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Physiology PHM > Special Senses: Vision > Flashcards

Special Senses: Vision Flashcards

1
Q

What is another name for the eyeball?

A

Bulbus oculi

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2
Q

State 3 functions of the eyelids

A
  1. Protection
  2. Cutoff light for sleep
  3. Lubrication when blinking
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3
Q

State 4 contents of the palpabrae

A
  1. Maeibomian glands + other Sebaceous glands
  2. Cilia
  3. Lacrimal gland
  4. Conjuctiva
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4
Q

Give the 2 parts of the conjuctiva.

A

Bulbous portion covers the eye

Palberal portion lines palpabrae inner surfaces

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5
Q

What are the functions of tears?

A
  1. Protection from infection

2. Keep conjuctiva moist

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6
Q

Contents of tears include _______ which kill bacteria.

A

Lysozymes

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7
Q

Which nerve controls the secretion of tears?

A

CN VII (Facial nerve) parasympathetic fibers

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8
Q

The wall of the eye ball has

a) 4 layers
b) 3 layers
c) 5 layers
d) 2 layers

A

b) 3 layers; outer, middle, and inner

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9
Q

The middle layer of the eyeball wall is also called

a) Tunica Medialis
b) Tunica Vastalis
c) Tunica Media
d) Tunica Medius

A

c) Tunica media

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10
Q

What part of the eye acts like the diaphragm of a camera?

A

The iris

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11
Q

Name the 3 layers of tears. Give their functions and what structure secretes each layer

A
  1. Lipid layer - Sebaceous glands
    - lubrication
    - prevents overflow
    - prevents evaporation
    - prevents air from entering
  2. Aqueous layer - Lacrimal gland
    - hydration
    - acts as buffer to changes in pH
  3. Mucin layer - Conjuctival goblet cells
    - lysozymes and antibodies for protection
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12
Q

Differentiate between intrinsic and extrinsic muscles of the eye.

A
  1. Intrinsic are smooth muscles. Extrinsic are skeletal muscles
  2. Intrinsic are innervated by autonomic fibers. Extrinsic innervated by somatic fibers.
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13
Q

List the extrinsic muscles of the eye as well as their innervations.

A

*SIMI Loves Slurping OATs.

Superior rectus
Inferior rectus
Medial rectus
Inferior oblique 
(all innervated by cranial Nerve III - Oculomotor nerve)
Lateral rectus (innervated by cranial nerve VI - Abducens nerve)
Superior oblique (innervated by cranial nerve IV - Trochlear nerve)
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14
Q

Give the 10 layers of the retina and their features.

A

FROM OUT GOING INWARDS

  1. Pigment epithelium (single layer of epithelial cells)
  2. Photoreceptive area (contains inner and outer segments of rods and cones)
  3. Outer limiting membrane (where inner segments connect to cell bodies of rods and cones)
  4. Outer nuclear layer (contains cell bodies of rods and cones)
  5. Outer plexiform layer (where axons of rods and cones synapse with dendrite of bipolar and amacrine cells)
  6. Inner nuclear layer (has cell bodies of bipolar cells, amacrine cells, and Muller cells)
  7. Inner plexiform layer (synapse between axons of bipolar and amacrine cells with dendrites of Ganglionic cells)
  8. Ganglionic layer (cell bodies of ganglionic cells)
  9. Nerve fiber layer (where axons of ganglionic cells form optic nerve
  10. Inner limiting membrane (made of only Muller fibers)
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15
Q

Major components of vitreous humor.

A

Albumin and Hyaluronic acid

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16
Q

Properties of aqueous humor

A
  1. 98.7% water
  2. 1.3% solids (organic and inorganic)
  3. alkaline pH (7.5)
  4. Refractory index - 1.34
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17
Q

Aqueous humor formation

A

Diffusion of plasma by ciliary processes’ capillary network

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18
Q

The interface where the greatest refraction occurs is?

A

Air to cornea transition because has largest refraction index change

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19
Q

Most of the refraction (80%) occurs in the …

A

Cornea

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20
Q

Enumerate drainage of aqueous humor.

A
  1. filtered through ciliary processes
  2. enters between suspensory ligaments to enter posterior chamber
  3. passes through pupil to enter anterior chamber
  4. Limbus
  5. Trabeculae
  6. Canal of Schlemm
  7. Anterior ciliary vein
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21
Q

Enumerate the layers of the cornea.

A
  1. Corneal epithelium
    - 5-7 layers thick
    - where cells are shed and completely replaced in 1 week
    - surface for tears
  2. Bowman’s layer
    - dense C.T.
    - protects eye from getting scratches *scratches past this layer cause irreparable damage to vision
  3. Stroma
    - the thickest layer (90%)
    - made of collagen arranged parallel which allows cornea to be clear
  4. Descemet membrane
    - thickens with age
  5. Endothelial layer
    - maintains aqueous humor
    * damage to this layer causes edema of eye
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22
Q

True or false: The anterior 5/6th of outer wall of eyeball is transparent and the posterior 1/6th is opaque.

A

False: the anterior 1/6th is transparent and the posterior 5/6th is opaque

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23
Q

Innervation to ciliary muscles is by…?

A

Oculomotor nerve parasympathetic fibers

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24
Q

The iris is a part of which layer of the eyeball?

A

Tunica Media

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25
Q

Fibrous tunic refers to which layer of the eyeball?

A

Outer layer consisting of cornea and sclera

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26
Q

True or false: axons of ganglionic cells are myelinated.

A

false; they are unmyelinated

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27
Q

Which layers of the retina contain retinal blood vessels?

A

Ganglionic cell layer

Nerve fiber layer

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28
Q

Which area of the eye has the most acute vision and why?

A

Fovea centralis on the macula centralis because it has only rods and cones

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29
Q

Define EXTRAFOVIAL VISION

A

When image falls on other part of retina other than the fovea centralis

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30
Q

Enumerate blood supply to the retina.

A

Outer 1/3rd gets the Choroid artery

Central 2/3rds gets the central artery

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31
Q

Describe clinical basis of cataracts.

A

Opaqueness of the lens caused by accumulation of cells in the capsule, and fluid causing denaturation of lens fibers. Can be caused by diabetes, long-term drug usage, excess alcohol, prolonged unprotected exposure to sun
Cataract can be removed by Phacoemulsification

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32
Q

Define intraocular pressure

A

the pressure exerted by aqueous humor

33
Q

Normal intraocular pressure

A

12-20 mmHg

34
Q

True or false: the lens is biconvex

A

TRUE

35
Q

True or false: the image on the retina is upside down, but not reversed from side to side

A

FALSE: the image on the retina is upside down, and reversed from side to side

36
Q

True or false: the eye has more rods than cones

A

TRUE; 12 million rods and 6 million cones

37
Q

Describe distribution of rods and cones as you move from the fovea to edges of retina

A

Fovea has only cones —> number of rods increases while cones decreases —> Edge of retina has only rods

38
Q

Compare the outer segments of rods and cones

A

For rods

  • have membranous disks
  • disks synthesized from inner segment and push older ones outwards
  • disks contain rhodopsin pigment
  • disks renewed every 3-4 hrs

Cones

  • have saccules instead
  • saccules made from more than one point
  • saccules take longer time to be renewed
  • saccules contain Porphyropsin, Iodopsin, and cyanopsin
39
Q

Define; Scotopic vision

A

dim light vision

40
Q

Components of rhodopsin.

A
  1. Opsin called scotopsin

2. Chromophore called retinal present as 11cis retinal also called retinine 1

41
Q

True or false: resynthesis of rhodopsin from 11-cis retinal is faster than from 11 cis retinol

A

True

42
Q

Explain the greater than usual resting membrane potential of photoreceptors (-40 mV)

A

Sodium ions pumped out through outer segment, but leak back in to inner segment carrying that positive charge with them and preventing the cell potential from sinking to -70mV

43
Q

What protein causes sodium to leak back into inner segment?

A

cGMP keeps sodium channels open

44
Q

Enumerate the mechanism of phototransduction.

A

Rodhopsin absorbs photon and decomposes to Metarodhopsin 2 –> which activates transducin G protein –> which goes to activate cGMP phosphodiesterase –> which converts cGMP to 5’-AMP = decrease in cGMP = closure of sodium channels = hyperpolarization because sodium no longer leaking back in = production of action potential = activation of bipolar cells

45
Q

State which light porphyropsin, iodopsin, and cyanopsin are sensitive to.

A

Porphyropsin –> Red
Iodopsin –> Green
Scotopsin –> Blue

46
Q

Mechanism for dark adaptation.

A

Resynthesis of rhodopsin for rods to function

Dilatation of pupil to allow more light to enter eye

47
Q

Nyctalopia

A

loss of vision when environment gets dark because rodhopsin not being resynthesized
caused by Vit A deficiency
1. diet low in vit A
2. poor absorption of vit A from intestines

if not treated, causes distortion and irreparable damage to layers of cornea

48
Q

Define VISUAL FIELD

A

part of the external world visible to the eye

49
Q

Differentiate binocular from monocular vision

A

Binocular vision - visual fields overlap

Monocular vision - there is very little overlap

50
Q

Where is the visual field NOT restricted?

A

Temporal part

51
Q

Define FAR-POINT OF VISION

A

the distance beyond which lens doesn’t need to change shape to focus (the farthest distance an object is and still remains clear)

52
Q

The most stressed muscles in the body are…?

A

Ciliary muscles

53
Q

Mechanism of focusing on close objects.

A
  1. Accomodation
    ciliary muscles contract, lens ligaments loosen, lens curves to increase its refractory power.
  2. Convergence
    eyes move medially
  3. Constriction
    pupil constricted to prevent divergent light rays from entering
54
Q

True or false: the ciliary muscles become less contractile with age, but the lens is not affected

A

False: the ciliary muscles do lose their contractility with age, but the lens is also affected because it also loses its contractility as it becomes more dense with age

55
Q

What nerve innervates ciliary muscles?

A

Oculomotor nerve parasympathetic fibers

56
Q

define EMMETROPIA

A

normal refractive power of the eye

57
Q

define ANISOMETROPIA

A

both eyes have different refractive powers

58
Q

Mechanism of astigmatism

A

light rays never meet because a meridian of the lens has an altered curvature OR meridian has different alterations

59
Q

Functions of private pathway and diffuse pathway in the visual pathway.

A

Private pathway is for acuity and discrimination of intensity
Diffuse pathway is for other vision

60
Q

Enumerate the visual pathway.

A

Receptor: Rods and Cones
1st Order neuron: Bipolar + Amacrine cells
2nd Order neuron: Ganglionic cell
3rd Order neuron: Lateral geniculate body nuclei
Center: Primary visual cortex occipital lobe (Brodmann 17)

61
Q

What are the 6 components of the visual pathway?

A 
Optic nerve
Optic chiasma 
Optic tract 
Lateral geniculate body 
Optic radiation 
Visual cortex
62
Q

The optic nerve leaves the eye through the…

A

Optic disk

63
Q

True or false: the optic tract is formed by fibers from opposite sides of the optic nerve

A

False: its lateral fibers are from the ipsilateral optic nerve while its medial fibers are from the contralateral optic nerve

64
Q

Fibers that go to superior collicus initiate…

A

visual reflexes

65
Q

Optic tract fibers that don’t end in the lateral geniculate body end up in the _____ or the ______.

A

superior colliculus

pretectal nuclei

66
Q

The anterior part of the visual cortex represents which kind of vision? And the posterior part?

A

Anterior part gets retinal representation (for peripheral vision)
Posterior part gets macular representation (for central vision)

67
Q

State the functions of the following parts of the visual cortex: Brodmann 17, 18, and 19.

A

Area 17 –> perception of visual impulses
Area 18 –> Interpretation of visual impulses
Area 19 –> movement of eyes

68
Q

Anopia refers to

A

loss of vision in on visual field

69
Q

Enumerate causes of lesion to optic pathway structures

A

Aneurysms of carotid artery causes compression
Increased intracranial pressure due to thrombosis, tumors, stroke, high blood pressure
Dilation of 3rd ventricle compresses carotid artery against other structures

70
Q

Type of anopia developed from damage to visual cortex.

A

If it’s the inferior visual cortex, patient gets inferior homonymous hemianopia

If it’s the superior visual cortex, patient gets superior homonymous hemianopia

71
Q

Why does macular sparing occur?

A
  1. Supra-geniculate fibers project to both visual cortices
  2. The fibers have their own blood supply
  3. Fibers project to both anterior and posterior parts of each visual cortex
72
Q

Define macular sparing

A

A phenomenon in which central vision is spared in supra-geniculate lesions

73
Q

Quadrantanopia is a result of lesion to

A

optic radiation

74
Q

The type of anopia resulting from lesions to optic radiation to temporal lobe is

A

superior quadrantanopia

75
Q

Differentiate Presbyopia, Anisometropia, and Astigmatism

A

Presbyopia is caused by old age and causes lens to become less flexible.
Anisometropia is differences in refractive power of the eyes.
Astigmatism is when light rays do not meet at all due to difference in meridians of the lens.

76
Q

Lesion to which area of the brain results in right superior quadrantanopia?

A

Lesion to the left temporal lobe

77
Q

Lens used to correct presbyopia

A

convex lens

78
Q

Describe glaucoma including causes, types, symptoms, and treatments.

A

Glaucoma refers to increase in intraocular pressure above 60 mmHg
The types of symptoms depend on the type of glaucoma involved.
1. Primary open-angle glaucoma caused by unknown obstruction. is the most common type. symptoms appear later and include headaches, rapid reduction of visual field, and heaviness around eyeball

  1. Primary angle-closure glaucoma caused by visible obstruction. results in severe headaches, nausea, blurry vision, and appearance of hallow rainbow around a light source

Treatment includes eye drops, laser eye surgery, or surgery

Physiology PHM (19 decks)

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