Specific Sensory Systems - Special Senses – Vision

Question 1

How does Vision work?

Answer 1

• Electromagnetic radiation – visible light
• The receptors found in the eye are sensitive to only a subset of wavelengths

Question 2

What are the Three Layers of the eyes?
(outlined superficial to deep)

Answer 2

1. Sclera
2. Choroid
3. Retina

Question 3

What is the sclera?

Answer 3

white connective tissue capsule, except at the cornea (where it is clear), site of ocular muscle attachmen

Question 4

What is the Choroid?
What is included in its anterior layer?

Answer 4

darkly pigmented posterior absorbs light, anterior layer includes the iris (which has smooth muscle that determines pupil size) and the ciliary muscle + zonular fibres (suspensory ligament) which determine the shape and focusing power of the lens

Question 5

What is the Retina?

Answer 5

extension of the CNS, contains numerous neuron types including photoreceptors

Question 6

What are the 2 Two Fluid-Filled Chambers of the eye?

Answer 6

Aqueous Humor

Vitreous Humor

Question 7

What is the Aqueous Humor Fluid Filled Chamber?

Answer 7

anterior chamber filled with clear fluid, between iris and cornea

Question 8

What is the Vitreous Humor Fluid Filled Chambers?

Answer 8

posterior chamber filled with viscous fluid, between lens and retina

Question 9

EYE ANATOMY

Answer 9

Question 10

Refraction of Light

Answer 10

light bends when entering new medium

Question 11

What happens when we are looking at a distance?

Question 12

What happens when we are looking at an object close to the eye?

Question 14

What are Myopia and Hyperopia?
(Near-Far Sighted)

Answer 14

Question 15

What are Photoreceptor Cells?

4

Answer 15

• Found in the retina
• Function to transduce light stimuli into signals that can be interpreted as visual information
• Supported by several different cell types in the retina that provide metabolic support and colour enhancement
• Each photoreceptor may contain over a billion molecules of photopigments (light-sensitive)

Question 16

An individula lose their ability to contract their ciliary muscles. What impact will this have on vision?

Answer 16

If an individual loses the ability to contract their ciliary muscles, it would affect their ability to adjust the shape of the lens in their eye. This means they would have difficulty focusing on objects at different distances. Specifically:

Question 17

Photoreceptor Cells

What are Rods and Cones?

found in the back of the retina

Answer 17

Rods

• Extremely sensitive
• Respond to low levels of illumination
• Outnumber cones ~20:1

Cones

• Less sensitive
• Respond only when light is bright

Question 18

What is the Structure of Photoreceptors?

Answer 18

Outer segment: stacked layers of membranes called “discs”

• “Discs” portion responds to light
• The shape of this segment gives the photoreceptors their name

Inner segment: mitochondria and other organelles, synaptic terminal that connects to other neurons in the retina

Question 19

What are Pigment Epithelium and Choroid?

Answer 19

Question 20

On photoreceptors:

What are Photopigments?
What are Opsin and Chromophore?

Answer 20

Opsin:

• protein component of photopigments that binds to the chromophore and undergoes a conformational change when exposed to light.
• Different types of opsins are found in different photoreceptor cells
• Opsins play a crucial role in initiating the phototransduction cascade, which converts light stimuli into electrical signals in the retina.

Chromophore:

• light-absorbing molecule that is bound to the opsin protein.
• In rods, the chromophore is 11-cis-retinal, derived from vitamin A.
• When light is absorbed by the chromophore, it undergoes a structural change, triggering a series of events that ultimately lead to the generation of an electrical signal in the photoreceptor cell.

Question 21

How does Sensory Transduction in Photoreceptors cause hyperpolarization in the dark?

Answer 21

Question 22

How does Sensory Transduction in Photoreceptors cause hyperpolarization in the light?

Answer 22

Question 23

explain

Answer 23

light increase conc of enzyme that degrades

wriiten in prevoius slide

Question 24

Other cells found in retina

Answer 24

photoreceptors
ganglion cells - initaie action potential
bipolar cells -

add direction of light and neural comms

Question 25

What impact would severe Vitamin A deficiency have on Vision?

Answer 25

decrease in retinal, less hyperpolarization, blurrier vision

decrease in light sensitivity

• Chromophore in all photopigments  retinal (derivative of vitamin A)
• Part of photopigment that is light-sensitive