Explain how the structures of the ear convert sound waves in air into electrical signals sent to the brain.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Sound waves travelling through air reach the outer ear and are eventually converted into nerve impulses detected by the brain.
Model answer (5 marks)
Sound waves in the air strike the tympanic membrane, causing it to vibrate.
The vibrations are transmitted and amplified by the ossicles – the malleus, incus and stapes – which act as a lever system.
The stapes pushes on the oval window, creating pressure waves in the fluid of the cochlea.
These fluid vibrations bend the stereocilia of the inner‑ear hair cells.
The deflection of the hair cells opens ion channels, generating receptor potentials that are converted into nerve impulses carried by the auditory nerve to the brain.
The vibrations are transmitted and amplified by the ossicles – the malleus, incus and stapes – which act as a lever system.
The stapes pushes on the oval window, creating pressure waves in the fluid of the cochlea.
These fluid vibrations bend the stereocilia of the inner‑ear hair cells.
The deflection of the hair cells opens ion channels, generating receptor potentials that are converted into nerve impulses carried by the auditory nerve to the brain.
Examiner tips
- Use the exact terms: tympanic membrane, ossicles (malleus, incus, stapes), oval window, cochlea, hair cells, auditory nerve.
- Show the sequence of events – each step earns a point.
- Mention amplification by the ossicles.
- Explain that hair cell deflection produces electrical signals.
Common mistakes
- Confusing the outer ear with the middle ear structures.
- Failing to mention the amplification function of the ossicles.
- Using vague terms like ‘inner ear’ instead of specifying the cochlea and hair cells.
Mark scheme (5 marks)
- Sound waves cause the eardrum (tympanic membrane) to vibrate
- The ossicles (three small bones / hammer, anvil and stirrup) transmit and amplify the vibrations
- The ossicles cause the oval window to vibrate, transmitting vibrations into the cochlea
- Vibrations in the fluid inside the cochlea stimulate hair cells
- Hair cells generate / produce electrical signals (nerve impulses) that are sent to the brain via the auditory nerve
Related
- All AQA A-Level Physics (7408) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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