The Human Ear – a magnificent organ
Ears play a vital role as they help us to interact with our surroundings. They are responsible for the sense of hearing and maintaining our body balance. Hearing can be defined as a phenomenon by which sound vibrations are converted into nerve impulses which are then sent to the brain where they are interpreted as specific sounds. A person is said to normal hearing ability if they can listen to sounds between 0 decibel – 25 decibel.
Decibel is defined as a unit of measurement for sound. The function of the ear is to transmit the sensation of sound to the brain through the outer ear, middle ear, and inner ear. Let’s now discuss these topics in a little more detail.
How do bones help me hear?
The sound vibrations reach the brain through three different parts of the ear – the outer ear, the middle ear, and the inner ear.
- Sound enters into the outer ear, travels through a narrow passage called the ear canal, and strikes the eardrum. The eardrum acts as a natural boundary between the outer ear and the middle ear.
- Eardrum on vibration transmits these vibrations to three tiny bones – malleus, incus, and stapes. These three bones together are called ossicles and form the middle ear.
- Inner ear consists of a structure called the cochlea which is filled with fluid. Waves traveling from the middle ear cause the fluid in the inner ear to vibrate. These vibrations generate an impulse that is sent to the brain. Brain on receiving the impulse translates the sensation of hearing.
What are the functions of the different parts present in the ear?
1. Outer Ear
The outer ear flap also called the pinna, has a cup-shaped structure. It is made up of cartilage and skin. The outer ear is responsible for capturing the sound waves from the air and sending them as vibrations to the eardrum.
The eardrum is made up of a disk with a membrane stretched over it. It acts as a barrier between the outer ear and the middle ear. On receiving the sound waves it vibrates and transmits it to the middle ear. It further hits the malleus causing the other ossicles to vibrate.
3. Middle Ear
The ossicles are present behind the eardrum. On receiving vibrations the eardrum pushes the malleus which pushes incus and then stapes. This domino effect is how sounds travel to the smallest bones in the body. The main function of the middle ear is to amplify the sound waves and send them to the inner ear.
4. Inner Ear
The inner ear is the innermost part of the vertebrate ear. It is made up of cochlea and semicircular canals. Sound waves from the middle ear vibrate through the fluid and transmit to the receptors. The main function of the inner ear is to convert sound waves to an electrical signal and send it to the brain.
The tiny hair-like receptors in the inner ear send an electrical impulse to the brain through a nerve called the vestibulocochlear nerve.
- Ultrasound at sufficient sound pressure levels can cause hearing damage even if it cannot be heard.
- Alcohol changes the volume and composition of fluid in the inner ear, which can cause dizziness and imbalance.
- Which bone is not present in the middle ear?
- Which structure contains fluid in the inner ear?
(d) none of these
- Which sounds cannot be heard by human beings?
(b) Infra-red sounds
(c) Both of the above
(d) None of the above
- Which nerve transmits electrical impulses to the brain?
(a) Vestibulocochlear Nerve
(b) Optic Nerve
(c) Facial Nerve
(d) Olfactory Nerve
- A person is said to have the normal hearing ability if they can listen up to 25 decibel. (T/F)
- The inner ear is responsible for capturing the sound waves from the air. (T/F)
- Receptors send an electrical impulse to the brain. (T/F)
- Ears are responsible for the sense of hearing and maintaining our body balance. (T/F)
- The eardrum acts as a natural boundary between the middle ear and inner ear. (T/F)