BAFANA BAFANA – EYE AND EAR ESSAY The Bafana Bafana goalkeeper dives to his right to prevent a ball from entering the goal post. He sees the ball coming towards him at speed, from 20 metres away and dives to save the day for South Africa, without falling over. Name all the sense organs involved and describe how each of them enables this goalkeeper to dive without falling over Content: 17 Synthesis: 3 The EYE When the ball leaves the 20 m mark, the eye is accommodated for distant vision / lens is flat the goalkeeper keeps his eye focussed through accommodation As the ball moves towards him the ciliary muscles (body) contract The ciliary body moves closer to the lens the sclera is pulled forward The suspensory ligaments become slack loose / lax / less taut The lens becomes thicker and shorter more convex / rounded/ fatter / bulges The refractive / bending power of the lens is increased to get a sharp image of the ball the light rays must be focussed onto the retina (max 5) The EAR To maintain balance and equilibrium sudden changes in direction and speed causes the endolymph within the semi-circular canals to move Since the semi-circular canals are in three planes, the fluid in at least one of the canals will move The movement of the fluid stimulates the receptors called crista within the ampullae situated at the base of the semi-circular canals (max 5) When the direction of the head changes, gravitational pull stimulates receptors called maculae within the utriculus and sacculus Within the cristae and maculae, the stimuli are converted into nerve impulses Impulses are transmitted by the vestibular branch of the auditory nerve to the cerebellum (max 5) From the cerebellum the impulses are sent to the proprioreceptors in the muscles to restore the balance (2) LIFE SCIENCE ACADEMICS - 2014
Posted on: Wed, 19 Nov 2014 16:51:12 +0000
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