Page 108 - NCERT Science Class 10 English Medium
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Figure 6.2
                                                      Figure
                                                      Figure
                                                      Figure 6.2 Reflex arc
                                                      Figure 6.26.2
                                                             6.2
                    Can you now trace the sequence of events which occur when a bright
                 light is focussed on your eyes?
                 6.1.2 Human Brain
                 Is reflex action the only function of the spinal cord? Obviously not, since
                 we know that we are thinking beings. Spinal cord is made up of nerves
                 which supply information to think about. Thinking involves more
                 complex mechanisms and neural connections. These are concentrated
                 in the brain, which is the main coordinating centre of the body.  The
                 brain and spinal cord constitute the central nervous system (Fig. 6.3).
                 They receive information from all parts of the body and integrate it.
                    We also think about our actions. Writing, talking, moving a chair,
                 clapping at the end of a programme are examples of voluntary actions
                 which are based on deciding what to do next.  So, the brain also has to
                 send messages to muscles.  This is the second way in which the nervous
                 system communicates with the muscles.  The communication between
                 the central nervous system and the other parts of the body is facilitated
                 by the peripheral nervous system consisting of cranial nerves arising
                 from the brain and spinal nerves arising from the spinal cord. The brain
                 thus allows us to think and take actions based on that thinking.  As you
                 will expect, this is accomplished through a complex design, with different
                 parts of the brain responsible for integrating different inputs and outputs.
                 The brain has three such major parts or regions, namely the fore-brain,
                 mid-brain and hind-brain.
                    The fore-brain is the main thinking part of the brain. It has regions
                 which receive sensory impulses from various receptors. Separate areas
                 of the fore-brain are specialised for hearing, smell, sight and so on.  There
                 are separate areas of association where this sensory information is
                 interpreted by putting it together with information from other receptors
                 as well as with information that is already stored in the brain.  Based on



                 Control and Coordination                                                                 103


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