Phonoreceptors and Hearing

• A phonoreceptor is a receptor for hearing, responsible for capturing and processing sound
• The ear's structure and function relate to the sense of hearing and equilibrium

The Sense of Hearing

• Sound arises from disturbances in the air, propagating as sound waves
• Hearing is the sense responsible for capturing and transforming these sound waves, with the ear as its organ

Ear Function

• The ear captures sounds and transforms them into nerve signals, which are sent to the brain
• It manages equilibrium by detecting changes in body position

Ear Structure

• The ear is divided into three main parts: the outer, middle, and inner ear
• The ear resides within the temporal bone on each side of the head

Outer Ear

• Formed by the auricle and the external auditory canal
• Sound waves are conducted to the eardrum

Middle Ear

• Comprised of the eardrum, ossicles, and the Eustachian tube
• Vibrations are carried from the eardrum to the inner ear, maintaining pressure on the eardrum
• The ossicles are a chain of small bones in the middle ear. These include the malleus (hammer), incus (anvil), and stapes (stirrup)

Inner Ear

• The inner ear consists of the cochlea, vestibule, and semicircular canals

Cochlea Structure

• The cochlea is divided into three spirally wound tubes around a bony axis called the modiolus
• The tubes are; the tympanic duct, the vestibular duct, and the cochlear duct
• The tympanic and vestibular ducts contain perilymph

Cochlea Details

• Internally formed by the basilar and Reissner's membranes, which form the vestibular, tympanic, and cochlear ducts

Cochlear Duct Function

• Considered a middle ramp between the vestibular and tympanic ducts.
• The organ of Corti is located inside

Organ of Corti

• The organ of Corti mechanically transforms impulses into electrical ones

Vestibule Function

• Contains the utricle and saccule, which are filled with endolymph and hair cells called maculae
• The three semicircular canals, positioned in three dimensions of space, contain an ampulla that processes information about balance

Physiology of the Ear

• Equilibrium is achieved by cells in the saccule and utricle
• When we move, endolymph and otoliths agitate the ciliated surface of receptor cells, translating information about our position

Reception of Sound

• Sound waves enter through the auricle, pass through the external auditory canal, and vibrate the eardrum.
• The sound then passes to the chain of ossicles (malleus, incus, stapes).
• Vibrations pass from the stapes to the oval window, transferring perilymph in the vestibular duct and then to the endolymph in the cochlear duct

Organ of Corti in Action

• In the organ of Corti, the wave produces vibrations in the basilar membrane, and the ciliary cells rub against the tectorial membrane, generating a nerve impulse

Inner Ear's Role

• The inner ear transforms information into a nerve impulse, which travels through the auditory nerve to the central nervous system
• The information is processed, leading to sensations