INTEXT QUESTIONS 23.1
1. Can you think of a real-life example, when team work helped you to achieve something that you could not have done by yourself? Please write about this incidence in 3-5 sentences.
Answer: There is no single correct answer. There may be diverse examples. For instance, in farming, a group of people till the land, another group sows the seeds, someone else takes care of the crops and only then everyone enjoys the bounty of a good harvest.
2. Give one example of coordination of a process taking place in our body which is brought about by both the nervous system and hormonal system.
Answer: One example is the secretion of digestive juices. When food enters the stomach, the nervous system sends signals to start digestion, and hormones also stimulate the digestive glands to release digestive juices. Thus, both systems work together to digest food properly.
INTEXT QUESTIONS 23.2
1. The structural and functional unit of nervous system is (encircle the correct alternative out of the following)
(a) Nephron (b) Neuron (c) Synapse (d) Axon
Answer: (b) Neuron .
[ A neuron is the structural and functional unit of the nervous system because it receives and transmits nerve impulses throughout the body.]
2. Consider that you are passing by a garbage disposal area and you immediately cover your nose. Arrange the events below in a logical order by marking them from 1 to 5 to trace the events that happen in the nervous system from detection of foul smell (stimulus generation) to covering your nose (response).
(i) At the end of the axon, electrical impulse releases chemicals
(ii) Stimulus received on the dendritic cells of a neuron sets off chemical reaction that creates an electrical impulse
(iii) Electrical impulse transmitted through cell body and axon
(iv) The chemicals cross the synapse and reach the next neuron. Similarly, the electrical impulse crosses several neurons
(v) Finally, the impulse is delivered from neuron to the gland that helps in recognition of the foul smell and muscle cells that help in covering the nose.
Answer: (ii) → (iii) → (i) → (iv) → (v)
[ The stimulus is first received by dendrites, creating an electrical impulse. The impulse travels through the neuron, chemicals are released at the axon end, cross the synapse to the next neuron, and finally reach the muscles to cover the nose.]
3. With the help of a suitable example, explain the term ‘stimulus.’
Answer: A stimulus is an agent or environmental change that initiates a response in the body. For example, touching a hot object makes us immediately pull our hand away. Here, heat acts as the stimulus and pulling back the hand is the response.
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