More Structures

• Tympanic membrane- where the middle ear begins– Sound is amplified by concentrating the sound

energy from the large tympanic membrane to the smaller oval window

• Eustachian Tube- permits the equalization of air pressure on either side of the eardrum– Yawning, swallowing and chewing gum– Ear infection can block the tube

More Structures

• Vestibule- establishes head position• Semicircular canals- filled with fluid that helps you

identify body movement• Oval window-sound is amplified• Organ of Corti- primary sound receptor in the cochlea.– Contains specialized hair cells that respond to vibrations.

Any movement of the hair cells will stimulate the sensory nerves.

• Basilar membrane- anchors the hair cells to the organ of Corti

Hearing and Sound

• Sound is a form of energy• Begins when sound waves push against the

eardrum. The vibrations are passed onto the three small bones of the middle ear. These bones concentrate and amplify the vibrations. The ossicles also increase this amplification. The oval windows movement will trigger waves of fluid within the inner ear. The cochlea receives this fluid and converts them to electrical impulses.

• The inner ear is able to identify pitch and loudness. Close to the oval window the membrane is narrow and stiff. This area is activated by high-frequency sound waves. This leads to us hearing high pitched sounds.

• Farther away the membrane widens and becomes more flexible.

Equilibrium

• Balance consists of two components: static and dynamic equilibrium– Static- along one plane– Dynamic- provides information about movement

• Head position is monitored by two fluid filled sacs called the saccule and utricle. Hair cells line these.

• Ololiths are tiny stones of calcium carbonate that are embedded in a gelatinous coating within the saccule and utricle

• When the head is in a normal position, the otoliths do not move. When the head is bent the otoliths will move causing the cilia on the hair cells to bend. This bending on the cilia activates the sensory nerve.

• Balance is maintained during movement by three fluid filled semi-circular canals.

• Rotational movement causes cilia attached to the cupula to move which activates the nerve impulse.

• Motion Sickness- caused by rapid continuous movement of the fluids

Hearing Loss

• Conductive Hearing Loss- sound waves have trouble entering the inner ear.

• Sensorineural Hearing Loss- where the auditory nerve is severed or damaged

• Hearing aids- amplify and transmit sound• Cochlear implants- help converts sound into

electrical impulses