Eye Reflex Pathways Flashcards
What is efferent limb for reflex tears?
CNVII
How do sympathetics get from chain to eye?
Exit spinal cord at T1, ascend within sympathetic trunk, synapse at superior cervical ganglion.
Post-synaptic neurones enter carotid nerves then surface of carotid arteries. Piggy back ophthalmic artery to the orbit
Other name for parasympathetic outflow?
Craniosacral outflow
Where do eye sympathetics synapse?
superior cervical ganglion
Three things that happens in the accommodation reflex (response to near)
Pupil constriction Cross eyed (medial) Lens becomes fat
What is Miosis?
Constriction of one pupil
What type of signals synapse at the ciliary ganglion?
Only parasympathetics
Name the four important steps/areas in pupillary reflexes (not to do with specific nerves)
Retinal ganglion cells to pretectal nucleus;
Pretectal nucelus to Edinger Westphal nucleus;
EW nucleus to ciliary ganglion;
Ciliary ganglion to sphincter pupillae muscles;
Where does CNIII exit the skull to provide for the eye muscles?
Superior orbital fissure
What are reflex tears?
Extra tears on top of basal ones in response to chemical or mechanical stimuli
What is a non-physiologically enlarged pupil called?
Mydriatic pupil
In blinking reflex, what is the efferent nerve?
CNVII
In the blinking reflex, what muscle is stimulated and by what nerve?
Eyelid part of orbicularis oculi, CNVII
Where do CNVII parasympathetic fibres synapse?
Pterygopalatine ganglion to provide for lacrimal gland
Muscle for pupil constriction and what type of control it is under
Sphincter pupillae, parasympathetic
What is the efferent nerve for pupil constriction?
CNIII, oculomotor nerve
Symptoms of Horner’s syndrome
Ptosis (droopy eyelid)
Miosis
Anhydrosis
Increased warmth and redness
What is the afferent nerve for pupil contriction?
CNII, optic nerve
What level is the sympathetic chain?
T1-L2 spinal nerves
Where do CNIII parasympathetic fibres synapse?
Ciliary ganglion to provide for iris and lens
What is the afferent limb for reflex tears?
CNV(1)
In blinking reflex, what is the afferent nerve?
CNV(1)
Muscle for pupil dilation and what type of control it is under
Dilator pupillae, sympathetic
What is the vestibule-ocular reflex
turns the eye in opposite direction of head movement to keep eye focused on still object.
Cause of a fixed miotic pupil?
Horners
Cause of pin-point pupil
Opiates
Cause of fixed dilated pupil
CNIII pathology, parasympathetic pathology origin
Is the ciliary muscle relaxed or contracted for near sight?
contracted and fat lens
Is the ciliary muscle relaxed or contracted for far sight?
Relaxed and thin lens
