April 10, 2026
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Chapter 7: Control and Coordination
Complete NCERT Solutions (Intext + Exercise) | CBSE Class 10 Science | Questions & Marks
Class 10- Science Solutions
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Class 10 (CBSE) - SYLLABUS
Class 10 (CBSE) - PYQ
Intext Questions (Page 119)
12 marks
What is the difference between a reflex action and walking?
Answer: Reflex action is an involuntary, rapid response to a stimulus (e.g., pulling hand from hot object). Walking is a voluntary action controlled by the brain, requiring conscious effort.
22 marks
What happens at the synapse between two neurons?
Answer: At the synapse, electrical signal from one neuron triggers release of chemical messengers (neurotransmitters). These cross the gap and generate an electrical signal in the next neuron.
32 marks
Which part of the brain maintains posture and equilibrium of the body?
Answer: Cerebellum.
42 marks
How do we detect the smell of an agarbatti (incense stick)?
Answer: Smell is detected by olfactory receptors in the nose. These receptors send electrical signals to the forebrain, which interprets the smell.
52 marks
What is the role of the brain in reflex action?
Answer: Reflex actions are mediated by the spinal cord without direct involvement of the brain. However, the brain receives information about the reflex later and can influence future responses.
Intext Questions (Page 122)
62 marks
What are plant hormones?
Answer: Plant hormones (phytohormones) are chemical substances produced in small amounts that regulate growth, development, and responses to stimuli. Examples: auxin, gibberellin, cytokinin, abscisic acid, ethylene.
72 marks
How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?
Answer: Sensitive plant movement (thigmonasty) is a rapid response to touch, not growth-dependent. Shoot movement towards light (phototropism) is a slow growth-related movement caused by differential cell elongation.
82 marks
Give an example of a plant hormone that promotes growth.
Answer: Auxin promotes cell elongation and growth. Gibberellins also promote stem elongation and seed germination.
92 marks
How do auxins promote the growth of a tendril around a support?
Answer: When a tendril touches a support, auxin accumulates on the opposite side, causing that side to grow faster. This differential growth makes the tendril curve and coil around the support.
102 marks
Design an experiment to demonstrate hydrotropism.
Answer: Plant a seedling in a porous pot placed in a water-filled container. Roots will grow towards the water source, showing positive hydrotropism. Control: dry conditions show random growth.
Intext Questions (Page 125)
112 marks
How does chemical coordination take place in animals?
Answer: Chemical coordination occurs through hormones secreted by endocrine glands. Hormones are transported via blood to target organs, where they regulate various physiological processes.
122 marks
Why is the use of iodised salt advisable?
Answer: Iodine is essential for the synthesis of thyroid hormone (thyroxine). Iodine deficiency causes goitre and other disorders. Iodised salt prevents these deficiencies.
132 marks
How does our body respond when adrenaline is secreted into the blood?
Answer: Adrenaline increases heart rate, blood pressure, and blood glucose levels. It diverts blood to muscles and brain, preparing the body for 'fight or flight' response.
143 marks
Why are some patients of diabetes treated by giving injections of insulin?
Answer: Diabetes occurs when the pancreas does not produce enough insulin. Insulin lowers blood glucose levels. Injections provide the missing hormone.
NCERT Exercise Questions (Page 125)
Ex 11 mark
Which of the following is a plant hormone? (a) Insulin (b) Thyroxin (c) Oestrogen (d) Cytokinin.
Answer: (d) Cytokinin.
Ex 21 mark
The gap between two neurons is called a (a) dendrite (b) synapse (c) axon (d) impulse.
Answer: (b) synapse.
Ex 31 mark
The brain is responsible for (a) thinking (b) regulating the heartbeat (c) balancing the body (d) all of the above.
Answer: (d) all of the above.
Ex 41 mark
What is the function of receptors in our body? Think of situations where receptors do not work properly. What problems are likely to arise?
Answer: Receptors detect stimuli (light, sound, touch, chemicals). If they malfunction, we may lose sensation (e.g., blindness if photoreceptors fail, deafness, inability to feel pain).
Ex 53 marks
Draw the structure of a neuron and explain its function.
Answer: A neuron has a cell body (cyton), dendrites (receive signals), and an axon (transmits impulses). It conducts electrical impulses from one part of the body to another, enabling communication between cells.
Ex 63 marks
How does phototropism occur in plants?
Answer: In a shoot, auxin distributes towards the shaded side, causing cells on that side to elongate more. This bends the shoot towards light (positive phototropism). Roots show negative phototropism.
Ex 73 marks
Which signals will get disrupted in case of a spinal cord injury?
Answer: Reflex actions (involving spinal cord) and voluntary movements below the injury site are disrupted. Sensation from limbs and trunk may also be lost.
Ex 83 marks
How does chemical coordination occur in plants?
Answer: Plant hormones (auxins, gibberellins, cytokinins, abscisic acid, ethylene) coordinate growth, flowering, fruit ripening, and responses to stimuli. They are produced in one part and transported to target cells.
Ex 93 marks
What is the need for a system of control and coordination in an organism?
Answer: Organisms need to respond to environmental changes to survive. Control and coordination systems (nervous and endocrine) ensure proper functioning, integration, and adaptation.
Ex 103 marks
How are involuntary actions and reflex actions different from each other?
Answer: Involuntary actions (e.g., heartbeat, salivation) are controlled by the brain (medulla) without conscious thought. Reflex actions are rapid, automatic responses to specific stimuli, often involving the spinal cord.
Ex 113 marks
Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.
Answer: Nervous: fast, short-lived, via electrical impulses and neurotransmitters, targeted. Hormonal: slower, long-lasting, via blood, widespread effects. Both enable integration.
Ex 123 marks
What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs?
Answer: Sensitive plant movement is a turgor-based non-growth movement (thigmonasty). Leg movement is a voluntary muscular movement coordinated by the nervous system.
Additional Important Questions
A12 marks
Name the hormone that regulates blood sugar level. Name the gland that secretes it.
Answer: Insulin, secreted by the pancreas (islets of Langerhans).
A22 marks
What is the function of the hypothalamus?
Answer: Hypothalamus regulates body temperature, hunger, thirst, and controls the pituitary gland.
A32 marks
Mention the role of abscisic acid in plants.
Answer: Abscisic acid inhibits growth, promotes stomatal closure during water stress, and induces seed dormancy.
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