Source: IndiaToday

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Context

• Bollywood playback singer Alka Yagnik has been diagnosed with a rare form of sensory hearing loss due to a viral attack.
• She has emphasized the importance of protecting one's hearing from loud music and excessive use of headphones.

Details

• Sensorineural hearing loss (SNHL) is a type of hearing loss caused by damage to the inner ear or the nerve pathways that transmit sound from the ear to the brain.

Causes

• Congenital Factors: Genetic factors or complications during pregnancy or childbirth.
• Noise Exposure: Prolonged exposure to loud noises can damage the hair cells in the inner ear, leading to noise-induced hearing loss.
• Ageing: Natural ageing processes can damage or destroy hair cells in the inner ear.
• Infections and Diseases: Conditions such as meningitis, mumps, measles, and autoimmune diseases like Meniere's disease.
• Trauma: Head injuries or inner ear trauma.
• Ototoxic Medications: Certain antibiotics and chemotherapy drugs.

Mechanism of SNHL

Inner Ear Structure

• Cochlea: A spiral-shaped organ within the inner ear containing tiny hairs called stereocilia.
• Function: Stereocilia convert vibrations from sound waves into neural signals that the auditory nerve transmits to the brain.

Damage Mechanism

• Noise Exposure: Sounds louder than 85 decibels can damage the stereocilia. Damage may not be apparent until 30-50% of these hairs are affected.
• Viral Infections: Can cause SNHL through direct cochlear invasion, immune-mediated damage, or disrupted blood supply to the inner ear.

Symptoms of SNHL

• Difficulty Understanding Speech: Struggling to comprehend spoken words, especially in noisy environments.
• Muffled or Distorted Sounds: Sounds may appear unclear or fuzzy.
• Tinnitus: Ringing, buzzing, or hissing sounds in the ears.
• Difficulty Hearing High-Pitched Sounds: Trouble perceiving higher frequencies.
• Balance Issues: Possible balance and coordination problems.

Treatment for SNHL

• Medications: To address underlying conditions contributing to SNHL.
• Cochlear Implants: Devices that can bypass damaged parts of the ear and directly stimulate the auditory nerve.
• Hearing Aids: Amplify sound to assist those with hearing loss.

Human Ear

• The human ear is a complex organ responsible for hearing and balance.
• It can be divided into three main parts: the outer ear, the middle ear, and the inner ear.

Outer Ear

Components:

• Pinna (Auricle): The visible part of the ear that collects sound waves and directs them into the ear canal.
• Ear Canal (External Auditory Meatus): A tube-like structure that channels sound waves to the eardrum.

Functions:

• Sound Collection: The pinna collects and funnels sound waves into the ear canal.
• Protection: The ear canal protects the eardrum from foreign objects and infections.

Middle Ear

Components:

• Eardrum (Tympanic Membrane): A thin membrane that vibrates in response to sound waves.
• Ossicles: Three tiny bones known as the malleus (hammer), incus (anvil), and stapes (stirrup) that amplify and transmit vibrations from the eardrum to the inner ear.
• Eustachian Tube: A tube that connects the middle ear to the throat and helps equalize pressure on both sides of the eardrum.

Functions:

• Sound Amplification: The ossicles amplify the sound vibrations from the eardrum.
• Pressure Equalization: The Eustachian tube equalizes air pressure in the middle ear with the external environment.

Inner Ear

Components:

• Cochlea: A spiral-shaped, fluid-filled structure that contains hair cells (cilia) which convert sound vibrations into electrical signals.
• Vestibular System: Includes the semicircular canals and otolithic organs (utricle and saccule) that help maintain balance and spatial orientation.

Functions:

• Hearing: The cochlea converts sound vibrations into electrical signals that are transmitted to the brain via the auditory nerve.
• Balance: The vestibular system detects changes in head position and motion, helping maintain balance.

Sound Transmission Pathway

• Sound Waves Enter: Sound waves enter the ear through the pinna and travel down the ear canal.
• Eardrum Vibrates: The sound waves cause the eardrum to vibrate.
• Ossicles Amplify: The ossicles in the middle ear amplify these vibrations and transmit them to the cochlea.
• Hair Cells Activate: The vibrations create waves in the fluid inside the cochlea, causing the hair cells to move and generate electrical signals.
• Signal Transmission: The auditory nerve carries these electrical signals to the brain, where they are interpreted as sound.

Disorders of the Ear

• Outer Ear Disorders: Include ear infections (otitis externa), earwax blockage, and injury to the pinna.
• Middle Ear Disorders: Include otitis media (middle ear infection), perforated eardrum, and otosclerosis (abnormal bone growth).
• Inner Ear Disorders: Include sensorineural hearing loss, Meniere's disease (affecting balance), and tinnitus (ringing in the ears).

Sources:

IndiaToday

PRACTICE QUESTION Q. With reference to the human ear, consider the following statements: The human ear is divided into three main parts: the outer ear, middle ear, and inner ear. The outer ear consists of the pinna (auricle), ear canal (external auditory canal), and eardrum (tympanic membrane). The cochlea, a part of the inner ear, is responsible for maintaining balance and equilibrium. Which of the statements given above is/are correct? a) 1 and 2 only b) 1 and 3 only c) 2 and 3 only d) 1, 2, and 3 Answer: a)