Theory question 101
Sense Organs(a) What is a sense organ?
(b) List four sense organs found in mammals.
(c) Describe the processes that will cause a person who has been spinning to feel dizzy.
(d) State two functions each of the following structures:
(i) Cerebellum; (ii) Cerebrum; (iii) Medulla Oblongata.
Show the model answer
(a) An organ made of specialised receptor cells that detect a particular stimulus and send impulses to the nervous system.
(b) Any four: eye, ear, nose, tongue, skin.
(c) Spinning sets the fluid (endolymph) in the semicircular canals moving; when the person stops, the fluid keeps moving; it bends the sensory hairs in the ampullae; impulses go along the auditory nerve to the cerebellum/brain; the brain reads this as the body still turning while the eyes say it is still; the conflicting messages cause dizziness.
(d)(i) Cerebellum: keeps balance and posture; coordinates voluntary muscle movement.
(ii) Cerebrum: controls voluntary actions; seat of memory, intelligence, reasoning and interpretation of senses.
(iii) Medulla oblongata: controls involuntary actions such as heartbeat and breathing; controls reflexes such as coughing, sneezing and swallowing; regulates blood pressure by constricting/dilating vessels.
For (c) link the moving inner-ear fluid to the brain's wrong reading of body position.