Eye Autonomics Flashcards
What is the sensory innervation of the eye and the skin associated with the eye?
Trigeminal nerve
What division is CN V1 called and what does it supply?
The ophthalmic division.
Supplies: Upper Eyelid Cornea Conjunctiva Skin of the root/bridge/tip of the nose
What division is CN V2 called and what does it supply?
The maxillary division.
Supplies: Skin of the lower eyelid Skin over the maxilla Skin of the ala of the nose Skin/mucosa of the upper lip
What division is CN V3 called and what does it supply?
The mandibular division.
Supplies:
Skin over the mandible and temporomandibular joint
Apart from the angle of the mandible- supplied by C2, 3 spinal nerves.
In the blink reflex, describe the sensory (afferent) limb.
Action potentials conducted from cornea via CN V1 branches.
To trigeminal ganglion, then along CN V
To pons
In the blink reflex, describe the motor (efferent) limb.
Action potentials conducted via CN VII
To eyelid part of obicularis oculi
The brain has no motor function. True or false?
True.
The smooth muscle of the iris controls what?
Pupil diameter.
The smooth muscle of the ciliary body controls what?
Focussing of the lens.
Sympathetic axons exit the spinal cord between what levels?
T1-L2.
Describe the presynaptic sympathetic axons from the CNS.
Exit the spinal cord in T1 spinal nerve
Ascend within sympathetic trunk
Synapse in superior cervical sympathetic ganglion
Describe the postsynaptic sympathetic axons.
Enter internal and external carotid nerves
Pass onto surface of the internal and external carotid arteries
Carried to the organs of the head on the surface of the branches of these arteries
Ophthalmic artery carries sympathetic axons into the orbit
All parasympathetic axons leave the CNS via which cranial nerves and via what else?
CN 3, 7, 9 and 10 and via sacral spinal nerves
The oculomotor (CN III) connects with the CNS where? Where does it pass through? And where does it exit?
At the junction between the midline and the pons
Passes through the cavernous sinus
Exits via the superior orbital fissure.
The superior division of CN III supplies which 2 extra-ocular muscles?
Superior rectus and levator palpebrae superioris.
The inferior division of CN III supplies which 3 extra-ocular muscles?
Medial rectus, inferior oblique and inferior rectus.
What do the ciliary nerves do?
Supply autonomic axons to control the diameter of the iris and refractive shape of the lens.
Long ciliary nerves are?
Sympathetic and somatic sensory.
Short ciliary nerves are?
Sympathetic and parasympathetic.
The accommodation reflex involves which part of the eye?
The lens.
Describe the vestibulo-ocular reflex.
Turns the eyes in the opposite direction to head movement
Stabilises gaze on an object during head movement
CNS connections between CN VIII and CNs III, IV and VI
Describe the Oculocardiac reflex.
Reflex bradycardia in response to tension on extraocular muscles or pressure on eye.
CNS connections between CN V1 and CN X.
Describe the sympathetic functions in terms of pupil size, amount of light entering the eyes and ability to focus on near/far objects.
Open eyes wider
Get more light into the eyes
Focus on far objects
Describe the parasympathetic functions in terms of amount of light entering the eyes and ability to focus on near/far objects.
Allows the obicularis oculi to work
Gets less light into the eyes (to protect the retina from bright light when asleep)
Focus on near objects
Reflex lacrimation (to wash away the stimulant foreign body and clean the cornea)
The levator palpebrae superioris contains which type of muscle?
Both skeletal muscle and smooth muscle.
Sympathetics dilate or contrict the pupil?
Dilate the pupil
A non-physiologically enlarged pupil is called what?
A MYDRIATIC pupil.
Dilator pupillae fibres are arranged how?
Radially
Parasympathetics dilate/constrict the pupil?
Constrict the pupil
A non-physiologically constricted pupil is called what? It is a component of which disease?
A MIOTIC pupil.
Horner’s syndrome
A fixed “pin-point” pupil is often a serious pathological sign and can mean what?
The person has taken opiate drugs.
A “fixed-dilated” (blown) pupil is often a serious pathological sign of?
CN III (oculomotor nerve) pathology
Sphincter pupillae fibres are arranged how and have what effect on the pupil?
Encircle the pupil and allow constriction of the pupil.
In the pupillary light reflex, the special sensory limb of the reflex is ………….
The motor limb of the reflex is………………….
The ipsilateral CN II (optic nerve)
The bilateral CN III (oculomotor nerve)
A light reflex can be direct or?
Consensual
What controls the circumference of the lens and the ciliary body?
The suspensory ligament of the lens.
What is the ciliary body?
Muscular and vascular smooth muscle like sphincter around the circumference.
Describe the ciliary muscle when looking into the distance.
The ciliary muscle relaxes
There are no parasympathetics involved
The ligament tightens and the lens flattens to focus on an object in the distance.
Describe the ciliary muscle when looking at something near you.
The ciliary muscle contracts.
There are parasympathetics involved.
The ligament relaxes and the lens becomes spherical to focus on near objects.
What is the accommodation reflex?
The response to near
What are the 3 components of the reflex?
Bilateral pupillary constriction via sphincter pupillae muscles
Bilateral convergence of both eyes towards midline via the medial rectus muscle
Bilateral relaxation of the lens due to the lens becoming spherical
Name the 3 types of tears.
Basal, reflex and emotional.
Describe basal tears.
Important in corneal health
Cleans/nourishes and hydrates the avascular cornea
contains lysozyme which hydrolyses bacterial cell walls.
Describe reflex tears.
Extra tears in response to mechanical or chemical stimulation
Afferent limb is CN V1 from cornea/conjunctiva
Efferent limb is parasympathetic axons originating from CN VII
List the 4 main symptoms of Horner’s syndrome.
Miosis (non-physiological constriction of the pupils)
Ptosis (drooping of the eyelid)
Anhydrosis (reduced sweating)
Increased warmth and redness
In Horner’s syndrome, what innervation is impaired to the head and neck?
Sympathetic
In Horner’s syndrome, list the causes of compression of the cervical parts of the sympathetic trunk.
Root of neck trauma Carotid dissection Internal Jugular Vein enlargement Deep cervical node metastases Pancoast tumour at lung apex
