Visual System

Question 1

Pupil Function

Answer 1

changes the amount of light that enters the eye

Question 2

Ciliary Muscle Function

Answer 2

contractions alter the curvature of the lens

Question 3

Lens Function

Answer 3

convex lensbends light to focus it on the retina

Question 4

Fovea

Answer 4

region of sharpest vision

Question 5

Optic Disk Function

Answer 5

blind spot, no photoreceptors but where the optic nerve and blood vessels leave the eye

Question 6

Photoreceptors function

Answer 6

transduce light energy into an electrical signal
- neurons collect the electrical signals to be transmitted along the optic nerve

Question 7

Light Refraction

Answer 7

2/3’s at the cornea
1/3 at the lens

Question 8

Lens Manipulation

Answer 8

1. Relaxed ciliary muscles
   - lens is flat
   - distant objects focused
2. Contracted ciliary muscles
   - lens is rounded
   - closer objects focused

Question 9

Presbyopia

Answer 9

loss of lens accommodation due to loss of lens elasticity

Question 10

Neural Cells of the Retina

Answer 10

1. Rods/Cones
2. Bipolar Neurons
3. Ganglion sensory neurons

Question 11

Rods and Cones

Answer 11

sensory cells
- convert light energy into electrical signals
- only create graded potentials

Question 12

Bipolar Cells

Answer 12

connect rods and cones to ganglion cells
- process and integrate info
- converge signals from several photoreceptors

Question 13

Ganglion Cells

Answer 13

Transmittint Cells
- carry info along the optic nerve
- produce AP

Question 14

Fovea Receptive Field

Answer 14

• small receptive field
• each photoreceptor has its own ganglion cell

Question 15

Periphery Receptive Fields

Answer 15

• larger receptive fields
• many photoreceptors converge onto one ganglion cell

Question 16

Pigment Epithelium Function

Answer 16

• absorbs extra light and prevents reflection

Question 17

Photoreceptor Outer Segment

Answer 17

• light transduction using membrane disks

Question 18

Photoreceptor inner segments

Answer 18

• major organelles
• photopigment synthesis and ATP production

Question 19

Membrane Disks

Answer 19

• light detection
  1. rhodopsin
  2. conopsin

Question 20

Rod Function

Answer 20

• low light / night vision
• rhodopsin is the signal transducer
• light hyperpolarizes the cell

Question 21

Cones Function

Answer 21

• sharp vision and color vision
• 3 types of cones with different photopigments for a different color (red/blue/green)
• light hyperpolarizes the cell

Question 22

Rhodopsin Details

Answer 22

• Opsin is the GPCR
• Retinal is the visual pigment
• Light hits rhodopsin and turns cis-retinal into trans-retinal

Question 23

Rods Phototransduction

Answer 23

G Protein = Transducin
- activates Alpha protein which breaks down cGMP

Question 24

Rod phototransduction in darkness

Answer 24

1) cGMP is high because there is no light to initiate breakdown
2) CNG channels are open, allowing Ca/Na to enter, depolarizing the cell to -40mV
3) nt glutamate is released

Question 25

Rod phototransduction in light

Answer 25

1) Rhodopsin activated, breaks down cGMP
2) no Ca/Na entrance, cell hyperpolarizes
3) decreased glutamate release
4) adjacent bipolar/ganglion cells are excited