Orbital Autonomics Flashcards
where do sympathetic nerve fibres for the eye leave the spinal cord?
T1 spinal nerve
where do sympathetics for the eye synapse?
the superior cervical sympathetic ganglion
where do post synaptic sympathetic axons for the eye enter after they synaose?
the internal and external carotid nerves which pass onto the carotid arteries
what carries the sympathetic axons into the orbit?
the ophthalmic artery
where do all parasympathetic axons leave the CNS?
cranial nerves 3,7,9 and 10 OR via sacral spinal nerves
what parasympathetic ganglion supplies the eye?
the ciliary ganglion
what cranial nerve contributes to the ciliary ganglion?
CN III
where is the ciliary ganglion located?
the bony orbit
what is CN III?
the oculomotor nerve
where does CN III connect with the CNS?
the junction of the midbrain and the pons
where does CN III exit the cranial cavity?
the superior orbital fissure
what two modalities does CN III carry?
somatic motor
parasympathetic
what does CN III carry somatic motor nerve to?
the majority of the extraocular muscles
what are the two divisions of CN III after it passes through the superior orbital fissure, and which is then part of the ciliary ganglion?
superior
inferior - this one
what supplies sensory innervation of the face?
the branches of the trigeminal nerve
where does the trigeminal nerve originate?
the lateral surface of the pons
what is another name for the corneal reflex?
blinking
what type of reflex is the corneal reflex?
sensory
what is the function of the corneal reflex?
to protect the eye
what are the three components of the corneal reflex?
sensory (afferent)
central
motor (efferent)
what happens in the sensory limb of the corneal reflex?
AP’s conducted from the cornea via CN V1 and taken to the trigeminal ganglion
travels along CN V to the pons
what are the central CNS connections involved in the corneal reflex?
connections between CN V and CN VII
what happens in the motor limb of the corneal reflex?
AP’s conducted from the brain via CN VII
to the palpebral part of orbicularis oculi = a blink
what does the vestibulo-ocular reflex do?
turns the eye in the opposite direction to head movement, to stabilise gaze
what are the CNS connections in the VOR?
between CN 7 and CN’s 3,4 and 6
what is the oculocardiac reflex?
when reflex bradycardia occurs in response to tension on extraocular muscles or pressure on the eye
what are the CNS connections in the oculocardiac reflex?
between CN V1 and CN X
what happens to the eyes in the sympathetic response?
open wider to get more light in
focus on far objects
emotional lacrimation
what happens to the eyes in the parasympathetic response?
get less light in
focus on near objects
reflex lacrimation
what two muscles are involved in opening the eyes wider?
levator palpebrae superioris (LPS)
mueller’s muscle
what does the LPS do?
raises the upper eyelid
what muscle type is found in the LPS?
skeletal and smooth
what is another name for mueller’s muscle?
superior tarsus muscle
where is the mueller’s muscle attached?
LPS
what type of muscle is mueller’s muscle and what innervates it?
smooth
sympathetics
what is the function of mueller’s muscle?
elevates the eyelid by an additional 2mm
what effect does parasympathetic stimulation have on the pupil?
constricts
what muscles are involved in the constriction of the pupil?
sphincter pupillae muscles - contract
what effect does sympathetic stimulation have on the pupil?
dilates
what muscle is involved in the dilation of the pupil?
dilator pupillae
what is another name for a non-physiologically enlarged pupil?
mydriatic
what is another name for a non-physiologically constricted pupil?
miotic
what makes up the sensory limb of the pupillary light reflex?
CN II on the side light is shone in
where do the CNS connections for the pupillary light reflex occur?
the midbrain
what makes up the motor limb of the pupillary light reflex?
CN III on both sides
where does the suspensory ligament of the lens attach?
the ciliary body
what type of muscle is found in the ciliary body?
smooth
what type of vision causes the ciliary body to relax?
far vision
what happens when the ciliary body relaxes?
suspensory ligament of the lens tightens and the lens flattens
this allows the eye to focus on distant objects
what type of vision causes the ciliary body to contract?
near vision
what happens when the ciliary body contracts?
suspensory ligament of the lens relaxes and the lens becomes spherical
this allows the eye to focus on near objects
what are the three different types of tears produced by the eyes?
basal
reflex
emotional
when are basal tears produced?
all the time
what is the function of basal tears?
clean and hydrate the cornea
what immune component is found in basal tears?
lysozyme
when are reflex tears produced?
in response to mechanical or chemical stimulation
what is the afferent limb for production of reflex tears?
CN V1 from the cornea and conjunctiva
what is the efferent limb for the production of reflex tears?
parasympathetic axons from CN VII
when are emotional tears produced?
due to an emotion e.g. sad, scared
