Chapter 7 · Control and Coordination

NCERT Exemplar Class 10 Science Chapter 7 Short Answer Questions

All 11 questions of NCERT Exemplar Class 10 Science Chapter 7 Short Answer Questions (Control and Coordination), in the book's order, each with its answer and a step-by-step solution.

1. Q34
   Label ​the ​parts (a), ​(b), ​(c) and ​(d) and show the direction ​of flow of electrical ​signals in ​Figure 7.2.

   Show answer

   (a) Sensory neuron, (b) spinal cord, (c) motor neuron, (d) muscle; the impulse flows one way, from receptor to effector.

   (a) Sensory neuron; (b) Spinal cord; (c) Motor neuron; (d) Muscle, the effector. Direction of flow: the impulse starts at the receptors in the skin of the hand and travels along the sensory neuron (a) to the spinal cord (b), where a relay neuron passes it to the motor neuron (c), which carries it to the muscle (d); the muscle contracts and the hand is pulled away. The flow is one way only, from receptor to effector.

   Step-by-step solution →
2. Q35
   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 →
3. Q36
   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 →
4. Q37
   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 →
5. Q38
   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 →
6. Q39
   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 →
7. Q40
   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 →
8. Q41
   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 →
9. Q42
   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 →
10. Q43
    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 →
11. Q44
    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 →