Module 3: Nervous System - Vision and the Eye

Question 1

What is a special sense and what are the 5 special senses? (2)

Answer 1

1) Specialized sensory organs with specialized receptor cells
a) Carry information via specialized somatic and visceral afferents

2) Vision, taste, smell, hearing, equilibrium

Question 2

Is Touch a special sense? (2)

Answer 2

1) No - touch is a somatic sense

2) Uses general receptors with modified dendrites of sensory neurons

Question 3

Eye Anatomy - Outer Layer - Sclera (2)

Answer 3

1) Posterior portion

2) “White of the eye”

Question 4

Eye Anatomy - Outer Layer - Cornea (3)

Answer 4

1) Anterior portion

2) Transparent part of the eye

3) Light enters

Question 5

Eye Anatomy - Outer Layer- Aqueous humor

Answer 5

Fills the space between the cornea and lens

Question 6

Eye Anatomy - Middle Layer - Choroid (4)

Answer 6

1) Darkly colored, posterior portion

2) Prevents light from dispersing throughout the eye

3) Highly vascular

4) Supplies blood to the layers of the eye

Question 7

Eye Anatomy - Middle Layer - Ciliary Body (2)

Answer 7

1) Anterior

2) Muscle attaches to lens to change shape of the lens, allow focus

Question 8

Eye Anatomy - Middle Layer - Iris (2)

Answer 8

1) Controls the amount of light that enters the pupil

2) Uses muscle fibers to conract or dilate based on environmental light

Question 9

Eye Anatomy - Middle Layer - Pupil

Answer 9

Hole in the center of the iris

Question 10

Eye Anatomy - Middle Layer - Lens (2)

Answer 10

1) Posterior to the iris and pupil

2) Circular ciliary muscle attaches all the way around the lens

Question 11

Eye Anatomy - Inner (Sensory) Layer - Retina (3)

Answer 11

1) Contains photoreceptors
a) Rods: Sensitive to dim light, do not generate sharp or color images
b) Cones: Operate in bright light, help detect color images

Question 12

Eye Anatomy - Interior of the Eye - Vitreous Body (2)

Answer 12

1) Posterior to the lens

2) Chamber filled with vitreous fluid, helps to hold the retina firmly to the choroid

Question 13

Vision Pathway - Cornea to Brain (6)

Answer 13

1) Cornea

2) Aqueuous Humor

3) Lens

4) Vitreous Humor

5) Posterior surface of the retina

6) Photoreceptors detect light

Question 14

Vision Pathway - Retina to Brain (7)

Answer 14

1) Optic Nerve

2) Optic Chiasm

3) Optic Tracts

4) LGN (Lateral geniculate nucleus) of the thalamus

5) Optic radiations - nerve fibers

6) Occipital Lobe

7) Interpreted as vision

Question 15

Visual fields - Nasal and Peripheral (2)

Answer 15

1) Nasal visual fields
a) Left and right eyes
b) Closest to the nose
c) Overlapping visual fields allow for 3D vision (Binocular)

2) Peripheral visual fields
a) Lateral side of each eye

Question 16

Visual fields - Left and Right (2)

Answer 16

1) Left Visual Fields (left of left eye and left of right eye)
a) Gathers information from left side of environment
b) Eventually interpreted in right side of brain

2) Right Visual Fields (right of left eye and right of right eye)
a) Gathers information from right side of the environment
b) Eventually interpreted in the left side of the brain

Question 17

Steps of left visual field

Answer 17

1) Left of the left eye sees through right portion of left retina (opposite side)
2) Left of the right eye sees through right portion of right retina (opposite side)
3) Information is sent through optic nerves
4) Because information is from LEFT visual field, it is all redirected at optic chiasm to the RIGHT side of the occipital lobe through the right optic tracts and LGN
5) Only medial fibers cross at optic chiasm

Question 18

Example - Right occipital lobe injury

Answer 18

1) Bilateral left visual field cut (from both left and right eyes)

Question 19

Example - Right optic nerve injury

Answer 19

1) Both visual fields of right eye will be blind because nothing will be perceived from left or right visual fields of eye

Question 20

Vision pathway picture (memorize)

Answer 20

Question 21

Medial Rectus (2)

Answer 21

1) Turns eye medially

2) Innervated by oculomotor nerve (CN III)

Question 22

Inferior Rectus (2)

Answer 22

1) Depresses eye, moves eye medially

2) Innervated by oculomotor nerve (CN III)

Question 23

Superior Rectus (2)

Answer 23

1) Elevates eye, moves eye medially

2) Innervated by oculomotor nerve (CN III)

Question 24

Inferior Oblique (3)

Answer 24

1) Elevates eye, moves eye laterally

2) External rotation

3) Innervated by oculomotor nerve (CN III)

Question 25

Superior oblique (3)

Answer 25

1) Internal rotation

2) Depresses eye, moves eye laterally

3) Innervated by trochlear nerve (CN IV)

Question 26

Lateral Rectus (2)

Answer 26

1) Turns eye laterally

2) Innervated by abducens nerve
a) CN VI

Question 27

LR6 - SO4 - RIII mneumonic

Answer 27

Lateral Rectus - CN VI
Superior Oblique - CN IV
Rest - CN III

Question 28

Graphic of eye muscles (memorize)

Answer 28

Question 29

Cataracts (2)

Answer 29

1) Lenses slowly become hardened and cloudy over time

2) Vision looks blurry, light is unable to freely enter lens to be refracted onto retina

Question 30

Cranial Nerve Damage - Example Abducens Nerve

Answer 30

1) Diplopia: Double Vision

2) Patient test: Look left and right with head still
a) Eye will be unable to rotate laterally
b) Affected eye deviates medially when looking forward (from lack of steady state muscle tone on lateral rectus)