Photoreception -12.2

Question 1

What is the percentage of how much vision supplies the sensory information reaching the brain?

Answer 1

80 to 90%

Question 2

Describe the human eye.

Answer 2

fluid filled hallow ball - 2.5cm in diameter

Question 3

How many layers does each eye have and what are they?

Answer 3

Three layers

Outer layer - sclera
Intermediate layer - choroid layer
Inner layer - retina

Question 4

What does the cornea do?

Answer 4

It bends light rays into the eye

Question 5

What does the choroid do?

Answer 5

Absorbs scattered light and contains blood vessels

Question 6

What does the pupil do?

Answer 6

It is the opening for light to enter the inner eye?

Question 7

What does the iris do?

Answer 7

It regulates the amount of light that enters the pupil
- adjusts size of pupil depending on light conditions (adaptation)

Question 8

What do ciliary muscles do?

Answer 8

They change the shape of the lens in order to focus

Question 9

What does the lens do?

Answer 9

Focuses light rays on the fovea centralis.

Question 10

What is the retina?

Answer 10

Thin layer of the eye - contains the photoreceptors - rods, cones, and the fovea centralis

Question 11

What are rods?

Answer 11

Rods are photoreceptors - they are sensitive to dim light, and allow us to see black and white

Question 12

What are cones?

Answer 12

Cones are photoreceptors - they are sensitive to different wave lengths of light, allow us to see different colors

Question 13

Where are cones most concentrated in?

Answer 13

The fovea centralis.

Question 14

How do the rods and cones send sensory information to the brain?

Answer 14

Through the optic nerve.

Question 15

What attaches ciliary muscles to the lens?

Answer 15

The suspensory ligaments

Question 16

What is the anterior chamber?

Answer 16

The area that is Infront of the lens

Question 17

What is the posterior chamber?

Answer 17

The area that is behind the lens

Question 18

What is the aqueous humour?

Answer 18

Liquidy, jelly substance

Maintains the shape of the cornea

Provides oxygen and nutrients for surrounding cells

Found in anterior chamber

Question 19

What causes glaucoma?

Answer 19

When cells in the eye detoriates due to lack of oxygen and nutrients - can lead to blindness

Question 20

What is the vitreous humour?

Answer 20

Liquidy, jelly substance

Found in the posterior chamber

Helps maintain the shape of the eye ball

Supports surrounding cells

Question 21

What does the lens do?

Answer 21

They focus light onto the fovea centralis and bend light rays

Question 22

What are the two main components of the eye that make it bend?

Answer 22

The cornea and the lens.

Question 23

What is the advantage of lens’ being flexible?

Answer 23

It allows for finer focus when viewing objects.

Question 24

What happens to a lens, ciliary muscles, and suspensory ligaments when an object is far away?

Answer 24

Lens becomes flat
Ciliary muscles relax
Suspensory ligaments taut

Question 25

What happens to a lens, ciliary muscles, and suspensory ligaments when an object is nearby?

Answer 25

Lens becomes more rounded Ciliary muscles contract Suspensory ligaments relax

Question 26

What is accomadation?

Answer 26

The ability of the lens to change shape so that it can focus images clearly on the retina

Question 27

What happens when lens' age?

Answer 27

They become lex flexible They become more opaque - hard for light to pass through

Question 28

What are cataracts?

Answer 28

Grey, white spots on lens'

Question 29

What is astigmatism?

Answer 29

Uneven curvature at part of the cornea Light rays cannot bend to meet at the correct focal point

Question 30

What is 20/20 vision?

Answer 30

When people can see a size 20 letter from 20 feet

Question 31

What does it mean to be nearsighted?

Answer 31

You can see close images - you cannot see size 20 letter from 20 feet

Question 32

What is myopia?

Answer 32

Associated with nearsightedness - eye ball is elongated Focused light falls in front of the retina - instead of on photoreceptors

Question 33

What can people with myopia do to fix this?

Answer 33

They can wear concave lenses - diverges light so it falls on the retina Corrective laser surgery - ophthalmologist reshapes cornea

Question 34

What is hyperopia?

Answer 34

Associated with farsightedness - eyeball is to short Can see 20 size letter from 20 feet - cannot see close objects Light rays focus behind the retina

Question 35

How can you fix hyperopia?

Answer 35

Where convex lenses - bends light rays at a sharper angle

Question 36

When does vision begin?

Answer 36

When light is focused on the photoreceptors

Question 37

Where are rods more concentrated?

Answer 37

In the outside edges of the retina

Question 38

What is responsible for peripheral vision?

Answer 38

Rods

Question 39

Where are cones more concentrated?

Answer 39

At the fovea centralis - back and centre of retina

Question 40

Which are more sensitive to light, rods or cones?

Answer 40

Cones - require a lot of light so that the fovea centralis can produce a sharp image Rods - can be stimulated by a simple photon of light

Question 41

What are the three types of cones?

Answer 41

Red sensing cones Blue sensing cones Green sensing cones

Question 42

What causes color deficiency (colour blindness)

Answer 42

Caused by lack of deficiency in particular cones (usually red and green)

Question 43

What light absorbing pigment are rods made from?

Answer 43

rhodspin

Question 44

What does rhodspin consist of?

Answer 44

retinal, vitmain A derivative, and protein opsin

Question 45

Describe how rods work to send a neural impulse to optic nerve.

Answer 45

In dark - rods release inhibitory neurotransmitters that inhibit neighboring nerve cells When rod absorbs light - rhodspin splits into retinal and protein opsin - triggers a chain of reactions - stops the release of inhibitory neurotransmitters - Allowing the transmission of a neural impulse to the optic nerve

Question 46

What is the pigment in cones?

Answer 46

Photospin - only reacts to certain wavelengths of light

Question 47

What are the three main layers of neurons in the retina?

Answer 47

Rod and cone layer Bipolar cell layer Ganglion cell layer

Question 48

What forms the optic nerve?

Answer 48

Axons from the ganglion cells

Question 49

What Lobe does the optic nerve send visual images?

Answer 49

occipital lobe

Question 50

What is the area called where the ganglion cells merge to form the optic nerve?

Answer 50

The blind spot - no photoreceptors - incapable of detecting light

Question 51

What is the complete passage for visual information starting from retina?

Answer 51

Retina - optic nerve - thalamus - occipital lobe of cerebral cortex

Question 52

What does it mean that the visual image is split in the occipital lobe?

Answer 52

Left optic tract - carries information about the right portion of the visual field Right optic tract - carries information about the left portion of the visual field

Question 53

What does it mean that humans have front facing eyes?

Answer 53

We have binocular vision - we both eyes to collect visual information about an object

Question 54

What is the leading cause of vision loss?

Answer 54

disorders of the retina

Question 55

What is diabetic retinopathy?

Answer 55

Capillaries to retina burst - spilling blood into vitreous fluid between lens and retina (Careful regulation of blood glucose can guard this disorder)

Question 56

What happens as a result from change in consistency of the vitreous fluid?

Answer 56

Retinal detachment - Retina becomes seperated from choroid vessels that supply it with oxygen and nutrients

Question 57

What is macular degeneration?

Answer 57

Cones are destroyed due to thickened choroid vessels - cannot function like before Result is blurring or the development of a blind spot in central vision