Theory question 102
Sense Organs(a) What is a receptor? (b) Describe the general features common to all receptors.
(c)(i) Make a labelled diagram 8 cm – 10 cm long, to show the outer and middle ear only of human.
(ii) List three ways of caring for the ear
Show the model answer
(a) A receptor is a sensory cell (or group of cells) that detects a stimulus and starts a nerve impulse, which is carried by sensory neurones to the central nervous system.
(b) Made of specialised sensory cells; each is sensitive to one kind of stimulus (light, sound, touch, chemicals, heat); the free ends of the cells often bear fine hair-like processes; the cells are connected at their bases to sensory nerve fibres; they change the stimulus into nerve impulses; they are often grouped together in sense organs.
(c)(i) Diagram (title, clear lines, correct size) labelled: outer ear – pinna, external auditory canal (meatus), ear drum (tympanic membrane); middle ear – malleus, incus, stapes (ossicles), oval window, round window, Eustachian tube, middle ear cavity.
(ii) Any three: do not push sharp objects (pins, sticks) into the ear; clean only the outer ear gently, e.g. with cotton buds; avoid very loud noise and loud earphones; do not pour hot or dirty liquids into the ear; see a doctor quickly about ear pain or discharge; treat infections such as measles, catarrh or meningitis promptly.
Only the outer and middle ear are asked for in the diagram; do not draw the inner ear.