3 Veterinary Term: Eyes and Ears (not done) Flashcards
(126 cards)
What are sense organs?
are receptors whose sensitive cells may be activated by a particular form of energy or stimulus in the external or internal environment.
The eye and the ear are what type of organs?
Sense organs
The sensitive cells in the eye and ear respond to a stimulus by?
initiating a series of nerve impulses along sensory nerve fibers that lead to the brain.
No matter what stimulus affects a particular receptor, the sensation felt is determined by what?
regions in the brain connected to that receptor.
mechanical injury that stimulates receptor cells in the eye and ear produces what?
sensations of vision (flashes of light) and sound (ringing in the ears).
If one could make a nerve connection between the sensitive receptor cells of the ear and the area in the brain associated with sight it would be possible to what?
perceive, or “see,” sounds.
What is the Pupil?
the dark opening of the eye where light rays enter
What is the iris?
the colored portion of the eye surrounding the pupil
What is the conjunctiva?
membrane lining the inner surfaces of the eyelids and anterior portion of the eyeball over the white of the eye.
The conjunctiva is clear and colorless except when blood vessels are dilated.
Dust and smoke may cause the blood vessels in the eye (conjunctiva) to do what?
dilate, giving the conjunctiva a reddish appearance—commonly known as bloodshot eyes.
What is the Cornea?
is a fibrous, transparent tissue that extends like a dome over the pupil and colored portion of the eye.
Light passes through cornea before passing through pupil when entering the eye.
What is the function of the Cornea?
is to bend, or refract the rays of light, so they are focused properly on the sensitive receptor cells in the posterior region of the eye.
What is avascular?
Having no blood vessels
A normal, healthy cornea is what?
avascular (has no blood vessels) but receives nourishment from blood vessels near its junction with the opaque white of the eye, the sclera.
What is the Sclera?
the opaque white of the eye.
is a tough, fibrous, supportive connective tissue that extends from the cornea on the anterior surface of the eyeball to the optic nerve in the back of the eye.
What is the choroid?
is a dark brown membrane inside the sclera.
It contains many blood vessels that supply nutrients to the eye.
The choroid is continuous with what other parts of the eye?
is continuous with the pigment‐containing iris and the ciliary body on the anterior surface of the eye.
Describe the Iris in relation to the Pupil
The iris is the colored portion of the eye, which has as a circular opening in the center that forms the pupil.
How is the amount of light entering the eye regulated?
Muscles of the iris constrict the pupil in bright light and dilate the pupil in dim light.
The ciliary body surrounds what?
surrounds the outside of the lens in a circular fashion for 360 degrees.
What are zonules?
are fine thread‐like attachments, which connect the ciliary body and the lens and allow the muscles in the ciliary body to adjust the shape and thickness of the lens.
The changes in the shape of the lens of the eye cause what?
refraction of light rays.
What is Refraction?
is the bending of rays as they pass through the cornea, lens and other tissues.
Muscles of the ciliary body produce?
produce flattening of the lens (for distant vision) and thickening and rounding (for close vision) (This refractory adjustment for close vision is accommodation.)