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Physiology III > Lecture 14: Special Senses: Vision > Flashcards

Lecture 14: Special Senses: Vision Flashcards

1
Q

What anterior portion of the eye contains what fluid

A

Aqueous humor

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2
Q

The posterior portion of the eye contains what fluid

A

Vitreous

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3
Q

___ is a clear specialization of the sclera

A

Cornea

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4
Q

Where are photoreceptors located

A

Retina

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5
Q

What nerve innervates the optic nerve

A

CN II

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6
Q

What nerve innervates dorsal rectus, ventral rectus, ventral oblique, medial rectus, ciliary, levator palpebrae, iris and sphincter muscles

A

CN III

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7
Q

What nerve innervates dorsal oblique

A

CN IV

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8
Q

What nerve innervates the lateral rectus and retractor bulbi

A

CN VI

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9
Q

What layer has melanin in the epithelial layer that absorbs light

A

Choroid layer

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10
Q

Do diurnal or nocturnal species have a more pronounced choroid layer

A

Dinurnal

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11
Q

What is the tapetum lucidum

A

Reflective layer behind the retina

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12
Q

Do diurnal or nocturnal species have a more pronounced tapetum lucidum

A

Nocturnal

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13
Q

Where does light focus in the retina

A

Fovea centralis

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14
Q

Who has a better developed fovea centralis, diurnal or nocturnal species

A

Diurnal

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15
Q

What species have multiple fovea

A

Birds

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16
Q

which layer of the retina is closest to the vitreous fluid

A

Inner retina

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17
Q

Which layer of the retina is closest to the choroid layer

A

Outer retina

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18
Q

What are the four neurons in the retina

A

Bipolar, horizontal, amacrine, and ganglion cells

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19
Q

Describe the pathway of light through the retina and what cells are involved

A
  1. Lights act on the rods and cones which then synapse with bipolar cells
  2. Horizontal cells are interacting at site of synapse between rods/cones and bipolar cells
  3. Bipolar cells synapse with ganglion cells
  4. Amacrine cells are interacting at site of synapse with bipolar and ganglion cells
  5. Ganglion cells send axons through optic disk to form optic nerve
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20
Q

Which photoreceptor is sensitive to low light

A

Rods

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21
Q

Which photoreceptor functions best in daylight

A

Cones

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22
Q

Which photoreceptor has high acuity

A

Cones

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23
Q

Which photoreceptor has low acuity

A

Rods

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24
Q

Which photoreceptor utilizes rhodopsin

A

Rods

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25
Q

Which photoreceptor utilizes opsin-retinal

A

Cones

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26
Q

Which photoreceptor is achromatic

A

Rods

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27
Q

Which photoreceptor sees color

A

Cones

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28
Q

Which photoreceptor has their cells converge on a single bipolar cell

A

Rods

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29
Q

Which photoreceptor does not converge on a single bipolar cell

A

Cones

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30
Q

Which photoreceptor is concentrated in the peripheral retina

A

Rods

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31
Q

Which photoreceptor is concentrated in the fovea

A

Cones

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32
Q

Describe how light is transduced to chemical energy

A
  1. In the dark there is an influx of Na+ ions
  2. Photons convert cis-retinal to all trans-retinal
  3. Trans retinal attached rhodopsin activate cGMP phosphosdiesterase
  4. CGMP decreases
  5. Na+ channels start to close
  6. Membrane hyperpolarizes
  7. More light, greater response, less transmitter released- results in graded potential
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33
Q

What ion is influxed in the dark

A

Na+

34
Q

Is the cis or trans-retinal form formed in response to light

A

Trans

35
Q

Which photoreceptor is more sensitive to structural detail

A

Cones

36
Q

What type of wiring allows cones to have greater structural detail

A

One to one wiring between cone and bipolar cell leads to high spatial discrimination

37
Q

What is the trade off for cones and their high spatial discrimination

A

Requires ample light

38
Q

How many opsins do most mammals have

A

Two

39
Q

How many opsins do primates have

A

3

40
Q

What species vision is tetrachromatic, four opsins that absorb red, green, blue and UV

A

Avian

41
Q

What species have UV sensitive cones

A

Lizards, turtles and fish

42
Q

What cells in the retina provide lateral transmission

A

Horizontal and amacrine

43
Q

Light influences the adjacent portion of the retina it does not hit and therefore ___contrast, provides ____sensitivity, and ___discrimination

A

Increased contrast, directional sensitivity, and color discrimination

44
Q

T or F: the direction of light travels in the same direction as visual processing

A

False, direction of light travels from the inside out, whereas the direction of visual process travels from outside in

45
Q

___inhibition increases contrast

A

Lateral

46
Q

Describe how lateral inhibition works

A
  1. Ganglion cells stimulated if photoreceptors of well defined field are illuminated BUT their response is inhibited if neighboring photoreceptors are excited
  2. Horizontal cells respond by sending an inhibitory signal to neighboring ganglion cells
47
Q

What does the retino-geniculo-striate pathway do

A

Conscious visual perception of form, movement, color, orientation and depth

48
Q

___ cells project to the ipsilateral and contralateral visual cortex

A

Ganglion cells

49
Q

Describe the pathway from the optic tract to the occipital cortex

A
  1. Fibers in the optic tract proceed to the thalamus
  2. In the thalamus they synapse on the lateral geniculate nucleus
  3. They then travel and innervates the occipital cortex
50
Q

Where do axons of the optic tract synapse in the thalamus

A

Lateral geniculate nucleus

51
Q

Injury to the left hemisphere will affect the left or right visual field

A

Right

52
Q

What is eye position

A

Convergence of two eyes to focus objects on the fovea, follow objects, fixate the visual field

53
Q

What is accommodation of the eye

A

Lenses adapt focal length

54
Q

What reflex are you testing when you test the eyes ability to follow objects and fixate on the visual field

A

Vestibulo-ocular reflex

55
Q

What is strabismus

A

Misalignment of the eyes, object is projected on different parts of the retina and causes double vision

56
Q

What is exotropia

A

Lateral displacement

57
Q

A patient with left lateral displacement could have a lesion where

A

Left oculomotor nucleus (CN3)

58
Q

What is esotropia

A

Eye turned inward

59
Q

Accommodation is altering of the shape of the lens by action of the ___muscle

A

Ciliary

60
Q

Ciliary muscle contraction results in…

A

Relaxation of tension of the lens causing the lens to be more curved

61
Q

Describe the pathway of accommodation

A
  1. Retina
  2. Optic nerve CN II
  3. Lateral geniculate nucleus
  4. Visual cortex
  5. Superior colliculus
  6. Oculomotor nucleus
  7. PNS motor efferent to ciliary muscle via CN III
62
Q

is iris sphincter muscle controlled by PNS or SNS

A

PNS

63
Q

Describe the pathway of constriction via iris sphincter muscle

A
  1. Optic tract
  2. Pretectal nucelus
  3. Preganglionic fibers in EW nucleus
  4. Synapse in ciliary ganglion
  5. Postganglionic innervation to iris sphincter muscle- eye constricts
64
Q

Is the iris dilatory muscle controlled by SNS or PNS

A

SNS

65
Q

Describe the pathway to the iris dilator muscle

A
  1. Preganglion neurons begin in thoracic segments of spinal cord
  2. Course to superior cervical ganglion
  3. Postganglionic fibers innervates dilator muscles
66
Q

What CN controls the iris sphincter muscle

A

CN III

67
Q

What CN controls the iris dilator muscle

A

CN VII

68
Q

What does the retina-tectal pathway do

A

Provides pupillary reflex and reflex orientation of the eyes to visual targets

69
Q

Describe the pathway of the retina-tectal pathway

A
  1. Ganglion cells
  2. Pretectal nucleus
  3. E-W nucleus
  4. oculomotor CN III
70
Q

What does the retino-hypothalamic pathway

A

Provides light to set physiological rhythms in suprachiasmatic nucleus

71
Q

Describe the eye blink reflex: touch the cornea/eyelid

A
  1. Free nerve endings in the cornea stimulate CN V
  2. CN V terminates in spinal trigeminal nucelus
  3. Reticular formation interneurons send bilateral axons to facial nucleus
  4. Facial motor neurons CN VII send axons down the facial nerve to obicularis oculi which close eyes
72
Q

What CN are activated in eye blink reflex, which is afferent and efferent

A

CN V: afferent
CN VII: efferent

73
Q

What is the pathway of the menace response test

A
  1. Visual stimulus relayed via CN II
  2. Travel to thalamus—> occipital cortex
  3. Motor neurons stimulate the ipsilateral facial nerves CN VII and activate orbicularis oculi to close eye
74
Q

Which CN are activated in menace response, which is afferent which is efferent

A

CN II: afferent
CN VII: efferent

75
Q

The menace response tests potential damage to __

A

Cortex, cerebral lesions may result in loss of menace response

76
Q

Light stimulates the ___ pathway

A

Retino-tectal pathway

77
Q

Describe the pupillary light reflex

A
  1. Retinal ganglion cells project to Pretectal nucleus via CN II
  2. Pretectal to E-W nucleus which give rise to preganglionic PNS
  3. Travel on CN III to ciliary ganglion
  4. Innervate sphincter muscle of iris
78
Q

Case ex: PLR
1. Shine light into left eye: No direct or consensual response
2. Shine light into right eye:
Normal direct and consensual response

Where is the lesion?

A

CN II, optic tract

79
Q

Case ex 2: PLR
1. Shine light in left eye:
No direct response, normal consensual response in right

  1. Shine light in right eye:
    Normal direct and no consensual response

Where is the lesion

A

CN III

80
Q

Case #3: PLR response- animal is blind in left eye

  1. Shine light into left eye, normal direct and consensual response
  2. Shine light in the right eye
    normal direct and consensual response

Where is the lesion

A

Right cerebral hemisphere

81
Q

What are some symptoms of horners syndrome

A

Miosis, ptosis, enophthalamus, prolapsed nictating membrane

82
Q

Is a prolapsed nictating membrane cause by insufficient SNS or PNS innervation

A

SNS

Physiology III (34 decks)

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