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1st yr-Med 2022-2023 > BMC L9 > Flashcards

BMC L9 Flashcards

(54 cards)

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1
Q

What are photons ?

A

Particles of light

Travel in wave like fashion

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2
Q

What is visible light ?

A

Small part of electromagnetic spectrum

VISIBLE to humans

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3
Q

What does the lacrimal apparatus consist of ?

A

Lacrimal gland

Lacrimal ducts (excretory + nasolacrimal)

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4
Q

State the function of the lacrimal gland

A

Secretion of tears

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5
Q

State the composition of tears

A

Dilute saline solution

(MAL: mucus, antibodies, lysozymes)

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6
Q

State the function of lacrimal ducts

A

Carry tears from caruncle to nasal cavity via lacrimal sac

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7
Q

Name the 6 extrinsic eye muscles

A

Superior rectus
Inferioir rectus
Lateral rectus
Medial rectus
Superior oblique
Inferior oblique

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8
Q

Where do the rectus muscles orignate in the eye

A

Common tendinous ring

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9
Q

Where do the oblique muscles originate in the eye

A

bony orbit

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10
Q

State the general function of extrinsic eye muscles

A

Movevement of eye
Maintain shape of eye

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11
Q

State the function of the lateral rectus

A

Moves eye laterally

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12
Q

State the function of the medial rectus

A

Moves eye medially

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13
Q

State the function of the superior rectus

A

Elevates eye, moves eye medially

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14
Q

State the function of the inferior rectus

A

Depresses eye, moves eye medially

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15
Q

State the function of the superior oblique

A

Depresses eye, moves eye laterally

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16
Q

State the function of the inferior oblique

A

Elevates eye, moves eye laterally

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17
Q

Describe what happens during distant vision

A

Sympathetic activation
This relaxes cillary muscles
Tightens cillary zonule
Flattens lens

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18
Q

Describe what happens during close vision

A

Parasympathetic activation
Contracts cillary muscle
Loosens cillary zonule
Lens bulges

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19
Q

How can we recognise if the eye

A
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20
Q

Describe the myopic eye

A

Myopic - nearsighted

Eyeball too long
Focal point in front of retina

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21
Q

How is the myopic eye corrected ?

A

Concave lens, moves focal point further back

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22
Q

Describe the hyperopic eye

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A

Farsighted

Eyeball too short
Focal point behind retina

23
Q

How is the hyperopic eye corrected

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A

Convex lens
Moves focal point further forward

24
Q

Describe the emmetropic eye

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A

Norml sighted

Focal point on retina

25
State the function of the cornea
Bending of light / refraction Foucses light on retina
26
State the function of lens
Adds fine control
27
State the 3 layers of the wall of the eyeball
Fibrous layer Vascular layer Sensory layer
28
What are the two segments of the internal eyeball cavity?
Anterior (aqueous humor) Posterior (vitrous humor)
29
What does the fibrous layer consist of?
Dense, avascular connective tissue Sclera + cornea
30
State the position + function of the sclera
Posterioir, opaque (white, not transparent) region Protects + maintains shape of eyeball Anchors 6 extrinsic eye muscles
31
State the position + function of the cornea
Anterior, transparent region Bends / refracts light as it enters eye Contains pain receptors, involved in tearing relfex, blink reflex
32
State the functions of the posterior segment
Vitreous humor Transmits light Supports posterior region of lens Intraocular pressure
33
State the functions of the anterior segment
Aqueous humor, blood plasma like, filtered continuosly by capillaries in cillary processes Supplies oxygen + nutrients to -lens -retina -cornea removes o2 + waste drained by scleral venous sinus - canal of shclemm at scleral - corneal junction
34
State the two chambers of the anterior segment
Anterior chamber: between cornea + iris Posterior chamber: between iris + lens
35
What is the cause of glaucoma and state the effects
Blockage of drainage of aqueous humor Leads to compression of retina + optic nerve
36
Describe the 2 types of glaucoma
Open angle glaucoma - slow exit / drainage of aqeous humor Closed angle glaucoma - iris completely blocks exit / drainage of aqueous humor
37
State what the sensory layer of the eyeball wall consists of
This is the retina - double membrane, 2 layers Pigmented layer Nueral layer
38
State the functions of the pigmented layer
Vit A storage Absorbs light, prevents it from scattering
39
State the functions of the neural layer
Photoreceptor cells - transduce light energy Bipolar cells - 1st order neurons, transmit impulses from photoreceptors to ganglion cells Amacrine cells - interneurones, transmit impulses to ganglion cells Horizontal cells - lateral interconnecting cells, integrate signals from multiple photoreceptors, for light adjustment Ganglion cells - 2nd order neurones. Transmit impulses to brain via optic tracts
40
Describe the blood supply of the retina
2 SOURCES OF BLOOD SUPPLY Inner layers - central artery and vein of retina Outer layers (photoreceptors) - choroid
41
State the two types of photoreceptors
Rods Cones
42
Describe the structure of photorecptors
Outer segment - of rodes + cones, embedded in pigmented layer of retina. contains Photopigements - molecules change shape when absorb light Inner segement - join synapse with cell bodies of horizontal / bipolar cells
43
Compare rod cells tro cone cells
Rod cells are found more commonly at the peripheral region of the retina, away from the macula lutea. Cones are found at the macula luta Rods have high sensitivity. Sensitive to dim light. Cones have low sensitivity. Sensitive to bright light Rods produce a grey image. Cones produce vivid coloured image as they can have 1 of 3 pigments In rods, pathways converge, therefore, producing "fuzzy" images. In cones, pathways do not converge, producing high resolution images
44
State the function of the Macula Lutea
This is the fovea It is a yellow spot. It filters some of the blue light to prevent chromatic abberation Focussing region
45
State the 3 different types of cone cells
Red cones (10%) L CONES Blue cones (45%) S CONES Green cones (45%) M CONES
46
Why is red-green colour blindness common in males?
The genes which code for the photopsin proteins (red + green forms of opsin pigments) found on X chromosomes Males only have one X chromosome. Therefore, only 1 copy of these genes Therefore, if any defect to these genes, men will have red-green colour blindness - dichromatic vision
47
Describe how visual pigments are formed
Visual pigments are formed from one of four proteins (opsin) and retinal protein.
48
State the two isomers of retinal protein
11-cis retinal All-trans retinal
49
What is retinal protein?
Light absorbing molecules formed from vitamin A
50
State the visual pigment of rods and describe its formation
Rhodopsin Opsin + 11-cis retinal
51
Explain the excitation of rods
Rods are activated in dim light. In dim light, regeneration of 11-cis retinal from all-trans retinal occurs. All-trans retinal (formed from Vit a) is converted into 11-cis retinal slowly by enzymes. This requires ATP. (11-cis retinal combines with opsin forming rhodopsin) Rhodopsin is broken down / bleached in bright light. Bright light stimulates a series of reactions leading to 11-cis retinal to be converted into all-trans retinal. Therefore, this leads to opsin separating from retinal. We end with all-trans retinal and opsin.
52
Explain signal transmission in the retina
1. Light hyperpolarises photoreceptor cells This stops them from releasing inhibitory neurotransmitter - glutamate 2. Bipolar cells no longer inhibited. DEPOLARISE AND They release excitatory neurotransmitter to ganglion cells 3. Ganglion cells transmit APs via optic nerve to brain
53
Explain light adaptation
Moving from darkness to bright light Instantaneous breakdown of rhodopsin - glare - pupils constrict rapid change in retinal sensitivity - rod function ceases, cones rapidly adapt visual acuity improves after 5 min
54
Explain dark adaptation
Moving from darkness to bright light Accumulation of rhodopsin Rapid change in retinal sensitivity, cone function ceases, rods rapidly adapt Pupils dilate

1st yr-Med 2022-2023 (57 decks)

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