Vision and hearing

Question 1

Sensation

Answer 1

The detection of external or internal stimuli through the stimulation of specialized receptors.

Question 2

Perception

Answer 2

what your brain makes of these stimuli

ex : your experience of colours etc..

Question 3

Photons

Answer 3

Particles that create light and travel in waves

Question 4

Electromagnetic energy

Answer 4

Light energy measured in wavelength

Question 5

Electromagnetic spectrum

Answer 5

The range of wavelength of light

it ranges from gamma rays to extremely low frequency wavelength

Question 6

Visible Spectrum

Answer 6

The narrow band of the electromagnetic spectrum ranging from 400 to 700 nm that can be perceived as colours ( by humans)
it has not been really decided on because it also depends on the light’s intensity and on the sensitivity of the observer.

Question 7

Photoreceptors & Transducers

Answer 7

Colour perception results from the brain processing the input of specialized receptors called photoreceptors they are transducers which are devices the converts on form of energy to the next
HERE : light energy from he visible spectrum to action potentials

Question 8

The pathway of the light to the human eye

Answer 8

1- Light enters the eye through the pupil .
2- Ciliary muscles control the zone fibres that pull on the lens allowing light to focus on the retina at the back of he eye.
3- the fovea is a little pit at the centre of the retina that picks up the light from the point in space being looked at ( a lot of photoreceptors
4- the optic nerve have a bundle of gangland cells that bring the visual information to the brain through the optic disk

Question 9

Blind spot

Answer 9

light refracted directly to the optic disk cannot be processed since there are no photoreceptors. It is not perceived since the visual s system fills it in with info processed by receptors in the surrounding area

Question 10

Refraction

Answer 10

the change in direction of the light rays as they travel from one medium to the next .
the cornea and then by the lens which result into a convergence of light rays into the middle of the retina

Question 11

Pigment epithelium

Answer 11

The layer of cells that nourishes the photoreceptors

Question 12

Accommodation

Answer 12

the ability of the eyes to keep objects in focus as they vary in distance

when the object moves towards the eyes , the ciliary muscle contract , the lens becomes more convex and increases is focusing power.
when the object moves away from the eyes , the ciliary ,muscles relaxes and the lens flattens decreasing its focusing power.

Question 13

The pathway of light from the eye to the brain

Answer 13

The flow off information in the retina begins the activation of the photoreceptors ( rods and cones ) which activate the bipolar cells and the retinal ganglion cells . Their axon form the optic nerve that sends info to the brain

Question 14

types of ganglia cells

Answer 14

midget cells : small size and are associated with colour vision .
Parasol cells : do not process info about colours but are sensitive to dark and light contrasts.

Question 15

Rods

Answer 15

they are used for peripheral vision . there are no rods at the fovea ( centre of retina )
they do not mediate colour perception but are sensitive to low levels of light.
rods do not have acuity : the precision of vision
Found on the periphery of retina

Question 16

Dark adaptation ( rods )

Answer 16

the eye’s ability to adjust to low levels of light .

Question 17

Cones

Answer 17

they are concentrated at the fovea and are adapted for daytime vision and are not very effective in low light conditions ( less degree in dark adaptation )
they are responsible for colour vision and are highly acuity

Question 18

Photopigments

Answer 18

Light absorbing molecules

produced by opsin

Question 19

3 types of cones

Answer 19

S cones ( blue )  : short wavelength 
M- cones( green )  : medium wavelength 
L- cones ( red ) : long wavelength

Question 20

Spectral sensitivity ( cone)

Answer 20

Each cone is differentially sensitive to a range of wavelength surrounding the one to which it best responds

Question 21

Photopigments in rods

Answer 21

it is known as rhodopsin and the spectral sensitivity is medium length

Question 22

Bleaching

Answer 22

when exposed to light photopigments undergo a certain amount of degeneration ( bright to light room )
it reduces the ability to transduce light .
when 20 min have passed the regeneration of rods is faster in rods

Question 23

Photo transduction

Answer 23

the process by which light rays are converted into nerve impulse

Question 24

Photo transduction in rods

No light

Answer 24

when rods are not stimulated by light, they are penetrated by a constant flow of Na 2+ ions through cGMP-gated Na + channels
( constant depolarization in the dark )
they release glutamate which inhibits bipolar neurons

Question 25

Photo transduction in rods

With light

Answer 25

the photopigment rhodopsin is activated by light, the G-protein transducin releases guanosine triphosphate (GTP). GTP activates the effector enzyme phosphodiesterase. Phosphodiesterase causes the second messenger cGMP to be converted to guanosine monophosphate (GMP). This results in the closing of cGMP-dependent Na+ channels.
hyperpolorization sips the release of glutamate and revives the inhibitory influence on them.

Question 26

Convergence

Answer 26

The ratio of connectivity between photoreceptors and retinal ganglion cells

Question 27

Convergence in rods

Answer 27

Rods confer low acuity because the rods that converge to excite a single retinal ganglion cell come from slightly different places on the retina ( lack of precision)
Rods are more sensitive to low light conditions because the summated input from the rods to retinal ganglion cells amplifies the light signal

Question 28

Convergence in Cones

Answer 28

a single cone receives info from a single ganglion cells so the location is quite precise .
there is less sensitivity to light since the summation does not occur.

Question 29

Lateral inhibition

Answer 29

how receptors in the surround of on-centre receptive fields have inhibitory connections with receptors located in the centre of the same receptor fields

Question 30

white light

Answer 30

what is perceived when all wavelength of the visual spectrum are mixed.

Question 31

Trichromatic theory

Answer 31

.the theory that the brain produces our perception of colours by reading out the combined input of three types of cone each responding best to a specific wavelength.
blue > short rejected and all others absorbed
red > long reflected and all others absorbed
white > all reflected
black > all absorbed

Question 32

Across neuron response

Answer 32

the idea that the precise information about stimuli is encoded not by a single neuron but by the response pattern of population of neurons
why ? each type of cone responds to a range of other wavelength with less intensity than he does attributed to them

Question 33

Protanopia

Answer 33

A type of red-green color deficiency due to the absence of L-cones.

Question 34

Deuteranopia

Answer 34

A type of red-green color deficiency due to the absence of M-cones.

Question 35

Tritanomaly

Answer 35

A type of blue-yellow color deficiency due to a limited number of functioning S-cones

Question 36

Monochromacy

Answer 36

Color blindness due to the absence or failure of two of the three types of cones.

Question 37

Rod monochromacy

Answer 37

Color blindness due to the absence of cones.

Question 38

Color afterimage

Answer 38

An image of an object that persists after having stared at it for several seconds.

Question 39

Nasal retina

Answer 39

portion of retina closest to the nose
The axons from the nasal retina of each eye cross over to the other side of the brain (contralateral) at the optic chiasm to form connections with the LGN ( lateral geniculate nucleus)
Beyond the optic chiasm, the optic nerves are renamed optic tract,

Question 40

temporal retina

Answer 40

the portion of the retina that is nearest to each of the temples
he axons from the temporal retinas remain on the same side (ipsilateral)
Beyond the optic chiasm, the optic nerves are renamed optic tract,

Question 41

Direction of the vision

Answer 41

The optic nerve from the nasal retina in the left eye and the temporal retina of the right eye convey information from the left visual field.
the optic nerve from the nasal retina in the right eye and the temporal retina of the left eye convey information from the right visual field.
Information from the center of the visual field is conveyed by projections from the fovea of both eyes to form the foveal image.

Question 42

Parvocellular ( P-cells)

Answer 42

the dorsal layers of the LGN. These consist of layers 3, 4, 5, and 6 and are known as the parvocellular layers. P-cells receive color information from the axons of midget ganglion cells of the retina.
process color > midget cells

Question 43

Magnocellular ( M- cells)

Answer 43

the ventral layers of the LGN. These consist of layers 1 and 2 and are known as the magnocellular layers. They convey information about motion and depth. Contrary to P-cells, M-cells are sensitive to contrast. They receive their information about contrast from the parasol ganglion cells
no color > parasol cells

Question 44

Koniocellular (K-cells)

Answer 44

They are located in six thin layers sandwiched in between each of the dorsal and ventral layers. Cells of the LGN that receive information from short-wavelength cones in the retina as well as from bistratified retinal ganglion cells, which convey information about spatial resolution.

Question 45

Color opponent cells

Answer 45

firing of cells located in the LGN depends on the wavelengths of light that illuminate the center or surround the receptive fields. The frequencies to which these receptive fields respond correspond to the pairs of opposing hues : blue /yellow, red/green ,
each of the pairs was found to activate and inhibit retinal ganglion cells in the pattern of opposition.
ex : Some of the P-cells in the LGN were found to be activated when the center of the receptive field of midget retinal ganglion cells in the retina was illuminated with yellow light. The same P-cells were inhibited by illumination of retinal midget ganglion cells’ surround with blue light

Question 46

Orientation selectivity

Answer 46

A property associated with simple cells in the primary visual cortex, which best respond when bars of a particular orientation are projected onto the retina.
it also depends on the combined input of sets of LGN neurons known as concentric cells

Question 47

Directional selectivity

Answer 47

A property associated with complex cells in the primary visual cortex, which best respond when bars of light moving in a particular direction are projected onto the retina.
the directional selectivity of these cells was found to depend on the combined input of several simple cells with the same orientation selectivity.

Question 48

P-pathway

Answer 48

The visual information pathway from the retina to the visual cortex that connects midget retinal ganglion cells to P-cells of the LGN.
In V1, the P-pathway processes information about form and color. However, in extrastriate areas such as V2, the P-pathway processes information about depth and form but not color. In V4, the P-pathway processes information about form and color.

Question 49

M-pathway

Answer 49

The visual information pathway from the retina to the visual cortex that connects parasol retinal ganglion cells to P-cells of the LGN.
one branch of it ends up in V2, which processes motion, depth, and form. The M-pathway then projects to area MT, where information about depth and motion is processed.

Question 50

the what are where

Answer 50

damage to the visual pathway that leads to the temporal lobe were impaired in the identification of objects, ( what ) whereas those that had damage to the pathway leading to the parietal lobes were impaired in assessing the positions of objects in space ( where)