Chapter 6: Control and Coordination

Important questions — the ones the board asked most (20)

1. Q1Long answer5 marksAsked: 2024

   35. (a) (i) Distinguish between hormonal co-ordination in plants and animals. (ii) Which part of the brain is responsible for - (1) intelligence (2) riding a bicycle (3) vomiting (4) controlling hunger (iii) How is brain and spinal-cord protected against mechanical injuries ? OR (b) (i) What are tropic movements ? Give an example of a plant hormone which (1) inhibits growth and (2) promotes cell division. (ii) Explain directional movement of a tendril in pea plant in response to touch. Name the hormone responsible for this movement.

   

   Medha Ma’am

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   Model answer · Tropic movements, plant hormones

   1. 1.(b) (i) Tropic movements are plant growth movements in response to stimuli in a particular direction. They are directional movements caused by stimuli such as light, gravity, etc. For example, a shoot grows and bends towards light, and a root grows downwards in response to gravity.1 mark
   2. 2.(1) A plant hormone that inhibits growth is Abscisic acid. Its effects include wilting of leaves.0.5 marks
   3. 3.(2) A plant hormone that promotes cell division is Cytokinins. They are present in greater concentration in areas of rapid cell division, such as fruits and seeds.0.5 marks
   4. 4.(ii) A pea tendril shows directional movement in response to touch. When the tendril comes in contact with a support, auxins move away from the point of contact with the support. So the side of the tendril away from the support has more auxin, and more growth occurs on that side than on the side touching the support. As a result, unequal growth occurs on its two sides, and the tendril coils around the support.2 marks
   5. 5.The hormone responsible for this movement is auxin (auxins). It is synthesised at the shoot tip and helps the cells to grow longer.1 mark

   • Define tropic movements as growth movements "in a particular direction" and name the stimuli, such as light and gravity.
   • For the tendril, write all three steps: "auxins move away from the point of contact", "more growth occurs on the side away from the support", and "unequal growth" makes the tendril coil around the support.
   • Name the hormones exactly: Abscisic acid inhibits growth, Cytokinins promote cell division and auxins coil the tendril.

   Marks split as in the board’s published marking scheme

2. Q2Long answer5 marksAsked: 2024

   (a) (i) Define a reflex arc. Why have reflex arcs evolved in animals ? Trace the sequence of events which occur, when you suddenly touch a hot object. (ii) Name the part of nervous system which helps in communication between the central nervous system and other parts of the body. What are the two components of this system ? OR (b) (i) Leaves of 'chhui-mui' plant begin to fold up and droop in response to a stimulus. Name the stimulus and write the cause for such a rapid movement. Is there any growth involved in the movement ? (ii) Define geotropism in plants. What is meant by positive and negative geotropism ? Give one example of each type.

   

   Medha Ma’am

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   Model answer · Reflex arc, peripheral nervous system

   1. 1.(a) (i) A reflex arc is the pathway that nerve impulses follow during a reflex action. The nerves that detect a stimulus are joined directly to the nerves that move muscles, and this connection is made in the spinal cord.1 mark
   2. 2.Reflex arcs have evolved in animals because the thinking process of the brain is not fast enough. They give a quick response that helps the animal avoid injury.0.5 marks
   3. 3.When we suddenly touch a hot object, these events happen in order: Receptors in the skin detect the heat → the sensory (input) nerve carries electrical impulses to the spinal cord → in the spinal cord, the reflex arc connects the input nerve to the motor (output) nerve → the motor nerve carries the impulses to the muscles of the arm (effector) → the muscles contract and the hand is pulled away at once. The information also goes on to reach the brain.1.5 marks
   4. 4.(ii) The Peripheral Nervous System helps in communication between the central nervous system and the other parts of the body.1 mark
   5. 5.The two components of the Peripheral Nervous System are: 1. Cranial nerves, which arise from the brain. 2. Spinal nerves, which arise from the spinal cord.1 mark

   • Write the hot-object sequence in order with arrows: receptors in the skin, sensory (input) nerve, spinal cord, motor (output) nerve, muscles.
   • For why reflex arcs evolved, write that "the thinking process of the brain is not fast enough".
   • Name both components of the Peripheral Nervous System: cranial nerves and spinal nerves.

   Marks split as in the board’s published marking scheme

3. Q3Long answer5 marksAsked: 2025

   (A) (a) Analyse the given situations and propose a probable reason for each case : (i) The probability of having a swollen neck disease increases due to the deficiency of iodine in a person's diet. (ii) Some individuals in a population are very short in height (dwarfs). (iii) Boys develop thick hair on their face at the age of 10-12 years. (b) Explain two reasons why chemical communication (signalling) becomes essential in multicellular organisms. OR (B) (a) Differentiate between voluntary and involuntary actions. (b) Define reflex action. With the help of a flow chart, show the path of a nerve impulse from its origin in the correct sequence.

   

   Medha Ma’am

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   Hear it from Medha Ma’am · 135 s

   Model answer · hormones and chemical coordination

   1. 1.(A)(a)(i) Iodine is needed by the thyroid gland to make thyroxin; with too little iodine, too little thyroxin is made and the person may get goitre (swollen neck). OR (B)(a) Voluntary actions are done by our will and controlled by the fore-brain (cerebrum); involuntary actions happen without our will and are controlled by the mid-brain and hind-brain (medulla).1 mark
   2. 2.(A)(a)(ii) A deficiency of growth hormone, secreted by the pituitary gland, in childhood leads to dwarfism. OR (B)(a) Examples: voluntary – walking, writing, speaking; involuntary – heartbeat, breathing, salivation.1 mark
   3. 3.(A)(a)(iii) At puberty the testes secrete testosterone, which brings changes such as thick facial hair. OR (B)(b) A reflex action is a sudden, automatic response to a stimulus, made without thinking and controlled by the spinal cord.1 mark
   4. 4.(A)(b) Electrical impulses reach only the cells connected by nervous tissue, not every cell; a hormone carried in the blood can reach all cells. OR (B)(b) Flow chart: Stimulus → Receptor (sense organ) → Sensory neuron → Spinal cord (relay neuron)1 mark
   5. 5.(A)(b) After sending an impulse a nerve cell needs time to reset, so it cannot send impulses continuously; hormones act steadily and continuously. OR (B)(b) → Motor neuron → Effector (muscle or gland) → Response.1 mark

   Marks split as in the board’s published marking scheme

4. Q4Long answer5 marksAsked: 2025

   36. (A) (a) Analyse the given situations and interpret the possible reason for each : (i) Iodine deficiency in diet increases the possibility of a disease of swollen neck in a person. (ii) Some people in population may have very short heights (dwarfs). (iii) Thick facial hairs develop in boys at the age of 10-12 years. (b) Explain two reasons which necessitate the need of chemical communication in multicellular organisms. OR (B) (a) Differentiate between voluntary and involuntary action. (b) Define reflex action. With the help of a flow diagram, show the correct sequence of path of Nerve impulse from place of its origin.

   How the model answer begins

   1. (A)(a)(i) Iodine is needed by the thyroid gland to make thyroxin; iodine deficiency lowers thyroxin and causes goitre (swollen neck). OR (B)(a) Voluntary actions are done by our will after thinking and are controlled by…

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5. Q5Long answer5 marksAsked: 2023

   (a) (i) List three points of difference between nervous and hormonal mechanisms for control and coordination in animals. (ii) How are auxins related with the bending of plant shoot towards unidirectional light ? Explain. OR (b) (i) Name the disorder which a person is likely to suffer from due to the following : (I) Over-secretion of growth hormone (II) Deficiency of oestrogen in females (III) Less secretion of thyroxine Also name the gland that secretes each of the hormones mentioned above. (ii) How is the timing and amount of hormone released regulated ? Explain with the help of an example.

   How the model answer begins

   1. (a) (i) Nervous and hormonal mechanisms for control and coordination in animals differ as follows: 1. Nervous control: messages are sent as electrical impulses; Hormonal control: messages are carried in the form of…

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6. Q6Long answer4 marksAsked: 2026

   Plants exhibit movements in response to various environmental stimuli to adopt and survive in their surroundings. These movements, influenced by external factors such as light, gravity, water and chemicals are regulated by specific plant hormones. For example, the differential growth of plant parts allows them to bend, grow or orient themselves in particular directions. Roots and shoots often show contrasting response to the same stimulus, highlighting the complex mechanisms involved in plant growth and development. (a) Why is hydrotropism essential for plants ? (b) What role does auxin play in the growth of plants ? (c) Differentiate between movement shown by the sensitive plant and tropic movement by plants (Two points). OR (c) How does movement of roots differ from that of shoots in response to gravity and light ?

7. Q7Case-based4 marksAsked: 2025

   In life, certain changes take place in the environment, which we call 'stimulus', and we respond to them in a suitable manner. A sudden touch of a flame is a dangerous situation for us. One way is that we take cognisance of the possibility of burning and then move our hand away from the flame, but our body is so designed that we immediately protect ourselves from such situations. (i) Write the name and definition of the action by which we protect ourselves in the above situation. (ii) Write the role of (a) motor neuron and (b) relay neuron. (iii) (A) What are the two types of nervous systems in the human body? Write the components of both of these. Or (iii) (B) Which part of the human brain is responsible for the following? (a) Thinking (b) Holding a pencil (c) Controlling blood pressure (d) Controlling hunger

   How the model answer begins

   1. (i) The action is called a reflex action.

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8. Q8Case-based4 marksAsked: 2025

   39. In life there are certain changes in the environment called 'stimuli' to which we respond appropriately. Touching a flame suddenly is a dangerous situation for us. One way is to think consciously about the possibility of burning and then moving the hand. But our body has been designed in such a way that we save ourself from such situations immediately. (i) Name the action by which we protect ourself in the situation mentioned above and define it. (ii) Write the role of (a) motor and (b) relay neuron. (iii) (A) What are the two types of nervous system in human body? Name the components of each of them. OR (iii) (B) Which part of the human brain is responsible for : (a) thinking (b) picking up a pencil (c) controlling blood pressure (d) controlling hunger

   How the model answer begins

   1. (i) The action is a reflex action.

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9. Q9Case-based4 marksAsked: 2025

   The growth movements of plant parts in which the direction of the stimulus determines the direction of the response is known as tropic movements or tropism. Plants also have non-directional movements which may not be growth dependent. (I) Name the movement which causes 'X' and 'Y' to grow downwards and upwards respectively. (Refer above figure) (II) Write the name of a hormone that plays a major role in (i) falling of leaves (ii) rapid cell division (III) (a) Leaves of the sensitive plant move very quickly in response to 'touch'. How is this stimulus of touch communicated and explain how the movement takes place. OR (III) (b) Name the plant hormone which is synthesized at the shoot tip. How does this hormone helps the plant to bend towards light ?

   How the model answer begins

   1. (I) 'X', the root, grows downwards because of positive geotropism. It grows towards the pull of earth or gravity.

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10. Q10Case-based4 marksAsked: 2025

    The growth movements of plant parts in which the direction of the stimulus determines the direction of the response is known as tropic movements or tropism. Plants also have non-directional movements which may not be growth dependent. (I) Name the movement which causes 'X' and 'Y' to grow downwards and upwards respectively. (II) Write the name of a hormone that plays a major role in (i) falling of leaves (ii) rapid cell division (III) (a) Leaves of the sensitive plant move very quickly in response to 'touch'. How is this stimulus of touch communicated and explain how the movement takes place. OR (III) (b) Name the plant hormone which is synthesized at the shoot tip. How does this hormone helps the plant to bend towards light ?

    How the model answer begins

    1. (I) 'X' is the root. It grows downwards in response to the pull of earth or gravity, so its movement is positive geotropism. Roots also bend away from light, so it is also negative phototropism.

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11. Q11Case-based4 marksAsked: 2026

    Read the following passage and answer the questions that follow : A middle-aged person is facing some cognitive changes in himself. His early symptoms included mild forgetfulness. For example, forgetting where he left his mobile or failing to find words to complete his sentences. He was facing problems in driving a car, climbing up and down the stairs, inserting a plug into an outlet. He slowly developed a sad mood and anxiety. (a) What are voluntary actions ? (b) Which part of the brain is responsible for precision of voluntary actions ? (c) (i) Explain the role of the medulla. OR (c) (ii) How do the animal muscles move ?

    How the model answer begins

    1. (a) Voluntary actions are actions done by our will, under the conscious control of the brain, such as walking, talking and writing.

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12. Q12Case-based4 marksAsked: 2025

    A person while climbing up a rocky hill comes into a panic state and fear. His body starts reacting in a "flight-or-flight" condition to adjust to the dangerous and stressful situation. Based on the above facts, answer the questions that follow. (a) (i) Name the hormone secreted in the blood of the person in this situation. OR (a) (ii) Name the source gland of the hormone secreted in this condition. (b) State any two responses in the body of the person as a result of the secretion of this hormone. (c) How does the action of the chemical signal in terms of hormones differ from the electrical impulses via nerve cells ?

    How the model answer begins

    1. (a)(i) Adrenaline is secreted into the blood. OR (a)(ii) Its source gland is the adrenal gland.

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13. Q13Short answer3 marksAsked: 2026

    Give reasons for the following : (a) Adrenal gland is known as the stress gland of the body. (b) Prenatal sex determination is banned in India. (c) Vegetative propagation is advantageous in some plants.

    How the model answer begins

    1. (a) The adrenal gland is known as the stress gland because it secretes the hormone adrenaline, which enables the animal body to face a scary situation. Adrenaline is secreted directly into the blood. It makes the heart…

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14. Q14Short answer3 marksAsked: 2025

    State two limitations of electrical impulses in multicellular organisms. Why is chemical communication better than electrical impulses as a means of communication between cells in multicellular organisms?

15. Q15Short answer3 marksAsked: 2024

    Define reflex action. With the help of a flow chart show the path of a reflex action such as sneezing.

    How the model answer begins

    1. A reflex action is a quick, involuntary and automatic response to a stimulus, made without thinking. Its pathway (reflex arc) passes through the spinal cord or, for reflexes of the head such as sneezing, the medulla of…

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16. Q16Short answer3 marksAsked: 2025

    29. Plants have neither a nervous system nor muscles, even then they respond to stimuli. For example, the leaves of chhui-mui (touch-me-not) plant when touched begin to fold up and droop. (a) How is the information communicated in "touch-me-not" plants ? (b) What enables the plant cells to bring out the observable response ? (c) Differentiate the movement mentioned above from the movement of tendrils in a pea plant.

    How the model answer begins

    1. (a) In the touch-me-not plant, the leaves move at a point different from the point of touch. So the information that a touch has occurred must be communicated. The plant cells use electrical-chemical means to convey…

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17. Q17Short answer3 marksAsked: 2025

    (a) Name the glands that secrete : (i) Adrenaline (ii) Thyroxin (b) Explain with example how the timing and amount of hormone released are regulated in the human body.

    How the model answer begins

    1. Adrenaline hormone is secreted by the adrenal gland.

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18. Q18Short answer3 marksAsked: 2025

    A hormone 'X' is secreted in blood when a person is under scary situation. (a) Identify the hormone 'X' and the gland that secretes it. (b) Explain its role in dealing with scary or emergency situations.

    How the model answer begins

    1. (a) The hormone 'X' is adrenaline.

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19. Q19Short answer3 marksAsked: 2025

    (a) Define the term hormone. (b) "The secretion of hormones should be in precise quantities. We have a feedback mechanism by which this is done." Justify this statement with the help of an example.

20. Q20Short answer3 marksAsked: 2025

    (a) What is meant by reflex arc ? Where are they formed in the human body ? (b) Why have reflex arcs evolved in animals ?

    How the model answer begins

    1. (a) A reflex action is a rapid, automatic response to a harmful stimulus, made without thinking (e.g. pulling the hand away from a flame). The pathway the impulse takes from the receptor through the spinal cord to the…

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18 more questions of this chapter, each with its model answer, in the AskMedha app.

Objective questions with the board’s key (10)

1. 1. CBSE 2026

   Human brain has various parts or regions that help in different actions, responses and coordination. From the following, identify the part responsible for precision of voluntary actions :

   • (A) Cerebrum
   • (B) Cerebellum ✓
   • (C) Medulla
   • (D) Pons

   Answer: (B)

2. 2. CBSE 2026

   Assertion (A) : Plants have hormones that do not control directional growth. Reason (R) : Abscisic acid inhibits growth.

   • (A) Both, Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
   • (B) Both, Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A). ✓
   • (C) Assertion (A) is true, but Reason (R) is false.
   • (D) Assertion (A) is false, but Reason (R) is true.

   Answer: (B)

3. 3. CBSE 2026

   Walking in a straight line and riding a bicycle are activities which are possible due to coordination of which part of the brain ?

   • (A) Fore-Brain Cerebrum
   • (B) Mid-Brain Cerebellum
   • (C) Hind-Brain Cerebellum ✓
   • (D) Hind-Brain Medulla

   Answer: (C)

4. 4. CBSE 2026

   In a synapse, the chemical signal is transmitted from :

   • (A) Dendritic end of one neuron to axonal end of another neuron.
   • (B) Axon to cell body of the same neuron.
   • (C) Cell body to axonal end of the same neuron.
   • (D) Axonal end of one neuron to dendritic end of another neuron. ✓

   Answer: (D)

5. 5. CBSE 2026

   The growth of tendrils in grapes plants is due to :

   • (A) Effect of light
   • (B) Effect of gravity
   • (C) Rapid cell division in tendril cells in contact with the support
   • (D) Rapid cell division in tendril cells that are away from the support ✓

   Answer: (D)

6. 6. CBSE 2026

   In plants, the role of cytokinin is to/in :

   • (A) promote cell division ✓
   • (B) wilting of leaves
   • (C) promote opening of stomatal pore
   • (D) growth of stem

   Answer: (A)

7. 7. CBSE 2026

   Following are the statements about the different parts of the brain. Select the correct statements. (i) The thinking part of the brain is the forebrain. (ii) Centres for smell, hearing, memory, sight are located in forebrain. (iii) Salivation, vomiting, blood pressure are controlled by medulla in the hind brain. (iv) Cerebellum does not control the posture and balance of the body.

   • (A) (i), (ii) and (iii) ✓
   • (B) (ii), (iii) and (iv)
   • (C) (i), (ii) and (iv)
   • (D) (i), (iii) and (iv)

   Answer: (A)

8. 8. CBSE 2026

   Assertion (A) : Reflex actions do not involve thinking. Reason (R) : Most reflex actions are controlled by the spinal cord.

   • (A) Both, Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A). ✓
   • (B) Both, Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
   • (C) Assertion (A) is true, but Reason (R) is false.
   • (D) Assertion (A) is false, but Reason (R) is true.

   Answer: (A)

9. 9. CBSE 2026

   Identify the type of tropic movement that is responsible for the movement of the pollen tube towards an ovule from the following options.

   • (A) Hydrotropism
   • (B) Geotropism
   • (C) Chemotropism ✓
   • (D) Phototropism

   Answer: (C)

10. 10. CBSE 2026

    Identify the endocrine gland that regulates the growth of the human body.

    • (A) Pituitary gland ✓
    • (B) Thyroid gland
    • (C) Pancreas
    • (D) Adrenal gland

    Answer: (A)

Questions parents and students ask

How many marks does "Control and Coordination" carry in CBSE Class 10 Science?

In the CBSE papers of 2023–2026, this chapter carried about 5 marks and about 3 questions a year; by marks it ranks 9 in Science.

Which are the most important (VVI) questions of "Control and Coordination"?

The 20 questions above are from the board’s real papers, each with the years it was asked; the most-asked come first with their full model answers. All 38 written questions of this chapter, with answers, are in the AskMedha app.

Do the answers follow the board’s marking scheme?

Yes. CBSE publishes its marking schemes; every model answer here is written point by point to the marks the board’s own scheme gives, and checked by a second, independent model.