Hearing, Ears and the Nervous System
How does hearing work? You probably already know that your ears are involved in the process, but there is a lot more to it than that. To understand how hearing works, you have to understand the processes that are going on in the nervous system and the brain. Your ears pick up sound vibrations, but your brain is what actually “hears” sounds. Read on to gain an overview of the functions of hearing and the nervous system.
A Basic Explanation of the Overall Process
When sound waves travel toward you, the first part of the process of hearing involves the ears. The sound waves enter the ear and the sensitive structures of the inner ear pick up the vibrations. These vibrations stimulate nerves and create a signal which contains the sound information. The sound signal is transmitted along the nerve toward the part of the brain that enables you to perceive the sensation of hearing as sound. In this way, hearing and the nervous system work together to enable you to hear.
How the Ear Functions
The ear is a complex organ. It not only enables the miraculous ability to hear, but it is also the main organ involved in keeping yourself balanced. The three main parts of the ear are the outer ear, the middle ear, and the inner ear.
The outer ear consists of the outer parts that you can see, the ear canal and the outer portion of the eardrum. The curved fleshy structure that is on the outside of your head is called the auricle. The outer rim of the auricle is called the helix, and the inner rim is the antihelix. The curved shape of the auricle is designed to capture and direct sound waves into the middle region of the ear.
The middle ear has four main components. These are the tympanic cavity, the ossicles, the auditory tube, and the round and oval windows. The ossicles are bones that amplify sound vibrations and transmit them to the inner ear. Sound waves are amplified by up to twenty times in the middle ear.
The inner ear consists of a cavity called the bony labyrinth with a central area called the vestibule. These two components are connected to the cochlea and the semicircular canals. The cochlea is shaped like a spiral shell, and it enables hearing. The semicircular canals enable balance.
Hearing and the Nervous System
When the ear receives sound vibrations, there are hair cells in the cochlea that vibrate and translate the sounds into electrical signals. These electrical signals are transmitted to the auditory nerve, which transmits the information to the brain.
The part of the brain that enables you to understand electrical signals as specific types of sounds is called the auditory cortex. It’s located within the temporal lobe, which is on either side of the brain in the region called the cerebral cortex. There are specific neurons in the auditory cortex that can process specific frequencies of sound that we perceive as high or low pitches. There are also parts of the brainstem and the midbrain that provide automatic reflex reactions to certain types of sounds.
How Sound Location is Perceived
Because humans and many other vertebrates have ears on either side of the head, there is some distance between them. This distance creates a slight difference in the amount of time it takes for a particular sound to reach either ear. The brain is able to take both sound inputs and create a sense of location based on the difference between when each ear picks up the sound.
You can’t consciously notice this time difference because it’s only microseconds, but hearing and the nervous system work together to make this miracle possible. That’s why a stereo speaker system enables sounds to seem like they are surrounding you rather than just coming from the speakers. When each speaker is positioned correctly, your ears will hear the same sounds at slightly different times, and your brain will give you a sense of the sounds being in various locations.
There are many parts of the body involved in the hearing process. If any of these parts are damaged, you could end up with some hearing impairment or even complete deafness. Hearing loss is a common problem, and many people’s hearing is diminished by aging, loud noises, illnesses or heredity.
About a third of elderly people have some hearing loss, and half of the entire population of people over 75 have impairment to the point where it’s less easy to understand speech. Some types of hearing loss are temporary while others are permanent. Earwax buildup and inflammation in the outer ear are common, and most people experience some temporary degradation in hearing from this that clears up on its own. When there is damage to the inner ear, it’s usually either permanent or surgery is required to restore hearing.
Age-related hearing loss, known as Presbycusis, happens gradually as some people age. This illness seems to be inherited, and researchers believe that it occurs due to changes that happen to the inner ear and the auditory nerves over time as some people age. This illness usually affects both ears, and it can cause people to be overly sensitive to loud noises or have difficulty making out speech.
Another common hearing problem in older people is tinnitus, which is most often a sensation of ringing in the ears. Tinnitus can also manifest as roaring, hissing, buzzing or clicking sounds. Tinnitus can be either constant or intermittent. People can develop tinnitus from a variety of health problems including allergies, high blood pressure, and medication side effects.
Loud noises can also cause hearing loss. If a person is exposed to loud noise for a long enough period of time, it can damage the inner ear and become permanent. Loud music is one of the most common causes of hearing loss, and gunshots are particularly dangerous as just one shot can permanently damage hearing. Viruses, diabetes, heart disease, stroke, and tumors can also lead to hearing loss.
Hearing is a fascinating process in the body, brain and nervous system. By learning some fundamental facts, you can take better care of your hearing and gain greater insight into some of the sound-related activities that you enjoy. If you begin to notice that you’re having any difficulties hearing, be sure to consult a healthcare professional right away.
If you need any help with your hearing, schedule an appointment today!