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Vision and visual pathway

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Based on PUM physiology presentations and own notes
Soheila Amri
Quiz by Soheila Amri, updated more than 1 year ago
Soheila Amri
Created by Soheila Amri almost 3 years ago
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Resource summary

Question 1

Question
Vision - choose correct
Answer
  • Electromagnetic radiation in this range of wavelengths is called visible light or simply light.
  • The optical spectrum is the portion of the electromagnetic spectrum that is visible to the animal eye.
  • The visible spectrum is approximately between 400nm to 750nm
  • 8% of men are colour blind, it's a Y-linked disease

Question 2

Question
Retina - rods & cones - choose correct
Answer
  • Both photoreceptors are found in the inner nuclear layer of the retina at the back of each eye
  • Bipolar and ganglion cells send information from photoreceptors to the brain are in front of the cones and rods
  • The human eye have 6 million cones and 120 million rods
  • Cones and rods are types neurons

Question 3

Question
Albinism; choose correct
Answer
  • Albinos don't have colour vision
  • Albinos have reduced pigment epithelium in sclera and choroid
  • Albinos have colour vision
  • Albinos have increased visual acuity, due to intra-ocular reflection of light

Question 4

Question
Vision - choose correct
Answer
  • Retinal ganglion cells that express the photopigment melanopsin.
  • In the absence of rods and cones, mammals retain the ability to detect light for various non-image-forming visual functions.
  • Phototransduction is conducted only by cones and rods
  • Cones have rhodopsin and rods have fotopsin

Question 5

Question
Retino-hypothalamic tract - choose WRONG
Answer
  • Photosensitive ganglion cells seem to serve as photoreceptors for the photic synchronization of circadian rhythms.
  • Cones innervate the midbrain pupillary control center.
  • They project to the circadian pacemaker of the brain - the suprachiasmatic hypothalamic nucleus
  • Photosensitive ganglion cells contribute to the pupillary light reflex and other behavioral and physiological responses to environmental

Question 6

Question
Neurotransmitters; choose WRONG
Answer
  • Rods/cones - Glutamate
  • Amacrine cells - Inhibitory neurotransmitters (GABA, Glycine, Dopamine, Ach, Indolamine)
  • Horizontal cells - Excitatory neurotransmitters.
  • Horizontal cells - Inhibitory neurotransmitters.

Question 7

Question
Retina; Choose correct
Answer
  • Ganglion cells - the only retinal cell of the pathway transmitting signals by mean of action potential.
  • Amacrine cells - Occasionally action potential is recorded in.
  • Remaining cells of the retina - conduct their visual signals by electrotonic conduction (graded conduction).
  • Ganglion cells - conduct their visual signals by electrotonic conduction (graded conduction).

Question 8

Question
Photoreceptors; choose correct
Answer
  • Rods are used to determine color, depth, and intensity.
  • Each particular photosensitive cell responds to monochromatic spectral stimuli
  • All 3 types of photoreceptors transduce light into a change in membrane potential through different signal transduction pathway.
  • All 3 types of photoreceptors differ in the nature of the opsin they contain and therefore in their function.

Question 9

Question
Vision; choose correct
Answer
  • Cones are divided into red, blue and green
  • Visual imaging occurs in the visual cortex, occipital lobe
  • Fovea has the lowest visual acuity
  • Rods are trichromatic

Question 10

Question
Generator potential; choose correct
Answer
  • Dark current - the voltage-gated sodium channels in the outer segment are opened due to cGMP bound to them.
  • Dark current - depolarising sodium channels to - 40mV, in dark conditions
  • Rods are also de-polarising in light conditions
  • Cones de-polarise in dark conditions

Question 11

Question
Signal tranduction pathway; choose correct
Answer
  • The opsin in the outer segment absorbs a photon, changing the configuration of a molecule inside the cell from the less- energetic cis-form to the more-energetic trans-form.
  • Night blindness can be caused by deficiency of vitamin E
  • The light acts as a ligand
  • Light is absorbed by rhodopsin or by one of the photopsins of cones, changing shape of the retina.

Question 12

Question
Signal transduction pathway; choose correct
Answer
  • Each photo-activated rhodopsin triggers activation of about 100 transducins
  • PDE inhibits the hydrolysis of cGMP
  • Each transducin then activates the enzyme cGMP-specific phosphodiesterase (PDE)
  • cGMP was keeping the Na(Ca channels closed

Question 13

Question
Signal transduction pathway ; choose correct
Answer
  • A photoreceptor actually releases less neurotransmitter when stimulated by light.
  • Hyper-polarization means that less glutamate is released to the bipolar cell than before.
  • GTP provided by the inner segment powers the sodium- potassium pump.
  • The opening of Na+ channels hyperpolarizes the cell

Question 14

Question
Which of these neurons do not belong to the visual pathway?
Answer
  • Neurons of layer 4 of the visual cortex (Brodman’s area 17).
  • Bipolar cells, Photosensitive cells and Ganglion cells.
  • Horizontal and amacrine cells
  • Cells of the lateral geniculate body of the thalamus.

Question 15

Question
Visual pathway; choose correct
Answer
  • Old system - Suprachasmatic nucleus of hypothalamus – SCN (circadian rhythms)
  • Old System - Lateral geniculate nucleus of thalamus (LGN)
  • Old system - Visual cortex (4th neuronal of Brodman’s field 17)
  • Old system - Pretectal nuclei of the midbrain (pupillary reflexes) & Superior colliculi (rapid eye movement of both eyes)

Question 16

Question
Functions of the lateral geniculate body (nucleus); choose correct.
Answer
  • Parvocellular portion of LGN - (shape, color, texture, fine detail).
  • Interlaminar path - conduct impulses from ipsilateral eye.
  • Magnocellular portion of LGN - (spatial organisation, movement, location)
  • Layers 1,4,6 - colour

Question 17

Question
Vision; Choose wrong
Answer
  • Right retina - Left hemisphere, calcarine fissure
  • Left retina - Right hemisphere, cuneus gyrus fissure
  • Temporal vision crosses at the optic chiasm
  • Nasal vision crosses at the optic chiasm

Question 18

Question
Functions of visual projection areas of the visual cortex - Choose wrong match
Answer
  • V2, V3, VP – Motion, control of movement.
  • V3A , MT/V5 – Continued processing – larger visual field.
  • V1 – Primary visual cortex – receives input from the LGN – processing in terms on orientation edges, etc.
  • LO – Recognition of large objects.
  • V8 – Color vision.

Question 19

Question
Refraction;
Answer
  • Light, passing from one transparent medium to another, changes its speed, and bends.
  • Angle of refraction - The angle between the light ray and the normal, as it leaves a medium.
  • Each medium has its own refractive index
  • Angle of incidence - The angle between the light ray and the normal as it enters a medium

Question 20

Question
Rate of bending of light depends on;
Answer
  • Strength of the light ray
  • The angle between the light ray and the line perpendicular to the surface separating both media
  • The refractive index of the media
  • Absence of other sources of light

Question 21

Question
Refraction;
Answer
  • Parallel light rays are bent to pass through a single point behind the lens (focal point)
  • Rays striking perpendicular lens surface pass the lens by bending
  • Convex lenses diverge light rays
  • Rays striking perpendicular lens surface pass the lens without being bent

Question 22

Question
Refraction;
Answer
  • In the focal length distant sources of light rays are parallell
  • In the focal length distant sources of light rays are converged
  • In the focal length the close source is parallell
  • Focal length - distance beyond midpoint of a convex lens, and the focal point

Question 23

Question
Refracted image of objects;
Answer
  • Reversed - Upside-down, left side-right
  • Inversed - Downside-up, left side-right
  • Each point source of light on the object comes to a separate point focus on the opposite side of the lens in line with the lens centre
  • Only one source of light on the object comes to a separate point focus on the opposite side of the lens in line with the lens centre

Question 24

Question
Power of lens;
Answer
  • Expressed in diopters
  • Spherical Convex lenses = -1 power
  • Spherical Concave lenses = +1 power
  • Spherical Convex lenses = + 10 power

Question 25

Question
Optics of the eye;
Answer
  • Interface between posterior surface of the cornea and aqueous humour is a part of the optic system
  • Interface on both sides of the lens are parts of the optic system
  • Interface between the retina and the optic nerve is a part of the optic system
  • Interface between air and the anterior surface of the cornea is a part of the optic system

Question 26

Question
Choose correct match of indexes of refraction to their medium;
Answer
  • Air = 1.0
  • The lens = 1.40
  • The cornea = 1.33
  • The aqueous humour = 1.38
  • The vitreous humour = 1.34

Question 27

Question
Optics of the eye;
Answer
  • 1/3 of all the refractive power of the eye is provided by the anterior surface of the cornea.
  • Total refractive power of the eye is 59 dioptres
  • 2/3 of all the refractive power of the eye is provided by the anterior surface of the cornea.
  • Total refractive power of the eye is 39 dioptres

Question 28

Question
Optics of the eye;
Answer
  • Reduced eye - a simplified design of the ocular optical system, represented as having a single refracting surface and a uniform index of refraction
  • Reduced eye - By close object the light rays are diverged and refraction power of the eye should be increased in order to focus eye on object and produce the image exactly on the retina.
  • Accommodation - By close object the light rays are diverged and refraction power of the eye should be increased in order to focus eye on object and produce the image exactly on the retina.
  • Accommodation - a simplified design of the ocular optical system, represented as having a single refracting surface and a uniform index of refraction

Question 29

Question
Accommodation;
Answer
  • Refraction power of the eye can be increased voluntary by approximately 14 dioptres by changing the shape of the lens from moderately convexed to more convexed.
  • In normal conditions tension of ligaments of the lens causes its to remain spherically shaped.
  • Contraction of the ciliary muscle depend on parasympathetic transmission via III CN.
  • Contraction of smooth muscle fibers in the ciliary muscle tenses the ligaments to the lens capsule and the lens assumes a more spherical shape.

Question 30

Question
The far point of vision;
Answer
  • Reduced eye – refraction power 59 D
  • With age gets farther away
  • Light rays are divergent
  • Picks up 6 m and more distant objects.

Question 31

Question
The near point of vision;
Answer
  • Parallell light rays, and the point of vision comes closer with age
  • About 20 cm in front of eyes
  • Does not require accommodation
  • The nearest point in front of eye which can be focused on retina

Question 32

Question
Choose correct elements of the near response;
Answer
  • Accomodation
  • Pupillary constriction
  • Pupillary dilation
  • Divergence of the visual axes

Question 33

Question
Choose correct for normal focusing ability;
Answer
  • Distant object - parallel light rays focuses on retina
  • Light rays focus behind the retina
  • Close object - contraction of ciliary muscle provide accommodation – diverge rays are focus on retina
  • Light rays focus in front of the retina

Question 34

Question
Defects of focusing;
Answer
  • Presbypia (senile farsightedness) is caused by decreased lens elasticity
  • Presbypia (senile farsightedness) is caused by decreased power of ciliary muscle
  • Astigmatism is caused by a cornea that isn't spherical
  • Astigmatism is corrected with concave lenses

Question 35

Question
Visual acquity does NOT depend on....?
Answer
  • Fixation of eye (fovea centralis)
  • Refraction index of medium
  • Astigmatism
  • Myopia

Question 36

Question
Visual acquity depends on
Answer
  • Optical factors (image-forming mechanisms of the eye)
  • Depth of vision
  • Retinal factors
  • Stimulus factors (illumination, brightness, contrast, time of exposure)

Question 37

Question
Depth of Vision;
Answer
  • Distance is perceived by - sizes of known objects, moving parallax and stereopsis
  • Distance is perceived by - sizes of unknown objects and stereopsis
  • Distance is perceived by - relative distance, fast moving close objects and slow moving far objects
  • Stereopsis is dependent on mono-ocular vision - image only created on retina

Question 38

Question
Photoreceptors;
Answer
  • Rhodopsin decompose in darkness
  • Rhodopsin is combined of scotopsin and retinene-1 (aldehyde of vit. A)
  • The only retinal neurons that transmit visual signal by means of action potential are the ganglia cells
  • Activated rhodopsin deactivates transducin

Question 39

Question
Phototransduction;
Answer
  • Photon activates an electron
  • Activated transducin activates rhodopsin
  • Activated transducin activates cGMP
  • Phosphodiesterase hydrolyzes cGMP (which normally causes Na-channels stay open), and Na-channels close

Question 40

Question
Blind spot;
Answer
  • Found 15 degrees temporally to visual axis
  • It is NOT visible through the ophtalmoscope as the optic disc.
  • The optic nerve leaves the eye at the point 3 mm medial to and slightly above the posterior pole of the globe
  • There are some photoreceptors in this area

Question 41

Question
Choose correct match between cranial nerve and activity of eye structure;
Answer
  • Optic N. (CN2) - Mediates vision
  • Oculomotor N. (CN3) - innervates superior oblique muscle
  • Trochlear N. (CN4) - innervates superior oblique muscle
  • Trigeminal N. (CN5) - sensory portion of corneal reflex
  • Abducens N. (CN6) - Innervates orbicularis oculi and lacrimal glands

Question 42

Question
Visual adaptation;
Answer
  • Light adaptation (photopic vision) - regeneration of photopigment, that in turn increases visual sensitivity
  • Dark adaptation (scotopic vision) - a reduction in the amount of rhodopsin, which in turn reduces visual sensitivity
  • Light adaptation time is 5min
  • Dark adaptation time is 20min

Question 43

Question
Visual fields; limitations
Answer
  • Laterally = 90 degrees
  • Downward = 50 degrees
  • Upward = 50 degrees
  • Medially 65-70 degrees

Question 44

Question
Visual pathway - choose correct order; 1. Geniculate body neurons 2. Bipolar cells 3. Cerebral cortex 4. Rods and cones 5. Ganglia cells
Answer
  • 1, 3, 2, 4, 5
  • 4, 2, 5, 1, 3
  • 2, 4, 5, 1, 3
  • 4, 5, 2, 1, 3

Question 45

Question
Visual pathway;
Answer
  • Axons of ganglia cells converge and leave eye as the optic nerve through optic disc.
  • The temporal optic fibers cross at the optic chiasm
  • Each optic tract fibres synapse in ventral lateral geniculate nucleus of lateral geniculate body (LGB) of the thalamus.
  • Geniculocalcarine fibres pass as optic radiation to the primary visual cortex in the calcarine fissure area of the medial occipital lobe (striate cortex)

Question 46

Question
Visual pathway;
Answer
  • Geniculate body has 6 layers, 2 main parts parvocellular and magnocellular
  • Parvocellular -carries signals for colour vision, texture, shape, fine detail
  • Parvocellular - carries signals for detection of movement, depth and flicker
  • Major input comes form the retina

Question 47

Question
Visual Cortex;
Answer
  • Primary cortex; Brodmann’s area 18 (V2),19
  • Secondary cortex; Brodmann’s area 17 ( also known as V1)
  • Area V8 concern with colour vision
  • Dorsal and parietal pathway – motion
  • Ventral and temporal pathway – shape and recognition of forms and faces

Question 48

Question
Defects of visual analyser;
Answer
  • Optic chiasm – right or left homonymus hemianopia (half-blindness in same side half of the visual field
  • Interruption of optic nerve – blindness in the eye
  • Occipital lesion – macular sparing (loss of peripheral vision with intact macular vision)
  • Optic tract - bitemporal heteronymous hemianopia (half-blindness in opposite sides of the visual field)

Question 49

Question
Reaction of pupil to light
Answer
  • Afferent pathway: photoreceptors, bipolar cells, ganglion cells, optic nerve, optic tract, nuleus pretectalis and farther to Edinger-Westphal nucleus bilaterally.
  • Efferent pathway: from Edinger-Westphal nucleus through oculomotor nerve to ciliary ganglion and n.n. ciliares breves to papillary sphincter.
  • Efferent pathway: photoreceptors, bipolar cells, ganglion cells, optic nerve, optic tract, nuleus pretectalis and farther to Edinger-Westphal nucleus bilaterally.
  • Afferent pathway: from Edinger-Westphal nucleus through oculomotor nerve to ciliary ganglion and n.n. ciliares breves to papillary sphincter.

Question 50

Question
Choose correct instrument to function;
Answer
  • Slit lamp - facilitates examination of the eyelid, sclera, conjunctiva, iris, natural crystalline lens, and cornea
  • Ophtalmoscopy - Used to determine the health of retina and the vitreous humour
  • Ophtalmoscopy - facilitates examination of the eyelid, sclera, conjunctiva, iris, natural crystalline lens, and cornea
  • Perimetry - maps and quantifies the visual field
  • Slit lamp - maps and quantifies the visual field
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