(a) What is the function of the following parts of the mammalian ear?(i) Tympanic membrane(ii) Eustachian tube(iii) Ear ossicles(b) Describe how semicircular canals performs their functions.
Answer Text: (a) (i) Receives sound waves (from the air) and vibrates sound waves into vibrations then transmit them to the ear ossicles.(ii) Equalizes the air pressure in the middle ear to that in the outer ear.(iii) Amplifies and transmits vibrations from the tympanic membrane in the middle ear to fenestra ovalis/ oval window.(b)There are three semi- circular canals, arranged in planes at right angle to each other. They contain receptors that respond to rotation of the head in any of the three planes. Thereceptors are located in an enlarged part of each semicircular canal called ampulla. Each ampulla has a cone shaped projection called cupula. Cupula is suspended by hairs that arise from sensory cells. The movement of the bodyin a given direction causes movement of the fluid in at least one canal in opposite direction. This deflects the cupula in the direction opposite to direction of movement of the head. This distorts the hairs of the sensory cells leading to generationof impulses in the neurons that are connected to the sensory cells. The impulses are transmitted to the brain via the auditory nerve where they are interpreted.
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