OP1 - reflexes of eye

Question 1

what is corneal reflex?

Answer 1

= blinking to stop irritants in eye

irritant to eye - stimulates CN V1 - interneurons between trigeminal & facial = connect & make blink (to protect eye)

Question 2

what is oculocardiac reflex?

Answer 2

just idea that connection between CN V1 & CN X = so if tension in eyes reduces HR via CN X

Question 3

what is done to eyes by sympathetic innervation?

Answer 3

• open eyes wider
• more light in eyes (pupils wider)
• focus on far objects
• emotional lacrimation

Question 4

what is done to eyes by parasympathetic innervation?

Answer 4

• less light to eyes (pupils narrower)
• focus on near objects
• reflex lacrimation (wash away foreign stimulus)

Question 5

what is mueller’s muscle?

Answer 5

little slip of smooth muscle off LPS (levator palpebrae orbicularis)
- it has sympathetic innervation to open eyes even wider in fight or flight

Question 6

what muscle makes pupil smaller?

Answer 6

sphincter pupillae fibres (iris muscle) = contracts making pupil smaller making less light - for parasympathetic, by CN III

Question 7

what muscle makes pupil bigger?

Answer 7

dilator pupillae fibres = pull sphincter open making pupil bigger - more light for sympathetic fight or flight response

Question 8

what are muscles of iris?

Answer 8

1. sphincter pupillae fibres
2. dilator pupillae fibres

Question 9

what is myotic pupil?

Answer 9

a constricted pupil

Question 10

what do mydriatic drugs do?

Answer 10

dilate pupil

Question 11

what is pupillary light reflex?

Answer 11

1. light shone into eye
2. CN II (optic) picks up light
3. both eyes should respond by constricting (making pupil smaller)

Question 12

what is muscle part of ciliary body?

Answer 12

ciliary body is part of middle vascular area of eye but also has suspensory ligaments that attach to lens controlling if lens flat or round (innervated by oculomotor CN VIII)

Question 13

when is ciliary body muscle doing when lens flat?

Answer 13

ciliary body muscle is like sphincter so lens flat when muscle relaxed = when lens flat - looking at objects in distance

when ciliary body relax (circle wider)= suspensory ligaments pulled tight = makes lens flat (see far away - sympathetic)

Question 14

what is ciliary body muscle doing when lens more rounded?

Answer 14

ciliary body muscle contracted making lens rounded = curved when focussing on near objects

when ciliary body contracted (circle closer together) so suspensory ligaments looser/relaxed = lens rounded (parasympathetic - see close)

Question 15

what are baseline tears?

Answer 15

tears there all the time - needed for corneal health (since corneal avascular so need nutrition from tears)

Question 16

what are reflex tears?

Answer 16

extra tears in response to mechanical or chemical stimulants - afferent from CN V1 & efferent from CN VII

Question 17

what is sympathetic nerve outflow?

Answer 17

thoracolumbar - T1-L2

Question 18

what is sympathetic route to eyes?

Answer 18

1. exits T1
2. passes through to cervical region & synapses in superior cervical ganglion
3. exit via internal & external carotid following internal carotid to cranial cavity then following ophthalmic artery

Question 19

what is parasympathetic nerves outflow?

Answer 19

craniosacral - CN III, VII, IX, X & sacral nerves

Question 20

what is the ganglion where parasympathetic nerve fibres synapse for eye?

Answer 20

ciliary ganglion is parasympathetic synapse location, CN III carries the fibres there (inferior division carries to ciliary ganglion)