(a) What is a sense organ?
(b)(i) State two main functions of the ear
(ii) Explain the mechanism involved in one of the functions stated in (b) (i) above.
(c) With the aid of a large labelled diagram, illustrate the eye defect of short-sight and its correction.
Explanation
(a) A sense organ is a group of specialised cells or tissues and receptors, which is able to receive or collect, perceive and detect stimulus and transmit the information; impulse and message to the central nervous system.
(b)(i)Two main functions of the ear are:
Hearing and maintenance of balance.
(ii) The mechanism involved in hearing are;
- The pinna; collects sound waves in the air, concentrates them and passes them on through the external auditor) canal or meatus.
- The waves; cause the tympanic membrane or ear drum to vibrate. The vibrations are passed on to the ear ossicles (mallens, inclus and stapes) which amplify them.
- The round oval window; fenestral oval is rotunda also vibrates, passing the waves into the cavity of the inner ear, cochlea, where the perilymph vibrates, transmits the waves in the cochlea which also causes the endolymph of the cochlea to vibrate. The vibrations are then transmitted across the organ of cot or sensory nerve cell or basilar membrane.
- The impulses; are set up and they stimulate the auditory nerve cells which then transmit the impulses to the brain, for interpretation.
The mechanisms involved in the maintenance of balancing are as follows:
Head movement in any direction affects the fluid or endolymphy, in the corresponding semicircular canals, which are at right angles to each other. This forces the sensory cells, gelatinous copula in the ampulla, to set up impulses through the auditory nerve to the brain and intern, for interpretation. The brain relays the impulses to the body muscles, for balancing/ determine the position of the body.
