Autonomics Of The Eye And Orbit Flashcards
Preganaglionic neuron cell body of sympathetic nervous system
T1-L2
Postganglionic neuron of sympathetic
Close by in the sympathetic chain
-longest fiber
NT for sympathetic
Epi/norepi
Where do all of the head and neck sympathetic synapse?
Superior cervical ganglion
Preganglionic nerve cell body in parasympathetic
Brainstem or sacral spinal cord
-long
What are the parasympathetic cranial nerves
3,7,9,10
Where is the postganglionic cell body in parasympathetic
In a ganglion near the target organ
Length of parasympathetic postganglionic fibers
Short
What is the NT of parasympathetic
Ach
Ocular structures innervated by the autonomic nervous system
- iris muscles (iris sphincter and iris dilator muscles)
- ciliary muscles
- smooth muscles of the eyelids (Mullers Muscle)
- choroidal and conjunctival blood vessels
- lacrimal glands
What are the main parasympathetic CN that innervate the eye
3,7
Where does the sympathetic nervous system originate
In the lateral gray column of the thoracic and upper lumbar segments of the spinal cord
Where doe sympathetic innervation for ocular structures originate?
Segments T1-T3
Where does the parasympathetic innervation of ocular structures originate
In the midbrain and pons (CN III and VII)
Where is the preganglionic neuron of the efferent pathway located of the ANS
In the brain or spinal cord
Where is the cell body of the second neuron in the ANS efferent pathway located
In a ganglion outside the CNS
Where does the preganglionic fiber of the ANS efferent pathway terminate?
Myelinated, terminates in an autonomic ganglion, where synapse occurs
Where does the postganglionic fiber of the ANS efferent pathway go
Nonmyelinated
-exits the ganglion and innervates the target structure
Sympathetic ganglia usually are located __________, whereas parasympathetic ganglia are located ________
- near the spinal column
- near the target structure
Ocular structures supplied by the sympathetic system
Iris dilator Ciliary muscle Smooth muscle of lids Lacrimal gland Choroidal and conjunctival blood
Ocular structures innervated by the parasympathetic
Iris sphincter
Ciliary muscle
Lacrimal gland
Blood vessels
What is the main difference between the structure that are innervated by the parasympathetic and the sympathetic
Iris muscles
Where do the sympathetic preganglionic fibers synapse that are going to ocular structures
Superior cervical ganglion
What do the postganglionic sympathetic fibers do after they leave the superior cervical ganglion?
- form the carotid plexus and the internal carotid artery
- and enter the skull through the carotid canal
How do the network of fine sympathetic fibers destined for ocular structures leave hte plexus?
In the cavernous sinus and take multiple pathways to the target structures
Where do all postganglionic sympathetic fibers go before they branch off to where they need to go?
Cavernous sinus
What is the first sympathetic pathway
Some travel with the ophthalmic division of trigeminal nerve
-once in orbit, they follow the nasociliary nerve, then travel with the long ciliary nerves to innervate the iris dilator and the ciliary muscle
What is the second sympathetic pathway
- other fibers follow same as #1 to nasociliary nerve and then branch to the ciliary ganglion as the sympathetic root
- these pass through ciliary ganglion without synapsing. Enter globe as the short ciliary nerves to innervate the choroidal blood vessels
What innervates the choroidal blood vessels
Short ciliary nerves
What is the pathway to the conjunctival vasculature through?
May be through either the long or shirt ciliary nerves
What is the 3rd sympathetic pathway in the ocular structures
- others fibers join the oculomotor nerve and go into orbit to innervate the smooth muscle of the upper eyelid (Mullers)
- follow same path as superior division of CN III as it supplies the levator muscle
What innervates the smooth muscle of the upper eyelid (Mullers muscle)
CN III
Alternate route to mullers muscle
From the infratrochlear or lacrimal nerve has been suggested but not confirmed
Activates the iris dilator, causing pupillary dilation and thereby increasing retinal illumination
Sympathetic
Causes vasoconstriction of the choroidal and conjunctival vessels
Sympathetic
Widens the palpebral fissure by stimulating the smooth muscle of the eyelids (mullers muscle)
Sympathetic
Exhibits a small inhibitory effect on the ciliary muscle
Sympathetic
What size are pupils when you sleep
Tiny
Where is the preganglionic neuron in the parasympathetic pathway to the intrinsic ocular muscles located?
In the midbrain in the parasympathetic accessory third nerve nucleus, also called the ending ER-westphal nucleus
What happens to the preganglionic parasympathetic neuron fibers going to ocular structures after it leave the nucleus?
With the motor fibers of the oculomotor nerve and follow the inferior division of that nerve into the orbit
-they leave the inferior division and enter the ciliary ganglion as the parasympathetic root
Where do the parasympathetic preganglionic fibers synapse that are headed to ocular structures?
Ciliary ganglion
Where is the ciliary ganglion located
Within the muscle cone between the lateral rectus muscle and the optic nerve, approximately 1cm anterior to the optic canal
What are the three roots located at the posterior edge of the ciliary ganglion?
- parsympathetic root
- Sensory root, carries fibers from globe and joins with nasociliary nerve
- Sympathetic root, which supplies the blood vessels
What kind of fibers synapse in the ganglion
Parasympathetic
What do the short ciliary nerves located at the anterior edge of the ciliary ganglion carry?
- Sensory
- Sympathetic
- Parasympathetic fibers
How do the postganglionic parasympathetic fibers exit the ganglion
In the short ciliary nerves, enter the globe, and travel to the anterior segment of the eye to innervate the sphincter and ciliary muscles
What do most of the parasympathetic fibers that enter the globe through the shirt ciliary nerves innervate
The ciliary body
Parasympathetic stimulation causes _____________, thus decreasing retinal illumination and reducing chromatic and spherical aberrations
Pupillary constriction
Parasympathetic stimualtion causes __________ enabling the eye to focus on near objects in accommodation
Contraction of the ciliary muscle
The iris contains muscles innervated by
Both autonomic systems
The PNS and SNS nerves are in some state of balance in the normal, healthy, awake individual, and the size of the pupil changes constantly and rhythmically, reflecting this balance, this is called what
Pupillary unrest called hippus
Pupils during sleep
Small because the SNS shuts down and the PNS predominates
The efferent autonomic pathway to the lacrimal gland
Lacrimal nucleus—facial nerve—-grater petrosal nerve—-Vivian nerve—-pterygopalatine ganglion—-maxillary nerve—–zygomatic nerve—–lacrimal nerve—-lacrimal gland
Fibers controlling the parasympathetic innervation originate in the pons in an area within the nucleus for cranial nerve VII designated as the
Lacrimal nucleus
Preganglionic fibers from the lacrimal nucleus exit the pons with the motor fibers of the facial nerve and enter
The internal auditory canal, and pass through the geniculate ganglion of the facial nerve without synapsing
How do the parasympathetic fibers to the lacrimal gland leave the geniculate ganglion of the facial nerve?
S the greater petrosal nerve, which exits the petrous portion of the tmpeoral bone
What is the Vivian nerve
The greater petrosal nerve is joined by the deep petrosal nerve, composed of sympathetic postganglionic fibers from the carotid plexus
Where does the Vivian nerve go once it is formed?
Enters the pterygopalatine ganglion, where the parasympathetic fibers synapse, sympathetic fibers pass through without synapsing
What do the autonomic fibers do once they leave the pterygopalatine ganglion?
Join with the maxillary branch of the trigeminal nerve, pass into the zygomatic nerve and then form a communicating branch to the lacrimal nerve
Alternate pathway bypasses the zygomatic nerve and travels from the ganglion directly to the gland
The parasympathetic fibers that innervate the lacrimal gland are of the secretomotor type and thus
Increase secretion
Sympathetic innervation of lacrimal gland
Sympathetic fibers innervate the blood vessels of the gland and might indirectly cause decreased production of lacrimal gland secretion by restricting blood flow
Sympathetic fibers to the lower eyelid
Sympathetic fibers from the zygomatic nerve also branch into the lower eyelid and innervate mullers muscle of the lower lid (opens eye larger)
Reflex tearing
Irritation of any branch of the trigeminal nerve activates a reflex afferent pathway, precipitating increased lacrimation
Corneal touch initiates the three part corneal reflex
- Lacrimation
- Miosis (shrinking pupil)
- Protective blink
Done by interneurons, no cerebral processing