Sense Organs High!!Yoooo-eeeee ???

drrrr – rrrr - rrrr

Alan Stevens

Ear Structure and functions of the different parts of the human ear

Functioning of the human ear in:

• Hearing (include the role of the organ of Corti without mention of its structure)• Balance

Adaptations of the various parts of the ear for their functions

Cause and treatment of the following hearing defects:

• Middle ear infections (treatment using grommets)• Deafness (treatment using hearing aids and cochlear implants)

The link between hearing defects and speech disorders

The use of sign language by deaf people

INVESTIGATIONS Model of the ear

ADDITIONAL

Attitudes towards blind and deaf people The rights of blind and deaf peopleAlan Stevens

Some Tips

• MODELS & APPARATUS even from the physical sciences, ARE CRUCIAL !

• The arrows in the previous slide show how various aspects from the Exam Guideline can be linked to save time

• Note the areas in red (previous slide). They are possible LO3 options

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StructureMODELS ARE CRUCIAL ! ! !

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Hearing Pinna

•“catches" the sound waves •helps you determine the direction of a sound

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The Eardrum (tympanic membrane)

• The eardrum is rigid, and very sensitive. Even the slightest air-pressure fluctuations (or sound) will move it back and forth.

• Separates outer ear from middle ear

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Ossicles Amplifies Sound

•The malleus, (hammer ): Picks up vibrations from eardrum ; is longer than the incus, moves a greater distance, transferring a greater force to the incus (energy = force x distance). •The incus (anvil): •The stapes (stirrup): The main amplification due to size difference between eardrum and stirrup. The eardrum surface area = 55 square millimeters, surface area of stapes faceplate =3.2 mm2. Sound energy from larger to smaller surface area, increases the pressure

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Fluid Wave in the Cochlea

• Stapes “pistons” sound waves

through oval window to fluid of cochlea

• Hair cells in cochlea (part of organ of Corti) convert mechanical vibrations into chemical impulse

• Impulse transported by cochlear nerves to brain

• High sounds (high frequency) let hair cells at beginning of cochlea vibrate,

• Lowest sounds (low frequency) at end of cochlea

• Round window vibrates ALTERNATELY with oval window to dissipate excess vibrations

Know: Stapes, Oval Window, Round Window, Organ of Corti, Hair cells

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Decibel scale (dB)The smallest audible sound (near total silence) is 0 dB. A

sound 10 times more powerful is 10 dB. A sound 100 times more powerful than near total silence is 20 dB. A sound 1,000 times more powerful than near total silence is 30 dB. Here are some common sounds :

• Near total silence - 0 dB • A whisper - 15 dB • Normal conversation - 60 dB • A lawnmower - 90 dB • A car horn - 110 dB • A rock concert or a jet engine - 120 dB • A gunshot or firecracker - 140 dB

Any sound above 85 dB can cause hearing lossAlan Stevens

Balance

Utricle + Saccule=

Utricle & Sacculus: Hair cells detect position of head

Semicircular canals: Hair cells detect movement of head & body

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Glue Ear and Grommets

• The lining of the middle ear 'sweats' fluid all the time and this fluid usually empties out automatically when our ears "pop", for example when we swallow or yawn.

• When a middle ear infection or a head cold occurs this fluid may not be able to empty out as it normally would (especially in children).

• The fluid is thin at first, but if the middle ear stays inflamed the fluid can't get out and air also can't get in, this fluid may become thick, like glue.

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Grommets are very small ventilation tubes

made of plastic that are about 2mm in width. The grommet sits in the eardrum with one flange sitting on the inside and one on the outside of the eardrum.

They have a small hole in the centre which allows fresh air to enter the middle ear to keep it free of fluid.

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Hearing Disorders and Deafness

Causes:• Heredity • Diseases such as ear infections and meningitis • Trauma • Certain medicines • Long-term exposure to loud noise • Ageing

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Two main types of hearing loss:• Damaged to your inner ear or auditory nerve.

This type is permanent.• The other kind happens when sound waves

cannot reach your inner ear. Earwax build-up, fluid or a punctured eardrum can cause it.

Possible treatments include hearing aids, cochlear implants, special training, certain medicines and surgery.

Alan Stevens

Hearing Aids

• A hearing aid is a small electronic device that you wear in or behind your ear. It magnifies sound vibrations entering the ear. That makes some sounds louder. A hearing aid can help people hear more in both quiet and noisy situations.

• Hearing aids help people who have hearing loss from damage to the small sensory cells in the inner ear. The damage can occur as a result of disease, aging, or injury from noise or certain medicines.

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Cochlear Implants

For people who are profoundly deaf or severely hard-of-hearing can get help from them. The implant consists of two parts.

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Parts of Cochlear Implant

External:• one or more microphones to pick up sound from the

environment• a speech processor sends electrical sound signals to

a transmitter,• a transmitter, behind the external ear, transmits

power and the processed sound signals to the internal device by electromagnetic induction,

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Internal:• A receiver and stimulator secured in bone beneath

the skin, converts the signals into electric impulses and sends them through an internal cable to electrodes,

• an array of up to 24 electrodes wound through the cochlea, sends impulses to the nerves in the cochlea and then directly to the brain through the auditory nerve system.

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Sign language

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• The elements of a sign are Handshape (or

Handform), Orientation (or Palm Orientation), Location (or Place of Articulation), Movement, and Non-manual markers (or Facial Expression), summarised in the acronym HOLME.

• The recipient of a signed message can read meanings carried by the hands, the facial expression and the body posture in the same moment.

Alan Stevens