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.

CBSE Class 10 Science previous year papers, with answers →

Questions · page 15 of 15

1. Q281 CBSE 2018
   1. (i)​What are endocrine glands ? Write one main feature of it.
   2. (ii)Name the hormone ​secreted ​by thyroid glands and state its main ​functions.
   3. (iii)​What is the importance of iodized salt in ​our daily life ?
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   Endocrine glands are ductless; the thyroid secretes thyroxine, which regulates metabolism, and iodised salt supplies the iodine needed to make it.

   (i) Endocrine glands are ductless glands that secrete hormones. Main feature: they have no ducts and pour their secretions (hormones) directly into the blood, which carries them to the target organs. (ii) The thyroid gland secretes thyroxine. Its main function is to regulate carbohydrate, protein and fat metabolism in the body so as to provide the best balance for growth. (iii) Iodine is essential for the thyroid gland to make thyroxine, since iodine is a part of this hormone. Iodised salt supplies this iodine in our daily diet; without enough iodine, too little thyroxine is made and a person may suffer from goitre, a swollen neck.

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2. Q282 CBSE 2018
   1. (a)State the role performed ​by plant hormones. Name a plant hormone ​which ​is essential for cell ​division.
   2. (b)Name and explain ​the role of ​plant ​hormone involved in phototropism.
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   Plant hormones coordinate growth and responses; cytokinin is essential for cell division; auxin makes the shaded side grow longer, bending the shoot towards light.

   (a) Plant hormones (phytohormones) are chemical substances that coordinate and control the growth, development and responses of a plant to its environment, such as cell division, cell enlargement, bending of shoots and roots, flowering, ripening of fruits and the wilting of leaves. They are made at one place and diffuse to the area where they act. The plant hormone essential for cell division is cytokinin. (b) 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 shaded side. The higher concentration of auxin there makes the cells on the shaded side grow longer than those on the lit side, so the shoot bends towards the light (phototropism).

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3. Q283 CBSE 2018
   What ​constitutes the central and peripheral nervous ​systems ? ​How are ​various parts ​of central ​nervous ​system protected ?
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   The CNS is the brain and spinal cord; the PNS is the cranial and spinal nerves; the skull, fluid and backbone protect the CNS.

   Central nervous system (CNS): the brain and the spinal cord. Peripheral nervous system (PNS): the nerves that connect the CNS with the rest of the body, namely the cranial nerves, which arise from the brain, and the spinal nerves, which arise from the spinal cord. Protection: the brain is protected by the bony skull (cranium), inside which it is held in a fluid-filled balloon that absorbs shocks; the spinal cord is protected by the vertebral column (backbone).

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4. Q284 CBSE 2018
   (a) ​Name the gland that ​secrete :

   1. (i)​insulin, ​
   2. (ii)thyroxin (b) Explain with an example how ​the timing and amount of ​hormone secreted are regulated ​in a ​human body.
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   The pancreas secretes insulin and the thyroid gland secretes thyroxin; feedback from the blood sugar level regulates when and how much insulin is released.

   (a) (i) Insulin is secreted by the pancreas. (ii) Thyroxin is secreted by the thyroid gland. (b) The timing and amount of hormone released are regulated by feedback mechanisms. For example, when the sugar level in the blood rises (say, after a meal), it is detected by the cells of the pancreas, which respond by producing more insulin. Insulin lowers the blood sugar level, and as the level falls, the secretion of insulin is reduced. So the blood sugar level itself decides when, and how much, insulin is released.

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5. Q285 CBSE 2018
   How does ​chemical ​co-ordination ​occur ​in ​plants ​?
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   Plants have no nervous system; hormones made in the stimulated part diffuse to nearby cells, which respond by changing growth.

   Plants have no nervous system; chemical co-ordination in plants is brought about by chemical compounds called plant hormones. (i) When a part of the plant is stimulated, cells in that specific part make and release a hormone. (ii) The hormone diffuses to the neighbouring cells, the area of action. (iii) The cells that recognise the hormone respond, bringing about the required change in growth; this is control and co-ordination. Examples: auxin makes cells grow longer (the shoot bends towards light); gibberellins help the stem to grow; cytokinins promote cell division; abscisic acid inhibits growth and causes wilting of leaves.

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6. Q286 CBSE 2018
   (a) ​Name the ​part of human brain which controls :

   1. (i)voluntary actions
   2. (ii)involuntary actions (b) State ​the significance of peripheral nervous system. Name the ​components ​of this nervous ​system and distinguish ​between their origins.
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   Fore-brain controls voluntary and medulla involuntary actions; the PNS links the CNS to the body via cranial nerves (brain) and spinal nerves (spinal cord).

   (a) (i) Voluntary actions are controlled by the fore-brain, mainly the cerebrum. (ii) Involuntary actions are controlled by the medulla (medulla oblongata) of the hind-brain; the mid-brain also controls some involuntary actions. (b) Significance: the peripheral nervous system makes communication possible between the central nervous system (brain and spinal cord) and all the other parts of the body. It carries messages from the receptors (sense organs) to the CNS, and instructions from the CNS to the muscles and glands. Components: cranial nerves and spinal nerves. Origins: cranial nerves arise from the brain ($12$ pairs in humans), whereas spinal nerves arise from the spinal cord ($31$ pairs).

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