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anatomy week 12
Terms in this set (52)
-The sensory system protects the individual by detecting changes in the environment.
-Many stimuli arrive from the external environment and are detected at or near the surface of the body.
-Others such as the stimuli from the viscera, originate internally and help to maintain homeostasis.
The part of the nervous system that detects a stimulus is the receptor. The following are examples of receptors:
-Free dendrite of a sensory neuron, such as a receptor for pain.
-An end-organ, on the dendrite of an afferent neuron, such as for touch and temperature.
-A special cell associated with an afferent neuron, such as the rods and cones of the retina of the eye and receptors in the other special sense organs.
detect chemicals in solutions (taste and smell).
respond to light (located in the retina)
detect changes in temperature (many located in the skin)
respond to movement
Any receptor must receive a stimulus of adequate intensity in order to respond and generate a nerve impulse
is localized in a special sense organ;
is widely distributed throughout the body
Heat & cold
Pain and touch from the skin and internal organs.
Sense of position from the muscles, tendons and joints.
Thin membrane lining the inner surface of the eyelid and covers the anterior part of the eyeball up to the edge of the cornea at the center.
-Cells produce mucus that aids in lubrication.
-With age there is a thinning and drying of the conjunctiva, resulting in inflammation and enlarged blood vessels
Tears keep the conjunctiva moist.
The fluid carries away small particles that have entered the conjunctival sacs.
Tears are carried into ducts near the nasal corner of the eye where they drain into the nose by way of the nasolacrimal duct.
-Any excess = runny nose!
The outermost layer; (white of the eye)---tough connective tissue
is the second tunic.
A delicate network of connective tissue interlaced with blood vessels
This coat is pigmented dark brown.
the innermost tunic.
The actual receptor of the eye.
Contains light sensitive cells known as rods and cones, which generate the nerve impulses associated with the sense of vision.
the bending of light rays as they pass from one substance to another substance of different density.
Eg. pencil in water
Refraction allows light from a very large area to be focused on a very small area of the retina
continuation of the sclera, transparent and colorless, whereas the rest of the sclera is opaque and white. It bulges forward slightly and is the main refracting structure of the eye.
The cornea has no blood vessels.
a watery fluid that fills much of the eyeball in front of the lens.
also called the crystalline lens, is a clear, circular structure made of a firm elastic material.
Has two bulging surfaces = biconvex.
The lens is important because it is elastic and its thickness can be adjusted to focus light for near or distance vision.
is a soft jellylike substance that fills the entire space behind the lens.
Photoreceptors that work in dim light to detect light in black and white (shades of gray)
-Rods are highly sensitive to light
-Do not provide sharp images
-More in number than cones
function in bright light are sensitive to colour
Give sharp images
Located in center of retina, especially in the...
(can see) red, green and blue light
is the point of sharpest vision.
Contained within the macula lutea
: it takes time for rods to adjust when you go into a dark room
Images appear blurred and in shades of gray
Rods are unable to differentiate colours
is the lack of one or more types of cones
are found in two circular structures within the eye
: coloured part of the eye composed of two types of muscles.
The size of the pupil is governed by the action of these two sets of muscles, one of which is arranged in a circular fashion and the other of which extends in a radial manner like a wheel.
The ciliary muscle alters the shape of the lens during the process of accommodation.
Optic Nerve (cranial nerve II):
visual information from the rods, cones to brain
Retina Thalamus Occipital cortex
Brain must reverse images
Opthalmic branch of the Trigeminal Nerve
pain, temperature, touch sensations from eye and surroundings to brain
Oculomotor nerve (cranial nerve III)
Trochlear nerves (cranial nerve IV)
Abducens nerve (cranial nerve VI)
farsightedness usually results from an abnormally short eyeball
Light rays focus behind the retina
nearsightedness usually results from eyeball is too long
: is caused by irregularity in the curvature of the cornea or lens
: is the deviation of the eye that results from lack of coordination of the eyeball muscle (convergent towards nose & divergent laterally)
loss of vision in a healthy eye because it cannot work properly with the other eye
inflammation of the conjunctiva
cocci or bacilli
is an acute eye infection caused by Chlamydia Trachomatis
introduced at birth (chlamydia, gonococcus, etc.)
the retina is damaged by blood vessel hemorrhages and growth of new vessels
separates from underlying layer of the eye as a result of trauma or accumulation of fluid or tissue between layers
materials accumulates on the retina
Wet: abnormal blood vessels grow under the retina causing it to detach
Dry: material accumulates on the retina causing gradual vision loss
is an opacity (cloudiness) of the lens or the outer covering of the lens
1st loss of visual acuity (sharpness)
Untreated leads to complete blindness
is a condition characterized by excess pressure of the aqueous humor
Interference with the normal reentry of this fluid to the blood stream
includes an outer projection and a canal
The external portion of the ear consists of the pinna (or the auricle) and a canal that lead into the deeper parts of the ear.
The pinna directs sound waves into the ear.
is an air space containing three small bones.
is the most complex and contains the sensory receptors for hearing and equilibrium
external auditory canal (meatus)
extends medially for about 2.5 cm. The skin lining this tube is thin and contains ceruminous glands, producing wax (cerumen).
is at the end of the auditory canal. It is also known as the eardrum which serves as a boundary between the external auditory canal and the middle ear cavity.
three small bones located in the middle ear cavity.
-They amplify the sound waves received by the eardrum and then transmit the sounds to the fluid in the inner ear.
-The malleus is the first bone, which is attached to the eardrum whereas the head like portion is connected with the second bone, called the incus. The innermost bone shaped like a stirrup is called the stapes.
-The base of the stapes is in contact with a membrane covering the oval window of the inner ear. This membrane in turn vibrates and transmits the sound waves to the fluid of the inner ear.
connects the middle ear cavity with the pharynx.
The tube opens to allow pressure to equalize on the two sides of the tympanic membrane.
The valve that closes the tube can be forced open by swallowing hard, yawning or blowing with the nose and mouth sealed.
The mucous membrane of the pharynx is continuous through the eustachian tube into the middle ear cavity making the area more prone to infections
The Inner Ear
Three separate areas hollowed out inside the temporal bone. The skeleton of the inner ear is called the bony labyrinth. It has three divisions:
The semicircular canal
All three divisions contain a fluid called perilymph
organ of Corti
is the organ of hearing.
Consists of ciliated receptor cells located inside the membranous cochlea or cochlear duct. Here is how it works:
Sound waves enter the external auditory canal and cause the eardrum to vibrate.
Vibrations are amplified by the ossicles and transmitted by them to the perilymph of the inner ear.
Sound waves enter the upper chamber of the cochlea, travel to the top of the cochlea, and then continue through the lower chamber of cochlea.
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