Page 68 - Biology_Form_3

Biology for Secondary Schools

balance and posture. It receives 10. The ear is the organ for hearing and
impulses from the organs in the inner maintenance of body balance. It is
ear and from stretch receptors in joints composed of three parts; the outer
and muscles. ear, the middle ear and the inner ear. It

6. The medulla oblongata is the most detects sound waves and vibration and
FOR ONLINE READING ONLY
posterior part of the brain. It controls provide information on the position of
involuntary and reflex activities such the organism to the cerebellum.
as breathing, heartbeat, digestion, 11. The eye is an organ for vision which
dilation and constriction of blood receives light from the environment
vessels, secretion of juices from and converts it into electrical
glands and temperature regulation. impulses. Eye defects are functional
and structural deviations of the eye
7. The spinal cord runs from the head to
the end of the trunk and is encased in that alter the focusing mechanism of
an eye.
meninges. It serves as a nerve impulse
conduction pathway. It also acts as 12. The nose is the olfactory organ with
a coordinating centre by controlling cells which detect smells in the nasal
involuntary actions which are fast passages. The epithelial layer of the
and automatic. Such responses are nasal cavity has a special group of
called reflex actions and they include sensory cells that can be stimulated
actions like coughing, sneezing, when chemicals dissolve in the
blinking and removing a hand or leg moisture on their surface.
when it accidentally touches a hot or 13. The primary function of the tongue is
sharp object. The neural pathway that to taste various substances. There are
control reflex action is called reflex five primary types of tastes; sweet,
arc. sour, salt, bitter and a savoury or
8. Sense organs are specialised organs meaty taste (umami). All these tastes
composed of sensory receptors are detected by the sensory cells
responsible for receiving and located in the taste buds located on
responding to stimuli around us. In the upper surface of the tongue.
mammals, there are five major sense 14. Drug or substance abuse is the
organs namely; ear, eye, nose, tongue, use of illegal drugs or excessive
and skin. use of legal drug. People become
9. The skin is the largest organ that forms addicted with drugs due to several
the outer covering of the body of the reasons misguided including peer
living organism. It protects the body pressure, social psychological and
and helps to regulate body temperature, environmental factors.
and responds to pain, pressure, touch,
heat, and cold sensations.

61 Student’s Book - Form Three

23/10/2025 11:52:40
BIOLOGY FORM 3 FINAL EDITED 16.09.2025.indd 61 KAMISHNA 23/10/2025 11:52:40 KAMISHNA
BIOLOGY FORM 3 FINAL EDITED 16.09.2025.indd 61