SENSORY ORGANS AND NERVOUS SYSTEM Flashcards
(189 cards)
Structures of the eye
- conjunctiva
- sclera
- cornea
- choroid
- pupil
- iris
- lens
- retina
conjunctiva
a clear membrane that covers the outside of the front of the eyeball and the inside surface of the eyelids. It isn’t part of the eyeball itself.
extrinsic
outer
sclera
the outermost layer of the eyeball, or “the white of the eye”. It protects the eye and serves as the surface to which the extrinsic (outer) muscles attach.
Cornea
the clear area of the sclera. It allows light to pass through. It’s clear because it has no blood vessels, and it consists of five layers of flat cells. There are pain and touch receptors in the cornea.
Choroid coat
The middle layer of the eyeball. This is the vascular structure of the eye that provides blood and oxygen through blood vessels.
In humans, this coat is a dark color because of melanin.
The color causes minimal reflection of light within the eye so the clarity of sight is maintained.
Pupil
Small, circular opening in front of the choroid coat.
It appears as a black dot in the middle of the eye and lets light pass through.
Iris
Surrounds the pupil.
contains intrinsic, or inner, muscles that adjust the size of the pupil according to the amount of light in the environment.
In bright light, the muscles constrict the pupils to restrict the amount of light passing through.
In dim light, the muscles dilate the pupils to allow more light to pass through.
In stressful situations, the sympathetic nervous system causes these muscles to dilate the pupils.
Lens
The durable crystalline disc behind the iris and the pupil that focuses light on the retina.
The lens is biconvex, which means that it’s a disk with a convex surface of both sides.
The anterior surface, toward the front of the eye, has slightly less of a curve than the posterior surface, toward the back of the eye; however, these curves change with age.
biconvex
means that it’s a disk with a convex surface of both sides (it bulges out on both sides)
anterior surface
toward the front of the eye, has slightly less of a curve than the posterior surface, toward the back of the eye;
Fibrous tissue called suspensory ligaments connect the lens to the ___?
ciliary muscles
The space between the lens and the structures in front of it is called the
anterior chamber
The anterior chamber is filled with a watery fluid called the aqueous humor. You can remember this because “aqueous” means “watery”. The fluid is continuously replenished by the blood vessels behind the iris.
aqueous humor
Watery fluid that fills the anterior chamber. Continuosly replenished by the blood vessels behind the iris.
Posterior chamber
The space or cavity behind the lens.
The posterior cavity is filled with vitreous humor, a transparent, gelatinlike substance.
This structure maintains the spherical shape of the eyeball and aids in focusing light onto the retina.
Retina
The innermost layer of the eyeball, but it doesn’t extend to the front part of the eye. It detects light and transmits signals back to the brain; the optic nerve sends the signals back to the occipital lobe in the brain, which interprets them.
Rod cells
Specialized cells in the retina.
Sensitive to dim light and are used for peripheral vision.
Cone cells
Specialized cells in the retina.
Are sensitive to bright light and color.
Pale optic disc
The part of the retina around the optic nerve.
This area doesn’t contain any rod or cone cells, and without rods or cones, there’s no visual perception; thus, this area is known as the “blind spot”.
The ear is divided into three parts:
external ear or outer ear
middle ear or tympanic cavity
inner ear or labyrinth
pinna or auricle
The outer part that looks like a cup of rubbery tissue.
Collects sounds from the environment and focuses them into the auditory canal.
auditory canal
The wax-producing tunnel that curves into the temporal bone and ends at the eardrum.
Many short hairs and glands lie across the auditory canal. The glands secrete cerumen, or earwax.
The hairs and wax protect the ear by preventing dirt particles and insects from getting inside.
eardrum or tympanic membrane
The tight membrane that transmits the vibrations of sound waves from the auditory canal to the middle ear. The eardrum separates the outer ear from the middle ear.
tympanic membrane
earddrum