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Ear and brain for hearing and balance

How we hear

Ear and brain work together for hearing and balance

Hearing is made up of complex steps that change sound waves in the ear into electrical signals. The brain reads these signals as speech, music and other sounds. The ear also works with the brain to maintain balance.​​

 

Ear and hearing

Outer ear

  • Sound waves enter outer ear, travel through ear canal, which leads to eardrum

Middle ear

  • Eardrum vibrates, sends vibrations to 3 tiny middle ear bones-malleus, incus, stapes

  • Bones increase sound vibrations and send to cochlea that is filled with fluid

Inner ear

  • Waves are formed in the fluid that travel along basilar membrane of snail-shaped cochlea

  • Hair (sensory) cells, on top of basilar membrane, detect sound and move up and down

  • Microscopic hair-like projections (stereocilia), on top of hair cells, open up

  • Chemicals rush in creating an electrical signal

Auditory nerve

  • Carries electrical signal from the inner ear to the brain

  • Brain interprets the electrical signal as sound and assigns meaning that you recognize and understand

Cerumen (ear wax)

  • It is produced by glands in the ear canal

  • It cleans, lubricates, protects ear canal from bacteria and fungus

  • Body disposes earwax it no longer needs

  • Chewing, other jaw movements, and skin growing inside the ear pushes old earwax out naturally

Stereocilia generates signals to send to brain

Brain and hearing

  • Brain is the center of intelligence and interprets all senses including sound

  • Nerve cells called 'Neurons' send and receive electrical and chemical signals that allow you to do everything

  • Neural circuits are information pathways connecting neurons to neurons

 

Sensory neurons carry information from sense organs (eyes and ears) to brain

  • Neurons for hearing are located in the auditory cortex of the brain

  • How these neurons communicate with each other makes each of us unique in how we think, feel, act

  • This includes sending messages for hearing and understanding sounds

Image of brain

Sensory neuron

​Ear, brain and balance

  • The semicircular canals in ear contain three fluid-filled ducts with stereocilia

  • When head is turned, the fluid moves, bends the stereocilia and sends nerve signal to brain

  • Between the semicircular canals and the cochlea are fluid-filled pouches called utricle and saccule

  • The stereocilia in the utricle and saccule tell the brain he position of the head with respect to gravity, such as sitting up, leaning back, or lying down and movements such as side to side, up or down, forward or backward

  • The ear works with the eyes and legs to control the position of your body and maintain balance

Balance system inside ear

Image credits: NIH

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