How Does Your Ear “Catch” Sound Waves? Your Ear Does Three Basic Things: Channels the sound waves into your ear (the job of the pinna) Vibrates due to the sound waves (the job of the ear drum and the bones of the inner ear) Translates the vibration into an electric signal that your brain recognises as sound (the job of the cochlea)

The Ear (hearing) To Receive sound To Help us maintain our balance The ear is a complex organ that has 3 functions: To Receive sound To Help us maintain our balance To Detect the body’s spatial movement *

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The ear is divided into 3 sections: The external ear The middle ear Inner ear

The outer ear The outer ear is composed of 2 parts: The pinna (outer ear) The auditory canal

The Pinna – Channels the Sound Waves Into Your Ear The pinna is the outside part of the ear It acts as a funnel that captures the sound It also helps you to determine where a sound is coming from

The auditory canal the auditory canal brings the sound to the middle ear It protects the ear drum and internal ear from insects, bacteria and dust The canal has hairs and secretes a wax that capture the foreign particles *

The Middle Ear The ear drum The ossicles The Eustachian tube Composed of : The ear drum The ossicles The Eustachian tube

2. The Eardrum – Very sensitive membrane that vibrates When It is Hit By a Sound Wave Sound waves travel down the ear canal and hit the tympanic membrane or ear drum (a cone-shaped piece of skin) The ear drum vibrates when this happens Eardrum seals the middle ear from the outside world.

The Ear Drum Is Connected to 3 Bones of the Inner Ear There are three tiny bones inside your inner ear that vibrate whenever the ear drum vibrates They “amplify” the vibrations (make the vibrations stronger)

The Ossicles (smallest bones in the body) The first bone is called the “hammer” The second is the “anvil” The third is the “stirrup” The bones transmit the sound vibrations of the ear drum to the inner ear *

The Eustachian tube This tube is about 4cm long that leads from the middle ear to the pharynx The tube is normally closed when one swallows or yawns Its purpose is to equalize the pressure on each side of the ear drum * Eustachian tube

The Inner Ear The inner has three parts The vestibule The semicircular canals The cochlea Semi-circular canals vestibule stirrup anvil hammer cochlea

The Vestibule The vestibule is located at the entrance to the cochlea It contains nerve cells that are sensitive to body movements and the earth’s gravitational force Info from the vestibule is processed in the cerebellum (balance and posture) *

Semi circular canals 3 rings filled with cochlear fluid oriented in different planes that allow us to orient ourselves in space *

When the head moves the liquid in the canals moves and this is sensed by the sensor cells and info is sent to and computed by the brain *

Cochlea- Changing a Vibration into an Electric Signal The main hearing organ (shaped like a snail shell) The cochlea is filled with liquid and lined with cilia that transform sound vibrations into nerve impulses Each cilia reacts to its own frequency (high near the vestibule low at the extremity) The sound info is sent to the brain via the auditory nerve *

The bones of the inner ear are connected to the cochlea When the bones vibrate they create fluid waves in the cochlear fluid

Inside the cochlea are tiny hairs When these hairs are moved (by the waves in the cochlear fluid) they send an electric signal through the cochlear nerve and to the brain Your brain interprets these electric signals as a sound

Auditory Pathway (Sound Path) Stimulus -> Pinna -> Auditory canal -> Eardrum -> Hammer -> Anvil -> Stirrup -> Vestibule ->Cochlea -> Cilia -> Nerve cells -> Auditory nerve -> Temporal lobe

Balance The ears also play an important role in balance Inner ear continuously monitors the position of the head The constant monitoring can, for example, help a diver find the water’s surface The cells also help keep your balance when you are not moving (stabilize our posture) (the ears and eyes work together in this…stand up and close your eyes and see what happens)

Balance in motion Other cells in the inner ear maintain balance when our bodies are moving They allow us to detect changes in speed and direction Helping us walk and dance without falling over