Special Sensory (vision)

Question 1

Which part of the eye has the highest number of cones?

Answer 1

• Fovea

- deals with color

Question 2

Which part of the eye deals with the control of light?

Answer 2

Iris

Question 3

The iris is divided into what 2 muscles?

Answer 3

• Outer radial muscle

- inner circular muscle

Question 4

How does the pupil react when bright light and low light hits it?

Answer 4

• bright light=pupil constriction

- low light=pupil dilation

Question 5

How does bright light affect the iris? Which part of the autonomic nervous system is activated?

Answer 5

• inner circular muscles contract (thickens) = pupil constriction
• activates parasympathetic nervous system

Question 6

How does low light affect the iris? Which part of the autonomic nervous system is activated?

Answer 6

• outer radial muscles contract = pupil dilation

- activates sympathetic system

Question 7

What determines the color of someones eye?

Answer 7

-pigments and other components of the iris

Question 8

Define the accommodation of vision

Answer 8

-lens ability to focus image on the retina

Question 9

How does distant vision affect how the eye is set to accommodate?

Answer 9

-cilliary muscles relax, suspensory ligaments tighten = lens thin and flat

Question 10

How does near vision affect how the eye is set to accommodate?

Answer 10

-cilliary muscles contract, suspensory ligaments relax= lens thicken and round

Question 11

Explain what Presbyopia is and why it is caused?

Answer 11

• the loss of accommodation (near or distant vision)

- lens is not flexible

Question 12

What is visual acuity?

Answer 12

-vision sharpness

Question 13

Define emmetropia

Answer 13

-normal eye ball shape

Question 14

What are the characteristics of Myopia (near sightedness)?

Answer 14

• abnormally curved cornea or eye ball longer than normal
• image falls before retina
• corrected with concave lens

Question 15

What kind of lens is needed to correct myopia (near sightedness)

Answer 15

-concave

Question 16

What are the characteristics of Hyperopia (farsightedness)?

Answer 16

• eye ball shorter than normal
• image falls after retina
• correction with convex lens

Question 17

What type of lens is needed to correct hyperopia (farsightedness)?

Answer 17

-convex lens

Question 18

What are the characteristics of an Astigmatism?

Answer 18

• asymmetry of the cornea

- corrected with uneven lenses

Question 19

How can an astigmatism be corrected?

Answer 19

-the use of an uneven lens

Question 20

What part of the eye is the light sensitive lining that contains photoreceptors?

Answer 20

-retina

Question 21

What are the types of photoreceptors of the retina? (2)

Answer 21

-rods and cones

Question 22

What makes up the rods of the retina?

Answer 22

-contain rhodopsin

Question 23

What is rhodopsin and what is it made of?

Answer 23

• photopigment that detects light

- contains opsin and retinal

Question 24

What are the cones of the retina made of?

Answer 24

-contains trichromatic rhodopsins (red, green, blue)

Question 25

Where do the photoreceptors send the light info to?

Answer 25

-bipolar cells

Question 26

The bipolar cells received light info from what source?

Answer 26

-photoreceptors

Question 27

Where do bipolar cells send their info?

Answer 27

-ganglion cells

Question 28

What are ganglion cells?

Answer 28

-axons that form the optic nerve

Question 29

What is the optic disk?

Answer 29

• the location of neurons of the visual pathway form the optic nerve (cranial nerve II) and exit the eye

Question 30

Explain the phototransduction of the eye in the dark

Answer 30

• High ICF (cGMP)
  
  • keeps cyclic nucleotide-gated channels open
• Ca+/Na+ influx
  
  • depolarization (dark current)

-Release neurotransmitter onto bilpolar cells

Question 31

Explain the phototransduction of the eye when light is present

Answer 31

• Light hits rhodopsin -> opsin will dissociate
  
  • Low ICF (cGMP)
  • cyclic nucleotide-gated channels close
• K+ efflux continues
  
  • hyperpolariztion

-Stop/decrease neurotransmitter release onto bipolar cells

Question 32

What is the step by step process of the phototransduction pathway?

Answer 32

1) photoreceptor neurotransmitter excites or inhibits bipolar cells
2) bipolar cells excite or inhibit ganglion cells
3) excited ganglion cells generate action potential
4) action potential travels along optic nerves

Question 33

After the phototransduction pathway, what is the pathway of the signal that is being transducted?

Answer 33

5) optic chiasm
6) optic tract
7) lateral geniculate nuclei (thalamus)
8) optic radiation
9) visual cortex