Anatomy: reflexes of the eye

Question 1

what nerve is responsible for sensory innervation of the face

Answer 1

CNV - trigeminal

Question 2

what part of the face does CNV1 sense and what is the nerve called

Answer 2

ophthalmic - upper eyelid, forehead, conjunctiva, tip and middle of nose

Question 3

what part of the face does CNV2 sense and what is the nerve called

Answer 3

maxillary - skin of lower eyelid, skin over maxilla and the sides of the nose, upper lip

Question 4

what part of the face does CNV3 sense and what is the nerve called

Answer 4

mandibular - skin over mandible, lower lip, side of fac

Question 5

what type of outflow do sympathetic nerves have

Answer 5

thoracic lumbar (T1-L2)

Question 6

where do sympathetic chains run with the vertebral column

Answer 6

parallel

Question 7

where do sympathetic nerves for the head and neck exit the vertebral column and how do they travel

Answer 7

T1 - pass onto peri-artial plexus eg ICA and ECA

Question 8

what type of outflow do parasymathetic nerves have

Answer 8

cranial sacral

Question 9

what cranial nerves leave as parasympathetic

Answer 9

3,7,9,10

Question 10

what 4 parasympathetic nerves are in head and neck

Answer 10

pterygopalatine, otic, submandibular and ciliary ganglion

Question 11

what cranial nerve is the ciliary ganglion related to

Answer 11

CN III - oculomotor

Question 12

describe the corneal blink reflex (briefly)

Answer 12

sensation on the cornea is relaye to the brain and causes the eyelid to blink

Question 13

what sensory (afferent) pathway takes sensation to the brain in the corneal blink reflex

Answer 13

cornea –> CNV1 –> CNV –> pons –> central CNS connections between CNV and CNVIII

Question 14

what motor (efferent) pathway causes blinking in the corneal blink reflex

Answer 14

AP conducted via CNVII causing the eyelid orbicularis oculi to blink (LPS then lifts it)

Question 15

name 6 autonomic reflexes of the eye

Answer 15

wide eye fight or flight / papillary light reflex / accommodation reflex / lacrimation reflex / vestibulo-ocular reflex (keeps eyes focused in eye movement) / oculocardiac reflex (reflex bradycardia in response to pressure in the eye)

Question 16

what effects does sympathetic innervation have on the eyes

Answer 16

opens eyes wider to get more light in, focuses on FAR objects, emotional lacrimation

Question 17

what effects does parasympathetic innervation have on the eyes

Answer 17

less light into eye to protect retina, focuses on NEAR objects, reflex lacrimation (to wash out eye)

Question 18

what muscles open the eye and what type of innervation do they have, why do eyes start to shut when we’re tired?

Answer 18

levatator palpebrae superioris has skeletal muscle (CN III) and sympathetic smooth muller’s muscle - when we get tires parasympathetic increases and sympathetic decreases which causes heavy eyelids

Question 19

parasympathetics contrict the pupil in bright light, what is a cause of a non-physiological constricted pupil

Answer 19

horner’s syndrome

Question 20

what can cause fixed pinpoint drugs

Answer 20

opiates eg heroin

Question 21

what can cause fixed dilated/ blown pupils

Answer 21

trauma causing CNIII pathology

Question 22

what is the sphincter pupillae and what does it do

Answer 22

encircles the pupil underneath the iris - when contracted by parasympathetics reduces light into eye and vice versa for sympathetics opening the eye

Question 23

what is the afferent pupillary light reflex

Answer 23

shining a light in one eye is ipsilateral reflex of CNII in that eye bit the motor reflex is bilateral in CNIII which causes both pupils to constrict

Question 24

where does light coming from the left hit the retinas of the eyes and vice versa

Answer 24

light from the left left nasal retina and right temporal retina - light from the right hits the left temporal retina and right nasal retina

Question 25

where does light from the left optic nerve ‘come from’ vs left optic tract

Answer 25

left optic NERVE receives light in the LEFT eye - the left optic TRACT receives light from the left temporal retina and right nasal retina ie light that hits the left part of the eyes but is actually coming from the right

Question 26

after the optic chiasm, describe the route light takes to get to the visual cortex

Answer 26

synapses in the thalamus at lateral GN –> optic radiations –> visual cortex in occipital lobe

Question 27

what is the lens suspended by

Answer 27

ligaments (zonules) that attach to ciliary muscles

Question 28

what is the natural state of the lens and state of the sphincter ciliary body

Answer 28

ciliary muscles are relaxed and so the lens is pulled flat by the zonules which helps you see FAR vision

Question 29

what causes the ciliary muscles to contract and what effect does this have of the lens and vision

Answer 29

NEAR vision causes by parasympathetics causes the ciliary muscles to contract which loosens the zonules and causes the lens to become more spherical

Question 30

what cranial nerve innervates the ciliary muscles and controls lens shape

Answer 30

CN III

Question 31

what are basal tears

Answer 31

for corneal help, clean and nourish cornea, contain lysosomes

Question 32

what are reflex tears

Answer 32

response to mechanic or chemical stimulation - afferent CNV1 and efferent CN VII