Lecture 9- Vision

Question 1

What is sensation?

Answer 1

-How cells of the nervous system detect stimuli in the environment (light, sounds, heat)
-they transduce these signals into a change in membrane potential and neurotransmitter release.

Question 2

What is perception?

Answer 2

To consciously experience and interpretation of sensation info

Question 3

Sensory neurons are specialized to detect specific categories of physical events such as:

Answer 3

-Specific molecules
-Physical temperature
-Temperature
-PH
-Electromagnetic radiation

Question 4

Sensory transduction:

Answer 4

Process by which sensory stimuli are transduce into receptor potentials

Question 5

Receptor potential:

Answer 5

Graded change in the membrane potentials of a sensory neuron caused by sensory

Question 6

Sensory neuron:

Answer 6

Specialized neuron detecting specific physical events

Question 7

Opsins are receptor proteins sensitive to light, they are inhibitory metabotropic receptors,
what are the 4 different opsins to detect light:

Answer 7

-Rhodopsin
-Red cone
-green cone
-Blue cone

Question 8

Photo receptors:

Answer 8

The sensory neurons responsible for vision by transducing electromagnetic energy of visible light into receptor potentials.

Question 9

Describe what the Red, blue and green cone opsins individually sensitive to:

And when red and green are too close, they appear:

Answer 9

Red: Sensitive to long wavelengths
Blue: Sensitive to short wavelengths
Green: Sensitive to medium wavelengths

-Yellow

Question 10

The 3 dimensions of perception of light and colour are:

Answer 10

1. Brightness (intensity)
2. Saturation (purity)
3. Hue (dominant wavelength)

Question 11

If brightness or saturation is at 0% the image will be:

Answer 11

brightness: black (no impact from saturation or hue)
saturation: middle colour/ no colour (equal contribution from all wavelengths=black and white images)

Question 12

Protanopia 1% of males:

Answer 12

The absence of red cone opsin, Red cone cells get filled with green opsin.
= cant distinguish green, yellow, red

Question 13

Deuteranopia 1% of males:

Answer 13

The absence of green cone opsin. Green cone cells get filled with red opsin.
=cant distinguish red, green, yellow

Question 14

Tritanopia:

Answer 14

Absence of blue cone cells. No compensation, but blue opsin is not too sensitive to light,
= visual acuity is not affected

Question 15

Achromatopsia:

Answer 15

Colorblindness: mutations in g proteins signalling cascade.

Question 16

What is the difference from Rod cells and Cone cells

Answer 16

rod cells are sensitive to visible light and cone cells and not very sensitive, but there are 3 so they are each uniquely sensitive to wavelengths.

Question 17

Describe simply the functions of
-Conjunctiva
-Cornea
-Iris
-Pupil
-Lens
-Retina
-Photoreceptor cells
-Fovea
-Optic disk

Answer 17

-Conjunctiva: mucous membrane lines the eyelid

-Cornea: outer, front layer focuses on incoming light

-Iris: ring of muscle (contraction of this determines size of pupil

-Pupil: determines how much light can enter eye

-Lens: Several transparent layers (allows eye to focus)

-Retina: interior lining of the eye

-Photoreceptor cells: either rod or cone cells

-Fovea: central of eye, little compression of visual info

-Optic Disk: Where optic nerve exits through back of eye (blind spot)

Question 18

what is foveal vision compared to peripheral vision

Answer 18

Foveal is sensitive to detail and colour, peripheral is sensitive to dim light

Question 19

Describe cones:

Answer 19

-Found in Fovea
-Sensitive to moderate to high levels of light
-provide info about hue
-excellent acuity

Question 20

Describe Rods:

Answer 20

-prevalent in peripheral retina
-sensitive to low levels of light
-monochromatic info
-poor acuity

Question 21

What is saccadic movement and pursuit

Answer 21

Saccadic is rapid jerky shifts of eye, pursuit allows us to maintain image of moving object.

Question 22

Bipolar cells vs Ganglion cells

Answer 22

bipolar: neurons that relay information form the photoreceptor cells to ganglion cells

ganglion: the only neurons in the retina that sends axons out of the eye, Receive info from bipolar cells and project to the rest of the brain

Question 23

When photoreceptors are more depolarized:

Answer 23

release more glutamate in the dark than in the light

Question 24

Off vs On bipolar cells:

Answer 24

OFF bipolar cells: ionotropic glutamate receptors, they are depolarized by glutamate, they are more active in the dark (depolarized)

ON bipolar cells: inhibitory metabotropic glutamate receptors so they are uncommonly inhibited by glutamate, more active in the light

Question 25

Receptive field:

Answer 25

Involved in visual processing defined as the area of visual space where the presence of light influences the firing rate of that neuron

Question 26

First, Second and Third cell pathways:

Answer 26

First cell pathway: when the correct wavelength of light is presented in a photoreceptor cells receptive field, hyperpolarizes and becomes less active Second cell pathway: bipolar cells, light is presented in the receptive field of bipolar cells, depolarizing and releasing more glutamate. Off bipolar cells, thye hyperpolarize and release less glutamate Third cell pathway: retinal ganglion cells generally integrate information form many on and off bipolar cells.

Question 27

Simple cells:

Answer 27

In the primary visual cortex are sensitive to lines of light, their receptive field are typically organized in a center surround fashion.

Question 28

Primary visual cortex:

Answer 28

-neurons have longer receptor field then he retinal ganglion cells -cell responds better when line is in a particular orientation -some neurons respond better to vertical lines, and some horizontal lines