Eye (Ch. 19) Flashcards
Vision
Dominant sense in humans: 70% of sensory receptors are in eyes, 40% of cerebral cortex devoted to processing visual info.
What are the 4 cranial nerves that are associated with vision?
Optic (CN 2)
Oculomotor (CN 3)
Trochlear (CN 4)
Abducens (CN 6)
List the structures of the eye
Lateral angle (outer corner of eye) Inferior palpebrum (eyelid) Lacrimal Caruncle Medial Angle (inner eye corner) Eyelashes Superior Palpebrum (eyelid)
What is the palpebrum?
The eyelid
What do the eyelids do?
Protect the eyes
What separates the upper and lower lids? Where do they meet?
Palpebral fissure separate upper and lower lids
Pangles are where they meet
What is the Conjunctiva?
Mucus membrane covering inner eyelids and sclera (NOT THE CORNEA!)
Lacrimal Apparatus
Lacrimal glands supply eyes with lacrimal fluid (tears)
Lacrimal fluid has immune fxns (mucus, antibodies, enzymes)
Drains into lacrimal sac and then nasolacrimal duct and nasal cavity = runny nose when crying
List the 6 extrinsic eye muscles.
Lateral rectus Medial rectus Superior rectus Inferior rectus Superior oblique Inferior oblique
What cranial nerve innervates the lateral rectus?
Abducens (CN 6)
What cranial nerve innervates the superior oblique?
Trochlear (CN 4)
What cranial nerve innervates the medial rectus, superior rectus, inferior rectus, and inferior oblique?
Oculomotor (CN 3)
Fxn of lateral rectus?
Abduct eye
Fxn of medial rectus?
Adduct eye
Fxn of superior rectus?
Elevate and adducts eye
Fxn of inferior rectus?
Depresses and adducts eye
Fxn of inferior oblique?
Elevates and abducts eye
Fxn of superior oblique?
Depresses and adducts eye
Eye Structure: Fibrous Layer
Most external
Includes Sclera and Cornea
Fibrous Layer: Sclera
Tough, outer covering of eye (white of eye). Protects eyeball
Fibrous Layer: Cornea
Continuation of sclera, transparent, allows right into eye, acts as fixed lens for focusing
*Cornea is avascular but lots of nerve endings
Eye Structure: Vascular Layer
Middle layer
Includes Choroid, Ciliary body/muscles, Iris, and Pupil
Vascular Layer: Choroid
heavily pigmented vascular layer. Melanin helps absorb light
Vascular Layer: Ciliary body/muscles
encircle lends, control lens shape for precise focusing
Vascular Layer: Iris
Colored part of eye, regulates light entering eye
Vascular Layer: Pupil
A space, not a structure! Allows light to enter eye.
Pupil contracts in bright light (parasympathetic innervation)
Pupil dilates in low light (sympathetic innervation)
Eye Structure: Inner Layer
Retina: converts light to nerve impulses Optic Nerve (CN 2): transmits nerve impulses to brain
Retina
Innermost layer of eyeball, photosensitive (sensitive to light)
2 layer:
- -pigmented layer = melanocytes. Absorb light and keep it from scattering
- -neural layer - nervous tissue w/ photoreceptive cells
Photoreceptor Cells
Rods: work best in dim light
Cones: perceive red, blue, green. Cones great for color vision, bright light.
Absorption spectra overlap, so combination of stipulations of cones - different colors
Retina: Macula Lutea, Fovea Centralis, and Optic Disc
Macula Lutea: area of concentrated cone cells at posterior pole
Fovea Centralis: area of only cone cells inc enter of macula lute. Highest visual acuity
Optic Disc: blind spot, location where optic nerve attaches. No photoreceptor cells
What is the blind spot in the eye?
Optic Disc
Lens
avascular, transparent disk, shape can be changed to adjust focus
Anterior Chamber
in front of lens
has aqueous humor
Posterior Chamber
behind lens. Has vitreous humor (jellylike). Most volume of eye
Vitreous and Aqueous humor help maintain ___ ___?
Vitreous and Aqueous humor help maintain intra-ocular pressure
Incoming Images
Since lens of eye is convex, images are upside down and reversed.
Cerebral cortex flips image back to “normal” so we can see properly
