Science case /data -based (4 Marks)

A student fixes a sheet of white paper on a drawing board using some adhesive materials. She places a bar magnet in the centre of it and sprinkles some iron filings uniformly around the bar magnet using a salt sprinkler. On tapping the board gently, she observes that the iron filings have arranged themselves in a particular pattern.
(i) The bar magnet kept at the centre of board has its magnetic field around it. The iron filings sprinkled on the board
experience a force on them due to the magnetic field of bar magnet. So, when the student taps the board the iron filings align themselves according to the magnetic field lines of the bar magnet.
(ii)
(iii)The direction of a magnetic field at a point is determined by placing a small compass needle. The N - pole of compass
indicates the direction of magnetic field at that point.
Two magnetic field lines do not intersect each other because if there was point of intersection, The compass needle would point towards 2 directions.
OR

We have seen that the different parts of our body have specific functions. Our mouth waters when we see the food we like without our meaning to. Our heart's beat without our thinking about it. In fact, we cannot control these actions easily by thinking about them even if we wanted to. 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 the 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

(i) Reflex Action is an unconscious, automatic and involuntary response of efforts, i.e., muscles and glands, to a stimulus, which is monitored through the spinal cord. Reflex action is controlled by the spinal cord.
(ii) Yes, reflex action involves all parts of the voluntary nervous system.
(iii)The part of the autonomic nervous system that controls involuntary actions are controlled or regulated by medulla (hindbrain).
OR
'Beating of heart muscle' is an example of involuntary action. Involuntary actions are slower than reflex actions.