NCERT Exemplar Solutions
Class 10 - Science
CHAPTER 7: Control and Coordination

Multiple Choice Questions

Choose the correct answer from the given four options:

Question.  1

Which of the following statements is correct about receptors?

(a)

Gustatory receptors detect taste while olfactory receptors detect smell

(b)

Both gustatory and olfactory receptors detect smell

(c)

Auditory receptors detect smell and olfactory receptors detect taste

(d)

Olfactory receptors detect taste and gustatory receptors smell

Question.  2

Electrical impulse travels in a neuron from

(a)

Dendrite → axon → axonal end → cell body

(b)

Cell body → dendrite → axon → axonal end

(c)

Dendrite → cell body → axon → axonal end

(d)

Axonal end → axon → cell body → dendrite

Question.  3

In a synapse, chemical signal is transmitted from

(a)

Dendritic end of one neuron to axonal end of another neuron

(b)

Axon to cell body of the same neuron

(c)

Cell body to axonal end of the same neuron

(d)

Axonal end of one neuron to dendritic end of another neuron

Question.  4

In a neuron, conversion of electrical signal to a chemical signal occurs at/in

(a)

Cell body

(b)

Axonal end

(c)

Dendritic end

(d)

Axon

Question.  5

Which is the correct sequence of the components of a reflex arc?

(a)

Receptors → Muscles → Sensory neuron → Motor neuron → Spinal cord

(b)

Receptors → Motor neuron → Spinal cord → Sensory neuron → Muscle

(c)

Receptors → Spinal cord → Sensory neuron → Motor neuron → Muscle

(d)

Receptors → Sensory neuron → Spinal cord → Motor neuron → Muscle

Question.  6

Which of the following statements are true?

(i) Sudden action in response to something in the environment is called reflex action

(ii) Sensory neurons carry signals from spinal cord to muscles

(iii) Motor neurons carry signals from receptors to spinal cord

(iv) The path through which signals are transmitted from a receptor to a muscle or a gland is called reflex arc

(a)

(i) and (ii)

(b)

(i) and (iii)

(c)

(i) and (iv)

(d)

(i), (ii) and (iii)

Question.  7

Which of the following statements are true about the brain?

(i) The main thinking part of brain is hind brain

(ii) Centres of hearing, smell, memory, sight etc. are located in fore brain

(iii) Involuntary actions like salivation, vomiting, blood pressure are controlled by the medulla in the hind brain

(iv) Cerebellum does not control posture and balance of the body

(a)

(i) and (ii)

(b)

(i), (ii) and (iii)

(c)

(ii) and (iii)

(d)

(iii) and (iv)

Question.  8

Posture and balance of the body is controlled by

(a)

Cerebrum

(b)

Cerebellum

(c)

Medulla

(d)

Pons

Question.  9

Spinal cord originates from

(a)

Cerebrum

(b)

Medulla

(c)

Pons

(d)

Cerebellum

Question.  10

The movement of shoot towards light is

(a)

Geotropism

(b)

Hydrotropism

(c)

Chemotropism

(d)

Phototropism

Question.  11

The main function of abscisic acid in plants is to

(a)

Increase the length of cells

(b)

Promote cell division

(c)

Inhibit growth

(d)

Promote growth of stem

Question.  12

Which of the following is not associated with growth of plant?

(a)

Auxin

(b)

Gibberellins

(c)

Cytokinins

(d)

Abscisic acid

Question.  13

Iodine is necessary for the synthesis of which hormone?

(a)

Adrenaline

(b)

Thyroxin

(c)

Auxin

(d)

Insulin

Question.  14

Choose the incorrect statement about insulin

(a)

It is produced from pancreas

(b)

It regulates growth and development of the body

(c)

It regulates blood sugar level

(d)

Insufficient secretion of insulin will cause diabetes

Question.  15

Select the mis-matched pair

(a)

Adrenaline : Pituitary gland

(b)

Testosterone : Testes

(c)

Estrogen : Ovary

(d)

Thyroxin : Thyroid gland

Question.  16

The shape of guard cells changes due to change in the

(a)

Protein composition of cells

(b)

Temperature of cells

(c)

Amount of water in cells

(d)

Position of nucleus in the cells

Question.  17

The growth of tendril in pea plants is due to

(a)

Effect of light

(b)

Effect of gravity

(c)

Rapid cell divisions in tendrillar cells that are away from the support

(d)

Rapid cell divisions in tendrillar cells in contact with the support

Question.  18

The growth of pollen tubes towards ovules is due to

(a)

Hydrotropism

(b)

Chemotropism

(c)

Geotropism

(d)

Phototropism

Question.  19

The movement of sunflower in accordance with the path of sun is due to

(a)

Phototropism

(b)

Geotropism

(c)

Chemotropism

(d)

Hydrotropism

Question.  20

The substance that triggers the fall of mature leaves and fruits from plants is due to

(a)

Auxin

(b)

Gibberellin

(c)

Abscisic acid

(d)

Cytokinin

Question.  21

Which of the following statements about transmission of nerve impulse is incorrect?

(a)

Nerve impulse travels from dendritic end towards axonal end

(b)

At the dendritic end electrical impulses bring about the release of some chemicals which generate an electrical impulse at the axonal end of another neuron

(c)

The chemicals released from the axonal end of one neuron cross the synapse and generate a similar electrical impulse in a dendrite of another neuron

(d)

A neuron transmits electrical impulses not only to another neuron but also to muscle and gland cells

Question.  22

Involuntary actions in the body are controlled by

(a)

Medulla in fore brain

(b)

Medulla in mid brain

(c)

Medulla in hind brain

(d)

Medulla in spinal cord

Question.  23

Which of the following is not an involuntary action?

(a)

Vomiting

(b)

Salivation

(c)

Heart beat

(d)

Chewing

Question.  24

When a person is suffering from severe cold, he or she cannot

(a)

Differentiate the taste of an apple from that of an ice cream

(b)

Differentiate the smell of a perfume from that of an agarbatti

(c)

Differentiate red light from green light

(d)

Differentiate a hot object from a cold object

Question.  25

What is the correct direction of flow of electrical impulses?

(a)

Option (a) figure

(b)

Option (b) figure

(c)

Option (c) figure

(d)

Option (d) figure

Question.  26

Which statement is not true about thyroxin?

(a)

Iron is essential for the synthesis of thyroxin

(b)

It regulates carbohydrates, protein and fat metabolism in the body

(c)

Thyroid gland requires iodine to synthesise thyroxin

(d)

Thyroxin is also called thyroid hormone

Question.  27

Dwarfism results due to

(a)

Excess secretion of thyroxin

(b)

Less secretion of growth hormone

(c)

Less secretion of adrenaline

(d)

Excess secretion of growth hormone

Question.  28

Dramatic changes of body features associated with puberty are mainly because of secretion of

(a)

Oestrogen from testes and testosterone from ovary

(b)

Estrogen from adrenal gland and testosterone from pituitary gland

(c)

Testosterone from testes and estrogen from ovary

(d)

Testosterone from thyroid gland and estrogen from pituitary gland

Question.  29

A doctor advised a person to take an injection of insulin because

(a)

His blood pressure was low

(b)

His heart was beating slowly

(c)

He was suffering from goitre

(d)

His sugar level in blood was high

Question.  30

The hormone which increases the fertility in males is called

(a)

Oestrogen

(b)

Testosterone

(c)

Insulin

(d)

Growth hormone

Question.  31

Which of the following endocrine glands is unpaired?

(a)

Adrenal

(b)

Testes

(c)

Pituitary

(d)

Ovary

Question.  32

Junction between two neurons is called

(a)

Cell junction

(b)

Neuro muscular junction

(c)

Neural joint

(d)

Synapse

Question.  33

In humans, the life processes are controlled and regulated by

(a)

Reproductive and endocrine systems

(b)

Respiratory and nervous systems

(c)

Endocrine and digestive systems

(d)

Nervous and endocrine systems

Short Answer Questions

Question. 34

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

Answer:

(a) Sensory neuron

(b) Spinal cord (CNS)

(c) Motor neuron

(d) Effector (muscle in arm)

Question. 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

Answer:

(a) Auxin

(b) Gibberellin

(c) Cytokinin

(d) Abscisic acid

Question. 36

Label the endocrine glands in Figure 7.3.

Answer:

(a) Pineal gland

(b) Pituitary gland

(c) Thyroid

(d) Thymus

Question. 37

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

Answer:

Figure (a) is more accurate because plant shoots are negatively geotropic and grow upwards, while roots are positively geotropic and grow downwards.

Question. 38

Label the parts of a neuron in Figure 7.5.

Answer:

(a) Dendrite

(b) Cell body

(c) Axon

(d) Nerve ending

Question. 39

Match the terms of Column (A) with those of Column (B).

Answer:

(a) → (iii)

(b) → (iv)

(c) → (i)

(d) → (ii)

Question. 40

What is a tropic movement? Explain with an example.

Answer:

Tropic movements are directional growth movements of plants toward or away from a stimulus. For example, in phototropism, shoots bend toward light while roots bend away from light.

Question. 41

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

Answer:

(a) Release of thyroxin from the thyroid gland will be reduced, affecting protein, carbohydrate and fat metabolism.

(b) A person may suffer from goitre due to iodine deficiency.

Question. 42

What happens at the synapse between two neurons?

Answer:

When an electrical signal reaches the axonal end of one neuron, it releases chemical substances that cross the synapse and generate a new electrical signal in the dendrite of the next neuron.

Question. 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?

Answer:

(a) Oestrogen

(b) Growth hormone

(c) Insulin

(d) Thyroxin

Question. 44

Answer the following:

(a) Name the endocrine gland associated with the 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?

Answer:

(a) Pituitary gland

(b) Pancreas

(c) Adrenal

(d) Testes

Long Answer Questions

Question. 45

Draw the structure of a neuron and explain its function.

Answer:

Structure of a Neuron

A neuron consists of three main parts:

  1. Cell body (Cyton): Contains the nucleus and cytoplasm. It performs metabolic activities of the cell.
  2. Dendrites: Short, branched extensions that receive impulses from other neurons or receptors.
  3. Axon: A long, cylindrical projection that carries impulses away from the cell body to other neurons, muscles or glands.

Functions of a Neuron

  1. Receives information through dendrites.
  2. Processes information in the cell body.
  3. Transmits nerve impulses along the axon.
  4. Transfers the signal to the next neuron, muscle or gland through synapses using chemical messengers.

Question. 46

What are the major parts of the brain? Mention the functions of different parts.

Answer:

The brain is divided into three major parts:

  1. Forebrain:
    • Controls intelligence, memory, learning and emotions.
    • Processes sensory information such as smell, touch, taste, vision and hearing.
  2. Midbrain:
    • Acts as a relay centre for auditory and visual reflexes.
  3. Hindbrain:
    • Cerebellum: Maintains posture, balance and coordination.
    • Pons: Helps in regulating breathing.
    • Medulla: Controls involuntary activities like heartbeat, blood pressure, swallowing and vomiting.

Question. 47

What constitutes the central and peripheral nervous systems? How are the components of central nervous system protected?

Answer:

Central Nervous System (CNS):

The CNS consists of the brain and spinal cord.

Peripheral Nervous System (PNS):

The PNS includes all nerves that connect the CNS to different parts of the body.

Protection of CNS

  1. Brain box (cranium): A bony structure that protects the brain.
  2. Vertebral column: Protects the spinal cord.
  3. Meninges: Three membrane layers that cover and protect the CNS.
  4. Cerebrospinal fluid (CSF): Cushions the CNS and absorbs shocks.

Question. 48

Mention one function for each of these hormones:

(a) Thyroxin
(b) Insulin
(c) Adrenaline
(d) Growth hormone
(e) Testosterone

Answer:

(a) Thyroxin: Regulates carbohydrate, protein and fat metabolism.

(b) Insulin: Regulates blood sugar levels.

(c) Adrenaline: Increases heart rate and supply of blood to organs during emergency situations.

(d) Growth hormone: Regulates growth and development of the body.

(e) Testosterone: Controls the changes of body features associated with puberty in males.

Question. 49

Name various plant hormones. Also give their physiological effects on plant growth and development.

Answer:

Plant Hormones and Their Functions

  • Auxins: Promote cell elongation and root growth.
  • Gibberellins: Stimulate stem growth and seed germination.
  • Cytokinins: Promote cell division and delay ageing in leaves.
  • Abscisic acid (ABA): Induces dormancy and causes falling of senescent leaves.

Question. 50

What are reflex actions? Give two examples. Explain a reflex arc.

Answer:

Reflex Actions

Reflex actions are automatic, quick responses to stimuli that do not involve conscious thought.

Examples:

  • Withdrawing hand from a hot object.
  • Knee-jerk reflex.

Reflex Arc

A reflex arc is the pathway through which nerve impulses travel during a reflex action.

  1. Receptor detects stimulus.
  2. Sensory neuron carries impulse to spinal cord.
  3. Interneuron processes the information.
  4. Motor neuron carries impulse to effector.
  5. Effector produces a response.

Question. 51

“Nervous and hormonal systems together perform the function of control and coordination in human beings.” Justify the statement.

Answer:

Coordination by Nervous System

The nervous system coordinates body activities through electrical impulses. It involves dendrites, axons, synapses and neurotransmitters. It controls actions of muscles and glands.

Coordination by Hormonal System

Endocrine glands secrete hormones that are released into the bloodstream. Hormones reach specific target tissues where they trigger biochemical changes.

Combined Coordination

  • Nervous system provides quick responses.
  • Hormonal system provides slow but long-lasting control.
  • Together they maintain balance and ensure proper functioning of the body.

Question. 52

How does chemical coordination take place in animals?

Answer:

Different endocrine glands secrete hormones, which are chemical messengers. These hormones are released into the blood and transported to target tissues or target organs.

In the target tissues, hormones trigger specific biochemical or physiological activities such as growth, metabolism, reproduction and development.

Question. 53

Why is the flow of signals in a synapse from axonal end of one neuron to dendritic end of another neuron but not the reverse?

Answer:

When an electrical signal reaches the axonal end of a neuron, it releases chemical substances (neurotransmitters). These chemicals cross the synapse and initiate an electrical signal in the dendrite of the next neuron.

The dendritic end does not release these chemicals; therefore, the reverse conversion from dendrite to axon cannot occur. Hence, signal transmission is unidirectional.

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