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 4 of 9

1. Q61 Exemplar · Short Answer Questions
   Name ​the plant hormones ​responsible for the following

   1. (a)elongation ​of cells ​
   2. (b)growth of stem
   3. (c)promotion of cell ​division
   4. (d)​falling of ​senescent leaves.
   Show answer

   The hormones are auxin, gibberellin, cytokinin and abscisic acid, respectively.

   (a) Auxin; (b) Gibberellin; (c) Cytokinin; (d) Abscisic acid.

   Step-by-step solution →
2. Q62 Exemplar · Short Answer Questions
   Label ​the ​endocrine ​glands ​in Figure ​7.3.

   Show answer

   The labelled glands are the pineal, pituitary, thyroid and thymus, in the order (a) to (d).

   (a) Pineal gland; (b) Pituitary gland; (c) Thyroid gland; (d) Thymus gland.

   Step-by-step solution →
3. Q63 Exemplar · Short Answer Questions
   In ​Figure 7.4 (a), (b) and (c), ​which appears ​more ​accurate and ​why?

   Show answer

   Drawing (a) is more accurate because it shows the shoot growing upward and the roots downward, as each responds to gravity.

   Drawing (a) appears more accurate. When a potted plant is left lying on its side, only the growing tips can respond, and they respond to gravity. The shoot grows away from gravity and so curves upward, which is negative geotropism, and it is also growing towards the light; the roots grow towards gravity and so turn downward, which is positive geotropism. Drawing (a) is the only one that shows both of these together. In (b) the shoot is right but the roots are shown growing upward, and in (c) the roots are right but the shoot is shown growing downward.

   Step-by-step solution →
4. Q64 Exemplar · Short Answer Questions
   Label ​the ​parts of ​a ​neuron in ​Figure 7.5.

   Show answer

   (a) Dendrite, (b) cell body (cyton), (c) axon, (d) nerve ending (axonal end).

   (a) Dendrite; (b) Cell body, also called the cyton; (c) Axon; (d) Nerve ending, also called the axonal end.

   Step-by-step solution →
5. Q65 Exemplar · Short Answer Questions
   Match ​the ​terms ​of ​Column (A) ​with ​those of Column (B)
   Show answer

   (a) Olfactory receptors - (iii) Nose; (b) Thermo receptors (temperature receptors) - (iv) Skin; (c) Gustatoreceptors - (i) Tongue; (d) Photoreceptors - (ii) Eye.

   Step-by-step solution →
6. Q66 Exemplar · Short Answer Questions
   What ​is a ​tropic movement? Explain ​with ​an ​example.
   Show answer

   A tropic movement is directional growth of a plant part in response to a stimulus, as a shoot bends towards light.

   A tropic movement (tropism) is a directional growth movement of a plant part in response to an external stimulus, in which the direction of the response is decided by the direction of the stimulus. Growth towards the stimulus is positive tropism and growth away from it is negative tropism. Example - phototropism: in a plant kept beside a window, auxin made at the shoot tip diffuses to the shaded side, where it makes the cells elongate more than those on the lit side; the two sides therefore grow unequally and the shoot bends towards the light. Roots of the same plant bend away from light (negative phototropism) and towards gravity (positive geotropism). Other tropisms are geotropism, hydrotropism, chemotropism and thigmotropism.

   Step-by-step solution →
7. Q67 Exemplar · Short Answer Questions
   What will ​happen ​if intake ​of ​iodine ​in our diet ​is low?
   Show answer

   Too little iodine means too little thyroxine, so metabolism slows and the thyroid gland swells, causing goitre.

   Iodine is the raw material the thyroid gland uses to make the hormone thyroxine, so a diet low in iodine leaves the gland unable to make enough of it. Two things follow. First, thyroxine regulates carbohydrate, protein and fat metabolism, so with it in short supply the body's metabolic rate falls: the person feels tired and sluggish, feels cold, gains weight and has dry skin, and in a growing child both physical growth and mental development are retarded. Second, the pituitary detects the low thyroxine level and secretes more thyroid-stimulating hormone; under this constant drive the thyroid tissue enlarges, producing the swelling of the neck known as goitre. The condition is preventable by using iodised salt.

   Step-by-step solution →
8. Q68 Exemplar · Short Answer Questions
   What happens at ​the synapse ​between two ​neurons?
   Show answer

   At a synapse the impulse releases a neurotransmitter that crosses the gap and starts a fresh impulse in the next neuron.

   The axon terminal of one neuron and the dendrite of the next are separated by a fine gap called the synaptic cleft; together with the two membranes it forms the synapse. When the electrical impulse travelling down the axon reaches the axon terminal it can go no further electrically, and instead causes vesicles there to release a chemical, a neurotransmitter such as acetylcholine, into the gap. The chemical diffuses across the cleft and binds to receptors on the membrane of the dendrite of the next neuron, where it starts a fresh electrical impulse that travels on through that neuron. So at a synapse the signal is converted from electrical to chemical and back to electrical. The same events occur at a neuromuscular junction, except that the chemical there makes the muscle cell contract.

   Step-by-step solution →
9. Q69 Exemplar · Short Answer Questions
   Answer the ​following ​:

   1. (a)Which hormone is responsible for ​the changes ​noticed in females at puberty?
   2. (b)Dwarfism results due to deficiency of which hormone?
   3. (c)Blood sugar level rises ​due to deficiency of which hormone?
   4. (d)Iodine ​is necessary for the ​synthesis ​of which hormone?
   Show answer

   The hormones are oestrogen, growth hormone, insulin and thyroxine, respectively.

   (a) Oestrogen, secreted by the ovary, is responsible for the changes noticed in females at puberty. (b) Growth hormone, from the pituitary gland; too little of it during childhood causes dwarfism. (c) Insulin, from the islets of Langerhans of the pancreas; its deficiency lets the blood sugar level rise, which is diabetes mellitus. (d) Thyroxine, made by the thyroid gland, for whose synthesis iodine is the essential raw material.

   Step-by-step solution →
10. Q70 Exemplar · Short Answer Questions
    Answer the following :

    1. (a)​Name the endocrine gland associated with brain?
    2. (b)Which ​gland secretes ​digestive enzymes as well as hormones?
    3. (c)Name the endocrine gland associated with kidneys?
    4. (d)Which endocrine gland is ​present in ​males but not in ​females?
    Show answer

    The answers are the pituitary, the pancreas, the adrenal glands and the testes.

    (a) The pituitary gland, which hangs from the base of the brain below the hypothalamus (the pineal gland also lies inside the brain). (b) The pancreas, whose acinar tissue secretes digestive enzymes into the pancreatic duct while its islets of Langerhans secrete insulin and glucagon into the blood; it is therefore a mixed gland. (c) The adrenal glands (suprarenal glands), one resting on the upper end of each kidney. (d) The testes, which secrete testosterone; females have ovaries in their place.

    Step-by-step solution →
11. Q71 Exemplar · Long Answer Questions
    Draw ​the ​structure of a ​neuron ​and ​explain ​its ​function.
    Show answer

    A neuron receives signals at the dendrites, conducts them along the axon as electrical impulses and passes them on chemically at the terminals.

    A neuron is the structural and functional unit of the nervous system and the longest cell in the body. Its parts and their functions are: dendrites, the short branched processes that receive the signal and carry it towards the cell body; the cell body (cyton), containing the nucleus and cytoplasm, which keeps the cell alive and adds together the signals arriving from all the dendrites; the axon, a single long fibre that carries the impulse away from the cell body; the myelin sheath, a fatty insulating cover broken at the nodes of Ranvier, which makes conduction much faster; and the axonal terminals, the fine end branches that release a chemical into the synapse. The function of the neuron is therefore to receive information at the dendritic end, conduct it as an electrical impulse along the axon, and pass it on chemically across the synapse to the next neuron or to a muscle cell, always in the order dendrite to cell body to axon to axonal terminal.

    Step-by-step solution →
12. Q72 Exemplar · Long Answer Questions
    What are ​the major ​parts ​of ​the ​brain? ​Mention the functions of ​different parts.
    Show answer

    The brain has three major parts, the fore-brain, mid-brain and hind-brain, with the fore-brain thinking and the other two running involuntary actions.

    The brain has three major parts - the fore-brain, the mid-brain and the hind-brain. Fore-brain: the cerebrum is the largest part and the main thinking part, with sensory areas that receive sight, hearing, smell, taste and touch, association areas that reason, learn and remember, and motor areas that start voluntary movement; the hypothalamus of the fore-brain controls hunger, thirst and body temperature and directs the pituitary gland. Mid-brain: it controls the reflex movements of the head, neck and trunk in response to sight and sound, and the change in the size of the pupil; these are involuntary. Hind-brain: the cerebellum gives precision to voluntary actions and maintains the posture and balance of the body; the pons helps regulate respiration and relays signals between the cerebrum and the cerebellum; and the medulla oblongata controls the involuntary actions of heartbeat, breathing, blood pressure, salivation and vomiting. In short, the fore-brain thinks and acts voluntarily, while the mid-brain and hind-brain run the body involuntarily.

    Step-by-step solution →
13. Q73 Exemplar · Long Answer Questions
    What constitutes ​the central ​and peripheral nervous systems? How are ​the ​components ​of central ​nervous system protected?
    Show answer

    The CNS is the brain and spinal cord and the PNS is the nerves from them; bone, meninges and cerebrospinal fluid protect the CNS.

    The central nervous system consists of the brain and the spinal cord; it receives information from the receptors, processes it, takes the decision and sends out the instructions. The peripheral nervous system consists of the nerves that arise from it - twelve pairs of cranial nerves from the brain and thirty-one pairs of spinal nerves from the spinal cord - whose sensory fibres carry information in to the central nervous system and whose motor fibres carry instructions out to the muscles and glands. The components of the central nervous system are protected in three layers. The brain is enclosed in a bony box, the cranium or brain box, and the spinal cord is enclosed in the vertebral column made of vertebrae. Inside the bone, both are wrapped in three membranes called the meninges, and the space between these membranes is filled with cerebrospinal fluid, which acts as a shock absorber and cushions the brain and the cord against injury.

    Step-by-step solution →
14. Q74 Exemplar · Long Answer Questions
    Mention ​one ​function for each of ​these hormones :

    1. (a)Thyroxin
    2. (b)Insulin
    3. (c)Adrenaline
    4. (d)Growth ​hormone
    5. (e)​Testosterone.
    Show answer

    Thyroxin regulates metabolism, insulin lowers blood glucose, adrenaline prepares for emergency, growth hormone controls growth, and testosterone brings male secondary sexual characters.

    (a) Thyroxin, from the thyroid gland, regulates the metabolism of carbohydrates, proteins and fats, that is, it sets the body's metabolic rate. (b) Insulin, from the islets of Langerhans in the pancreas, lowers and regulates the level of glucose in the blood; its deficiency causes diabetes mellitus. (c) Adrenaline, from the adrenal glands, prepares the body to meet an emergency by raising the heartbeat and breathing rate, diverting blood to the skeletal muscles and raising the blood glucose level. (d) Growth hormone, from the pituitary gland, controls the growth and development of the body, chiefly of the bones and muscles; too little in childhood causes dwarfism and too much causes gigantism. (e) Testosterone, from the testes, brings about the male secondary sexual characters at puberty and controls the production of sperm.

    Step-by-step solution →
15. Q75 Exemplar · Long Answer Questions
    Name ​various plant ​hormones. ​Also give ​their ​physiological effects on ​plant growth and development.
    Show answer

    Auxin, gibberellins, cytokinins, abscisic acid and ethylene; the first three promote growth, abscisic acid inhibits it, and ethylene ripens fruit.

    The plant hormones, or phytohormones, are auxin, gibberellins, cytokinins and abscisic acid, together with the gaseous hormone ethylene. Their physiological effects are: auxin, made at the shoot tip, promotes the elongation of cells so the stem grows longer, and its uneven distribution on the shaded side makes a shoot bend towards light; gibberellins help in the growth of the stem by lengthening the internodes, break the dormancy of seeds and buds and promote germination, flowering and fruit growth; cytokinins promote cell division, are present in greater concentration in fruits and seeds, and delay the ageing of leaves; abscisic acid inhibits growth, causes the wilting of leaves, closes the stomata when water is short and brings on the dormancy of buds and seeds, so it is called the stress hormone; and ethylene promotes the ripening of fruits and the falling of leaves and flowers and checks stem elongation. The first three promote growth and abscisic acid opposes them, so that a plant can both grow and stop growing as conditions require.

    Step-by-step solution →
16. Q76 Exemplar · Long Answer Questions
    What ​are ​reflex ​actions? Give ​two ​examples. ​Explain a reflex arc.
    Show answer

    A reflex is a sudden, automatic response made through the spinal cord by the reflex arc, such as withdrawing the hand from heat.

    A reflex action is a sudden, rapid and automatic response of the body to a stimulus, made without any conscious thought. Two examples are withdrawing the hand at once on touching a hot object, and the blinking of the eye when an object suddenly comes close to it. The response is so quick because the decision is not taken in the brain: thinking involves a complex interaction of many nerve impulses and is slow, so the connection is made in the spinal cord, through which the nerves from the body already pass on their way to the brain. The pathway the impulse takes is called the reflex arc, and its links are: the receptor - heat and pain receptors in the skin of the finger detect the stimulus; the sensory neuron - carries the impulse to the spinal cord; the spinal cord - a relay neuron passes the signal straight across; the motor neuron - carries the instruction out to the effector; and the effector - the arm muscle contracts and pulls the hand away. A copy of the message also travels up to the brain, so the pain is felt a moment later, by which time the hand has already been withdrawn.

    Step-by-step solution →
17. Q77 Exemplar · Long Answer Questions
    “Nervous and hormonal systems ​together perform ​the ​function of control ​and coordination ​in human beings.” Justify the ​statement.
    Show answer

    Nerves give fast, brief control and hormones give slow, widespread, lasting control, and the two act together, as in fright.

    The statement is justified because each system does what the other cannot, and because the two act on the same responses. The nervous system coordinates by electrical impulses along neurons: it is extremely fast, which is why a hand is withdrawn from a flame in a fraction of a second. But an electrical impulse reaches only the cells a nerve fibre ends on, and a neuron must reset itself before carrying the next impulse, so it can neither address every cell of the body nor sustain a message for long. The hormonal system supplies exactly these: endocrine glands pour hormones into the blood, which carries them everywhere, and each acts on the target organs whose cells carry the matching receptor, slowly but widely and lastingly, which is how growth hormone builds the body over years and the sex hormones bring about puberty. The two also work on the same response together: on sudden fright the brain orders the adrenal gland through a nerve so the heart jumps at once, and the adrenaline released then keeps the heart racing and the blood glucose high for minutes afterwards. They are physically joined as well, since the hypothalamus of the brain controls the pituitary, which controls the thyroid, adrenal cortex and gonads; and hormone levels are held steady by feedback, as when a rise in blood sugar makes the pancreas secrete more insulin. Speed without persistence, or persistence without speed, would each leave the body uncoordinated, so control and coordination in human beings is carried out by the two systems together.

    Step-by-step solution →
18. Q78 Exemplar · Long Answer Questions
    How ​does ​chemical coordination ​take place ​in animals?
    Show answer

    Endocrine glands pour hormones into the blood, which carries them everywhere, but only target organs with the matching receptor respond; feedback regulates secretion.

    Chemical coordination in animals is carried out by hormones. The endocrine glands - the pituitary, thyroid, adrenals, pancreas and the testes or ovaries, with the hypothalamus above them - are ductless, so they pour their hormones directly into the blood, and only very small amounts are needed. The blood carries a hormone all over the body, but it acts only on its target organ, whose cells carry a receptor of the shape that fits that hormone; cells without the receptor are unaffected, which is how a messenger delivered everywhere produces an effect in one place. At the target the hormone changes the activity of the cells: growth hormone makes the bones and muscles grow, thyroxin regulates carbohydrate, protein and fat metabolism, insulin lowers the blood glucose level, adrenaline prepares the body for an emergency, and testosterone and oestrogen bring about the secondary sexual characters. How much is secreted is controlled by feedback, so the level stays in balance: when the blood sugar rises the pancreas secretes more insulin, and as the sugar falls insulin secretion is reduced. The pituitary, the master gland, is itself directed by the hypothalamus of the brain, so chemical coordination is joined to nervous coordination rather than separate from it.

    Step-by-step solution →
19. Q79 Exemplar · Long Answer Questions
    Why ​is the flow of signals in a synapse ​from axonal end of ​one neuron to ​dendritic ​end of ​another neuron but not the reverse?
    Show answer

    Only the axonal end has vesicles to release the neurotransmitter and only the dendritic end has receptors to detect it.

    Because the two neurons do not touch, the signal has to cross the synaptic cleft as a chemical, and the machinery for that chemical crossing is placed on one side only. The neurotransmitter, such as acetylcholine, is stored in vesicles that exist only in the axonal terminal of the first neuron, so only the axonal end can release it into the gap; and the receptors that the neurotransmitter fits are present only on the membrane of the dendritic end of the second neuron, so only the dendritic end can detect it. A crossing needs both a release at one side and a detection at the other, and both conditions are met only in the direction axonal end to dendritic end. In the reverse direction neither is met: the dendritic end has no vesicles and the axonal end has no receptors. The transmitter left in the cleft is also rapidly broken down or taken back up, so it cannot linger and act backwards. The synapse therefore works as a one-way valve, which is what allows an ordered pathway such as a reflex arc to run from receptor through sensory neuron, spinal cord and motor neuron to the effector and never in reverse.

    Step-by-step solution →
20. Q80 CBSE 2026
    Select the gland ​that ​secretes ​digestive ​enzymes as well ​as ​hormones.

    1. (a)Thyroid
    2. (b)Pituitary
    3. (c)Pancreas
    4. (d)Adrenal
    Show answer

    (c) Pancreas

    Step-by-step solution →