the eye anatomy and physiology + intro ch.17 mt

the iris in bright light and dim light

Bright light-> constrict the pupil Dim light -> dilate the pupil - thereby regulating the amount of light entering the eye

optic tract

How information from the optic nerve travels to the thalamus.

optic nerve

Cranial nerve carrying impulses from the retina to the brain (cerebral cortex).

Conjuctiva of the eye

Delicate membrane lining the eyelids and covering the eyeball - clear and almost colorless except when blood vessels are dilated

retina

Light-sensitive nerve cell layer of the eye containing photoreceptor cells (rods and cones).

anterior chamber of eye

area behind the cornea and in front of the lens and iris.' - contains aqueous humor

pupil

central opening of the eye, surrounded by the iris, through which light rays pass, it appears dark

Uvea of eye

choroid, iris, ciliary body

aqueous humor

fluid produced by the ciliary body and found in the anterior chamber. A humor (Latin humidus means moist) is any body fluid, including blood and lymph. - maintain the shape of the anterior portion of the eye and nourishes the structures in that region

accommodation

normal adjustment of the eye to focus on objects from far to near -The ciliary body adjusts the lens (rounding it) and the pupil constricts. When the eye focuses from near to far, the ciliary body flattens the lens and the pupil dilates.

The pathway of light rays

pic

iris of the eye

pigmented (colored) layer that opens and closes to allow more or less light into the eye. The central opening of the iris is the pupil. (color portion of the eye)

optic chiasm

point at which optic nerve fibers cross in the brain

fundus of the eye

posterior, inner part of the eye; visualized with an ophthalmoscope

most common color blindness

red-green color blindness

olfactory

relating to the sense of smell

left visual field (purple area)

right hemisphere -sensitive cells—rods and cones—in the right half of each retina (labeled A in the figure) are stimulated.

binocular vision

the ability to focus the two eyes in a coordinated manner in order to see one image

what can brain damage do do the eyes?

Brain damage to nerve cells in the right visual cerebral cortex (such as in a stroke) causes loss of vision in the left visual field (purple), whereas damage in the left cerebral cortex causes loss of vision in the right visual field (gold).

vitreous humor

Soft, jelly-like material behind the lens in the vitreous chamber; helps maintain the shape of the eyeball retract light too

ciliary body

Structure on each side of the lens that connects the choroid and iris. It contains ciliary muscles, which control the shape of the lens, and it secretes aqueous humor.

Cornea

Fibrous transparent layer of clear tissue that extends over the anterior portion of the eyeball (over pupil and iris)

What can stimulated receptor cells produce?

They can produce sensations in the ear and eye causing vison (flash of light) and sound (ringing in ear) -If a workable connection could be made between the sensitive receptor cells of the ear and the area in the brain associated with sight, it would be possible to "see" sounds.

fovea centralis

Tiny pit or depression in the retina that is the region of clearest vision.

The sclera of the eye

Tough, white outer coat of the eyeball. white part of the eye that may show inflammation

macula

Yellowish region on the retina lateral to and slightly below the optic disc; contains the fovea centralis, which is the area of clearest vision.

Thalamus

the brain's sensory control center, located on top of the brainstem; it directs messages to the sensory receiving areas in the cortex and transmits replies to the cerebellum and medulla

vitreous chamber

the large inner cavity of the eyeball

what occurs if macula or fovea is damaged?>

vision is reduced and central vision blindness occurs

Cones

Photoreceptor cell in the retina that transforms light energy into a nerve impulse. Cones are responsible for color and central vision. -approx 6.5 mil

Conjunctivitis

inflammation of the conjunctiva - blood vessels may dilate when the eye is infected or inflamed by allergies - dust and smoke may also cause blood vessels to dilate

hemianopsia; hemianopia

lack of vision in half the visual field

right visual field (orange color)

left half of each eye, left hemisphere -rods and cones are stimulated in the left half of each retina.

What does the choroid contain?

many blood vessels that supply nutrients to the eye

choroid

middle, vascular layer of the eye, between the retina and the sclera

rods

Photoreceptor cell of the retina essential for vision in low light and for peripheral vision. - approx 120 mil

The function of the cornea

Refracts light into the eye (to bend or to refract the rays of light so they are focused properly on the sensitive receptor cells in the posterior region of the eye) (Bending of light rays by the cornea, lens, and fluids of the eye to bring the rays into focus on the retina.)

optic disc

Region at the back of the eye where the optic nerve meets the retina. It is the blind spot of the eye because it contains only nerve fibers, no rods or cones, and is thus insensitive to light

The events that occur when stimuli as light and sound are received...

by sense organs such as eye and ear

lens

circular fashion 360 degrees - there are fine, thread-like attachments (zonules) that connect to the ciliary body and the lens, allowing the muscles in the ciliary body to adjust the shape and thickness of the lens