To describe how a sound wave travels through the ear, you must first understand how the ear works. This article will teach you about the cochlea, the tympanic membrane, and the stapes. In addition, you will learn about the inner and outer hair cells in the ear.
Cochlea
The ear is an organ that captures sound waves and converts them into brain messages. Several parts work together to help the ear perform.
The outer part of the ear, called the pinna, is shaped like a funnel to catch the waves. The inner part of the ear, called the cochlea, is a snail-shaped liquid-filled tube. This tubular structure consists of over 16,000 hair cells that help the cochlea detect different pitches.
The hair cells contain a bundle of fibers known as cilia. These fibers bend with the movement of the fluid in the ear. The movement causes the hair cells to turn, which creates nerve impulses. These impulses travel along the auditory nerve to the auditory cortex. The nerves then transmit information about the pitch and timing of a particular frequency.
The cochlea is divided into three compartments, separated by two membranes. The basilar membrane is a mechanical analyzer that helps the cochlea differentiate pitches. The stiffness of the membrane changes as it progresses from the base to the apex.
Sound is transmitted to the cochlea through the eardrum and malleus. The ossicles also transmit the vibrations of the middle ear to the cochlea. The three bones of the middle ear are the malleus, stapes, and incus.
A series of small muscles, the middle ear muscles, are situated between the stapes and eardrum. These muscles fatigue quickly, which can limit the protection of the ear against high-level noise. The forces also don’t protect the ear against sudden, intense noise.
When the ossicles vibrate, they move the fluid inside the cochlea. This motion causes the hair cells to bend in the same way as a gust of wind. The movement of the cilia then triggers the generation of nerve impulses in the attached neurons.
Tympanic membrane
A human’s ear is divided into three sections. These are the outer ear, middle ear, and inner ear. Each performs a different function in transmitting sound to the brain.
The outer ear is the part of the ear visible. Its functions include collecting and directing airborne sounds. The external auditory canal runs these sounds to the tympanic membrane, a thin, paper-thin membrane that sits between the outer and middle ear. The tympanic membrane absorbs these sounds, transforming them into vibrations and sending them to the inner ear.
The middle ear is a cylindrical, air-filled chamber that sits between the tympanic membrane and the inner ear. It functions as a mechanical amplifier to amplify sound waves. The middle ear is made up of three ossicles. The two main ossicles are the stapes and the malleus.
The stapes is a small bone located in the cochlea’s oval window. The footplate of the stapes is attached to the tympanic membrane. The stapes exert pressure on the tympanic membrane to push it back and forth. The oval window contains a small amount of fluid, which moves in response to the stapes’ vibrations.
The basilar membrane separates the tympanic and vestibular compartments. The basilar membrane vibrates in response to changes in air pressure and electrical charge. It serves as a stimulant for the organ of Corti. The hair cells of the basilar membrane convert mechanical energy from the tympanic membrane into electrical impulses.
The inner ear is a hollow space containing several organs. These organs, known as the eardrum, organ of Corti, and ossicular chain, work together to transmit vibrational energy from the tympanic and vestibular windows to the brain.
Stapes
When a person hears a sound, the sound travels through the ear. The ear acts like a mechanical amplifier, concentrating sound and transmitting it to the brain. It is a complex system.
The outer ear consists of the eardrum and pinna. The eardrum vibrates in response to a sound. The vibrations are transferred to the tiny bones of the middle ear, called ossicles. These ossicles are made up of malleus, incus, and stapes.
The three bones of the ear form a chain that allows sound to be transmitted to the cochlea. The ossicles move back and forth in the ear, applying the sound to the cochlea’s oval window. The oval window is one of two membranes separating the inner and middle ear.
The round window is smaller than the stapes footplate. When the oval window moves, it gives the same effect as vibrating the stapes.
The tympanic membrane, the larger of the two membranes, is attached to the malleus, incus, and a part of the stapes. It is a 69 square mm membrane, compared to the stapes footplate, which is 43 square mm.
The inner ear, which contains the organ of Corti, receives the incoming sound using the oval window. A series of microscopic ‘hair cells’ transforms the vibrations into electrical impulses. The basilar membrane’s motion causes the cochlea fluid to change, stimulating the hair cells. This action sets up pressure waves in the inner ear, which are converted into nerve impulses and transmitted to the brain.
The incus, malleus, and stapes are connected to the auditory nerve, which transmits the information to the brain. The stapes muscles are part of the middle-ear reflex arc, which contracts when exposed to high-level sounds. The stapes muscle is thought to help protect the cochlea from sudden impulsive sounds.
Corti (spiral organ)
The organ of Corti (also referred to as the spiral organ) is a vital organ of the mammalian ear, which converts mechanical vibrations into electrical signals. It is located inside the cochlea.
The ear is divided into three sections: the outer ear, middle ear, and inner ear. Each team has a different role in transmitting sound waves to the brain.
In the outer ear, the pinna is the part of the ear that filters the sound waves. It also funnels the sound waves through the ear canal. The outer ear is separated from the middle ear by the tympanic membrane. The tympanic membrane vibrates when the sound waves hit it.
The outer ear is a mix of muscles, nerves, and vessels. The tympanic membrane is separated from the middle ear by the oval window. This membrane is lined with hair cells, which convert mechanical energy from the basilar membrane into electrical impulses. The ossicles are the tiny bones that move to cause the displacement of the cochlear fluid. These small bones are connected to the stapes.
The inner ear consists of the auricle and the cochlea. The auricle catches the sound waves, passing through the tympanic membrane and into the middle ear. The tympanic membrane then vibrates to set up pressure waves in the perilymph. These waves travel through the scala tympani, the media, and the vestibule. The scala tympani, media, and hall are each filled with perilymph.
The organ of Corti, which sits on top of the basilar membrane, is the organ that converts mechanical vibrations into nerve impulses. This organ is surrounded by the endolymph, which is rich in potassium. The reticular lamina, a rigid structure, also covers it.
Inner hair cells
The hair cells of the ear play a critical role in hearing. These cells act as sensory receptors and translate vibrational energy into electrical impulses. These impulses travel along complex pathways to the brain. Afferent and bipolar neurons carry this information.
These neurons are found in two parts of the brain: the pons and the midbrain. They send nerve impulses to the auditory cortex in the brain. These impulses are receptive to vibrations in the cochlea. The sound waves are then converted into electrical impulses that travel through the cochlea and reach the brain.
The auditory system is vital to predation and predator defense. It allows the brain to recognize changes in the external environment, including the position of objects.
Hair cells are the primary receptors of the ear. They detect sound and movement in the fluid inside the inner ear. They are sensitive to four different frequencies. The response of each type of hair cell to a particular frequency is determined by its location on the basilar membrane.
The cochlea contains approximately 16,000 hair cells. The outer cells are arranged in three or four rows, whereas the inner cells are arranged in a single row. Each hair cell has a bundle of fibers called cilia. When the cilia move in one direction, they open pore-like channels and permit an inward K+ current to depolarize the cell. This causes the hair cell to release neurotransmitters.
The number of stimulated hair cells determines the volume of the sound. High-frequency sounds register at the base of the cochlea, and the lowest-pitched sounds are detected at the broadest end. The amplitude of vibration in the basilar membrane increases as the distance of the sound wave from the entrance port increases.
