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Sense of Sight
A. __ organs, namely the __, __, and __, aid the __ in its function.
- lacrimal aparatus
- extrinsic muscles
Visual Accessory Organs
1) What does teh eyelid do?
2) The __ produces __ that __ and __ the eye.
2a) Two small __ drain tears into the __.
2b) Tears also contain an __ enzyme called __.
3) The __ of the eye attach to the __ and move the eye in all directions.
- 1) protects the eye from foreign objects and is made up of the thinnest skin of the body lined with conjunctiva
- 2) lacrimal apparatus/ tears/ lubricate/ cleanse
- 2a) ducts/ nasal cavity
- 2b) antibacterial/ lysozyme
- 3) extrinsic muscles/ sclera
C. Structure of the Eye
1) The eye is a __-filled __ sphere with __ distinct layers, or __.
The Outer Tunic
a) The outer (__) tunic is the __ at the front of the eye, and the __ of the anterior eye.
b) The __ and __ pierce the __ at the __ of the eye.
- a) fibrous/ transparent cornea/ white sclera
- b) optic nerve/ blood vessels/ sclera/ posterior
The Middle Tunic
a) The middle, __ tunic includes the __, __, and __.
b) The __ is highly __ and __ pigmented and performs two functions: __(2)__
c) The __ forms a ring around the front of the eye and contains __ and __ that hold the __ in position and change its shape (__).
- a) vascular/ choroid coat/ ciliary body/ iris
- b) choroid coat/ vascular/ darkly/ (1) to nourish other tissues of the eye and (2) to keep the inside of the eye dark
- c) ciliary body/ ciliary muscles/ suspensory ligaments/ lens/ focus
The Outer Tunic cont.
d) The ability of the lens to adjust shape to facilitate focusing is called __.
e) The __ is a thin, smooth muscle __ that adjusts the amount of light entering the __.
f) The __ (between the __ and __) and the __ (between the __ and __ and __) make up the __, which is filled with __.
g) The __ circulates from one chamber to the other through the __.
- d) accommodation
- e) iris/ diaphragm/ pupil
- f) anterior chamber/ cornea and iris/ posterior chamber/ iris and vitreous body adn housing the lens/ anterior cavity/ aqueous humor
- g) aqueous humor/ pupil
The Inner Tunic
a) The inner tunic consists of the __, which contains __; the inner tunic does what?
b) In the center of the __ is the __ in its center, the point of sharpest vision in the retina.
c) Medial to the __ is the __, where nerve fibers leave the eye and where there is a __.
d) The large __ of the eye is filled with __.
- a) retina/ photoreceptors/ covers the back side of the eye
- b) retina/ fovea centralis
- c) fovea centralis/ optic disk/ blind spot
- d) posterior cavity/ vitreous humor
D. Light Refraction
1) __ must bend to be focused, a phenomenon called __.
2) Both the __ and __ bend __ that are focused on the __.
- 1) Light waves/ refraction
- 2) cornea/ lens/ light waves/ retina
E. Visual Receptors
1) Two kinds of modified neurons comprise the __: __ and __.
2) __ are more sensitive to light and function in __; they produce __ vision.
3) __ provide sharp images in __ and enable us to see in __.
3a) To see something in detail, a person moves the eyes so the image falls on the __, which contains the highest concentration of __.
- 1) visual receptors; elongated rods/ blunt-shaped cones
- 2) Rods/ dim light/ colorless
- 3) Cones/ bright light/ color
- 3a) fovea centralis/ cones
F. Visual Pigments
1) The light-sensitive pigment in rods is __, which breaks down into a protein, __, and __ (from __) in the presence of __.
1a) __ of __ activates an enzyme that initiates changes in the __, generating a nerve impulse.
1b) Nerve impulses travel away from the __ and are interpreted as __.
2) The light- sensitive pigments in cones are __; there are __ sets of cones, each containing a different visual pigment.
2a) The __ of light determines the __ perceived from it; each of the __ pigments is sensitive to different __ of light.
2b) The __ perceived depends upon which sets of cones the light stimulates: if all three sets are stimulated, the color is __; if none are stimulated, the color is __.
- 1) rhodopsin/ opsin/ retinal/ vitamin A/ light
- 1a) decomposition/ rhodopsin/ rod cell membrane
- 1b) retina/ vision
- 2) isodopsins/ three
- 2a) wavelength/ color/ three/ wavelengths
- 2b) color/ white/ black
G. Visual Nerve Pathways
1) The __ leave the eyes to form the __.
2) Fibers from the __ half of the __ cross over in the __.
3) Impulses are transmitted to the __ and then to the __ of the __ lobe.
- 1) axons/ optic nerves
- 2) medial/ retina/ optic chiasma
- 3) thalamus/ visual cortex/ occipital