Mechanoreception and chemoreception (the ear)

Outer ear

Pinna

Collects and funnels sound waves to the auditory canal

Outer ear ends at tympanum

Auditory canals

Concentration sound

Lined with ear wax to protect from skin growth particles

Middle ear

Tympanum

ossicles

Oval window

Round window

Eustachian tube

Functions of middle ear

1. Convert sound energy into mechanical energy

2. Amplify the energy as it moves toward the inner ear

3. Protection from excessive noise

4. Equilibrium of pressure between the outer and inner ear

Converting sound energy to mechanical energy

Sounds waves vibrate the tympanum

Vibrations move to ossicles

Last ossicle strikes the oval window on the cochlea

Amplify the energy as it moves toward the inner ear

Concentrating the energy from the larger tympanum to the smaller oval window

This triples the force

Protection from excessive noise

Restrict the continuous movement of the ossicles when exposed to continuous noise in order to avoid damage to the cochlea.

Equalizing air pressure

The eustachian tube maintains equal pressure on both sides of the tympanum for it to vibrate freely.

This tube opens and closes to aid with this

Inner ear

Cochlea - hearing

Semicircular canals - balance

Vestibule - Balance when stationary (non curricular)

Cochlea

Spiraling snail shell

Contains specialized hair cells (stereocilia)

Identifies and translates sound vibrations into electrical signals for the auditory nerve. (depol)

This is done by pushing vibrations from ossicles to oval window, moving fluid in the cochlea and relieving pressure in the round window

Hair cells are embedded in the organ of corti

Organ of Corti

Distinguish both frequency (pitch) and amplitude (intensity/volume)

Frequency

High - stimulates hair cells closest to oval window

Low - stimulates hair cells furthest away from oval window.

Amplitude

Louder = greater pressure in the fluid of the cochlea. Constant exposure to loud sounds can damage hair cells, leading to hearing loss.

Semicircular canals

Three fluid filled bone chambers

Sensitive nerve hair cells that detect the motion of fluid in the canals which helps maintain balance and orientation.

Dynamic equilibrium