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.