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INN CHUAH CAM304 > Eye Anatomy, Phototransduction > Flashcards

Eye Anatomy, Phototransduction Flashcards

1
Q

Describe the development of the eye -

What happens at Week 4

A

Eye development begins @w4.
Depression in the neural fold - OPTIC SULCUS.
on each side an OPTIC VESICLE grows out from the prosencephalon (diencepthalon)

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2
Q

Describe the development of the eye -

the optic stalk connects the optic vesicle of each side. What is the optic stalk?

A

Optic stalk is the optic nerve

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3
Q

Describe the development of the eye -

What happens at week 5

A

@W5 optic esicle folds on itself to form a two layerd optic cup, which partly envelopes the lens vesicle (derived from surface ectoderm)

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4
Q

Describe the development of the eye -

What happens at W6

A

At week k6 the lens vesicle is pinched off, and the remaining surface ectoderm has begum to form the epithelial covering of the cornea.
The outer layer of the 2 layered optic cup witll form the RETINAL PIGMENTAL EPTIHELIUM
The inner layer will form the NEURAL RETINA

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5
Q

What are the three tissue layers of the eye?

A

Fibrous outer layer
Uvea (middle layer)
Retina (neural layer)

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6
Q

What is in the fibrous outer layer?

A

Sclera: site of attachment of extraoccular muscles muscles (continues posteriorly at sheath of optic nerve)
Cornea: anterior part of sclera- innervated by V1
Conjunctiva: continuous with outer laer of cornea, inner surface of eyelids

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7
Q

What is in the middle layer?

A

Choroid: branches of anterior and posterior ciliary artieres
Ciliary body: w suspensory ligament of lens and ciliary muscle
Iris

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8
Q

What is in the Internal Retinal layer

A

Neural (optc retina)

Retinal pigmented epithelium

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9
Q

Where is the anterior chamber and what does it ave in it?

A

Anterior to the iris! contains aqueous humour - watery similar to CSF

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10
Q

Where is the posterior chamber and what does it have in it?

A

between iris and lens: aqueous humour

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11
Q

Where is the posterior compartment and what does it have in it?

A

Vitreous humour! thick and gel like

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12
Q

what is the drainage of the eye?

A

Canal of Schlemm (at corneoscleral junction) -> ciliary vein -> ophthalmic vein -> cavernous sinus

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13
Q

What is a glaucoma?

A

Problem with drainage, causing increased intraocular pressure -> decreased retinal blood flow -> interferes with axonal transport in optic nerve -> retinal damage and loss of vision

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14
Q

explain the Corneal blink reflex

A

Sensory receptor/corneal nociceptor —-> V1 ciliary nerve – trigeminal ganglion – spinal trigeminal tract -< synapses in the spinal trigeminal nucleus (bilateral projection -< facial motor nucleus — travels via CNVII (zygomatic and temporal branches) —< orbicularis oris

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15
Q

How does the LENS increase focusing power

A

By contraction of ciliary muscles which causes loosening of tension on suspensory ligament -> lens becomes more curved or ‘thick’

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16
Q

What are the
parasympathetic
sympathetic components affecting the IRIS

A

Parasympathetic causes constriction on the iris through sphincter pupillae (CN3)

Sympathetic DILATION: hypothalamus -> spinal cord -> T1 ventral nerve root -> superior cervical ganglion -> dilator pupillae

17
Q

What is the cellular composition of the retina ? Name all of the layers

A

‘In New Generations, It Is Only Ophthalmologists Examining Patients Retina’ pathway of light 1-..

  1. Inner Limiting Membrane
  2. Nerve Fibre Layer
  3. Ganglion cell layer
  4. Inner plexiform lyer
  5. Inner nuclear layer
  6. Outer Plexiform layer
  7. Outer Nuclear Layer
  8. External limiting membrane: MULLER cells (specialised glial cells)
  9. Photoreceptor layer: rods and cones
  10. Retinal pigmented epithleium
18
Q

What is the blood supply of the orbit?

A

Branches of the OPHTHALMIC ARTERY (branch of ICA)

  • ciliary arteries in choroid - outer layers of the retina
  • central retinal artery - inner layers of the retina
19
Q

What is your blind spot?

A

Where axons of the retinal ganglion cells exit as the optic nerve; where light falls: there are no photoreceptors to pick it up.
blindness is not percieved, information is filled in

20
Q

What is the FOVEA?

A

Spot in the retina directly in the line of vision- it is a thin tissue layer which is

  • rich in CONES
  • Located in macula lutea
  • Directly in line with the visual axis
  • Highest acuity
  • Axons of cones take a slanted course
21
Q

What is the function of the pigmented epithelium?

A

Absorption of light

Phagocytosis of portions of outer segment receptor cells

22
Q

Photoreceptor cells have an:
OUTER and INNER segment. What are the function of each?
- cell body
- synaptic terminal

A

OUTER segment: membranes are continuously sloughed off - stacks of membranes filled with RHODOPSIN (visual pigment protein which captuures light photons) . Site of visual TRANSDUCTION

INNER SEGMENT: mitochondria: energy for transduction and synthesis of inner segments

23
Q

What are the functions of RODS

A

DIM LIGHT
120 million
Rods responses are SLOW and HIGHLY SENSITIVE- can only respond to moonlight .
All contain RHODOPSIN- cant discriminate colour

24
Q

What is the function of CONES

A

COLOUR< LIGHT< SPATIAL DETAIL
Low sensitivity.
6 million
Efficient for: high acuity, colour vision, require more light.
Less visual pigment brief single photon responses which makes them faster

25
Q

Explain how the Retina is regionally specialised

A

Optic Disk: NO photoreceptors, interneurons or ganglion cells
FOVEA: high concentration of cones, highest acuity, midget bipolar and ganglion cells -> bright light. Cone linked ganglion cells- small receptive fields

EXTRAFOVEAL REGIONS
Higher sensitivity, more rods, less cones. Rod linked ganglion cells- large receptive field

26
Q

Explain the process of phototransduction

A

Ligand (11-cis retinal) -> G protein -> activated phophodiesterases -> hydrolyses cGMP
:: ie: light -> eye -> retina -> outer segment of photreceptors -> light captured by photo pigment -> retinal changes in configuration which triggers G protein activatio n-> hydrolyses cGMP -> cell hyperpolarises (sodium chanels close)

Signal is amplified : 1 photon interaction -> 2500, 00 Sodium channels close

27
Q

Explain how CONEs make you see COLOURS

A

Absorption peaks are determined by the type of OPSIN (photopigment) a particular cone makes.
Green & red cones - chromosome X genes
Blue cones - chromosome 7

28
Q

Describe the path of the optic nerves

A

Ooptic nerves converge at optic chiasma => continue as optic tracts ->

(1) most- lateral geniculate nucleus of the thalamus OR (2)suprachiasmatic nucleus of the hypothal -circadian rhythm
(3) superior colliculus and pretectal area in the midbrain
- –>
(1) LGN -> optic radiation which travels through temporal and parietal lobes and terminates in the primary visual cortex located in the upper and lower borders of the CALCARINE SULCUS

29
Q

Pupillary light reflex

A

CNII -> eedinger westphal nucleus -> occulomotor n constricts the ipil

30
Q

dilation response

A

Sympathetic: preganglionic neuron cell bodies are in the lateral horn of T1`/2 spinal cord. Axons travel through vental root, spinal nerve, ventral ramus and white ramus communcans to the sympathetic chain, ascend to cervical ganglion of sympathetic chain and synapse. POSTGANGLIONIC: travel along internal carotid artery, ophthalmic artery and branches and join with other nerves in the orbit to innervate the superior tarsal muscle & pupillary chelator

31
Q

Where are PREGANGLIONIC sympathetic neurons located?

A

Controlled by hypothalamic neurons- consequence is that a pathology in the brainstem, cervical r upper thoracic spinal cord, thorax or neck may lead to inability of eye to dilate (constricted pupil = miosis) .
Loss of sympathetic innervation to the head also causes slight drooping of the eyelid (mild ptosis) because of paralysis to superior tarsal muscle.

32
Q

What structures travel through the optic canal?

A

Optic nerve and ophthalmic artery

33
Q

What structures travel through superior orbital fissure?

A 
CNV1- frontal, nasociliary, lacrimal
Occulomotor nerve (s and inf divisions
Trochlear nerve (IV)
Abducens nerve (VI)
Ophthalmic vein S & I divisions
Sympathetic fibres from the cavernous plexus
34
Q

What structures travel through the inferior orbital fissure

A

Branch of V2- zygomatic branch of maxillary
Infraorbital vessels
Ophthalmic vein

35
Q

What are the branches of V1 present

A

Frontal n: supra trochlear , supraorbital n

Opthalmic branch- nasociliary (somatosensory for the eye)

36
Q

Main artery of the orbit and where is it from

A

ophthalmic artery from ICA

37
Q

Lacrimal gland innervation

A

Parasympathetics:
Preganglionics and postganglionic parasympathetic neuronal cell bodies in superior salivatory nucleus in PONS -> caxons travel with CNVII to pterygopalatine ganglion and synapse -> postganglionics with V2 and V1 to lacrimal gland

38
Q

What muscles cause eye to blink and what is their innervation

A

orbicularis orbis: CNVII- zygomatic and frontal branches

INN CHUAH CAM304 (7 decks)

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