A person is sitting in a quiet room when a loud sound is made behind them. Explain how the ear detects this sound and converts it into a nerve impulse that travels to the brain.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (5 marks)
1. Sound waves reach the ear and cause the tympanic membrane to vibrate.
2. The vibrations are transmitted through the ossicles – malleus, incus and stapes – in the middle ear.
3. The stapes pushes on the oval window, creating waves in the fluid of the cochlea.
4. Hair cells in the cochlear duct sense the fluid motion and are stimulated.
5. The stimulated hair cells generate a nerve impulse that travels along the auditory nerve to the brain.
2. The vibrations are transmitted through the ossicles – malleus, incus and stapes – in the middle ear.
3. The stapes pushes on the oval window, creating waves in the fluid of the cochlea.
4. Hair cells in the cochlear duct sense the fluid motion and are stimulated.
5. The stimulated hair cells generate a nerve impulse that travels along the auditory nerve to the brain.
Examiner tips
- Use the exact terms: tympanic membrane, ossicles, oval window, cochlea, hair cells, auditory nerve.
- Show the sequence of mechanical to neural transduction – the examiners look for a clear chain of events.
- Mention that the impulse is carried by the auditory nerve to the brain.
Common mistakes
- Confusing the eardrum with the oval window; they are separate structures.
- Omitting the role of the ossicles or the cochlear fluid in the transduction process.
- Using vague language such as “ear” instead of specifying the middle or inner ear components.
Mark scheme (5 marks)
- Sound waves cause the eardrum (tympanic membrane) to vibrate
- The vibrations are passed through the three ossicles (malleus, incus, stapes) / the three small bones in the middle ear
- The ossicles transmit vibrations to the oval window, which causes fluid in the cochlea to vibrate / move
- Hair cells (sensory cells) in the cochlea detect the vibrations in the fluid and are stimulated
- Stimulated hair cells generate / send a nerve impulse along the auditory nerve to the brain
Key terms in this question
Related
- All Pearson Edexcel A-Level Biology A (9BI0) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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