The Sense of Hearing: The Ears
The ears have two types of receptors. They are phonoreceptor and statoresreceptor. Phonoreceptor receives the auditory stimuli and have the power to convert them into auditory impulses. Statoresreceptor control postural changes and changes the orientation of the body or balance. That is why ear is called not only the organ of hearing. There are external ear, the middle ear, and the internal ear.
- The external ear:
The external ear consists of two parts: pinna and external auditory canal.
Pinna is funnel shaped and has ridges and grooves. Pinna is immovable and it is supported by an elastic cartilage which has a funnel-shaped aperture called concha. It collects and directs the sound waves by concha of the pinna to the external auditory canal.
- External auditory canal
External auditory canal is an oblique and tubular canal which runs inward from the canal to the ear drum. The inner wall is provided with ceruminous glands. Its produces ear wax which protects the eardrum. It separates the external ear from the middle ear.
- The middle ear
The middle ear consists of an air filled cavity called tympanic cavity. that is connected to the pharynx by a eustachian tube. The tympanic membrane is oval, delicate membrane capable of vibrating. Tympanic cavity consists of 3 tiny bone called ear ossicles. They are incus, malleus, and stapes. Malleus is a hammer-shaped outer bone. The incus is an anvil-shaped middle bone.It articulates with the malleus on one side and stapes on other side. Stapes is an inner bone and attached to the internal ear.
- The internal ear
The internal ear consists of the vestibule, semicircular canal, and cochlea. The vestibule is a small rounded chamber that forms the central part of the internal ear. The vestibule consists of two delicate membranes, oval window and round window. Semicircular canals are three in numbers and they are mutually perpendicular to each other and form ampulla. It is directly concerned with the balance of the body and plays no part of the internal ear. The cochlea is spirally coiled like snail’s shell which receives the vibration of the sound. It is surrounded by the bony part called cochlear canal.
Working mechanism of ears
The external ear collects the sound waves and the sound waves passes into the auditory tube. The sound waves then enter the middle ear and strike the eardrum, ear oscicles and finally reach to the cochlea. Sound waves set the fluid of cochlea in motion. Due to which the auditory cells are activated. The stimulus or impulse is carried to the brain by the auditory nerves.
Care and protection of the ears
- We should not take out the earwax from ear normally. If it interferes the hearing, it should be taken out safely.
- We should not use sharp things like the tooth pick, key etc. to prick the ears.
- We should consult the doctor in case of pain, pus formation, bleeding etc. in ears.
- We should protect our ears from loud noisy sounds.
- We should not take out any foreign body from our ears that may enter our ears by different causes.
Things to remember
- The ears have two types of receptors. They are phonoreceptor and statoresreceptor.
- Pinna is immovable and it is supported by an elastic cartilage which has a funnel-shape aperture called concha.
- External auditory canal is an oblique and tubular canal which runs inward from the canal to the ear drum.
- The middle ear consists of an air filled cavity called tympanic cavity.
- The internal ear consists of the vestibule, semicircular canal and cochlea.
- It includes every relationship which established among the people.
- There can be more than one community in a society. Community smaller than society.
- It is a network of social relationships which cannot see or touched.
- common interests and common objectives are not necessary for society.
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Questions and Answers
While spinning, the endolymph of the ear goes to one side and strong impulses pass to the brain through the semi-circular canal. As we stop spinning, the endolymph rushes back to normal and cerebellum cannot work properly. Thus the person feels dizziness.
When the airplane takes height suddenly, then the atmospheric pressure suddenly reduces outside the eardrum. At that time, swallowing opens the Eustachian tube and air can pass from pharynx into middle ear cavity which equalizes the air pressure on the both sides of the eardrum. This prevents the distortion of eardrum by
the difference of pressure on the both sides of it. Thus, we are given chocolates to chew while travelling by an airplane.
Eardrum (Tympanic membrane) is the part of ear which receives and transmits the sound to the brain through middle and inner ear. If it is damaged, it receives less sound which cannot pass into the brain to hear properly. Due to this reason, a person feels difficulty in hearing when the eardrum gets ruptured.
Sound waves are collected by pinna and then those waves are directed towards auditory canal which vibrates eardrum. The vibration of eardrum is transmitted through middle ear and three bones of middle ear start to vibrate. This vibration is transmitted to the fluids in the cochlea and received in the hearing center of brain through auditory nerves. As a result, sound is heard.
We can take care of our ear by following ways:
a) We should not insert sharp things like toothpick, key and pencils inside the ears.
b) For taking out earwax, we must first make it moist by using glycerin and use ear buds to take it out.
c) We should consult ear specialist if there is pain, bleeding or pus formation inside the ears.
d) We should protect our ears from the loud sound as it may rupture the eardrum.
A person having hole in the eardrum does not hear properly because the eardrum receives less sound which cannot pass into brain through the cochlea.
A person cannot balance after spinning sometime because the endolymph of the ear goes to one side and strong impulses from semi-circular canals pass to the brain.
Again, when the spinning stopped endolymph rushes back to normal. It means cerebellum cannot work properly. This creates giddiness and one cannot overcome the felling of falling down.