The Ear, Taste, Smell and Touch

Sound Waves

Small changes in air pressure caused by a vibrating source

Functions of Ear

• ear transforms sound waves into nerve impulses

• ear also maintains gravitational and dynamic balance

Pinna

Out ear, focuses sound waves into auditory canal. Supportive cartilage gives it strength

Auditory Canal

A pathway that transmits sound waves towards the tympanic membrane

• contains hair and produces wax

Tympanic Membrane

• thin cone-shaped membrane that moves as sound waves strike surface

Malleus (hammer)

First bone attached to tympanic membrane in air-filled space

Incus (anvil)

Second bone within the inner ear that transmitters vibrations from mallus to stapes

Stapes (stirrup)

• third bone that transmits vibrations from incus to oval window

Tympanic Cavity

Air filled cavity containing ossicle bones

Eustachian Tube

Air-filled tube connecting the tympanic cavity to throat. This allows for equalization of air pressure

Oval Window

A flexible membrane that vibrates when sound waves move the ossicles. The membrane transfers this motion into the compression of fluid within the cochlea

Cochlea

A coiled structure that contains the organ of corti. IT transforms physical motion into nerve impulses

Cochlear Nerve

A nerve that collects sensory sound information from the Organ of Corti located in Cochlea

Semicircular Canals

Three interconnected fluid filled tubes that convert dynamic motion into nerve impulses

Vestibule

An area located within the cochlea. It allows for static (upright) balance

Vestibular Nerve

Nerve that collets sensory fluid motion info from the semi-circular canals and vestibule

Inner Ear

• tube has fibers located along a structure called organ of corti

• pressure within the tube causes the organs membrane to move against the fibers (hair cells), converts sound pressure waves into neural impulses.

• high frequencies are read near the beginning, low frequencies are read near the end

• attached auditory nerve transfers these neural impulses into temporal lobe

Taste

• Saliva is used to dissolve molecules

• generate nerve impulse which travel to parietal lobe for interpretation

Smell

• Olfactory chemoreceptors line to nasal cavity

• impulses are generated and interpreted in frontal lobe

• 80-90 percent of taste is generated through smell

Touch

• Mechanoreceptors are sensitive to specific stimuli → touch, pressure, pain and temp

• Unevenly distributed over body

• each sensor uses a complex series of receptors linked to chemical messengers called hormones

Static + Dynamic Balance

• Static: depends on otoliths within the liquid of vestibule

• Dynamic: depends on cilia and liquid filled semicircular canals