Page 110 - NCERT Science Class 10 English Medium

6.1.3 How are these Tissues protected?

A delicate organ like the brain, which is so important for a variety of
activities, needs to be carefully protected. For this, the body is designed
so that the brain sits inside a bony box. Inside the box, the brain is
contained in a fluid-filled balloon which provides further shock
absorption. If you run your hand down the middle of your back, you
will feel a hard, bumpy structure. This is the vertebral column or
backbone which protects the spinal cord.

6.1.4 How does the Nervous Tissue cause Action?

So far, we have been talking about nervous tissue, and how it collects
information, sends it around the body, processes information, makes
decisions based on information, and conveys decisions to muscles for
action. In other words, when the action or movement is to be performed,
muscle tissue will do the final job. How do animal muscles move? When
a nerve impulse reaches the muscle, the muscle fibre must move. How
does a muscle cell move? The simplest notion of movement at the cellular
level is that muscle cells will move by changing their shape so that they
shorten. So the next question is, how do muscle cells change their shape?
The answer must lie in the chemistry of cellular components. Muscle
cells have special proteins that change both their shape and their
arrangement in the cell in response to nervous electrical impulses. When
this happens, new arrangements of these proteins give the muscle cells
a shorter form. Remember when we talked about muscle tissue in
Class IX, there were different kinds of muscles, such as voluntary muscles
and involuntary muscles. Based on what we have discussed so far, what
do you think the differences between these would be?

Q U E S T I O N S

?
1. What is the difference between a reflex action and walking?
2. What happens at the synapse between two neurons?

3. Which part of the brain maintains posture and equilibrium of the body?
4. How do we detect the smell of an agarbatti (incense stick)?
5. What is the role of the brain in reflex action?

ANTS
6.2 COORDINATION ANTS
6.2 COORDINA
6.2
6.2 COORDINACOORDINATION ININ PLANTS
6.2 COORDINATION IN PLTION IN PL PLTION IN PLANTSANTS
Animals have a nervous system for controlling and coordinating the
activities of the body. But plants have neither a nervous system nor
muscles. So, how do they respond to stimuli? When we touch the leaves
of a chhui-mui (the ‘sensitive’ or ‘touch-me-not’ plant of the Mimosa
family), they begin to fold up and droop. When a seed germinates, the
root goes down, the stem comes up into the air. What happens? Firstly,
the leaves of the sensitive plant move very quickly in response to touch.

Control and Coordination 105

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