(a) What is a receptor? (b) Describe the general features common to all receptors. (c)(i) Make a labelled diagram 8cm - 10cm long, to show the outer and mid...

(a) Receptor

A receptor is a specialised sensory cell or group of sensory cells that detects a particular stimulus and converts it into nerve impulses which are transmitted to the central nervous system.

(b) General features common to receptors

• They are made up of specialised sensory cells, often occurring in groups.
• The free ends of the sensory cells usually bear short hair-like processes or dendrites that receive the stimulus.
• Nerve fibres arise from, or are connected to, their basal regions.
• These nerve fibres lead through sensory neurones to the cranial nerves or spinal nerves and then to the central nervous system.
• Each receptor is adapted to respond most readily to a particular kind of stimulus.

(c)(i) Labelled diagram of the outer and middle ear of a human

The diagram is drawn to a length of approximately 9 cm and shows only the outer and middle ear.

(c)(ii) Ways of caring for the ear

1. Avoid inserting sharp objects, pins or matchsticks into the ear.
2. Keep the outer ear clean and dry; do not force objects deeply into the auditory canal.
3. Avoid prolonged exposure to loud noise and excessive use of earphones at high volume.
4. Report ear pain, discharge, injury or difficulty in hearing promptly to a medical doctor.
5. Seek prompt treatment for infections such as measles and meningitis, which may cause deafness.