Class 10 Science · Chapter 6

Control and Coordination

175 Class 10 Science questions on Control and Coordination from the NCERT textbook, NCERT Exemplar and CBSE board papers 2024–2026, each with its answer and a step-by-step solution.

CBSE Class 10 Science previous year papers, with answers →

Questions · page 2 of 9

1. Q21 NCERT · Intext Questions (Page 108)
   How do auxins promote the ​growth of a ​tendril ​around ​a support?
   Show answer

   Auxin collects on the side away from the support and speeds its growth, so the tendril curves around the support.

   A tendril is sensitive to touch. When it comes into contact with a support, the auxin present in it moves away from the side that is touching the support and collects on the side away from it. Auxin stimulates cells to grow longer, so the cells of the free side, which now have more auxin, elongate faster, while the part of the tendril in contact with the object does not grow as rapidly. Because one side of the tendril grows longer than the other, the tendril cannot remain straight: it curves towards the side that is growing less, that is, towards the support. As growth goes on, the tendril circles around the support and thus clings to it. This directional growth in response to touch is called thigmotropism.

   Step-by-step solution →
2. Q22 NCERT · Intext Questions (Page 108)
   Design ​an ​experiment ​to ​demonstrate hydrotropism.
   Show answer

   Roots bend towards a water-filled porous pot in dry soil but grow straight down in the control, showing positive hydrotropism.

   Aim: to show that roots grow towards water, that is, to demonstrate hydrotropism. Materials: two troughs, dry sandy soil, germinated gram or bean seedlings, a small porous unglazed earthen pot and water. Method: (i) Fill the first trough with dry soil and sink the porous pot, filled with water, into the soil near one end, keeping it filled throughout; water seeps slowly through its wall so that only the soil near it stays moist. (ii) Plant two or three germinated seedlings in the middle of this trough, at a distance from the pot. (iii) Set up a second, control trough with the same soil and the same seedlings, but water it evenly all over and use no porous pot, keeping light and temperature the same for both. (iv) Leave both undisturbed for about a week, keeping the pot filled. (v) Dig the seedlings out carefully without breaking the roots and wash off the soil. Observation: in the test trough the roots have bent sideways and grown towards the porous pot instead of growing straight down, while in the control trough the roots have grown straight down. Conclusion: the roots grow in the direction in which water is available, so roots show positive hydrotropism. The control rules out gravity as the cause of the bending, since the only difference between the two troughs was where the water lay.

   Step-by-step solution →
3. Q23 NCERT · Intext Questions (Page 111)
   How ​does ​chemical ​coordination ​take place in animals?
   Show answer

   Endocrine glands secrete hormones into the blood, which carries them to target organs; feedback regulates the amount secreted.

   Chemical coordination in animals is carried out by hormones, which make up the endocrine system — a second means of control and coordination alongside the nervous system, needed because electrical impulses reach only those cells that are joined by nervous tissue. A stimulus or a change in the body causes an endocrine gland, which is ductless, to secrete its hormone directly into the blood. The blood carries the hormone to all parts of the body, so it can reach every cell whatever the nerve connections. Even so, it acts only on its target organs — the specific tissues whose cells carry the special molecules that recognise it — and it is effective in very small amounts, producing changes that are slow to begin but widespread and long lasting. The timing and the amount of hormone released are regulated by feedback mechanisms, so that hormones are secreted in precise quantities: when the sugar level in the blood rises, the cells of the pancreas detect it and produce more insulin, and as the blood sugar falls, insulin secretion is reduced. For example, in a frightening situation adrenaline is secreted by the adrenal glands into the blood; acting on its target organs, it makes the heart beat faster, diverts blood from the digestive system and the skin to the skeletal muscles, and increases the breathing rate, so that the body is ready to fight or to run away.

   Step-by-step solution →
4. Q24 NCERT · Intext Questions (Page 111)
   Why ​is the use of ​iodised ​salt ​advisable?
   Show answer

   Iodine is needed for thyroxin; its lack causes goitre, and iodised salt supplies it cheaply to everyone.

   Iodine is necessary for the thyroid gland to make the hormone thyroxin, and thyroxin regulates carbohydrate, protein and fat metabolism in the body so as to provide the best balance for growth. If iodine is deficient in the diet, the gland cannot make enough thyroxin: metabolism and growth are poorly regulated, and there is a possibility of suffering from goitre, one symptom of which is a swollen neck, since the thyroid gland itself lies in the neck and enlarges. In children a continued shortage also holds back physical and mental development. Ordinary food and plain salt supply very little iodine, and in many places the soil and water contain almost none, whereas salt is eaten daily by everybody in small and fairly steady amounts. Adding a small measured quantity of an iodine compound to common salt is therefore a cheap and reliable way of supplying the daily requirement of iodine to the whole population, and this is why the use of iodised salt is advisable.

   Step-by-step solution →
5. Q25 NCERT · Intext Questions (Page 111)
   How ​does our ​body ​respond ​when ​adrenaline is secreted into ​the blood?
   Show answer

   Adrenaline makes the heart beat faster, diverts blood to the skeletal muscles and increases breathing, preparing the body to fight or run away.

   Adrenaline is secreted by the adrenal glands directly into the blood, which carries it to different parts of the body, and it acts on its target organs. The heart beats faster, so that more oxygen is supplied to the muscles. The blood going to the digestive system and to the skin is reduced, because the muscles around the small arteries in these organs contract, and this diverts the blood to the skeletal muscles. The breathing rate also increases, because of stronger contractions of the diaphragm and the rib muscles, so that more oxygen is taken in. In addition the pupils of the eyes widen and stored glycogen is broken down to glucose, giving the muscles fuel as well as oxygen. All these responses together enable the body to be ready to deal with the situation, that is, to fight or to run away.

   Step-by-step solution →
6. Q26 NCERT · Intext Questions (Page 111)
   Why are some ​patients ​of ​diabetes treated ​by ​giving injections of ​insulin?
   Show answer

   Their pancreas makes too little insulin, so injections replace it; insulin is a protein, so it is not given by mouth.

   Insulin is a hormone produced by the pancreas which helps in regulating the blood sugar level; normally, when the sugar level in the blood rises, the cells of the pancreas detect it and secrete more insulin, and secretion falls again as the level drops. In these patients the pancreas does not secrete insulin in proper amounts, so the sugar level in the blood rises and stays high, which causes many harmful effects; this condition is diabetes. Insulin is therefore given from outside to make up for what the pancreas fails to produce, and it brings the raised blood sugar down and keeps it within the normal range. It has to be given as an injection and not by mouth because insulin is a protein: swallowed, it would be broken down into amino acids by the digestive enzymes of the alimentary canal before it could act, whereas injected it reaches the blood unchanged. Since the injections only replace the missing hormone and do not repair the pancreas, they have to be continued.

   Step-by-step solution →
7. Q27 Exemplar · Multiple Choice Questions
   Which ​of the following statements ​is ​correct ​about ​receptors?

   1. (a)Gustatory receptors detect taste while olfactory receptors detect smell
   2. (b)Both gustatory and olfactory receptors detect smell
   3. (c)Auditory receptors detect smell and olfactory receptors detect taste
   4. (d)Olfactory receptors detect taste and gustatory receptors smell
   Show answer

   (a) Gustatory receptors detect taste while olfactory receptors detect smell

   Step-by-step solution →
8. Q28 Exemplar · Multiple Choice Questions
   Electrical ​impulse travels ​in a ​neuron ​from

   1. (a)$\text{Dendrite}\to \text{axon}\to \text{axonal end}\to \text{cell body}$
   2. (b)$\text{Cell body}\to \text{dendrite}\to \text{axon}\to \text{axonal end}$
   3. (c)$\text{Dendrite}\to \text{cell body}\to \text{axon}\to \text{axonal end}$
   4. (d)$\text{Axonal end}\to \text{axon}\to \text{cell body}\to \text{dendrite}$
   Show answer

   (c) $\text{Dendrite}\to \text{cell body}\to \text{axon}\to \text{axonal end}$

   Step-by-step solution →
9. Q29 Exemplar · Multiple Choice Questions
   In a ​synapse, chemical ​signal ​is transmitted ​from

   1. (a)dendritic end of one neuron to axonal end of another neuron
   2. (b)axon to cell body of the same neuron
   3. (c)cell body to axonal end of the same neuron
   4. (d)axonal end of one neuron to dendritic end of another neuron
   Show answer

   (d) axonal end of one neuron to dendritic end of another neuron

   Step-by-step solution →
10. Q30 Exemplar · Multiple Choice Questions
    In a ​neuron, conversion ​of electrical ​signal to ​a ​chemical ​signal occurs ​at/in

    1. (a)cell body
    2. (b)axonal end
    3. (c)dendritic end
    4. (d)axon
    Show answer

    (b) axonal end

    Step-by-step solution →
11. Q31 Exemplar · Multiple Choice Questions
    Which is the correct ​sequence ​of the ​components ​of a ​reflex ​arc?

    1. (a)$\text{Receptors}\to \text{Muscles}\to \text{Sensory neuron}\to \text{Motor neuron}\to \text{Spinal cord}$
    2. (b)$\text{Receptors}\to \text{Motor neuron}\to \text{Spinal cord}\to \text{Sensory neuron}\to \text{Muscle}$
    3. (c)$\text{Receptors}\to \text{Spinal cord}\to \text{Sensory neuron}\to \text{Motor neuron}\to \text{Muscle}$
    4. (d)$\text{Receptors}\to \text{Sensory neuron}\to \text{Spinal cord}\to \text{Motor neuron}\to \text{Muscle}$
    Show answer

    (d) $\text{Receptors}\to \text{Sensory neuron}\to \text{Spinal cord}\to \text{Motor neuron}\to \text{Muscle}$

    Step-by-step solution →
12. Q32 Exemplar · Multiple Choice Questions
    Which of the ​following statements ​are ​true?

    1. (i)Sudden action in response to something in the environment is called reflex action
    2. (ii)Sensory neurons carry signals from spinal cord to muscles
    3. (iii)Motor ​neurons carry ​signals from receptors to spinal cord
    4. (iv)The path through which signals are transmitted from a receptor ​to a muscle or a ​gland is called ​reflex arc

    1. (a)(i) and (ii)
    2. (b)(i) and (iii)
    3. (c)(i) and (iv)
    4. (d)(i) , (ii) and (iii)
    Show answer

    (c) (i) and (iv)

    Step-by-step solution →
13. Q33 Exemplar · Multiple Choice Questions
    Which of the following ​statements are true about the ​brain?

    1. (i)The main thinking part of brain is hind brain
    2. (ii)Centres of hearing, smell, memory, ​sight etc ​are located in fore brain.
    3. (iii)Involuntary actions like salivation, vomiting, blood pressure are controlled by the medulla in the ​hind brain
    4. (iv)Cerebellum does not ​control posture and balance of the body

    1. (a)(i) and (ii)
    2. (b)(i), (ii) and (iii)
    3. (c)(ii) and (iii)
    4. (d)(iii) and (iv)
    Show answer

    (c) (ii) and (iii)

    Step-by-step solution →
14. Q34 Exemplar · Multiple Choice Questions
    Posture ​and balance ​of ​the ​body is controlled ​by

    1. (a)cerebrum
    2. (b)cerebellum
    3. (c)medulla
    4. (d)pons
    Show answer

    (b) cerebellum

    Step-by-step solution →
15. Q35 Exemplar · Multiple Choice Questions
    Spinal cord originates from

    1. (a)cerebrum
    2. (b)medulla
    3. (c)pons
    4. (d)cerebellum
    Show answer

    (b) medulla

    Step-by-step solution →
16. Q36 Exemplar · Multiple Choice Questions
    The ​movement of shoot ​towards ​light ​is

    1. (a)geotropism
    2. (b)hydrotropism
    3. (c)chemotropism
    4. (d)phototropism
    Show answer

    (d) phototropism

    Step-by-step solution →
17. Q37 Exemplar · Multiple Choice Questions
    The ​main function ​of ​abscisic acid in plants is ​to

    1. (a)increase the length of cells
    2. (b)promote cell division
    3. (c)inhibit growth
    4. (d)promote growth of stem
    Show answer

    (c) inhibit growth

    Step-by-step solution →
18. Q38 Exemplar · Multiple Choice Questions
    Which of ​the following is not ​associated ​with ​growth of plant?

    1. (a)Auxin
    2. (b)Gibberellins
    3. (c)Cytokinins
    4. (d)Abscisic acid
    Show answer

    (d) Abscisic acid

    Step-by-step solution →
19. Q39 Exemplar · Multiple Choice Questions
    Iodine is necessary ​for ​the synthesis ​of ​which ​hormone?

    1. (a)Adrenaline
    2. (b)Thyroxin
    3. (c)Auxin
    4. (d)Insulin
    Show answer

    (b) Thyroxin

    Step-by-step solution →
20. Q40 Exemplar · Multiple Choice Questions
    Choose ​the incorrect ​statement ​about insulin

    1. (a)It is produced from pancreas
    2. (b)It regulates growth and development of the body
    3. (c)It regulates blood sugar level
    4. (d)Insufficient secretion of insulin will cause diabetes
    Show answer

    (b) It regulates growth and development of the body

    Step-by-step solution →