathetic outputs that go to the head/neck and what is this location on the spinal cord called?
Levels T1-T5 (mostly T1-T3) where sympathetic preganglionic fibers leave CNS at the ciliospinal center of Budge (intermediolateral horn) to then synapse in the cervical ganglia
How does the postganglionic neuron of the sympathetic innervation to the eye travel?
Follows the internal carotid artery into the cavernous sinus, then may travel with CNIII to the Superior Tarsal Muscle (Mullers) or with V1 through nasociliary and long ciliary nerves to reach the iris dilator and the ciliary muscle
(other similar pathways to reach the blood vessels of eye for sympathetic innervation)
What is the Horner’s syndrome triad?
ptosis, miosis, anhidrosis
Which type of innervation is affected by Horner’s syndrome?
Horner’s affects the sympathetic innervation to the eye (head and neck also) and can be congenital or acquired (possible sign of tumors, aneurysms, damage to ICA, or CNS problems)
Which cranial nerve carries sensory information from ocular structures (and face)?
CNV - trigeminal nerve
Which are the cranial nerves that innervate the extraocular muscles and which one does which?
CNIII - oculomotor: SR, MR, IR, IO, (LPS)
CNIV - trochlear: SO
CNVI - abducens: LR
What are the three big branches of the trigeminal nerve and what are the foramina or spaces they travel through?
V1 - ophthalmic nerve travels through the supraorbital fissure, V2 - maxillary nerve travels through the foramen rotundum, and V3 - mandibular nerve which travels through the foramen ovale
T/F: the trigeminal ganglion is a location of sensory cell bodies (pseudounipolar cells)
True
What are the three branches of the ophthalmic nerve?
Nasociliary, Frontal, Lacrimal
What are the five branches of the nasociliary nerve?
Infratrochlear, anterior ethmoid, posterior ethmoid, long ciliary nerves, and the sensory root to the ciliary ganglion (which gives off short ciliary nerves)
Which nerve carries sensory information from the medial canthal area of the eyelid
Infratrochlear (travels below trochlea to front of eye, along the upper border of the medial rectus)
What areas do the ethmoid nerves innervate?
the sensory skin along center of nose, nasal mucosa, ethmoid sinuses, and sphenoid sinus (posterior)
travel through foramina with arteries of the same name
What are the areas and types of innervation that are controlled by the long ciliary nerves?
Sensory of the cornea, and carries sympathetic motor to the iris dilator
(there are 2 nerves, one medial and one lateral and they travel between the choroid and sclera)
What is an axenfeld loop?
a normal variation in pathway of the long ciliary nerves, usually seen 2mm from the limbus on either the nasal or temporal side, may have pigment, raised area, and painful to touch as the nerve is looping into the sclera from the suprachoroidal space
What are the areas and types of innervation that are controlled by the short ciliary nerves?
sensory of the cornea, sensory for some other anterior segment structures like the iris, ciliary body, etc. and carries sympathetic and parasympathetic motor
What is the pathway of the short ciliary nerves?
travel in the choroid, exits the back of the sclera as 6-10 short nerves making a ring around the optic nerve with the SPCAs, travels through the ciliary ganglion (no sensory synapse) joins the nasociliary nerve as the sensory root of ciliary ganglion to travel back to the brain
Which branch of the ophthalmic nerve travels through the common tendinous ring?
the nasociliary (frontal and lacrimal go above)
Besides the nasociliary of V1, which other cranial nerves travel through the common tendinous ring and which goes above?
the oculomotor (superior and inferior divisions) travel through the common tendinous ring as well as the abducens nerve. the trochlear nerve travels above
What are the branches of the frontal nerve (off of the ophthalmic)and what do they innervate?
supratrochlear carries sensory information from the skin and muscles of the forehead and upper eyelid, and the supraorbital nerve carries sensory from the same structures but more lateral to the supratrochlear
What areas and types of innervation are carried by the lacrimal nerve (branch of ophthalmic)?
carries sensory from the upper eyelid and temple area, and the lacrimal gland itself. runs along the upper border of the LR and receives a branch from the zygomatic nerve (from maxillary branch V2 which carries parasympathetic info from the facial nerve)
The infraorbital nerve and the zygomatic nerve travel through the inferior orbital fissure and are branches of which other nerve?
V2 - the maxillary branch of the trigeminal nerve
What does the infraorbital innervate and where is it?
Sensory information from the cheek, upper lip, and lower eyelid (travels through the infraorbital foramen/canal/ and groove)
What do the zygomaticotemporal and zygomaticofacial nerves innervate?
sensory information from the lateral aspect of the forehead (zygomaticotemporal) and sensory from the lateral aspect of the cheek and lower eyelid (zygomaticofacial)
Which cranial nerve carries autonomic fibers to the iris sphincter, ciliary muscle, and the smooth muscles of the eyelid?
CNIII - oculomotor nerve
Which cranial nerve carries parasympathetic innervation to the lacrimal gland (by way of the zygomatic nerve)?
CNVII - facial nerve, starts at the superior salivatory nucleus and has a synapse in the pterygopalatine ganglion
What is the main motor function of CNVII - facial nerve and where does it go?
Both sensory and motor parts of CNVII travel through the internal acoustic meatus, then the motor component exits through the stylomastoid foramen to innervate the muscles of facial expression (including orbicularis oculi)
Summarize how the parasympathetic innervation reaches the iris sphincter or ciliary muscle
preganglionic neurons begin in the Accessory Oculomotor Nucleus (Edinger-Westphal) travel with CNIII through the inferior division, synapses in the ciliary ganglion and then reaches target (iris sphincter or ciliary muscle) through the short ciliary nerves
Summarize how the parasympathetic innervation reaches the lacrimal gland
preganglionic neuron begins from the superior salivatory nucleus (pons) travels through the greater petrosal nerve (VII) to synapse in the pterygopalatine ganglion, joins maxillary nerve -> zygomatic n. -> communicates to the lacrimal nerve and reaches the lacrimal gland!
CN II fibers travel to one of four final destinations:
- LGN - visual information to primary visual cortex
- Pretectal nucleus - involved in pupil innervation
- Superior colliculus - involved in the control of saccades
- Hypothalamus - involved in circadian rhythms
Which EOM receives fibers that have decussated from the sub-nuclei (CNIII)?
SR - a lesion of the right SR sub-nucleus will result in poor control of the left SR muscle
the uvula deviates away from the side of the lesion and the palate does NOT elevate in what CN palsy?
CN X, patient also will report a hoarse voice
the tongue will deviate towards the side of the lesion in what CN palsy?
CN XII
Medial longitudinal fasciculus connects the nuclei of which CNs?
CNIII, CNIV, CNVI, and CNVIII
Fibers that leave the sub-nuclei for the MR, IR, and IO muscles project to the ipsilateral or contralateral side?
Ipsilateral
SR fibers are the only ones to decussate
How many nuclei are there for the levator palpebrae muscle?
Just one central sub-nucleus, a lesion will result in a sudden onset bilateral ptosis
A CNIII palsy that is pupil-involving should immediately raise suspicion for an aneurysm of what artery?
Posterior communicating artery
What is a pupil-sparing CNIII palsy likely caused by?
Ischemia of the small blood vessels that nourish the inner fibers of CNIII, most likely as a result of diabetes or hypertension
What nerve do the sympathetic fibres for Mullers muscle travel with?
CN3 superior division
What nerve do the sympathetic nerves fibres travel with to the iris dilator muscle?
V1 - LCPNs
What nerve do the parasympathetic fibres for the iris sphincters travel through?
CN3 inferior division
MLF
Highly specialized, highly myelinated, paired. Connects CN3,4,6 to make conjugate eye movements (saccades, pursuits, VOR)
