WAEC Biology 2020 Theory — Question 1

Model answer

(a) When the head is moved in a particular direction, it affects the fluid (endolymph) in the corresponding semi-circular canal. This causes the sensory cells in the ampulla to set up impulses through the auditory nerve to the brain, where the impulse is interpreted. The brain then sends impulses to the muscles so that balancing occurs. NB: The cochlea is the part of the ear concerned with hearing, while the semi-circular canal is concerned with the maintenance of balance. (b) [Drawing: fully labelled diagram of the human ear, showing the outer ear (pinna, auditory canal), middle ear (ear drum, hammer, anvil, stirrup) and inner ear (semicircular canals, cochlea, auditory nerve).]