(1) CONTROL AND COORDINATION Class 10th Science Control and Coordination For survival, an organism’s body must respond correctly to various stimuli it receives. Some important terms: • Stimulus: An agent or sudden change in the external or internal environment which causes a change in an organism or any of its body parts. • Response: The change in organisms resulting from a stimulus. • Receptors: Nerve cells which initiate waves of impulses towards the central nervous system on receiving a stimulus. • Effectors: Muscles or glands which contract or secrete substances on receiving an impulse from the brain or spinal cord. Functions of the Nervous System • Keeps us informed about the outside world through sensory organs. • Controls and harmonises all voluntary muscular activities. Example- running andwriting. • Enables us to remember, think and reason. • Regulates involuntary activities such as breathing and beating of the heart. Neuron A neuron is the structural and functional unit of the nervoussystem. The three main parts of a neuron are: • Cell Body- It has a well defined nucleus and granular cytoplasm. • Dendrites- Dendrites are branched cytoplasmic projections of the cell body. • Axon- It is a long process of the cell body. The end portions of the axons have swollen bulb-like structures which store neurotransmitters. Address: Mumbai, M.H. 400101, Email:
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