Senses- Ears Hearing and balance are the main functions of

hearing. Hearing works with the other 4 senses to aid us in obtaining information and keeping our

bodies upright.

I. Functions of the Ear

• Hearing • Balance

II. Parts of the Ear

• 1. Outer Ear– Pinna- fleshy curved part that is attached to each

side of the head. It collects sound waves and directs them into the ear.

– External Auditory Canal- a passageway about 1in. Long. Is lined with fine hairs and wax producing glands.

– Tympanic Membrane (eardrum)- a thin sheet of tissue about ¼ inch across. Separates the outer ear from the middle ear

Parts of the Ear

• 2. Middle Ear - Ossicles- 3 small bones that are linked together and connect from the eardrum to the inner ear.

1. Malleus- Hammer bone is the first and largest of the 3 ossicles.

2. Incus- Anvil bone is the middle bone3. Stapes- Stirrup bone is the last and

smallest of the 3 ossicles. Also, connects the middle ear to the inner ear.

Parts of the Ear

• 2. Middle Ear cont.Mastoid process- small air-filled

spaces in the bones that lie behind the middle ear.

Eustachian Tube- 1.5 inch long tube that connects the ear to the throat. Equalizes pressure on either side of the

ear.

Parts of the Ear

• 3. Inner EarOval Window- where stapes

connects to the vestibule.

Vestibule- (snail head) tiny baglike structures

lined with hairs (balance).Semicircular Canals- 3 canals set

at right angles to one another that control your balance.

Inner Ear Continued

Cochlea- (snail shell) 3 fluid filled tubes that contain thousands of tiny hair cells. Organ of Corti located inside.

Auditory Nerve- nerves attached to hairs in cochlea that convert sound waves to brain for processing.

Round Window- expands as oval window is pushed in from vibrations.

The Hearing Process

• Vibrations in the air cause sound waves• Sound waves are collected by the pinna• Continue through external auditory canal• Eardrum vibrates • Malleus, Incus, Stapes vibrate• Oval window moves in and out with the vibrations• Vibrations travel into cochlea where hairs are stimulated• Hairs trigger nerve impulses to auditory nerve• Auditory nerve send impulses to brain for processing

Balance

• Semicircular canals are responsible for balance• Fluid in the crista of the semicircular canals

move hairs when body is moved• When body moves, hairs bend and send

impulses to brain.• Brain sends impulses to muscles to

compensate for movement

Prolonged exposure to loud noise can lead to hearing loss!!!!

• The longer you are exposed to these loud sounds, the tiny hairs are damaged permanently!!!!!

• They do not grow back if they are damaged!!!!• Sounds above 80db are considered potentially

hazardous

Sound is measured by decibels.Here are some examples of different sounds.

• Sounds dB SPL• Rocket Launching 180• Jet Engine 140• Thunderclap, Air Raid Siren 1 Meter 130• Jet takeoff (200 ft) 120• Rock Concert, Discotheque 110• Firecrackers, Subway Train 100• Heavy Truck (15 Meter), City Traffic 90• Alarm Clock (1 Meter), Hair Dryer 80• Noisy Restaurant, Business Office 70• Air Conditioning Unit, Conversational Speech 60• Light Traffic (50 Meter), Average Home 50• Living Room, Quiet Office 40• Library, Soft Whisper (5 Meter) 30• Broadcasting Studio, Rustling Leaves 20• Hearing Threshold 0

What else does loud noise affect?• Noise not only affects hearing. It affects other parts of the body and

body systems.• It is now known that noise:• Increases blood pressure• Has negative cardiovascular effects such as changing the way the heart

beats• Increases breathing rate• Disturbs digestion• Can cause an upset stomach or ulcer• Can negatively impact a developing fetus, perhaps contributing to

premature birth• Makes it difficult to sleep, even after the noise stops• Intensifies the effects of factors like drugs, alcohol, aging

Protect Yourself from Noise

• Limit your exposure• Pump down the volume!• Educate yourself and others• Have your hearing tested regularly• Wear ear protection