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NCERT Exemplar · Class 10 Science Control and Coordination

53 questions · 53 still being checked

Short Answer Questions 34–44 (part 4 of 5)

  1. Exercise 34

    Label the parts (a), (b), (c) and (d) and show the direction of flow of electrical signals in Figure 7.2. NCERT_Question_Class10_Science_Exemplar_Ch7_Q34

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    NCERT’s answer
    (a)
    Sensory neuron
    (b)
    Spinal cord (CNS)
    (c)
    Motor neuron
    (d)
    Effector = Muscle in arm
    (a)
    Sensory (afferent) neuron, carrying the impulse from the skin receptor.
    (b)
    Spinal cord, where the sensory neuron synapses with a relay neuron.
    (c)
    Motor (efferent) neuron.
    (d)
    Effector muscle of the forearm.
    Flow of the signal: a \(\displaystyle \rightarrow\) b \(\displaystyle \rightarrow\) c \(\displaystyle \rightarrow\) d.
    Answer: a-sensory neuron, b-spinal cord, c-motor neuron, d-effector muscle; impulse travels a\(\displaystyle \to\)b\(\displaystyle \to\)c\(\displaystyle \to\)d, and the muscle contracts, withdrawing the hand.

  2. Exercise 35

    Name the plant hormones responsible for the following
    (a)
    elongation of cells
    (b)
    growth of stem
    (c)
    promotion of cell division
    (d)
    falling of senescent leaves.

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    NCERT’s answer
    (a)
    Auxin
    (b)
    Gibberellin
    (c)
    Cytokinin
    (d)
    Abscisic acid
    (a)
    Auxin — promotes cell elongation at the growing shoot tip.
    (b)
    Gibberellin — promotes growth of the stem by lengthening internodes.
    (c)
    Cytokinin — promotes cell division; concentrated in fruits and seeds.
    (d)
    Abscisic acid — the growth-inhibiting stress hormone; induces senescence and leaf fall.
    Answer: (a) Auxin, (b) Gibberellin, (c) Cytokinin, (d) Abscisic acid.

  3. Exercise 36

    Label the endocrine glands in Figure 7.3. NCERT_Question_Class10_Science_Exemplar_Ch7_Q36

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    NCERT’s answer
    (a)
    Pineal gland
    (b)
    Pituitary gland
    (c)
    Thyroid
    (d)
    Thymus
    (a)
    Pineal gland — deep in the brain, secretes melatonin.
    (b)
    Pituitary gland — below the hypothalamus; the master gland.
    (c)
    Thyroid gland — front of the neck at the larynx; secretes thyroxine.
    (d)
    Thymus gland — upper chest below the thyroid; active in immunity.
    Answer: (a) Pineal, (b) Pituitary, (c) Thyroid, (d) Thymus.

  4. Exercise 37

    In Figure 7.4\displaystyle 7.4 (a), (b) and (c), which appears more accurate and why? NCERT_Question_Class10_Science_Exemplar_Ch7_Q37

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    NCERT’s answer
    Figure (a) is more appropriate because in a plant shoots are negatively geotropic hence, grow upwards and roots are positively geotropic so grow downwards.
    \[\text{Root: gravity} \Rightarrow \text{grows } \downarrow \;\Rightarrow\; \text{positively geotropic} \]
    \[\text{Shoot: gravity} \Rightarrow \text{grows } \uparrow \;\Rightarrow\; \text{negatively geotropic} \]
    (a)
    shows exactly this: roots curve down, shoot curves up.
    (b)
    is wrong: the roots turn \(\displaystyle \uparrow\), away from gravity.
    (c)
    is wrong: the shoot droops \(\displaystyle \downarrow\), toward gravity.
    Answer: (a) is the accurate diagram; the root grows toward gravity and the shoot grows away from it.

  5. Exercise 38

    Label the parts of a neuron in Figure 7.5. NCERT_Question_Class10_Science_Exemplar_Ch7_Q38

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    NCERT’s answer
    (a)
    Dendrite
    (b)
    Cell body
    (c)
    Axon
    (d)
    Nerve ending
    (a)
    Dendrite — receives the nerve impulse.
    (b)
    Cell body (cyton) — contains the nucleus.
    (c)
    Axon, sheathed in myelin — conducts the impulse away from the cell body.
    (d)
    Axon terminal — passes the impulse to the next neuron across a synapse.
    Answer: (a) Dendrite, (b) Cell body, (c) Axon, (d) Axon terminal.

  6. Exercise 39

    Match the terms of Column (A) with those of Column (B)
    Column (A)Column (B)
    (a) Olfactory receptors(i) Tongue
    (b) Thermo receptors (temperature receptors)(ii) Eye
    (c) Gustatoreceptors(iii) Nose
    (d) Photoreceptors(iv) Skin

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    NCERT’s answer
    (a)
    — (iii)
    (b)
    — (iv)
    (c)
    — (i) (d) — (ii)
    (a)
    Olfactory receptors — (iii) Nose, detect smell.
    (b)
    Thermoreceptors — (iv) Skin, sense temperature.
    (c)
    Gustatoreceptors — (i) Tongue, taste buds.
    (d)
    Photoreceptors — (ii) Eye, retina detects light.
    Answer: (a)-(iii), (b)-(iv), (c)-(i), (d)-(ii).

  7. Exercise 40

    What is a tropic movement? Explain with an example.

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    NCERT’s answer
    The directional growth movements of plants due to external stimuli are called tropic movement. It can be either towards the stimulus, or away from it. For example, in case of phototropic movement, shoots respond by bending towards light while roots respond by bending away from it.
    Tropic movement: a plant part's growth bends toward or away from a directional stimulus (light, gravity, touch, chemicals), the direction set by the stimulus.\[\text{light from one side} \Rightarrow \text{auxin accumulates on the shaded side} \Rightarrow \text{shaded cells elongate more} \Rightarrow \text{shoot bends toward light} \]Answer: Directional growth response to a stimulus; e.g. phototropism — a shoot bends toward light.

  8. Exercise 41

    What will happen if intake of iodine in our diet is low?

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    NCERT’s answer
    (a)
    When iodine intake is low, release of thyroxin from thyroid gland will be less by which protein, carbohydrate and fat metabolisms will be affected.
    (b)
    A person might suffer from goitre in case of iodine deficiency in the body.
    Iodine is needed by the thyroid to make thyroxine.\[\text{iodine}\downarrow \Rightarrow \text{thyroxine synthesis}\downarrow \Rightarrow \text{TSH}\uparrow \Rightarrow \text{thyroid enlarges (goitre)} \]Metabolic rate falls; in children, physical and mental growth is impaired.Answer: Goitre, with lowered metabolism and (in children) stunted growth and mental development.

  9. Exercise 42

    What happens at the synapse between two neurons?

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    NCERT’s answer
    When an electrical signal reaches the axonal end of one neuron it releases certain chemical substances that cross the synapse and move towards the dendritic end of next neuron generating another electrical signal.
    \[\text{impulse} \to \text{axon terminal (neuron A)} \Rightarrow \text{vesicles release neurotransmitter into the gap} \Rightarrow \text{receptors on neuron B's dendrite} \Rightarrow \text{new impulse in neuron B} \]The chemical hand-off at the gap lets the signal cross in one direction only.Answer: The electrical signal converts to a chemical signal that crosses the gap and restarts an electrical impulse in the next neuron, one-way only.

  10. Exercise 43

    Answer the following :
    (a)
    Which hormone is responsible for the changes noticed in females at puberty?
    (b)
    Dwarfism results due to deficiency of which hormone?
    (c)
    Blood sugar level rises due to deficiency of which hormone?
    (d)
    Iodine is necessary for the synthesis of which hormone?

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    NCERT’s answer
    (a)
    Oestrogen
    (b)
    Growth hormone
    (c)
    Insulin
    (d)
    Thyroxin
    (a)
    Estrogen, from the ovary.
    (b)
    Growth hormone (somatotropin), from the pituitary.
    (c)
    Insulin, from the pancreas.
    (d)
    Thyroxine, from the thyroid.
    Answer: (a) Estrogen (b) Growth hormone (c) Insulin (d) Thyroxine.

  11. Exercise 44

    Answer the following :
    (a)
    Name the endocrine gland associated with brain?
    (b)
    Which gland secretes digestive enzymes as well as hormones?
    (c)
    Name the endocrine gland associated with kidneys?
    (d)
    Which endocrine gland is present in males but not in females?

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    NCERT’s answer
    (a)
    Pituitary
    (b)
    Pancreas
    (c)
    Adrenal
    (d)
    Testes
    (a)
    Pituitary — the 'master gland', attached to the brain's base.
    (b)
    Pancreas — digestive enzymes (exocrine) and hormones such as insulin (endocrine).
    (c)
    Adrenal gland — sits atop each kidney.
    (d)
    Testis — present only in males.
    Answer: (a) Pituitary (b) Pancreas (c) Adrenal gland (d) Testis.