Vision

Question 1

What is sensory transduction?

Answer 1

The process whereby the characteristics of a stimulus are converted into nerve impulses

Question 2

Which stimulus is used for vision?

Answer 2

Electromagnetic energy (light waves)

Question 3

Which wavelengths are we sensitive to and what is the difference between them?

Answer 3

Between 380 and 760 nanometres
Different wavelengths have different colours, e.g. 380 is violet and 760 is red

Question 4

How are human eyes protected?

Answer 4

Our eyelids, eyelashes and eyebrows stop foreign objects entering the eyes
Our eyelids also close automatically at the sudden approach of an object

Question 5

Where do light waves enter the eye?

Answer 5

The cornea

Question 6

What is the pupil?

Answer 6

An adjustable opening behind the cornea that controls the amount of light that enters the eye

Question 7

What does the iris do?

Answer 7

Contains muscles that cause dilation or constriction of the pupil in order to either allow more or less light to enter the eye

Question 8

What is the lens?

Answer 8

A flexible structure that either becomes thinner (to focus on distant objects) or thicker (to focus on nearby objects)
It also causes images to be focused on the retina

Question 9

What is accommodation?

Answer 9

The process where an image is focused directly and sharply onto the retina
It is what determines good all-round vision

Question 10

What is myopia?

Answer 10

Shortsightedness / nearsightedness

Question 11

What is myopia caused by?

Answer 11

The visual image is focused in front of the retina because the eyeball is longer than normal

Question 12

What is hyperopia?

Answer 12

Longsightedness / farsightedness

Question 13

What is hyperopia caused by?

Answer 13

The visual image is focused behind the retina because the lens doesn’t thicken enough

Question 14

What is the retina?

Answer 14

A multi-layered light sensitive tissue at the rear of the eyeball

Question 15

What are the two main types of light sensitive receptor cells that are found in the retina?

Answer 15

Rods
Cones

Question 16

What are rods?

Answer 16

Black and white brightness receptors that function best in dim light

Question 17

What are cones?

Answer 17

Colour and detail receptors that function best in bright illumination

Question 18

What is the fovea?

Answer 18

A small area in the centre of the retina that contains no rods but many densely packed cones
It is responsible for our most detailed vision

Question 19

What are the rods and cones synaptically connected to ?

Answer 19

The bipolar cells

Question 20

What are the bipolar cells synaptically connected to?

Answer 20

The ganglion cells

Question 21

What is the role of the horizontal cells?

Answer 21

They collect information from the rods and cones and compress it so it can be sent to the bipolar cells

Question 22

What is the role of the amacrine cells?

Answer 22

They collect information from the bipolar cells and compress it so it can be sent to the ganglion cells

Question 23

How is the optic nerve formed?

Answer 23

Axons of the ganglion cells are collected into a bundle

Question 24

What creates the blind spot?

Answer 24

An absence of photoreceptors where the optic nerve exits the eye

Question 25

What does the lens to the image it projects onto the retina?

Answer 25

It reverses the image from right to left and top to bottom

Question 26

How is the image then translated to be the right way around?

Answer 26

Activity of the photoreceptors and their associated neurons send input to the brain which reconstructs it

Question 27

What are photopigments?

Answer 27

Protein molecules that allow rods and cones to translate light waves into nerve impulses

Question 28

What is the role of photopigments?

Answer 28

They produce a chemical reaction that increases the rate of neurotransmitter release, causing a stronger signal to be passed onto the bipolar and ganglion cells - this sends a message through the visual system

Question 29

What is dark adaptation?

Answer 29

The progressive improvement in brightness sensitivity that occurs over time under conditions of low illumination

Question 30

Explain the process of regeneration of photopigment molecules

Answer 30

Bright light causes a depletion of photopigments in the rods and cones, meaning we cannot see in the dark
Over time, they regenerate, allowing us to see in the dark
Cones regenerate fully within about 10 minutes as they are less sensitive in the dark, while rods regenerate fully within about 30 minutes since they are more sensitive in the dark

Question 30

How does dark adaptation occur?

Answer 30

Through the regeneration of photopigment molecules

Question 31

Where is the visual message sent once it reaches the retina?

Answer 31

The optic nerve sends it to the thalamus, from where it is routed to the primary visual cortex (found in the occipital lobe)

Question 32

What are feature detectors?

Answer 32

Cells within the primary visual cortex that fire selectively in response to visual stimuli that have specific characteristics

Question 33

What happens in the visual association cortex?

Answer 33

It combines and interprets the information