Module 3: Nervous System - Vision and the Eye Flashcards
What is a special sense and what are the 5 special senses? (2)
1) Specialized sensory organs with specialized receptor cells
a) Carry information via specialized somatic and visceral afferents
2) Vision, taste, smell, hearing, equilibrium
Is Touch a special sense? (2)
1) No - touch is a somatic sense
2) Uses general receptors with modified dendrites of sensory neurons
Eye Anatomy - Outer Layer - Sclera (2)
1) Posterior portion
2) “White of the eye”
Eye Anatomy - Outer Layer - Cornea (3)
1) Anterior portion
2) Transparent part of the eye
3) Light enters
Eye Anatomy - Outer Layer- Aqueous humor
Fills the space between the cornea and lens
Eye Anatomy - Middle Layer - Choroid (4)
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
Eye Anatomy - Middle Layer - Ciliary Body (2)
1) Anterior
2) Muscle attaches to lens to change shape of the lens, allow focus
Eye Anatomy - Middle Layer - Iris (2)
1) Controls the amount of light that enters the pupil
2) Uses muscle fibers to conract or dilate based on environmental light
Eye Anatomy - Middle Layer - Pupil
Hole in the center of the iris
Eye Anatomy - Middle Layer - Lens (2)
1) Posterior to the iris and pupil
2) Circular ciliary muscle attaches all the way around the lens
Eye Anatomy - Inner (Sensory) Layer - Retina (3)
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
Eye Anatomy - Interior of the Eye - Vitreous Body (2)
1) Posterior to the lens
2) Chamber filled with vitreous fluid, helps to hold the retina firmly to the choroid
Vision Pathway - Cornea to Brain (6)
1) Cornea
2) Aqueuous Humor
3) Lens
4) Vitreous Humor
5) Posterior surface of the retina
6) Photoreceptors detect light
Vision Pathway - Retina to Brain (7)
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
Visual fields - Nasal and Peripheral (2)
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
Visual fields - Left and Right (2)
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
Steps of left visual field
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
Example - Right occipital lobe injury
1) Bilateral left visual field cut (from both left and right eyes)
Example - Right optic nerve injury
1) Both visual fields of right eye will be blind because nothing will be perceived from left or right visual fields of eye
Vision pathway picture (memorize)
Medial Rectus (2)
1) Turns eye medially
2) Innervated by oculomotor nerve (CN III)
Inferior Rectus (2)
1) Depresses eye, moves eye medially
2) Innervated by oculomotor nerve (CN III)
Superior Rectus (2)
1) Elevates eye, moves eye medially
2) Innervated by oculomotor nerve (CN III)
Inferior Oblique (3)
1) Elevates eye, moves eye laterally
2) External rotation
3) Innervated by oculomotor nerve (CN III)
Superior oblique (3)
1) Internal rotation
2) Depresses eye, moves eye laterally
3) Innervated by trochlear nerve (CN IV)
Lateral Rectus (2)
1) Turns eye laterally
2) Innervated by abducens nerve
a) CN VI
LR6 - SO4 - RIII mneumonic
Lateral Rectus - CN VI
Superior Oblique - CN IV
Rest - CN III
Graphic of eye muscles (memorize)
Cataracts (2)
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
Cranial Nerve Damage - Example Abducens Nerve
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)
