Explain how sound waves are detected by the ear and how nerve impulses are sent to the brain.

Edexcel A-Level Biology A: Salters-Nuffield (9BN0) — 4.4 Vision and hearing · Explain · 5 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

The ear is a sense organ that detects sound. Sound waves enter the ear and are converted into nerve impulses that travel to the brain for processing.

Model answer (5 marks)

Sound waves reach the ear and cause the eardrum to vibrate.
The vibration is transmitted through the three ossicles – the hammer, anvil and stirrup – which amplify the sound.
The amplified vibration reaches the cochlea, where hair cells (receptor cells) detect the movement of the fluid.
The hair cells convert the mechanical stimulus into nerve impulses.
These impulses travel along the auditory nerve to the brain for processing.

Examiner tips

Use the exact terms: eardrum, ossicles, cochlea, hair cells, auditory nerve.
Show the sequence of steps – vibration, amplification, detection, conversion, transmission.
Keep the answer concise and avoid unnecessary detail.
Mention the amplification function of the ossicles to earn the full marks.

Common mistakes

Confusing the ossicles with the eardrum or cochlea.
Omitting the role of hair cells or the auditory nerve.
Using vague terms like ‘sound organ’ instead of specific structures.

Mark scheme (5 marks)

Sound waves cause the eardrum to vibrate
Vibrations are transmitted through the three ossicles (hammer, anvil and stirrup) / middle ear bones
The ossicles amplify the vibrations
Vibrations pass to the cochlea, which contains hair cells / receptor cells that detect the vibrations
Hair cells / receptor cells generate nerve impulses that travel along the auditory nerve to the brain

Key terms in this question

nerve impulses