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VISION.MCQ
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1993-08-06
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D:Created 14.52 06/08/1993
D:Subject : Physiology
D:Topic : Vision
D:Level : Moderate
D:
D:Authors : Department of Physiology
D: The University
D: Leeds LS2 9NQ
I:MCQ SB 1
G:3
G:1:Dental Students
Q:1,2,3,4,5,7,8,9,10,11,13,14,15,16,17,18,19,21,22
G:2:Medical Students
Q:1,2,3,4,5,7,8,9,10,11,13,14,15,16,17,18,19,21,22
G:3:Science Students
Q:1,2,3,4,5,7,8,9,10,11,13,14,15,16,17,18,19,21,22
T:A
L:2
#:1
G: 10464 1 2 3
S:1
:Aqueous humour:
B:N:5
B:1:F:1
:is an ultrafiltrate of plasma
B:2:T:1
:contains more bicarbonate than plasma
B:3:F:1
:is produced by the canal of Schlemm
B:4:F:1
:is under a pressure of about 50 mmHg
B:5:T:1
:is responsible for the nutrition of the cornea
F:7
:Aqueous humour is produced by the ciliary body,
:circulates through the pupil and is reabsorbed by the canal
:of Schlemm. Its pressure is normally less than 20 mmhg. It
:is a modified ultrafiltrate of plasma which contains excess
:HCO3 due to carbonic anhydrase in the ciliary body. The
:cornea is avascular and receives its nutrients from the
:aqueous humour.
E:------
#:2
G: 10464 1 2 3
S:1
:Consider visual evoked potentials in man:
B:N:5
B:1:T:2
:the visual evoked potential has a latency of around 100
:msec
B:2:F:2
:the visual evoked potential has a latency of around 20
:msec
B:3:T:2
:the visual evoked potential is due to activation of
:visual cortical neurones by a sudden visual stimulus
B:4:T:2
:the visual evoked potential originates from the striate
:cortex
B:5:T:2
:delay in latency of the visual evoked potential can be
:due to demyelination in the visual pathway
F:4
:The visual evoked potential has a latency of about 100
:msec and is due to activation of cortical neurones in the
:striate (visual, calcarine) cortex. Delay can be due to
:demyelination in the visual pathway.
E:------
#:3
G: 10464 10464 1 2 3
S:2
:The retina is a multi-layered structure and light
:impinges on the rods and cones:
B:N:5
B:1:T:1
:many rods converge on to a single ganglion cell
B:2:F:1
:this photoreceptor system has very high visual acuity
B:3:F:1
:the rods are concentrated in the fovea centralis
B:4:F:1
:the ganglion cells of the retina are spikeless neurones
B:5:T:2
:in the spikeless neurones of the retina transmitter
:release is a continuously graded phenomenon
F:10
:The ratio of rods/ganglion cells is large (greater than
:30/1); the rods occur in the periphery of the retina and
:visual acuity during rod vision (scotopic vision) is less
:than when cones are used. The ganglion cells of the retina
:give rise to optic nerve axons which project to the neurones
:of the lateral geniculate nuclei: ganglion cells transmit
:information by sending trains of spikes. The amacrine cells
:of the retina do not initiate spikes, and transmitter release
:by these cells is a graded phenomenon that depends on
:membrane potential.
E:------
#:4
G: 10464 1 2 3
S:1
:The visual pathway is retinotopically organised and:
B:N:5
B:1:F:2
:there are six visual fields represented in the
: ventrobasal nuclei of the thalamus
B:2:T:2
:hyper-complex cells of the visual cortex respond to
: specifically oriented bars in the visual field
B:3:F:2
:the "opponent colours theory" suggests that blue/green
: and red/yellow receptors exist in the retina
B:4:F:1
:there is evidence for the receptors described in (c)
B:5:T:2
:there is evidence for red, green and blue receptors in
: the retina
F:7
:Retinal ganglion cells project to the lateral geniculate
:bodies, which have three layers in cats and six in primates.
:These neurones project to the visual (striate) cortex and
:there the complex cells do respond to bars of a specific
:orientation. Modern evidence supports the trichomatic theory
:of colour vision: receptors for red, green and blue are
:present in the retina.
E:------
#:5
G: 10464 1 2 3
S:2
:The main central connections of the optic nerve
:include the following:
B:N:5
B:1:F:1
:the nucleus of the inferior colliculus
B:2:F:1
:the mamilliary bodies
B:3:F:1
:the medial geniculate body
B:4:T:1
:the nucleus of the superior colliculus
B:5:T:1
:the lateral geniculate body
B:N:5
B:1:F:1
:the nucleus of the inferior colliculus
B:2:F:1
:the mamilliary bodies
B:3:F:1
:the medial geniculate body
B:4:T:1
:the nucleus of the superior colliculus
B:5:F:1
:a pineal tumour
F:8
:The usual course for bi-temporal hemianopnia (loss of the
:temporal field of vision on both sides) is an expanding
:tumour of the anterior pituitary. Such tumours may secrete
:growth hormone and produce acromegaly, or produce destruction
:of the pituitary producing hypopituitarism and amenorrhoea.
:The expanding tumour causes bitemporal hemianopnia by
:invading optic nerve fibres that cross the midline in the
:optic chiasma.
E:------
#:7
G: 10464 1 2 3
S:1
:Visual acuity is dependent upon:
B:N:5
B:1:F:1
:dark adaptation
B:2:T:1
:concentration of cones in fovea
B:3:F:1
:scotopic visibility curve
B:4:T:1
:wavelength of light
B:5:F:1
:adequate supply of rhodopsin
F:15
:Visual acuity is dependent on being able to focus rays of
:light on the fovea: normal refraction is necessary therefore
:and any opacities in the lens (cataract), cornea (keratitis)
:or vitreous humour can lessen visual acuity. Normal visual
:acuity is 1 minute of arc, and depends on the density of
:cones at the fovea: two rays of light which subtend an angle
:of one minute of arc at the fovea fall on adjacent cones.
:The wavelength of the light, and its intensity, as well as
:the integrity of central visual pathways also contribute to
:normal visual acuity.
N:Rhodopsin, the pigment found in rods is necessary for night
:vision; it is responsible for the scotopic visibility curve
:which indicates that the most sensitive part of the visual
:spectrum in low intensities of lighting is in the blue
:region.
E:------
#:8
G: 10464 1 2 3
S:1
:The central part of the retina:
B:N:5
B:1:F:1
:contains high concentrations of rhodopsin
B:2:T:1
:contains high concentrations of cones
B:3:T:1
:contains cells which can sense colour
B:4:F:1
:is responsible for dark adaptation
B:5:T:1
:is the region of greatest visual acuity in the retina
F:5
:The colour sensitive elements in the retina are the
:cones, and the high density of cones at the fovea is why that
:region of the retina has the greatest visual acuity.
N:Rhodopsin exists in rods and is responsible for dark
:adaptation.
E:------
#:9
G: 10464 1 2 3
S:1
:Consider the refracting system of the eye:
B:N:5
B:1:T:1
:the cornea causes more refraction than the lens
B:2:F:2
:more refraction occurs at the inner surface of the
: cornea than at its outer surface
B:3:F:2
:the lens can double the refractory power of the eye
: during accommodation in the young adult
B:4:F:2
:accommodation is brought about by the sympathetic
: nervous system
B:5:T:2
:in myopia the eye tends to be longer than average from
: lens to retina
F:8
:The refractive power of the cornea is much greater than
:the lens (42D cf 15D). During accommodation in a young
:person the power of the lens can be increased by about 14D,
:and this is brought about by the parasympathetic system in
:the oculomotor nerve. The sympathetic does not participate
:in accommodation. In myopia, the eyeball is long and light
:is focused in front of the retina unless corrected by a
:concave lens (negative D).
E:------
#:10
G: 10464 1 2 3
S:1
:The rods in the retina:
B:N:5
B:1:F:2
:contain visual pigment which is more sensitive to light
: in the red than the blue frequency bands
B:2:T:1
:are rendered insensitive by bright light
B:3:T:1
:are more numerous in nocturnal animals
B:4:F:2
:comprise a substantial proportion of receptor cells in
: the fovea
B:5:T:1
:contain the most light sensitive pigment in the retina
F:4
:Rhodopsin is most sensitive to blue light, and is the
:most sensitive of the visual pigments. It is bleached by
:high intensities of light, and is absent at the fovea.
:Nocturnal animals have a predominance of rods.
E:------
#:11
G: 10464 1 2 3
S:1
:Pupillary dilatation:
B:N:5
B:1:F:1
:occurs when focusing on a near object
B:2:T:1
:occurs when the intensity of lighting is reduced
B:3:T:1
:can occur during stress
B:4:F:1
:occurs when the cervical sympathetic is transected
B:5:T:1
:can be induced with atropine
B:N:5
B:1:F:1
:occurs when focusing on a near object
B:2:T:1
:occurs when the intensity of lighting is reduced
B:3:T:1
:can occur during stress
B:4:F:1
:occurs when the cervical sympathetic is transected
B:5:T:2
:the genes that control the synthesis of cone pigments
: are on the X chromosome
F:5
:The most common forms of colour blindness are carried on
:the X chromosome and the greater incidence in males is due to
:the fact that inheritance is sex linked. Vitamin A is
:essential for the synthesis of rhodopsin, the pigment in rods
:that is used for night vision, not colour vision.
E:------
#:13
G: 10464 1 2 3
S:1
:Consider the optical properties of the eye:
B:N:5
B:1:T:1
:the focusing power of the eye is normally about 58D
B:2:T:2
:the main structure responsible for this power in the
:cornea
B:3:F:1
:the main structure responsible for this power is the lens
B:4:T:2
:the power of the lens can be increased by activation of
:the parasympathetic fibres in the III cranial nerve
B:5:F:1
:accommodation increases with age
F:7
:The power of the refracting system of the young adult eye
:during distant vision is about 57 dioptres and can increase
:further by about 15 dioptres due to accommodative changes in
:the nucleus of the oculomotor (III) nerve which synapse on
:the postganglionic cells in the ciliary ganglia.
:Accommodation decreases with age and is usually absent after
:the age of 45. The cornea accounts for about 42D.
E:------
#:14
G: 10464 1 2 3
S:2
:The following structures are part of the visual
:system:
B:N:5
B:1:T:1
:occipital cortex
B:2:F:1
:somatosensory cortex
B:3:T:1
:lateral geniculate body
B:4:F:1
:inferior colliculus
B:5:F:1
:pons
F:1
:No explanation available.
E:------
#:15
G: 10464 10464 1 2 3
S:1
:The following are statements about the retina:
B:N:5
B:1:F:1
:rod cells are found only at the fovea
B:2:T:1
:rod cells hyperpolarise in response to light
B:3:F:1
:cone cells depolarise in response to light
B:4:T:1
:rod and cone cells have circular receptive fields
B:5:T:1
:ganglion cell axons make up the optic tract
F:1
:No explanation available.
E:------
#:16
G: 10464 1 2 3
S:1
:Lesions of area V4 of the visual cortex cause:
B:N:5
B:1:T:1
:loss of colour vision
B:2:F:1
:loss of motion vision
B:3:F:1
:loss of form vision
B:4:F:1
:loss of visual reflexes
B:5:F:1
:total loss of vision
F:1
:No explanation available.
E:------
#:17
G: 10464 1 2 3
S:1
:Simple cells in the visual cortex:
B:N:5
B:1:T:2
:receive an afferent input from the lateral geniculate
: nucleus
B:2:F:1
:have circular receptive fields
B:3:T:1
:are orientation sensitive
B:4:T:1
:can be driven by inputs to both eyes
B:5:T:1
:are not excited by diffuse light
F:1
:No explanation available.
E:------
#:18
G: 10464 1 2 3
S:2
:Recordings from the visual cortex show that changes
:in stimulation of the cortex can be elicited by:
B:N:5
B:1:T:1
:moving an object across the retinal field
B:2:T:1
:changing an object's intensity
B:3:T:1
:changing an object's contrast gradient
B:4:T:1
:changing the orientation of an object's borders
B:5:F:1
:changing the hue of an object at the same intensity
F:8
:Recognition of visual perceptions is mediated by the
:occipital lobes. The visual cortex is stimulated by changes
:in light intensity, movement of an object across the retina,
:changes in orientation of an object's borders, and changes in
:the gradient of contrast (light to dark). The visual cortex
:is especially sensitive to contrast signals as opposed to
:perception of steady signals. Specific points in the retina
:are linked with specific points in the visual cortex.
E:------
#:19
G: 10464 1 2 3
S:2
:Visual accommodation involves which of the
:following mechanisms?
B:N:5
B:1:T:1
:release of acetylcholine by parasympathetic nerves
B:2:T:1
:change of lens shape to a more bi-convex form
B:3:T:1
:contraction of the ciliary muscle
B:4:F:1
:contraction of lens ligaments
B:5:F:1
:The eye adopting a more spherical shape
B:N:5
B:1:T:1
:release of acetylcholine by parasympathetic nerves
B:2:T:1
:change of lens shape to a more bi-convex form
B:3:T:1
:contraction of the ciliary muscle
B:4:F:1
:contraction of lens ligaments
B:5:F:1
:transformation of vitamin A to retinene
F:8
:The light-sensitive chemical in the retinal rods is
:called rhodopsin. It is a combination of retinene (in the
:cis configuration) and scotopsin. Light immediately changes
:the cis structure of retinene to the trans structure. Other
:reactions follow because the physical structure of the trans
:retinene no longer combines in a stable fashion with
:scotopsin. Rhodopsin's decomposition upon exposure to light
:excites the nerve fibres in the eye.
E:------
#:21
G: 10464 1 2 3
S:2
:Mydriasis, or pupillary dilatation, involves all
:the following EXCEPT:
B:N:5
B:1:F:1
:contraction of the radial fibres of the iris
B:2:F:1
:relaxation of the sphincter muscles
B:3:T:1
:stimulation of the Edinger-Westphal nucleus
B:4:T:1
:sympathetic nerve discharge
B:5:F:1
:impulse transmission by the superior cervical ganglion
F:10
:Sympathetic nerves from the superior cervical ganglion
:innervate the radial fibres of the iris, and their excitation
:induces pupillary dilatation. Constriction of the pupil in
:response to light is mediated via afferent fibres to the
:pretectal area of the pons, from which efferent fibres pass
:to the nucleus of Edinger-Westphal. From the point,
:parasympathetic cholinergic fibres pass via the ciliary
:ganglion to the ciliary muscles and sphincter of the iris.
:When dilatation of the pupil occurs, the nucleus of Edinger-
:Westphal is inhibited.
E:------
#:22
G: 1 2 3
S:1
:Eye movements:
B:N:5
B:1:T:2
:are produced by the synergistic actions of the three
:pairs of extraocular muscles
B:2:T:2
:may be initiated by angular acceleration of the fluids in
:the semicircular canals
B:3:F:2
:may be described as saccadic movements when following an
:object moving across the visual field
B:4:T:1
:may be as rapid as 1000 degrees per second
B:5:F:2
:are described as nystagmus during casual inspection of a
:stationary object
F:1
:No explanation available.
E:------
::