Class 10 Science · Chapter 6
Control and Coordination
286 Class 10 Science questions on Control and Coordination from the NCERT textbook, NCERT Exemplar and CBSE board papers 2018–2026, each with its answer and a step-by-step solution.
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Questions · page 6 of 15
- Q101 CBSE 2026Question No. 8 & 9 consists of two statements – Assertion (A) and Reason (R). Answer these questions selecting the appropriate option from (a), (b), (c) and (d) given below :
Assertion (A): Motor neurons carry signals from the spinal cord to the effector organ.
Reason (R): Sensory neurons carry signals from receptors towards 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.
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(b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A). - Q102 CBSE 2026What are hormones ? State any one function of the following hormones :
- (i)Insulin
- (ii)Adrenaline
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Hormones are chemical messengers secreted into the blood; insulin lowers blood sugar and adrenaline makes the heart beat faster in an emergency.
Hormones are chemical messengers secreted in small amounts by endocrine (ductless) glands directly into the blood, which carries them to target organs, where they control and coordinate particular activities of the body. (i) Insulin, secreted by the pancreas, regulates the blood sugar level: it lowers a raised level by helping cells take up glucose (too little insulin causes diabetes). (ii) Adrenaline, secreted by the adrenal glands, prepares the body for dealing with stress or an emergency: it makes the heart beat faster so that more oxygen reaches the muscles. - Q103 CBSE 2026“The timing and the amount of hormone secreted by a gland are regulated in the human body.” Justify this statement with the help of an example.Step-by-step solution →
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Feedback mechanisms regulate hormone release; for example, rising blood sugar makes the pancreas release more insulin and falling sugar reduces it.
The timing and the amount of hormone released are regulated by feedback mechanisms. Example: when the sugar level in the blood rises, it is detected by the cells of the pancreas, which respond by producing more insulin; as the blood sugar level falls, insulin secretion is reduced. The hormone is therefore released when it is needed and in the amount needed. - Q104 CBSE 2026Electrical impulse is an excellent means to transmit information in the animal body, but there are some limitations to the use of electrical impulses. State any two limitations.Step-by-step solution →
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Impulses reach only cells connected by nervous tissue, and a cell needs time to reset before it can generate a new impulse.
1. Electrical impulses reach only those cells that are connected by nervous tissue, not each and every cell in the animal body. 2. Once an electrical impulse has been generated and transmitted, the cell takes some time to reset its mechanisms before it can generate and transmit a new impulse, so cells cannot continually create and transmit electrical impulses. - Q105 CBSE 2026A squirrel in a scary situation requires its body to prepare for either ‘fight or flight’ to save itself. State the immediate changes that will take place in its body so that it can face the situation.Step-by-step solution →
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Adrenaline makes the heart beat faster, diverts blood to the skeletal muscles and speeds up breathing, preparing the squirrel to fight or run away.
The adrenal glands secrete adrenaline directly into the blood, and it acts on target organs: (i) The heart beats faster, supplying more oxygen to the muscles. (ii) The blood supply to the digestive system and skin is reduced, because the muscles around their small arteries contract, and the blood is diverted to the skeletal muscles. (iii) The breathing rate increases as the diaphragm and rib muscles contract faster. Together these changes prepare the squirrel to fight or run away. - Q106 CBSE 2026Discuss two limitations to the use of electrical impulse for coordination, by animals.Step-by-step solution →
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An electrical impulse reaches only cells connected by nervous tissue, and a cell needs time to reset before it can send another impulse.
Two limitations of using electrical impulses for coordination are: (1) An electrical impulse travels only along nervous tissue, so it reaches only those cells that are connected by nervous tissue and not each and every cell of the animal's body. (2) Once an electrical impulse has been generated in a cell and transmitted, that cell takes some time to reset its mechanisms before it can generate and transmit a new impulse, so cells cannot continually create and transmit electrical impulses. Because of these two limits most multicellular animals also use chemical communication: hormones released into the blood can reach all cells regardless of nervous connections, and the signal can be sent steadily and persistently. - Q107 CBSE 2026Name the hormone which is responsible for the bending of plants towards light and also explain the process of bending of plants.Step-by-step solution →
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Auxin, made at the shoot tip, moves to the shaded side and makes those cells grow longer, so the shoot bends towards light.
The hormone is auxin, which is synthesised at the tip of the shoot. When light falls on the shoot from one side, auxin diffuses towards the shady side of the shoot. This higher concentration of auxin stimulates the cells on the shaded side to grow longer than the cells on the side facing the light, so the shaded side grows faster and the shoot bends towards the light. This growth response to light is called phototropism. - Q108 CBSE 2026State two differences between the act of chewing food and salivation on sight of food.Step-by-step solution →
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Chewing is voluntary and controlled by the fore-brain; salivation on sight of food is involuntary and controlled by the medulla.
1. Chewing food is a voluntary action: we decide to chew and can start or stop it at will. Salivation on sight of food is an involuntary action: the mouth waters automatically and we cannot stop it by thinking. 2. Chewing is controlled by the fore-brain (cerebrum) and is carried out by the muscles of the jaw. Salivation is controlled by the medulla in the hind-brain and is carried out by the salivary glands. - Q109 CBSE 2026Observe the given figure and identify the labelled parts P, Q, R and S :Step-by-step solution →
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P is the receptor, Q the sensory neuron, R the relay neuron and S the effector (arm muscle).
P - Receptor: the heat and pain receptors in the skin of the hand, which detect the stimulus. Q - Sensory neuron: it carries the impulse from the receptor to the spinal cord. R - Relay neuron: the neuron inside the spinal cord that passes the impulse from the sensory neuron to the motor neuron. S - Effector: the muscle of the arm, which contracts and pulls the hand away. - Q110 CBSE 2026Electrical impulses are an excellent means to respond to stimuli in animal bodies. List any two limitations to the use of electrical impulses.Step-by-step solution →
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Electrical impulses reach only cells connected by nervous tissue, and a cell needs time to reset before it can send another impulse.
Two limitations are: (i) An electrical impulse reaches only those cells that are connected by nervous tissue, so it cannot reach every cell of the animal body; and (ii) after a cell has generated and transmitted an impulse it needs time to reset its mechanisms before it can send another, so impulses cannot be created and transmitted continuously. Because of these limits, animals also use chemical communication through hormones carried in the blood. - Q111 CBSE 2026Which of the plant hormones are responsible for the following processes ?
- (i)Promote cell division
- (ii)Inhibition of growth
- (iii)Detection of light
- (iv)Wilting of leaves
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Cytokinin promotes cell division, abscisic acid inhibits growth and causes wilting, and auxin bends the shoot towards light.
(i) Cytokinin - it promotes cell division. (ii) Abscisic acid - it is the growth inhibitor among the plant hormones. (iii) Auxin - it gathers on the shaded side of a shoot, makes those cells grow longer and bends the shoot towards the light. (iv) Abscisic acid - it closes the stomata under water stress, and wilting of leaves is among its effects. - Q112 CBSE 2026Explain how the pea plant climbs up the support by means of tendrils.Step-by-step solution →
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Unequal growth on the two sides makes the tendril curve round the support, so the pea plant climbs.
Tendrils are thread-like outgrowths of the pea plant that are sensitive to touch. When a growing tendril comes into contact with a support, the part of the tendril in contact with the object does not grow as rapidly as the part away from the object. This unequal growth makes the tendril curve, so that it circles around the support and clings to it, and the weak stem of the pea plant is thereby held up and carried higher. Since the response is directional and is brought about by growth, it is a growth movement called thigmotropism. - Q113 CBSE 2026Give differences between the following :
- (a)Sensory nerve and motor nerve
- (b)Consumers and decomposers
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Sensory nerves carry impulses towards the brain or spinal cord, motor nerves away; consumers feed on producers or consumers, decomposers on dead remains.
(a) A sensory nerve carries impulses from the receptors in the sense organs to the brain or spinal cord (for example, the optic nerve from the eye). A motor nerve carries impulses from the brain or spinal cord to the effectors, which are muscles or glands. (b) Consumers feed on producers or on other consumers (herbivores, carnivores, omnivores, parasites) and pass food energy along the food chain (for example, deer and lion). Decomposers (bacteria, fungi) feed on dead remains and wastes, breaking them into simple inorganic substances that return to the soil and are used again by plants. - Q114 CBSE 2026The sensitive plant shows movement of leaves in response to touch. Explain such movement briefly.Step-by-step solution →
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On touch, cells at the leaflet base lose water and shrink, so the leaflets fold; this nastic movement does not depend on growth.
The folding of the leaves of the sensitive plant on being touched is a movement that is independent of growth, that is, a nastic movement. The stimulus is touch. The plant has no nervous tissue, so the information that a leaf has been touched is passed on from one cell to the next as an electrical and chemical signal until it reaches the cells at the base of the leaflets. Plants have no muscle cells; instead, their cells change shape by changing the amount of water in them. The cells in the swelling at the base of each leaflet lose water, become flaccid and shrink, so the leaflets fold up in pairs and the leaf droops. When these cells take up water again they swell, and the leaflets spread out as before, so the movement is reversible. - Q115 CBSE 2026Varun is diabetic. His latest ultrasound reports showed a blockage in his pancreatic duct. How will this affect the dual functioning of the pancreas?Step-by-step solution →
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The blocked duct affects digestion, as pancreatic juice cannot reach the small intestine, but insulin reaches the blood without the duct.
The pancreas is a dual gland. Exocrine function: it secretes pancreatic juice, containing trypsin, pancreatic amylase and lipase, which reaches the small intestine (duodenum) through the pancreatic duct. With the duct blocked, these digestive enzymes cannot be transported to the small intestine, so the digestion of proteins, carbohydrates and fats will be affected. Endocrine function: its islets of Langerhans secrete insulin directly into the blood, without using the duct. Varun is diabetic, so his insulin secretion is already affected; the blockage does not change it further, because insulin does not travel through the duct. - Q116 CBSE 2026Sunil unconsciously touched the hot iron rod and immediately withdrew his hand. Which type of action is involved? Also define this action. Draw a flow chart to show the path followed for this action.Step-by-step solution →
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The action is a reflex action: a rapid, automatic, involuntary response to a stimulus, without conscious thinking.
The action involved is a **reflex action**. A reflex action is a sudden, rapid, automatic and involuntary response of the body to a stimulus, which occurs without conscious thinking; the withdrawal of the hand is controlled by the spinal cord. The path followed is the reflex arc: Stimulus (heat of the hot iron rod) Receptor (heat and pain receptors in the skin of the hand) Sensory neuron Spinal cord (relay neuron) Motor neuron Effector (muscle of the arm) Response (the hand is withdrawn). - Q117 CBSE 2026Give differences between the following :
- (a)Nephron and neuron
- (b)Sensory nerve and motor nerve
- (c)Consumers and decomposers
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Nephron forms urine, neuron conducts impulses; sensory nerves carry impulses to the CNS, motor nerves from it; consumers eat, decomposers break down dead remains.
(a) Nephron: the structural and functional unit of the kidney; it filters the blood and forms urine. Neuron: the structural and functional unit of the nervous system; it receives and conducts information as electrical impulses. (b) Sensory nerve: carries impulses from the receptors of the sense organs to the brain or spinal cord. Motor nerve: carries impulses from the brain or spinal cord to the effectors, that is, muscles and glands. (c) Consumers: get their food directly or indirectly from the producers by eating plants or other animals, and pass food energy along the food chain. Decomposers: micro-organisms such as bacteria and fungi that feed on dead remains and wastes, breaking them down into simple substances that return to the soil. - Q118 CBSE 2026
- (a)Mention the gland and the hormone secreted by it in scary situation in human beings.
- (b)Write two responses that enable the human body to be ready to deal with such situation.
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The adrenal gland secretes adrenaline; the heart beats faster and the breathing rate rises, readying the body for danger.
(a) The gland is the adrenal gland, one of which lies on top of each kidney, and the hormone it secretes in a frightening situation is adrenaline, also called epinephrine. It is poured directly into the blood, which carries it to the heart and to other target organs. (b) Two responses that ready the body are: (1) the heart beats faster, so more oxygen-rich blood is supplied to the skeletal muscles; and (2) the rate of breathing increases, because the diaphragm and the rib muscles contract faster, so more oxygen is taken into the blood. (A third acceptable response is that the small arteries supplying the digestive system and the skin contract, diverting blood to the skeletal muscles.) - Q119 CBSE 2026Plants 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).
- (c)OR : How does movement of roots differ from that of shoots in response to gravity and light ?
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Roots grow towards water; auxin lengthens cells so shoots bend to light; sensitive plants move without growth; roots and shoots respond oppositely.
(a) A plant is fixed in one place and cannot move to find water, so its roots must grow to reach it. Roots are positively hydrotropic: they bend and grow towards the area of water availability in the soil, so that they can absorb water and the minerals dissolved in it, even when the water does not lie directly below the seed. That water is needed for photosynthesis, for carrying minerals up the plant, for keeping cells turgid and for transpiration, and the spreading root system it produces also anchors the plant. (b) Auxin is a hormone made at the tip of the shoot. It makes cells grow longer, so it controls the rate and the direction of growth. When light comes from one side, auxin diffuses to the shaded side; those cells elongate more than the ones in the light, so that side becomes longer and the shoot bends towards the light. (c) Two differences. First, the sensitive plant's movement is non-directional - the leaflets fold the same way whichever side is touched - whereas a tropic movement is directional, its direction set by the direction of the stimulus. Second, the sensitive plant's movement involves no growth: cells at the base of the leaflets rapidly lose water, so it takes seconds and is reversible, whereas a tropic movement is a slow, permanent growth movement caused by unequal cell elongation. OR (c) Roots and shoots respond in opposite directions. To gravity, roots grow downwards in the direction of gravity (positive geotropism) while shoots grow upwards against it (negative geotropism). To light, shoots grow towards the light (positive phototropism) while roots grow away from it (negative phototropism). - Q120 CBSE 2026Read 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 ?[1]
- (b)Which part of the brain is responsible for precision of voluntary actions ?[1]
- (c)(i)Explain the role of the medulla.[2]
- (c)(ii)OR : How do the animal muscles move ?[2]
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Voluntary actions are done by will; the cerebellum gives precision; the medulla controls involuntary actions; muscle proteins change shape and the muscle contracts.
(a) Voluntary actions are actions we perform consciously, by our own will after thinking, such as writing, talking, walking or driving; they are controlled by the fore-brain (cerebrum). (b) The cerebellum (in the hind-brain) is responsible for the precision of voluntary actions; it also maintains the posture and balance of the body. (c)(i) The medulla, in the hind-brain, joins the brain to the spinal cord and controls involuntary actions such as blood pressure, salivation and vomiting (it also helps to regulate the heartbeat and breathing). OR (c)(ii) Muscle cells contain special proteins that, in response to a nerve impulse, change their shape and their arrangement in the cell. This gives the muscle cells a shorter form, so the muscle contracts and moves the part of the body; it relaxes again when the impulses stop.