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Medsci 316 > Module A - Vision > Flashcards

Module A - Vision Flashcards

1
Q

ON-centre neuron

A

A visual neuron whose receptive field centre is excited by light

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2
Q

Retinoid cycle

A

Process in which retinal is restored to a form capable of signalling photon capture.

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3
Q

Horizontal cells

A

Retinal neurons that mediate lateral interactions between photoreceptor terminals and the dendrites of bipolar cells.

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4
Q

Transducin

A

G-protein involved in the phototransduction cascade.

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5
Q

Sclera

A

The external connective tissue coat of the eyeball.

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6
Q

Photopic vision

A

Vision at high light levels, which is mediated almost entirely by cone cells. Contrast with scotopic vision.

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7
Q

Trichromatic

A

Referring to the presence of three different cone types in the human retina, which generate the initial steps in colour vision by differentially absorbing long, medium and short wavelength light.

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8
Q

Macula lutea

A

The central region of the retina that contains the fovea (the term derives from the yellowish appearance of this region in opthalmoscopic examination); also, the sensory epithelia of the otolith organs.

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9
Q

Bipolar cells

A

Retinal neurons that provide a direct link between photoreceptor terminals and ganglion cell dendrites.

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10
Q

Fovea

A

Area of the retina specialised for high acuity in the centre of the macula; contains a high density of cones and few/no rods.

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11
Q

Fovea

A

Area of the retina specialised for high acuity in the centre of the macula; contains a high density of cones and few rods.

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12
Q

Cones

A

Photoreceptor cells specialised for high visual acuity and the perception of colour.

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13
Q

Amacrine cells

A

Retinal neurons that mediate lateral interactions between bipolar cell terminals and the dendrites of ganglion cells.

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14
Q

Posterior chamber

A

The region of the eye between the lens and the iris.

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15
Q

Mesopic vision

A

Vision in light levels at which both the rods and cones are active.

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16
Q

Phototransduction

A

The process by which light is converted in electrical signals in the retina.

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17
Q

Cornea

A

The transparent surface of the eyeball in front of the lens, continuous with the sclera; the major refractive element in the optical pathway.

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18
Q

Ciliary body

A

Two-part ring of tissue encircling the lens of the eye. The muscular component is important for adjusting the refractive power of the lens. The vascular component produces the fluid that fills the front of the eye (aqueous humor).

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19
Q

Scotopic vision

A

Vision in dim light, where the rods are the operative receptors.

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20
Q

Zonule fibres

A

Radially arranged connective tissue bands that hold the lens of the eye in place.

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21
Q

Pupil

A

The perforation in the centre of the iris that allows light to enter the eye. The pupillary light reflex mediates pupillary constriction in full light and expansion (dilation) in dim light; these receptors can also be induced by chemicals and by certain emotional states, and thus clinically important.

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22
Q

Emmetropic

A

Having normal vision.

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23
Q

Optic nerve (II)

A

The nerve (cranial nerve II) containing the axons of retinal ganglion cells; extends from eye to the optic chiasm.

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24
Q

Cataracts

A

Opacities in the lens of the eye that cause a loss of transparency and, ultimately, degrading vision.

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25
Q

Rods

A

Photoreceptor cells specialised for operating at low light levels.

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26
Q

Light adaptation

A

Gain control of vision according to the prevailing level of illumination.

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27
Q

OFF-centre neuron

A

A visual neuron whose receptive field centre is inhibited by light.

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28
Q

Rhodopsin

A

The photopigment found in rods.

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29
Q

Presbyopia

A

The condition in which ageing affects the accommodative ability of the eye.

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30
Q

Arrestin

A

A protein that binds to rhodopsin.

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31
Q

Myopic

A

Near sighted

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32
Q

Aqueous humor

A

A clear, watery liquid that supplies nutrients to the cornea and lens of the eye. Produced by vascular component of ciliary body.

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33
Q

Interphotreceptor retinoid binding protein (IRBP)

A

A critical protein in the retinoid cycle. Present in the extracellular space between photoreceptors and the RPE. IRBP is known to bind visual retinoids.

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34
Q

Uveal tract

A

A layer of eye tissue adjacent to the retina that includes three distinct but continuous structures: the choroid, the ciliary body, and the iris.

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35
Q

Luminance

A

The physical measure of light intensities.

36
Q

Luminance contrast

A

The difference between the level of illumination that falls on the receptive field centre and the level of illumination that falls on the surround.

37
Q

Scotoma

A

A small deficit in the visual field resulting from changes in some component of the primary visual pathway.

38
Q

Ganglion cells

A

Neurons located in the ganglion.

39
Q

Anomalous trichromats

A

Individuals with one or more atypical opsins.

40
Q

Retinal

A

A light-absorbing chromophore; the aldehyde form of vitamin A.

41
Q

Vitreous humor

A

A gelatinous substance that fills the space between the back of the lens and the surface of the retina.

42
Q

Optic papilla

A

The region of the retina where the axons of retinal ganglion cells exit to form the optic nerve and where the opthalmic artery and vein enter the eye. Also called the optic disk.

43
Q

Ciliary muscle

A

Muscle that controls the shape of the lens.

44
Q

Hyperopic

A

Far-sighted.

45
Q

Anterior chamber

A

The part of the that is just behind the cornea and in front of the lens.

46
Q

Fundus

A

The inner surface of the retina.

47
Q

Retina

A

Laminated neural component of the eye that contains the photoreceptors and the initial process machinery for the primary (and other) visual pathways.

48
Q

Optic disk

A

The region of the retina where the axons of retinal ganglion cells exit to form the optic nerve and where the opthalmic artery and vein enter the eye. Also called the optic papilla.

49
Q

Photoreceptors

A

The specialised neurons of the eye that are sensitive to light.

50
Q

Foveola

A

Capillary-free and rod-free zone in the centre of the fovea.

51
Q

Accommodation

A
  1. Dynamic changes in the lens of the eye that enable the viewer to focus. When viewing distant objects, the lens is made relatively thin and flat; for near vision, the lens becomes thicker and rounder and has more refractive power.
52
Q

Glaucoma

A

Condition in which the eye’s aqueous humor is not adequately drained, resulting in increased intraocular pressure, reduced blood supply to the eye, and eventual damage to the retina.

53
Q

Binocular field

A

The two symmetrical, overlapping visual hemifields. The left hemifield includes the nasal visual field of right eye and the temporal visual field of the left eye; the right hemifield includes the temporal field of the right eye and the nasal field to the left eye.

54
Q

Brodmann’s area 17

A

Another name for the primary visual cortex (V1) in the occipital lobe; major cortical target of the retinal sensory cells. Also called striate cortex because the prominence of layer 4 in myelin-stained sections gives this region a striated appearance.

55
Q

Cerebral achromatopsia

A

Loss of colour vision as a result of damage to the extrastriate visual cortex.

56
Q

Cerebral akinetopsia

A

A rare disorder in which one is unable to appreciate the motion of objects.

57
Q

Cortex

A

The superficial mantle of grey matter (a sheet-like array of nerve cells) covering the cerebral hemispheres and cerebellum, where most of the neurons in the brain are located.

58
Q

Diplopia

A

Double vision.

59
Q

Dorsolateral geniculate nucleus

A

The portion of the thalamus that sends (and receives) axons to the cerebral cortex via the internal capsule.

60
Q

Edinger-Westphal nucleus

A

Midbrain visceral motor nucleus containing parasympathetic preganglionic neurons that constitute the efferent limb of the pupillary light reflex.

61
Q

Far cells

A

Visual cortical neurons that change their rate of firing in response to retinal disparities that arise from points beyond the plane of fixation.

62
Q

Homonymous hemianopsia

A

A loss of vision in both left and right hemifields due to lesions of the optic tract.

63
Q

Inferior division

A

Referring to the region of the visual field of each eye that corresponds to the bottom half of the retina.

64
Q

Koniocellularly (K-cell) pathway

A

A third, poorly understood pathway from retina to cortex characterised by the anatomical location of IT cells in the lateral geniculate nucleus that process of short wavelength light.

65
Q

Magnocelluar layers

A

A component of the primary visual pathway specialised for the perception of motion; so named because of the relatively large (“magno”) cells involved.

66
Q

Middle temporal area (MT)

A

Region of the extrastriate cortex in which neurons respond mainly to movement without regard to colour.

67
Q

Near cells

A

Visual cortical neurons that respond to retinal disparities that arise from points in front of the plane of fixation.

68
Q

Ocular dominance columns

A

The segregated termination patterns of thalamic inputs representing the two eyes in the primary visual cortex of some mammalian species.

69
Q

Optic chiasm

A

The junction of the two optic nerves on the ventral aspect of the diencephalon, where axons of the nasal divisions of retina cross the midline.

70
Q

Optic radiation

A

Portion of the internal capsule that comprises the axons of LGN that carry visual information to the striate cortex.

71
Q

Optic tract

A

The axons of retinal ganglion cells after they have passed through the region of the optic chiasm en route to the LGN of the thalamus.

72
Q

Parvocellular layers

A

A component of the primary visual pathway specialised for the detection of detail and colour; so named because of the relatively small cells involved.

73
Q

Point of fixation

A

The point in visual space that falls on the fovea of each eye.

74
Q

Pretectum

A

A group of nuclei located at the junction of the thalamus and the midbrain; these nuclei are important in the pupillary reflex, relaying info from the retina to the Edinger-Westphal nucleus.

75
Q

Primary visual cortex (V1)

A

Brodmann’s area 17 in the medial occipital lobe; major cortical target of the retinal sensory cells. Also called striate cortex because the prominence of layer 4 in myelin-stained sections gives this region a striated appearance.

76
Q

Primary visual pathway

A

Pathway from the retina via the LGN of the thalamus to the primary visual cortex; carries information that allows conscious visual perception. Also known as the retinogenticulocortical pathway.

77
Q

Pupillary light reflex

A

The reduction in the diameter of the pupil that occurs when sufficient light falls on to the retina.

78
Q

Retinogenticulostriate pathway

A

Another term for primary visual pathway.

79
Q

Rertinohypothalamic pathway

A

The route by which variation in light levels influences the broad spectrum of functions that are entrained to the day-night cycle.

80
Q

Stereopsis

A

The perception of depth that results from the fact that the two eyes view the world from slightly different angles.

81
Q

Superior colliculus

A

Laminated grey matter that forms part of the roof of the midbrain; plays an important role in orientating movements of the head and eyes.

82
Q

Suprachiasmatic nucleus (SCN)

A

Hypothalamic nucleus lying just above the optic chiasm that receives direct input from the retina; involved in light entrainment of circadian rhythms.

83
Q

Temporal division

A

Referring to the region of the visual field of each eye in the direction of the temple.

84
Q

Tuned zero

A

Optic neurons that respond selectively to points that lie on the plane of fixation.

85
Q

V4

A

Region in the extrastriate cortex that contains a high percentage of neurons that respond selectively to colour without regard to motion.

86
Q

Visual field

A

The area in the external world normally seen by one or both eyes (referred to, respectively, as the monocular and binocular fields.

Medsci 316 (1 decks)

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