Important Questions Class 10 Science Chapter 7

Important Questions Class 10 Science Chapter 7 – Control and Coordination

Science is an important subject you study in school. In this chapter, you will study control and coordination. Control and coordination determine the reflex and reactions of living beings. From trees to human beings, every living being has a way of reacting to the outer environment.

Chapter 7 of Class 10 Science discusses different means and organs of coordination. It largely studies the human brain and the basics of its functional system. Students will also know how coordination works on plants. It is a very important chapter, and students should solve as many  questions  as possible to build their concepts.

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Important Questions Class 10 Science Chapter 7 – With Solutions

The subject experts of Extramarks have collected the questions from different sources such as textbook exercises, CBSE sample papers, CBSE past years’ question papers and important reference books. They have not only collected the questions but provided the answers too. Experienced professionals have further checked the answers to ensure the best quality  content for students. Thus, the Important Questions Class 10 Science Chapter 7 will help students to prepare better and score well in exams.  Some of the important questions are given below-

Question 1: Mention the difference between walking and the reflex action?

Answer 1: Reflex action is an involuntary response to a stimulus controlled by the spinal cord within a fraction of a second. Walking is a voluntary response which is controlled by the brain and takes a longer time.

Question 2: What happens at synapse  between two neurons?

Answer 2: The gap present between the two neurons is called a synapse. The axon terminal of one neuron is close to the dendrite of the second neuron. The electrical signals are released at the nerve endings. At the synapse, the nerve impulse is transmitted from one neuron to the other neuron.

Question 3: Posture and equilibrium of the body are maintained by which part of the brain?

Answer 3: Cerebellum, a part of the hindbrain maintains the posture of the body. 

Question 4: How is the smell of an incense stick detected?

Answer 4: Olfactory organs are present in the nose. They detect the smell and set off a chemical reaction. This generates nerve impulse which is transmitted to the sensory nerve. This relay the information in the form of nerve impulses via the spinal cord to the brain. The message is interpreted in the olfactory lobe and the smell is interpreted.

Question 5: What role does the brain play in reflex action?

Answer 5. Reflex action takes place in the spinal cord. The information provided by the reflex action reaches the brain where the information is stored and remembered for future use.

Question 6: What are plant hormones?

Answer 6. A chemical substance produced naturally by the plant to regulate growth and physiological processes to bring about control and coordination in various activities of the plant.

Question 7: How do the two movements differ from each other: the movement of leaves from the sensitive plants and the movement of shooting toward light?

Answer 7: Nastic movement involves the movement of leaves from the sensitive plant. Its stimulus is touch and is not regarded as a growing movement.

The movement of shooting towards light is an example of tropic movement and the stimulus is light. It is regarded as the growth movement.

Question 8: Which plant hormone promotes growth? How does it promote the growth of tendrils around support?

Answer 8. Auxin is the plant hormone promoting growth. Tendrils are sensitive to touch or contact with other objects. When a tendril touches support, the auxin from the tendril tip diffuses towards the side of the tendril that is not in contact with the support. There is faster growth of the side that is not in contact  than with the side which has contact with the support. Due to this,  the tendril bends  towards the support.

Question 9. Demonstrate the bending of roots in the direction of water stimulus.

Answer 9: For the experiment, first, take two glass troughs A and B. Fill them two-thirds with soil. 

• In trough A, plant a tiny seedling and water  it daily. 
• In trough B, plant a similar seedling followed by placing a small ‘clay pot’ inside the soil. Do not water the soil but add some water to the clay pot and bury it in the soil thereby leaving it for a few days. The clay pot is kept on the right side 
• Dig  the soil from both the troughs ensuring  the roots of seedlings should not be damaged
• In trough A, the roots will be straight due to uniform watering of the soil.
• In trough B, the roots will be bent towards the right side because roots get water oozing out from the clay 

pot which is kept on the right side.

• The roots of a plant grow towards water. This means they are positively hydrotropic.

Question 10. How does chemical coordination take place in animals?

Answer 10. The endocrine glands present in animals release chemical substances called hormones. Hormones are released directly into the blood from where it is carried to the target organ. The hormones bring about the effect in the target organ.

Question 11. Iodised salt is advisable. Why?

Answer 11. Thyroxine is produced by the thyroxine gland. For the formation of this hormone, iodine is required by the thyroid gland. Thyroxine is responsible for carrying out the metabolism of carbohydrates, fats and proteins in the body. They are required for the growth of the body. Goitre is a condition that results in the enlargement of the thyroid gland due to the deficiency of iodine. The neck is swollen in this condition. So the use of iodised salt is advisable to prevent the  disease.

Question 12. What happens when the adrenaline is secreted into the blood?

Answer 12. Adrenaline is also called an emergency hormone and is produced by the adrenal glands. The hormone is rapidly secreted in response to stress or an emergency situation. The hormone is associated with the increase in the heartbeat, respiration rate and the elevation of glucose levels. This adds a lot of energy to the body and helps in fighting the emergency situation.

Question 13. Why are insulin injections used in diabetic patients?

Answer 13. Insulin is involved in the metabolism of sugar. It lowers the blood sugar level. The secretion of insulin is reduced in some patients with diabetes so to compensate for this reduced secretion, insulin injection is given..

Question 14. Answer the following questions:

• Draw the diagram of the neuron.

• What are the parts of neurons?

• Where is information acquired

• How does impulse travel?

Answer 14: 1. 

1. The parts of the neuron are the axon, dendrites and cell body.
2. The information is acquired by the dendrites and a chemical reaction is set off which creates an electrical impulse
3. The electrical impulse travels from the dendrite to the cell body and then along the axon to its nerve ending. At the end of the axon, the electrical impulse sets off the release of chemicals which cross the synapse and start a similar electrical impulse in a dendrite to the next neuron. This is a scheme of how an impulse travels in the body.

Question 15. How does phototropism occur in plants?

Answer 15. 

The directional movement of the plant part towards light response is called phototropism. This is positive when the part of the plant moves towards the light. When the part of the plant moves away from the light, it is called negative tropism. For example, the shooting of a growing plant towards the light is called positive phototropism, while the roots of a plant away from the light are called negative phototropism.

The hormone which is responsible for this phototropic action is the auxin hormone. The given experiment below demonstrates the phototropic activity of the plant:

• Take two potted plants. Keep one open so that it gets sunlight from above. Keep the second one in a closed room near the window so that it receives the sunlight from one side. After a few days, observe these plants.
• The plant kept open grows straight towards the light. While the second plant bends towards the light.
• The diagram is given above to explain the concept. The stem bends towards the light is the result  of the experiment.

Question 16. What happens in a spinal cord injury?

Answer 16: The spinal cord in the human body is enclosed within a bony cage called the vertebral column. It protects from spinal cord injury.

In case of spinal cord injury, the  signals from the spinal cord to the brain are disturbed. The reflex action is also disrupted.

Question 17. Explain how chemical coordination occurs in plants. Mention the role of auxin and Abscisic acid.

Answer 17: In plants, the cells which are stimulated release the chemical compounds. These chemicals are plant hormones. They play an important role in growth, development and responses to the environment. They are synthesised at other places from the place of action and they get diffused.

The function of auxin is:

• Auxin is a phytohormone and a growth promoter.
• It promotes cell enlargement
• It is responsible for cell differentiation
• Induces tropism
• Formation of seedless fruits without fertilisation, in the number of plants. This is parthenocarpy.
• It promotes apical dominance which means, a phenomenon where lateral buds fail to grow due to the presence of the apical bud. Auxin is released by the apical buds which inhibit the growth of the lateral buds by releasing auxins.

The functions of abscisic acid are:

• This is a phytohormone and a growth inhibitor.
• The production of abscisic acid is promoted by drought, water logging and other adverse conditions where stress is induced. So it is a type of stress hormone.
• It promotes dormancy in the seeds and buds and inhibits growth.
• It promotes the abscission of flowers and fruits
• It promotes falling and senescence in leaves.
• It affects the transpiration and the wilting of the leaves. This is due to the closing of the stomata due to the release of abscisic acid.

Question 18. Why does an organism need control and coordination?

Answer 18. When an activity is performed, it is the result of coordination between the different organs of the body. When food is taken, the eyes locate it and the nose detects the smell, the teeth and jaw coordinate and the chewing of food occurs. It maintains a balance between the internal conditions of an organism and the external environment.

Question 19. How are involuntary and reflex actions different?

Answer 19. Involuntary action does not require thinking and is a set of muscular movements. They are controlled by the brain. These types of actions are concerned with the functioning of the internal body parts like a heartbeat, breathing, etc.

Reflex action is an unconscious and automatic response of the effectors. They are monitored by the spinal cord. Eyes  close due to the bright intense light. They are connected to emergencies.

Question 20. What is the nervous mechanism and hormonal mechanism?

Answer 20. The nervous mechanism is carried out by the nervous system in which electrical impulses are transmitted instantaneously and the effects are short-lived.

The hormonal mechanism is performed by the chemical substances which are secreted by the endocrine glands. The rate of information transmission is slow and the effect is prolonged.

Question 21. How is the movement in sensitive plants different from the movement in our legs?

Answer 21: The sensitive movement in plants occurs in response to a touch stimulus. The information is transmitted from cell to cell by electrochemical signals as the plant lacks specialised tissue for the conduction of impulses. There is a change in the shape of plant cells by changing the amount of water.

Movement in the legs is due to voluntary action. The signals are passed to the brain and hence they are controlled consciously. There are proteins present in animals which allow movement to take place..

Question 22. Multiple choice questions:

• Which of the following options shows plant hormone?

• Insulin

• Thyroxine

• Oestrogen

• Cytokinin

Answer: (d) cytokinin

Explanation:

In the option given, insulin, thyroxine and oestrogen are the animal hormones.

• The gap between the two neurons is called

• Dendrite

• Synapse

• Axon

• Impulse 

Answer: (b) synapse

Explanation:

The gap between the two neurons is called a synapse.

• Which of the following functions is performed by the brain?

• Process of thinking

• Heartbeat regulation

• Body balance

• All the above

Answer :  (d) all of the above

Explanation:

The brain carries the functions related to thinking, heartbeat regulation and body balance.

• How many pairs of cranial nerves are present in a man?

• 12

• 21

• 31

• 41

Answer: (a) 12

Explanation:

There are 12 pairs of cranial nerves present in the human body.

• The life process in human are controlled and regulated by

• Reproduction and endocrine system

• Respiratory and nervous system

• Endocrine and digestive system

• Nervous and endocrine system

Answer: (d) nervous and endocrine system

Explanation:

Reproductive, respiratory and digestive systems are not responsible for control and coordination because the process involves nervous and endocrine systems.

• Why is injection of insulin advised?

• Low blood pressure

• Slow heartbeat

• Goitre

• High blood sugar level

Answer: (d) high blood sugar level

Explanation:

The insulin injections are given to diabetic  patients to regulate their blood sugar level.

• Which hormone increases fertility in males?

• Oestrogen

• Testosterone

• Insulin

• Growth hormone

Answer: (b) testosterone

• Mention the unpaired endocrine glands.

• Adrenal

• Testes

• Pituitary

• Ovary

Answer: (c) pituitary

Explanation:

Adrenal glands are paired glands at top of the kidney. Testes is a paired gland producing male sex hormones and paired ovaries produce female sex hormones. The pituitary is the master gland present below the brain independently.

• What is the cause of dwarfism?

• Excess thyroid

• Less growth hormone

• Less adrenaline

• Excess growth hormone

Answer: (b) less growth hormone

Explanation:

Growth hormones are involved in the growth of the body. Over-secretion and under-secretion result in imbalanced growth.

• Involuntary actions are controlled by which part of the brain?

• Fore brain

• Midbrain

• Hindbrain

• Spinal cord

Answer: (c)

Explanation:

The medulla present in the hindbrain controls involuntary actions.

• Tendril growth in pea plant is due to 

• Light effect

• Gravity

• Rapid cell division of the cells away from the support

• Rapid cell division in contact with the support

Answer: ( c)

Explanation:

There is rapid cell division in the tendrillar cells that are away from the support.

Question 23. Fill in the blanks.

• __________ is the movement of shooting towards light.

• _________is the movement of growth of the plant in response to the gravitational force.

• The plant growth in response to the chemical is called __________

• The growth of the plant roots towards and away from the moisture is known as __________

• Iodine is responsible for the synthesis of __________

• Spinal cord originates from __________

• Conversion of electrical signal to chemical signal occur in a neuron at ___________

• The shape of guard cells changes due to the __________

• The main function of abscisic acid in plants is to __________

• __________ increase the length of the cell.

• __________ receptors detect taste.

• __________ receptors detect smell.

• __________are the long cells of the body.

• The box enclosing the brain is called __________

• _________act as both endocrine and exocrine gland.

• __________regulates the ionic balance.

• _____________disappears with advancing age.

• __________ is mediated by the spinal cord.

• The leaves of Mimosa are sensitive to _________

• __________ is used to keep the flowers fresh.

• ___________ synthesises growth hormones in plants.

• _______________ is concerned with memory, will and power.

• ___________ is responsible for muscular coordination in the body.

• __________  is called the master gland.

Answer 23.

1. Phototropism  is the movement of shooting towards light.
2. Geotropism is the movement of growth of plants in response to the gravitational force.
3. The plant growth in response to the chemical is called chemotropism
4. The growth of the plant roots towards and away from the moisture is known as hydrotropism
5. Iodine is responsible for the synthesis of Thyroxine
6. The spinal cord originates from the medulla
7. Conversion of the electrical signal to chemical signal occurs in a neuron at the axonal end
8. The shape of guard cells changes due to the water content
9. The main function of abscisic acid in plants is to inhibit growth
10. Auxin increases the length of the cell.
11. Gustatory receptors detect taste.
12. Olfactory receptors detect  smell.
13. Nerve cells are the long cells of the body.
14. The box enclosing the brain is called the cranium
15. Pancreas act as both the endocrine and exocrine gland.
16. Vasopressin regulates the ionic balance.
17. Thymus disappears with advancing age.
18. Reflex action is mediated by the spinal cord.
19. The leaves of Mimosa are sensitive to touch
20. Cytokine is used to keep the flowers fresh.
21. Shoot tip synthesises growth hormones in plants.
22. Cerebral hemisphere is concerned with memory, will and power.
23. Cerebellum is responsible for muscular coordination in the body.
24. Pituitary gland is called the master gland.

Question 24. State true or false

• Reflex action without the involvement of the brain is an autonomic motor response.

• Insulin is used in the management of goitre

• Iodine is involved in the production of thyroxine

• Plant hormones help in the coordination of plant behaviour with environmental changes

• Stimulus is characteristic of animals only.

• Negative tropism is a bend of a plant stem towards sunlight.

• Receptor is a particular type of cell which respond to the stimulus

• Testosterone is involved with female puberty

• The central nervous system collects information from all the receptors in the body

• Reflex arc works faster than the thinking process of the brain.

• Brain is a delicate organ protected from injury.

• Plants use electrochemical means to convey information from cell to cell.

• Olfactory receptors detect taste and gustatory senses detect smell.

Answer 24:

1. True
2. False. Insulin is given in diabetes patients
3. True
4. True
5. False. This is seen in both plants and animals
6. False. This is seen in positive tropism
7. True
8. False. Testosterone is male hormone
9. True 
10. True 
11. True 
12. True 
13. False. Olfactory is for smell and gustatory is for taste.

Question 25. Answer the following questions:

• Which hormone causes changes in puberty?

• Which growth hormone causes dwarfism?

• Which hormone deficiency causes a rise in blood sugar level?

• Which hormone requires Iodine for synthesis? 

• Which endocrine gland is associated with the brain?

• Which gland secretes both digestive enzymes and hormones?

• Which endocrine gland is present in males and not in females?

• Which endocrine gland is associated with Kidneys? 

• Give the location of gustatory and olfactory receptors.

• What are the two components of the central nervous system?

• How is the spinal cord protected?

• Which part is involved in coughing, sneezing and vomiting?

• Name the stimuli acting on the plants.

Answer 25:

1. Oestrogen causes a change in puberty.
2. Dwarfism is due to the deficiency of growth hormones.
3. Insulin is used in diabetes.
4. Thyroxine requires iodine.
5. The pituitary gland is associated with the brain.
6. The pancreas secretes both digestive enzymes and hormones.
7. Testes are present in males not in females.
8. The adrenal gland is related to kidneys.
9. Gustatory receptors are located in the cerebrum of the forebrain and olfactory in the olfactory lobe of the forebrain.
10. The two components are the brain and the spinal cord.
11. Spinal cord is protected by the vertebral column.
12. Medulla of hind-brain.
13. Light, gravity, water and touch

Question 26.  Answer the following questions:

•  What are hormones chemical messengers?

• Why is the pituitary the master gland?

• Why are endocrine glands ductless?

• What are receptors?

• What do you understand by stimulus?

• Mention the control centre and the route taken by the reflex action.

• Name one gustatory receptor.

• Name one olfactory receptor

Answer 26:

1. Hormones are chemical messengers as they are carried in the blood to all the parts of the body.
2. Pituitary is the master gland because it controls the activities of the other endocrine glands.
3. They are called the ductless glands as they do not have any extended ducts to discharge the secretion into the bloodstream.
4. Receptors are specialised groups of cells to detect a stimulus and initiate impulse transmission via the sensory nerves.
5. Stimulus means a change in the external and internal environment of an organism which provokes a physiological and behavioural response in the organism.
6. The control centre of the reflex action is the spinal cord. The route taken is the reflex arc.
7. Tongue
8. Nose 

Question 27. The pancreas and gonads perform the dual function. Justify the statement.

Answer 27. It is said that the pancreas and the gonads perform a dual function. The pancreas secretes both digestive enzymes and hormones, namely, insulin and glucagon. Gonads produce gametes and male and female sex hormones. So these are dual functions.

Question 28. What is the difference between exocrine and endocrine glands?

Answer 28: Exocrine glands have ducts and they secrete the enzymes. They function in situ or pour the secretions directly near the target through a duct.

Endocrine glands are ductless glands and they secrete hormones. They pour the secretions directly into the blood

Question 29. What type of role is played by the hypothalamus in the human body?

Answer 29: Hypothalamus produces both releasing and inhibiting hormones. If the level of the growth hormones reduces, then the hypothalamus releases neurohormones to stimulate the pituitary gland to release the hormone.

Question 30. Pancreas overall control the blood glucose level. Why?

Answer 30: Pancreas produces insulin to lower the blood glucose level. It releases glucagon to increase blood glucose so it overall regulates the blood glucose level.

Question 31. Explain releasing hormones.

Answer 31. They are the chemical substances which are responsible for regulating the hormonal secretion from the pituitary glands. They are released from the hypothalamus.

Question 32. State the function of the different parts of the brain.

Answer 32: The major parts of the brain are the forebrain, midbrain and hindbrain.

The forebrain includes the cerebrum and olfactory lobes. The hindbrain includes the cerebellum, pons and the medulla oblongata.

• Forebrain has a specific region which is accountable for stimulus and response. The occipital lobe is for visual perception. The temporal lobe is for auditory reception. Speech, facial muscular activities and higher mental activities are controlled by the frontal lobe. The parietal lobe is responsible for taste, smell, touch and conscious association. The sensation of smell is received by the olfactory organ..
• Midbrain is responsible for controlling the reflex type of movement from the head, neck and trunk.
• Hindbrain has cerebellum, pons and the medulla oblongata. The cerebellum controls the coordination of body movements and posture. Pons is involved in respiration regulation. The medulla oblongata is responsible for coughing, sneezing, swallowing and vomiting.

Question 33. Give an outline of plant movements.

Answer 33. The plant movements can be explained as

• Phototropism is the orientation of the plant in response to the light stimulus. If the plant part moves towards the light, it is called positive phototropism. When it moves away from the light, it is called negative phototropism.
• Seismonastic movements are responses to touch and shock. They  are very quick and can be seen in the touch-me-not plant (Mimosa pudica), which is a sensitive plant.
• Geotropism is a type of directional movement. It is the orientation of the plant that is a response to gravity. Positive geotropism means the plant part moves in the direction of gravity. If it moves against the direction of gravity it is called negative geotropism. The roots of a plant move down in the soil so it is an example of positive geotropism. The stem of the plant moves against the direction of gravity so it is the negative geotropism.
• Nyctinastic movement refers to the movement which involves the diurnal variation in the position of flowers and leaves during day and night. They include photonastic and thermonastic movement. In the photonastic movement, there is diurnal variation in the position of the plant parts e.g. flowers and leaves, caused by the light stimulus with the non-directional movements. An example is the dandelion flower.

In the thermonastic movement, there is diurnal variation in the position of the plant parts eg flowers and leaves of plants which are caused due to the temperature changes of the surrounding.

• Chemotropism is the directional movement of the part of the plant in response to the chemical stimulus. Positive chemotropism is the movement towards the chemical and negative tropism is the movement away from the chemical. An example of positive chemotropism can be given as during fertilisation, the pollen tube grows towards the ovule in the ovary.
• Hydrotropism is the directional movement in response to the water stimulus. Positive hydrotropism is the movement towards the water stimulus and the negative is away from the water stimulus. The bending of the plant roots towards the water is an example of positive hydrotropism.
• Thigmotropism is the directional response to the touch. It is seen in plants with tendrils. Tendrils are positively thigmotropic as they grow towards things they happen to touch. Bitter gourd, bottle gourd and grapevine are such examples.

Question 34. Why chemical communication is important in multicellular organisms.

Answer 34: Chemical communication is  important  in the following conditions:

• To deal with the emergency demands like infection, trauma, starvation, dehydration, haemorrhage and extreme temperature.
• The coordination is fast and short-lived.
• The nerve cells do not connect to all the cells of the body and there is a need for continuous monitoring of the cellular functions, so it requires special coordination and integration which has to be provided. So this is the role played by the hormones.
• The physiological functioning of the body is regulated by the endocrine and nervous systems.

Question 35. List the functions of the hormones with the glands by which they are secreted.

Answer 35: 

• Growth hormones are secreted by the pituitary glands. They are responsible for the stimulation of growth in all the organs of the body. The height of the person depends on these hormones. When they are normally secreted, the height is normal but when they are secreted in excess amounts, the person is very tall. Dwarfism is associated due to a decrease in the secretion of growth hormones. There are many tissues related to this like bones, cartilage, muscles, fat, liver and the heart.
• Thyroxine secreted by the thyroid gland controls the rate of metabolism of carbohydrates, fats and proteins in the body.
• Pancreas secrete insulin which regulates the blood sugar level. It also acts to inhibit glucagon and insulin release.
• Testes produce testosterone which regulates sexual drive, the mass of bone, the distribution of fat, the mass of muscles and sperm production. The secondary sexual characteristics in males are developed by testosterone.
• Ovaries produce progesterone and oestrogen. The development of the breast and the reproductive organs in females is regulated by oestrogen. It also maintains pregnancy. Progesterone, on the other hand, thickens the lining of the uterus to prepare the female body for pregnancy.
• Releasing hormones produced by the hypothalamus regulates the secretion of the hormones from the pituitary gland. The hypothalamus controls the pituitary hormones.
• Adrenaline secreted by the adrenal gland regulates the heart rate, breathing rate, blood pressure and the metabolism of carbohydrates.

Question 36. What is a neuromuscular junction?

Answer 36: This is a point where a muscle fibre comes in contact with a motor neuron carrying nerve impulses from the central nervous system. The impulses are conducted from the neuron to the muscle fibre by a neurotransmitter in the same manner as the impulse transmission across the synapse between the two neurons.

Question 37. Mention the largest part of the brain with function.

Answer 37: Cerebrum is the largest part of the brain. It has various regions which carry out the activities like vision, auditory reception, touch, smell, temperature, consciousness and muscular activities.

Question 38. What is the difference between the spinal and cranial nerves?

Answer 38: There are 31 pairs of spinal nerves arising from the spinal cord. Cranial nerves arise from the brain and they are a  total of 12 pairs.

Question 39. What are the sensory and motor neurons?

Answer 39: Sensory neurons transmit the information from the receptor to the central nervous system. Motor neurons transmit the information from the brain to the effector organs.

Question 40. How do unicellular organisms respond to stimuli? Do plants respond to the stimuli? If yes, how?

Answer 40: Chemical communication plays an important role in the following conditions. So it responds to the stimuli.

Similarly, the roots of the plant, in response to the gravitational force, move down and the shoot of the plant moves towards the light. This shows that plants do respond to stimuli.

Question 41. What do you understand by the reflex action? Explain the steps involved in it. What happens when we touch a hot object?

Answer 41: Reflex action is defined as the unconscious, automatic and involuntary response of effectors which means to the muscles and glands, to a stimulus, which is monitored by the spinal cord.

The mechanism of reflex action is:

• Skin is the receptor and it receives the stimulus, this leads to the activation of the sensory nerve impulse.
• The sensory organ carries the message to the spinal cord in the form of the sensory impulse.
• Spinal cord plays the role of a modulator, spinal cord neurons transmit sensory nerve impulses to the motor neuron.
• Motor nerve conducts the impulses to the effectors like the muscles of the leg due to which there is pulling back the organ away from the harmful stimulus.

In case of touching the hot object:

• Skin being the receptor organ receives the stimulus and activates the nerve impulse. The spinal cord receives the message and the motor nerves conduct the impulse to the effector organ hands which are pulled back after touching the hot object.

Question 42. Answer the following questions.

• Classify the movement as tropic or nastic

• Flower opening

• Downward movement of root

• Upward movement of shoot

• Twirling of a tendril

• Which hormone is present in greater concentration in the areas of rapid cell division.

• How do plants carry out control and coordination?

• What are the types of plant hormones?

• Mention the functions of the plant hormones.

Answer 1. The movements are given below

1. Nastic
2. Tropic
3. Tropic
4. Nastic

2. Cytokines are in higher concentration in the areas of rapid cell division.
3. Phytohormones are responsible for carrying out the function of control and coordination in plants.
4. There are four types of plant hormones. They are auxins, gibberellins, cytokinins and abscisic acid
5. The functions of the plant hormones are:

• To break the dormancy of the seeds
• Germination
• Stem, root and leaves growth
• Flowering of plants
• Fruit ripening
• Stomatal movement in leaves
• Phototropism
• Geotropism
• Chemotropism
• Nastic movements

Question 43. Mention the functions of the nervous system

Answer 43. The functions of the nervous system are:

• Regulation of the involuntary actions
• Control and coordination between voluntary activities of the muscle
• Sense organs give a sense of awareness of the outside world
• The system provides us with the ability to think, reason and remember
• To control the reflex action and thereby offer protection from the harmful stimulus.

Question 44. Which part of the brain will carry out activities like picking up a pencil and riding a bicycle?

Answer 44: Such type of function is performed by the hindbrain and cerebellum respectively.

Question 45. Give the order in which the impulse is transmitted in the neurons.

Answer 45: Dendrite —- cell body ——- axon ——- end point of neuron

Question 46. Which plant hormone is responsible for promoting cell division and stem growth?

Answer 46: Cell division is regulated by Cytokinin and stem growth by Gibberellins.

Question 47. Give the significance of reflex action

Answer 47: This gives the ability of the animal to respond quickly and it provides relief to the brain in the excess work.

Question 48. Add a note on plant hormones.

Answer 48. 

1. Auxins:

• Cell enlargement and cell differentiation in plants
• Promotion of cell and stem growth
• To regulate plant growth movements meaning tropism
• Inducing parthenocarpy

2. Gibberellins

• Cell enlargement and cell differentiation in the presence of auxins
• Promotion of growth of stems and fruits
• Rosette plants which show the profuse development of leaf and the reduced development of the internode, tend to show bolting and flowering when they are treated with the gibberellins.

3. Cytokines

• Promotion of cell division in the plants
• Morphogenesis in plants which is the vital role
• To break the dormancy of seeds and the buds
• To delay the ageing in the leaves
• To open the stomata
• To promote the growth of the fruit

4. Ethylene

• Promote growth and ripening of the fruits
• Break the dormancy in the buds and the seeds
• Stimulates the formation of the separation layer in leaves, flowers and fruits
• To promote yellowing and the leaves senescence.

5. Abscisic acid (ABA)

• It inhibits growth by promoting dormancy.
• After wilting of the leaves since it closes the stomata
• Promote the falling of the leaves and the senescence or ageing of leaves.

Question 49. Write a short note on the plant movements.

Answer 49: Plants do not show locomotion but there occurs movement of certain parts of the plant like leaves, shoots and roots. This is possible due to the exposure of the plants to the external environment like light, temperature, water, the force of gravity, chemicals, touch, etc. these are caused by an unequal growth in their two regions by the action of plant hormones. This happens under the influence of the stimulus.

Question 50. What is the feedback mechanism?

Answer 50: A feedback mechanism is in which the timing and the number of hormones released by the glands are controlled by the mechanism which is in-built into the body. For example, when the blood sugar level is high, this is detected by the beta cells of the pancreas. The response generated in response to this is the production and secretion of more insulin into the blood. When there is a balance in the blood sugar level, insulin secretion is reduced automatically.

Question 51. Write notes on

• Parathyroid gland

• Thymus

• Thyroid gland

• Pineal gland

Answer 51:

1. Parathyroid glands are four small oval-shaped bodies which lie embedded in the lobe of the thyroid gland. They produce parathormone or parathyroid hormone (PTH). This hormone regulates calcium and phosphate levels in the blood. Then the level of blood calcium level is below normal, there is the mobilisation of calcium released into the blood from the bone. The action of this hormone is opposite to calcitonin.
2. Thymus gland is located in the upper chest near the front side of the heart. There is gradual atrophy of the gland in the adult. The gland secretes the hormone thymosin. It stimulates the development and the differentiation of lymphocytes (white blood cells).
3. Thyroid gland is situated in the neck region in the vertebral region of the body. It has two lateral lobes on either side of the trachea. There are two hormones secreted; they are thyroxine and triiodothyronine. T3 and T4 stimulate the rate of cellular oxidation and metabolism.
4. Pineal gland is located between the two cerebral hemispheres of the brain. It secretes the hormone melatonin. The hormone is responsible for circadian rhythm.

Question 52. What would happen in the body when the receptors do not work properly? What are the problems that are likely to arise in this situation?

Answer 52. The main function of the receptor is to collect information which is related to the changes in the environment. Then this information is passed to the central nervous system for the interpretation of the message. The appropriate instructions are sent to the effector which reveals the response. 

The receptors are located in the sense organs. If these receptors do not work properly then the stimuli received from the environment cannot be converted into impulses so there would be no response produced by the body. 

Gustatory receptors are present on the tongue for the perception of taste. If these receptors do not function properly there would be no taste perception and one cannot enjoy the taste of the food. Olfactory receptors are present in the nasal cavity for the perception of a smell. If these cannot function properly, the smell cannot be experienced by an individual.

Question 53. Give examples of the reflex action. Explain with the diagram.

Answer 53: Examples of reflex action include knee jerk, movement of the diaphragm during respiration, coughing, yawning, blinking of the eyes, sneezing, etc. coughing is a reflex action to clear the windpipe. When the bright light falls on the eyes, the pupils get smaller, this provides protection to the retina from damage due to too much light.

Question 54. Write a note on the human endocrine system.

Answer 54: The endocrine system comprises the endocrine glands and the hormones secreted by them. Hormones are those chemical substances which coordinate the essential activities of living organisms and also are responsible for the growth of the organism. They are secreted in very small amounts by the gland. They are poured directly into the blood and then carried throughout the body by means of the circulatory system. They are made at the other site and their action is generated on some other side. This is why they are also called chemical messengers. They have the target organ or the specific organs on which they act. 

Endocrine glands are structures which secrete hormones. Exocrine glands have ducts whereas endocrine glands do not have ducts.

Question 55. Explain the components of neurons.

Answer 55: The components of neurons are:

• Cell body of the neuron is called the cyton. It is a broad, rounded, pyriform or stellate part of the neuron. The cell body has abundant cytoplasm called neuroplasm in which the Nissl’s granules are present. The nucleus is relatively large and spherical. This is concerned with the metabolism and the growth, it transmits the nerve impulses to the axon which are received from the dendrites.
• Dendrites are short and branched protoplasmic processes which stretch out from the cell body of the neuron. The sensations are acquired in this region which travels as the electrical impulse toward the cell body.
• Axon is a long and cylindrical nerve fibre of uniform diameter arising from the body of the cell. It is branched at the terminal end. The terminals are often knob-like which form synapses with dendrites of the other neurons. The axons conduct the nerve impulses away from the body.

Question 56. Write a note on thyroxine and tri-iodothyronine.

Answer 56: These hormones are the iodinated forms of the amino acid tyrosine. They have the following functions:

• They maintain the basal metabolic rate of the body as they regulate the oxidation of carbohydrates, fats and proteins and produce energy in the body.
• Promote growth of the body tissues and the mental faculties.
• Stimulate tissue differentiation
• They increase heat production so they maintain the body temperature also.

Question 57. What are the different types of receptors?

Answer 57:The different types of receptors is:

• Photoreceptors which detect light are present in the eyes.
• Phonoreceptors detect sound and are present in the ears.
• Olfactory receptors are present in the nose and detect the smell
• Gustatory receptors are present on the tongue and detect the taste
• Thermoreceptors are present in the skin and detect the cold.

Question 58. Write a note on the medulla oblongata.

Answer 58: The medulla oblongata is responsible for controlling involuntary activities like the heartbeat, breathing, blood pressure and the peristaltic movement of the alimentary canal. It is also the controlling centre for coughing, swallowing, sneezing, salivary secretion and vomiting.

Question 59. Write a note on the spinal cord.

Answer 59. The spinal cord is a cylindrical structure which begins in the continuation with the medulla oblongata of the brain. It extends down to the early lumbar region and then extends to the end of the vertebral column as filum terminale(FT) which is the fibrous connective tissue.

It is enclosed in a bony cage which is called the vertebral column. It is surrounded by a membrane called the meninges. 31 pairs of spinal nerves arise from the spinal cord. This is concerned with the spinal reflex actions and the nerve impulse conduction to and from the brain. 

There are two important functions provided by the spinal cord, they are the conduction of sensory and motor impulses to and from the brain. So the spinal cord is the centre of the reflex action. It reduces the work of the brain.

Question 60. Match the following column:

Answer 60:

Question 61. Classify the nervous system

Answer 61: 

Question 62. Answer the following questions:

• Name the tissue providing control and coordination in multicellular animals.

• Why is movement shown by living organisms?

• Which part of the brain is concerned with will, power and memory?

• How information is conveyed by the plants?

• What is the difference between the cerebrum and the cerebellum

• Why does the impulse flow in one direction in the reflex arc?

• State the function of the neuron.

Answer 62:

1. Nervous system and the endocrine system.
2. To make use of changes in the environment according to their advantage.
3. Cerebral hemisphere.
4. By means of chemical coordination
5. The cerebrum is the largest and the highly developed prominent part of the brain. It controls the senses, memory, intelligence, etc.

The cerebellum is the second largest part of the brain and is present in the posterior part of the brain. It is responsible for controlling skeletal activities and is responsible for maintaining the equilibrium of the body.

1. Impulse flow in one direction in the reflex arc, as each synapse in the reflex arc allows impulses to cross in a single direction.
2. To carry the information to the long distance in the body

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