Receptors are spread throughout the body
receptors are concentrated in specific location
Examples of types of somatic sences
temperature, pressure,, pain, and proprioceptors
What is a proprioceptor?
awareness of position in space
Examples of sensory sences
vision, hearing and equilibrium, gustatory, smell
Theese are the complex sensory organs
Sensory inputs with localized clusters of receptors
taste buds, olfactory epithelium of nose
What is the retina?
single region of delicate white nervous tissue
What is the lens?
not a layer of the eye wall, but is a transparent structure suspended from the ciliary body by suspensory ligaments
What does the suspensory ligaments do?
holds the lens in place.
What is the cornea?
Where light enters
There are many nerve endings here
This is transparent and contains no blood vessells, can be transplanted
What is the function of the sclera?
protects and gives shape to eye
This is the white, tough, connective tissue
What covers 5/6 of the eyeball
This is the most anterior portion of the eye
This is the hole in the center of the iris
Theese act like the diaphragm on camera
radial smooth muscles, and circular smooth muscles
The radial smooth muscles do what?
make the pupil larger
Dialation is for what kinda vision and light?
Long distance and dim light
The circular smooth muscles do what?
Make pupil smaller
Constriction is for what kinda vision and light?
close vision, and bright light
What is the cicilary body?
Smooth muscle to which the lens is attached
What is the thickest area of the vascular tunic?
the ciliary body
What is the darkly pigmented layer of the posterior eye?
Why is the choroid pigmented darkly?
So it can absorb the excess light entering eye.
What is the largest portion of vascular coat?
What is the optic disk?
blind spot where the optic nerve emerges from the eye
What is the macula lutea?
a yellow spot on the retina: lateral to the optic disk
What is the fovea centralis?
depression in center of the macula lutea containing cones
Where is the point of sharpest vision?
Caused by a lack of cones
Deficiancy in vitamin a caused by malfunction of the rods?
What are celiary glands?
modified sweat glands that are btw eyelids
Theese carry tears down toward the nasal cavity
What is the conjuctiva?
membrane on front of the eye and lining eyelid
What is the function of the conjuctiva?
lubricates with mucus and keeps eye moist.
Where is the anterior cavity?
Space between back of the cornea and front of the lens
Where is the anterior chamber?
posterior cornea to anterior iris
Where is the posterior chamber?
posterior iris to the anterior len
What is aqueous humor?
Watery fluid filling anterio cavity which mantains presure, nourishes, and refracts light
What produces the aqueous humor?
The epithelial cells of the cilliary body
Describe the pathway of the aqueous humor
ciliary body, to the posterior chamber, then the pupil, then the anterior chamber,, the the scleral venous sinus aka canal of schlemm
What is the canal of schlemm?
Permealble blood vessel at junction of cornea and sclera that reabsorbs aqueous humore
Where is the posterior cavity?
Between the posterior lens and the retina
What keeps the eyeball from collapsing?
What is the function of the vitous humor?
Holds the fragile retina in place
this humor helps maintain intraocular pressure
What is the function of the rods, and what do they contain?
outline black and white vision at night, and provide peripheral vision
What is the function of the cones?
they are for sharp color vision
describe the pathway of light
cornea>aqueous humor of the anterior chamber>pupil>aqueous humor of the posterior chamber>lens>victreous humor>retina>optic disk>optic neve>cerebrum
What is refraction?
when light rays bend as they pass from one transparent substance to another with varrying density
Theese have constant light bending power
cornea and aqueous humor
How does the lens refract light?
by varrying and making itself less or more convex greater convexity the more the light bends, the flatter the lens, the less the lens bends
What do convex transparent structures do to light?
bend rays together
What do concave transparent structures do?
spread rays apart
This contracts the lens to become more or less convex
What are the convex structures within the eye that converge light?
the cornea and lens
What is the real image?
image found on the retina as a result of the bending activity of the lens
What happens if the eyeball is to short?
light rays converge behind the retina and results in far sightedness
What happens if the eyeball is too long?
light rays converge in front of the retina and results in near sightedness
what is distance vision?
when the object is 20 feet or more from the eye
What should happen in distance vision?
light rays will be parrallel lines to the eye, there is less refraction to focus on retina
What is close vision?
less than 20 feet from object to the eye
What should happen in close vision?
light rays will spread apart as they enter the eye, more refraction is needed to focus on retina
What does the ciliary body muscle do during each type of vision?
distance it relaxes, close it contracts
What happens to the suspensory ligaments during each type of vision?
distance they are taut, close they are relaxed
What happens to the lins during each type of vision?
distance the lens is less convex, and close the lens is more convex
Define photopupillary reflex
eyes are exposed to brith light and the pupil constrict.