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

BMC L9 Flashcards

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

A

Farsighted

Eyeball too short
Focal point behind retina

23
Q

How is the hyperopic eye corrected

A

Convex lens
Moves focal point further forward

24
Q

Describe the emmetropic eye

A

Norml sighted

Focal point on retina

25
Q

State the function of the cornea

A

Bending of light / refraction
Foucses light on retina

26
Q

State the function of lens

A

Adds fine control

27
Q

State the 3 layers of the wall of the eyeball

A

Fibrous layer
Vascular layer
Sensory layer

28
Q

What are the two segments of the internal eyeball cavity?

A

Anterior (aqueous humor)

Posterior (vitrous humor)

29
Q

What does the fibrous layer consist of?

A

Dense, avascular connective tissue
Sclera + cornea

30
Q

State the position + function of the sclera

A

Posterioir, opaque (white, not transparent) region
Protects + maintains shape of eyeball
Anchors 6 extrinsic eye muscles

31
Q

State the position + function of the cornea

A

Anterior, transparent region
Bends / refracts light as it enters eye
Contains pain receptors, involved in tearing relfex, blink reflex

32
Q

State the functions of the posterior segment

A

Vitreous humor

Transmits light
Supports posterior region of lens
Intraocular pressure

33
Q

State the functions of the anterior segment

A

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
Q

State the two chambers of the anterior segment

A

Anterior chamber: between cornea + iris

Posterior chamber: between iris + lens

35
Q

What is the cause of glaucoma and state the effects

A

Blockage of drainage of aqueous humor

Leads to compression of retina + optic nerve

36
Q

Describe the 2 types of glaucoma

A

Open angle glaucoma - slow exit / drainage of aqeous humor

Closed angle glaucoma - iris completely blocks exit / drainage of aqueous humor

37
Q

State what the sensory layer of the eyeball wall consists of

A

This is the retina - double membrane, 2 layers

Pigmented layer

Nueral layer

38
Q

State the functions of the pigmented layer

A

Vit A storage
Absorbs light, prevents it from scattering

39
Q

State the functions of the neural layer

A

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
Q

Describe the blood supply of the retina

A

2 SOURCES OF BLOOD SUPPLY

Inner layers - central artery and vein of retina
Outer layers (photoreceptors) - choroid

41
Q

State the two types of photoreceptors

A

Rods
Cones

42
Q

Describe the structure of photorecptors

A

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
Q

Compare rod cells tro cone cells

A

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
Q

State the function of the Macula Lutea

A

This is the fovea

It is a yellow spot. It filters some of the blue light to prevent chromatic abberation

Focussing region

45
Q

State the 3 different types of cone cells

A

Red cones (10%) L CONES
Blue cones (45%) S CONES
Green cones (45%) M CONES

46
Q

Why is red-green colour blindness common in males?

A

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
Q

Describe how visual pigments are formed

A

Visual pigments are formed from one of four proteins (opsin) and retinal protein.

48
Q

State the two isomers of retinal protein

A

11-cis retinal

All-trans retinal

49
Q

What is retinal protein?

A

Light absorbing molecules formed from vitamin A

50
Q

State the visual pigment of rods and describe its formation

A

Rhodopsin

Opsin + 11-cis retinal

51
Q

Explain the excitation of rods

A

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
Q

Explain signal transmission in the retina

A
  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
Q

Explain light adaptation

A

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
Q

Explain dark adaptation

A

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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