Page 109 - NCERT Science Class 10 English Medium

all this, a decision is made about how to respond and the information is
passed on to the motor areas which control the movement of voluntary
muscles, for example, our leg muscles. However, certain sensations are
distinct from seeing or hearing, for example, how do we know that we
have eaten enough? The sensation of feeling full is because of a centre
associated with hunger, which is in a separate part of the fore-brain.

Figure
Figure
Figure 6.3 Human brain
Figure 6.3
6.3
Figure 6.36.3
Study the labelled diagram of the human brain. We have seen that
the different parts have specific functions. Can we find out the function
of each part?
Let us look at the other use of the word ‘reflex’ that we have talked
about in the introduction. Our mouth waters when we see food we like
without our meaning to. Our hearts beat without our thinking about it.
In fact, we cannot control these actions easily by thinking about them
even if we wanted to. Do we have to think about or remember to breathe
or digest food? So, in between the simple reflex actions like change in
the size of the pupil, and the thought out actions such as moving a
chair, there is another set of muscle movements over which we do not
have any thinking control. Many of these involuntary actions are
controlled by the mid-brain and hind-brain. All these involuntary actions
including blood pressure, salivation and vomiting are controlled by the
medulla in the hind-brain.
Think about activities like walking in a straight line, riding a bicycle,
picking up a pencil. These are possible due to a part of the hind-brain
called the cerebellum. It is responsible for precision of voluntary actions
and maintaining the posture and balance of the body. Imagine what
would happen if each of these events failed to take place if we were not
thinking about it.

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