Chapter 6: Control and Coordination

Multiple Choice Questions

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 .

Answer: (a) Gustatory receptors detect taste while olfactory receptors detect smell.

[ Gustatory receptors are responsible for taste perception, while olfactory receptors detect odors in the sense of smell.]

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

Answer: (c) Dendrite → cell body → axon → axonal end.

[ The impulse typically starts at the dendrites, moves through the cell body, travels down the axon, and reaches the axonal end where it can transmit signals to other neurons or cells.]

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 .

Answer:  (d) axonal end of one neuron to dendritic end of another neuron.

[  In a synapse, the chemical signal (neurotransmitters) is transmitted from the axonal end of one neuron to the dendritic end of another neuron.]

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

Answer: (b) axonal end of a neuron.

 [ At the axonal end, neurotransmitters are released into the synapse to transmit the signal to the next neuron or target cell. ]

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

Answer: (d) Receptors → Sensory neuron → Spinal cord → Motor neuron → Muscle.

[ The signal starts with the receptors detecting a stimulus, and the information is then transmitted through the sensory neuron to the spinal cord, where a quick response is generated through the motor neuron to the effector muscle.]

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)

Answer:  (c) (i) and (iv)

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

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

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)

Answer:  (c) (ii) and (iii)

[ (ii) Centers of hearing, smell, memory, sight, etc., are located in the forebrain. (iii) Involuntary actions like salivation, vomiting, blood pressure are controlled by the medulla in the hindbrain. ]

8. Posture and balance of the body is controlled by

(a) cerebrum       (b) cerebellum       (c) medulla      (d) pons

Answer:  (b) cerebellum.

 [ The cerebellum is responsible for coordinating voluntary movements and maintaining posture and balance in the body.]

9. Spinal cord originates from

(a) cerebrum     (b) medulla       (c) pons     (d) cerebellum

Answer: (b) medulla

[ The spinal cord originates from the medulla, which is part of the brainstem.]

10. The movement of shoot towards light is

(a) geotropism        (b) hydrotropism        (c) chemotropism    (d) phototropism

Answer: (d) phototropism

[ The movement of a shoot towards light is phototropism. ]

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

Answer: (c) inhibit growth

[ The main function of abscisic acid in plants to inhibit growth. It plays a role in inducing dormancy and promoting abscission (shedding of leaves and fruits). ]

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

(a) Auxin           (b) Gibberellins       (c) Cytokinins    (d) Abscisic acid

Answer: (d) Abscisic acid .

[ Abscisic acid is not associated with the promotion of growth in plants. It is involved in inhibiting growth, inducing dormancy, and promoting abscission (shedding of leaves and fruits).]

13. Iodine is necessary for the synthesis of which hormone?

(a) Adrenaline     (b) Thyroxin        (c) Auxin     (d) Insulin

Answer: (b) Thyroxin

[ Iodine is necessary for the synthesis of  the thyroxin, which is a thyroid hormone.]

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

Answer : (b) It regulates growth and development of the body.

[  Insulin primarily regulates blood sugar levels and does not directly control the growth and development of the body. ]

15. Select the mis-matched pair

(a) Adrenaline : Pituitary gland

(b) Testosterone: Testes

(c) Estrogen : Ovary

(d) Thyroxin : Thyroid gland

Answer: (a) Adrenaline: Pituitary gland.

[ Adrenaline is produced by the adrenal glands, not the pituitary gland.]

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

Answer: (c) amount of water in cells.

[ The turgidity of guard cells, influenced by the water content, is crucial in controlling the opening and closing of stomata in plant leaves. ]

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

Answer: (d) rapid cell divisions in tendrillar cells in contact with the support

[ The growth of tendril in pea plants is due to rapid cell divisions in tendrillar cells in contact with the support. Tendrils typically exhibit thigmotropism, a response to touch or contact with a support, which triggers the rapid cell division and coiling around the support.]

18. The growth of pollen tubes towards ovules is due to

(a) hydrotropism       (b) chemotropism         (c) geotropism          (d) phototropism

Answer: (b) chemotropism.

[ Chemotropism is the growth or movement of an organism in response to a chemical stimulus, and in this case, it involves the attraction of pollen tubes toward chemicals released by ovules. ]

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

(a) phototropism      (b) geotropism    (c) chemotropism    (d) hydrotropism

Answer: (a) phototropism.

[ Phototropism is the growth or movement of an organism in response to light, and in the case of sunflowers, it causes them to follow the sun across the sky. ]

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

Answer: (c) abscisic acid.

[ Abscisic acid is involved in promoting abscission, which is the shedding of leaves and fruits from a plant.]

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

Answer :  (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.

[ This statement is inaccurate because, in a synapse, it is the release of chemicals (neurotransmitters) from the axonal end that influences the generation of an electrical impulse in the dendrite of another neuron.]

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

Answer : (c) medulla in hind brain .

[ Involuntary actions in the body are primarily controlled by medulla in the hindbrain.]

23. Which of the following is not an involuntary action?

(a) Vomiting         (b) Salivation        (c) Heart beat      (d) Chewing

Answer: (d) Chewing

[ Chewing is not an involuntary action because it is controlled by our will. We can choose when to chew and when to stop.]

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

Answer : (b) differentiate the smell of a perfume from that of an agarbatti .

[ When a person is suffering from severe cold, he or she cannot differentiate the smell of a perfume from that of an agarbatti. This is because a blocked or congested nose can affect the sense of smell.]

25. What is the correct direction of flow of electrical impulses?

                       Fig. 7.1

Answer : (c)

[ Electrical impulses pass from the dendrites to the cell body, then move along the axon to the axon terminal and cross the synapse to reach the dendrites of the next neuron.]

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

Answer:  (a) Iron is essential for the synthesis of thyroxin.

[ Iodine is essential for the synthesis of thyroxin, not iron.]

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

Answer:  (b) less secretion of growth hormone.

[ Insufficient production of growth hormone during childhood can lead to a slower rate of growth and result in dwarfism.]

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

Answer: (c) testosterone from testes and estrogen from ovary.

[ Puberty-related changes in body features are primarily driven by the increased secretion of sex hormones, with testosterone being more prominent in males and estrogen in females.]

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

Answer: (d) his sugar level in blood was high .

[ The doctor advised the person to take an injection of insulin because his sugar level in the blood was high. Insulin is a hormone that helps regulate blood sugar levels.]

30. The hormone which increases the fertility in males is called

(a) oestrogen       (b) testosterone        (c) insulin       (d) growth hormone

Answer: (b) testosterone

[ The hormone that increases fertility in males is testosterone.]

31. Which of the following endocrine glands is unpaired .

(a) Adrenal     (b) Testes      (c) Pituitary    (d) Ovary

Answer: (c) Pituitary.

[ The pituitary gland is a single, pea-sized gland located at the base of the brain.]

32. Junction between two neurons is called

(a) cell junction     (b) neuro muscular junction

(c) neural joint      (d) synapse

Answer: (d) synapse

[ The junction between two neurons is called synapse. ]

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

Answer: (d) nervous and endocrine systems

[ Nervous and endocrine systems are primarily responsible for controlling and regulating life processes in humans.]

Short Answer Questions

34. Label the parts (a), (b), (c) and (d) and show the direction of flow of electrical signals in Figure 7.20.

  

                        Fig. 7.20

Answer:  (a) Sensory neuron   (b) Spinal cord   (c) Motor neuron  (d) Effector = Muscle in arm

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) Auxins are responsible for the elongation of cells. They help the plant cells grow longer.

(b) Gibberellins help in the growth of the stem by increasing its length.

(c) Cytokinins promote cell division in plants and help in the formation of new cells.

(d) Abscisic acid (ABA) is responsible for the falling of senescent (old and dried) leaves.

36. Label the endocrine glands in Figure 7.3.

    

                              Fig.7.3

Answer:  (a) Pineal gland      (b) Pituitary gland     (c) Thyroid gland        (d) Thymus

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

   

                                 Fig. 7.4

Answer: Figure (a) appears more accurate.

This is because in a plant cutting, roots usually grow from the lower end of the stem due to positive geotropism, while shoots and branches grow upward due to negative geotropism .

38. Label the parts of a neuron in Figure 7.5.

  

                       Fig. 7.5

Answer:   (a) Dendrite    (b) Cell body     (c) Axon     (d) Nerve ending

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

Answer:  (a) Olfactory receptors → (iii) Nose

(b) Thermoreceptors (temperature receptors) → (iv) Skin

(c) Gustatoreceptors → (i) Tongue

(d) Photoreceptors → (ii) Eye

40. What is a tropic movement? Explain with an example.

Answer: Tropic movement is the directional growth movement of a plant part in response to an external stimulus like light, water, or gravity. It can be towards or away from the stimulus.

Example: The bending of a plant shoot towards light is called phototropism. Shoots grow towards light to help the plant prepare food by photosynthesis.

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

Answer: If the intake of iodine in our diet is low, the thyroid gland will not be able to produce enough thyroxine hormone. This affects the metabolism of carbohydrates, proteins and fats in the body. Iodine deficiency can cause goitre, in which the thyroid gland enlarges and the neck appears swollen. In children, severe iodine deficiency may also lead to stunted physical and mental growth.

42. What happens at the synapse between two neurons?

Answer: At the synapse between two neurons, an electrical signal triggers the release of neurotransmitters from the presynaptic neuron. These chemicals cross the synaptic gap and bind to receptors on the postsynaptic neuron, converting the signal back into an electrical impulse.

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) The hormone responsible for the changes noticed in females at puberty is estrogen.

(b) Dwarfism results due to the deficiency of growth hormone.

(c) Blood sugar level rises due to the deficiency of insulin.

(d) Iodine is necessary for the synthesis of thyroxine.

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?

Answer: (a) The endocrine gland associated with the brain is the pituitary gland.

(b) The gland that secretes digestive enzymes as well as hormones is the pancreas.

(c) The endocrine gland associated with the kidneys is the adrenal gland.

(d) The endocrine gland present in males but not in females is the prostate gland.

Long Answer Questions

45. Draw the structure of a neuron and explain its function.

Answer: A neuron is the structural and functional unit of the nervous system. It helps in receiving and transmitting messages in the form of electrical impulses.

Structure of a Neuron:  A neuron has three main parts -

(i) Dendrites: They receive impulses from receptors or other neurons.

(ii) Cell body (Cyton): It contains the nucleus and controls the activities of the neuron.

(iii) Axon: A long fibre that carries impulses away from the cell body to another neuron or an effector organ.

   

Function of a Neuron : The main function of a neuron is to transmit nerve impulses from one part of the body to another. It helps the body respond to different stimuli such as heat, light, sound and touch.

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

Answer:  The major parts of the brain are forebrain, midbrain and hindbrain.

The functions of the major parts of the brain are:

(i) Forebrain: It is the main thinking part of the brain. It controls thinking, memory, intelligence, emotions and voluntary actions. It also receives sensory information.

(ii) Midbrain: It controls reflex movements related to sight and hearing.

(iii) Hindbrain: It consists of the cerebellum, pons, and medulla. The cerebellum controls balance and body movements, while the medulla controls involuntary actions like breathing, heartbeat and blood pressure.

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

Answer: The nervous system is divided into the central nervous system (CNS) and peripheral nervous system (PNS). The CNS consists of the brain and spinal cord. The PNS consists of all the nerves that arise from the brain and spinal cord and connect them to different parts of the body.

The brain is protected by the skull, while the spinal cord is protected by the vertebral column. Both are also covered by three membranes called meninges and are surrounded by cerebrospinal fluid, which protects them from injury and shock.

48. Mention one function for each of these hormones :

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

Answer: (a) Thyroxin: Regulates the metabolism of carbohydrates, proteins, and fats in the body.

(b) Insulin: Controls the blood sugar level by helping cells absorb glucose.

(c) Adrenaline: Prepares the body to face emergency situations by increasing heartbeat and breathing rate.

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

(e) Testosterone: Controls the development of male secondary sexual characters.

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

Answer: The major plant hormones are auxins, gibberellins, cytokinins and abscisic acid .

(i) Auxins: Promote cell elongation and help in the growth of roots and shoots.

(ii) Gibberellins: Stimulate stem growth, seed germination, and flowering.

(iii) Cytokinins: Promote cell division and help in the growth of lateral buds.

(iv) Abscisic acid (ABA): Inhibits growth and causes wilting and falling of leaves. It also helps plants tolerate stress.

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

Answer: Reflex actions are quick, automatic and involuntary responses to a stimulus.

Examples: (i) Pulling back the hand after touching a hot object.    (ii) Blinking of eyes when dust enters them.

A reflex arc is the pathway followed by nerve impulses during a reflex action. In a reflex arc, receptors detect the stimulus and send impulses through sensory neurons to the spinal cord. The spinal cord passes the message through motor neurons to the effector muscles, which respond immediately.

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

Answer: The nervous system controls and coordinates body activities through electrical impulses for quick responses, while the hormonal system uses hormones carried by blood for slower but long-lasting effects. Both systems work together to maintain balance and proper functioning of the body. For example, during stress, nerves signal the adrenal glands to release adrenaline, increasing heartbeat and energy supply. Thus, the nervous and hormonal systems together regulate growth, metabolism, movement and responses to different situations in human beings.

52. How does chemical coordination take place in animals?

Answer: Chemical coordination in animals takes place through hormones secreted by endocrine glands. In scary situations, the adrenal glands release adrenaline into the blood. It reaches different body parts and prepares the animal for fight or flight. The heartbeat and breathing rate increase, more oxygen reaches the muscles, and blood supply to the digestive system decreases. These changes help the body respond quickly to danger. Thus, hormones carried through blood provide control and coordination in animals along with the nervous system.

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: The flow of signals in a synapse is from the axonal end of one neuron to the dendritic end of another because neurotransmitters are released only from the axon terminal. The dendrites of the next neuron contain receptors to receive these chemical signals and produce a new electrical impulse. The reverse flow is not possible because dendrites do not release neurotransmitters and axon terminals do not have receptors for receiving them. Thus, nerve impulses travel only in one direction for proper coordination.