CONTROL AND COORDINATIONChapter 5
Lesson 2
OBJECTIVES
List the sensory receptors in each sense organ.
Explain what type of stimulus each sense organ responds to and how.
Explain why healthy senses are needed.
SENSE ORGANS
Light rays, sound waves, heat, chemicals or pressure that comes into your personal territory will stimulate your sense organs.
Sense organs are adapted for interpreting these different stimuli.
SEEING- THE EYE
Retina- tissue at back of eye that is sensitive to light Rods-Respond to
dim light, also help one to detect shape and movement
Cones- Respond to bright light and color
Optic Nerve Carries impulses to
visual area of the cortex
THE EYE
Light enters eyes Passes through the cornea
Light is refracted
Light passes through the lensand is refracted again
Light is directed toward the retina.
Rods respond to dim lightand cones respond to brightlight and color
Light impulse passesThrough the optic nerve
Visual area of cortexIn the cerebrum
LENSES
Convex lenses are shaped so that the rays converge together(F is the focal point)
Concave lenses are shaped to spread rays apart.
NEARSIGHTEDNESS
Eyeball is too long from front to back
Light from objects is focused in front of the retina.
Image that reaches the retina is blurred.
Concave lenses are used to correct the problem.
FARSIGHTEDNESS
Eyeball is too short from front to back.
Light from objects is focused behind the retina
Convex lenses correct farsightedness.
CATARACTS Normally, the lens of the eye is clear. When a
cataract develops, the lens becomes cloudy, similar to a frosted window.
Located near the front of the eye, the lens focuses light on the retina at the back of the eye. Light passes through it to produce a sharp image on the retina. When a cataract forms, the lens can become so opaque and unclear that light cannot easily be transmitted to the retina.
Often, however, a cataract covers only a small part of the lens and if sight is not greatly impaired, there is no need to remove the cataract. If a large portion of the lens becomes cloudy, sight can be partially or completely lost until the cataract is removed.
GLAUCOMA
Glaucoma usually occurs when intraocular pressure increases. This happens when the fluid pressure in the eye's anterior chamber, the area between the cornea and the iris, rises.
GLAUCOMA
Normally, this fluid, called aqueous humor, flows out of the eye through a mesh-like channel. If this channel becomes blocked, fluid builds up, causing glaucoma. The direct cause of this blockage is unknown, but doctors do know that it is most often inherited, meaning it is passed from parents to children.
The increased pressure, called intraocular pressure, can damage the optic nerve, which transmits images to the brain. If damage to the optic nerve from high eye pressure continues, glaucoma will cause loss of vision. Without treatment,
HEARING
Sound waves are necessary for hearing sound.
Sound energy is to hearing as light energy is the seeing.
When sound waves reach the ear, they stimulate nerve cells deep within your ear.
PROCESS OF HEARING
Outer ear Intercepts sound waves and funnels themdown the canal to the middle ear.
Eardrum vibrates
Vibrations move the anvil, stirrup and hammer in the middle ear.
Vibrating stirrup causes fluids in the cochlea to vibrateHair cells in cochlea
vibrate
Electrical impulsessent to the brain by anerve
HEARING- THE EAR
BALANCE- CONTROLLED BY INNER EAR
Cristae ampullaris Contain tiny hair cells React to rotating body movements Gel-like fluid surrounding hair cells moves and
stimulates the nerve cells at the base of the hair cells.
Maculae Contain tiny hair cells React to the tipping or tilting of the head
SMELL
One smells food because it gives off molecules into the air.
These molecules stimulate sensitive nerve cells called olfactory cells in your nasal passages.
These cells are kept moist with mucus.
TASTE
Taste buds Major sensory receptors for taste.
Food Mouth begins to water Saliva and food wash overthe taste buds
Impulses sent to the brainYou identify the taste
TASTING FOOD
The five taste sensations are sweet, salty, sour, bitter, and the taste of MSG.
OTHER SENSORY RECEPTORS IN THE BODY
Your internal organs have several kinds of sensory receptors.
These receptors respond to touch, pressure, pain and temperature.
They pick up changes in touch, pressure, pain and temperature and transmit impulses to the brain and spinal cord.
Your body then responds to this new information.
Question
What are the sensory receptors for the nose and eyes?
Answer
Nose- olfactory cellsEyes- rods and cones
Question Why is it important to have sensory receptors for
pain and pressure in your internal organs?
Answer Internal sensory receptors alert the brain when
something is wrong. This allows the body to respond and protect itself and to maintain homeostasis.