Nervous and Endocrine Systems Essay

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Bio 318 Lab Exam 1
The Eyes
-Facts and identify:

Rods- made of rhodospin which is a pigmented compound. Forms from a protein opsin which combines with retinal vitamin A derivative. Very light sensitive. There are a lot more rods than cones in the eye. Specialized receptors for dim light;shades of dark and light, shapes and movements. visual interpretation of their activity is in gray tones.
Cones- three types; composed of photosensitive chemical called iodopsin plus retinal. Brighter light is necessary to break it down. Cones act in color perception and fine (sharpness) images.
Anterior segment- anterior to the lens; contains a clear watery fluid called the aqueous humor; further divided into the anterior and posterior chambers.
Posterior segment- between the lens and the retina; filled with a gel-like substance, the vitreous humor. This fluid helps maintain the shape of the eyeball and holds the retina in place. The level of fluid remains constant.
Anterior chamber of anterior segment- lies between the cornea and in front of the iris; is filled with aqueous humor.
Posterior chamber of anterior segment- lies between the iris and in front of the suspensory ligaments which holds the lens in place (iris to lens). The aqueous humor flows freely and is replaced by the choroid plexus which maintains its pressure. When you have too much pressure, you get glaucoma.
Aqueous humor- contained inside of the anterior segment. Too much pressure on this can cause glaucoma.
Vitrious humor- contained inside the posterior segment. It is formed before birth and it helps keep the retina pressed firmly against the wall of the eyeball. It also helps maintain the shape of the eyball.
Cornea- a transparent, nonvascular fibrous coat found at the anterior part of the eye and continues toward the posterior at the sclera.
Sclera- a tough fibrous connective tissue covering on the outer surface which gives shape to the eyeball and protects it.
Pupil- a rounded opening through which light passes.
Iris- pigmented part of the eye. A circular-donut shaped band of smooth muscle which controls the amount of light that enters the eye. It is the most anterior part of the uvea.
Choroid layer- pigmented and vascularized. It nourishes the retina and it adsorbs light so it is not reflected back out.
Cilliary body- the anterior section of the choroid layer which connects to the iris by means of muscles. Composed mainly of ciliary muscles, which are important in controlling lens shape, and ciliary processes which secrete aqueous humor.
Retina- the innery layer of the eyeball in the posterior portion only. Its primary function is image formation. It has two parts: the pigmented layer and nervous layer
Pigmented layer- lies next to the choroid layer and extends over the ciliary bodies and iris- it is nonvisual
Nervous layer- transparent; lies over the pigmented layer and ends at the ora serrata (the end of the visual portion of the eye). It is composed of three zones of neurons necessary for image formation. It contains the rods and cones.
Suspensory ligament- a muscle that holds the lens vertical in the eye's interior.
Lens- a distinct portion of the eye that is composed of several layers of protein fibers just beind the pupil and iris. It is held in place by suspensory ligaments of the ciliary body.
Macula lutea- “yellow spot”; an area of high cone density
Fovea centralis- a minute pit about .4 mm in diameter, which contains mostly cones and is the area of greatest visual activity. Focusing for the discriminative vision occurs in the fovea centralis.
Optic nerve- the nerve of the eye
Optic disc- the area where the optic nerve leaves the eyeball; the blind spot. There are no photoreceptor cells located here.
Eye muscles- lateral rectus, medial rectus, superior rectus, inferior rectus, inferior oblique, superior oblique.
Conjuctiva- a mucous membrane that lines the internal surface of the eyelids and continues over the