Control and Coordination: Class 10 Science answers, notes

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Get summaries, questions, answers, solutions, notes, extras, PDF and guides for Chapter 6 Control and Coordination : Class 10 Science textbook, which is part of the syllabus for students studying under SEBA (Assam Board), NBSE (Nagaland Board), TBSE (Tripura Board), CBSE (Central Board), MBOSE (Meghalaya Board), BSEM (Manipur Board), WBBSE (West Bengal Board), and all other boards following the NCERT books. These solutions, however, should only be treated as references and can be modified/changed.

Summary

Living things show movement. Some movements, like a plant seedling pushing through soil, are part of growth. If growth stops, these movements stop. Other movements, like a cat running or children playing, are not caused by growth. We often see movement as a response to changes in the surroundings. For example, a cat might run because it saw a mouse. Plants grow towards sunshine, and children swing for fun. When we touch something hot, we move to protect ourselves. All these movements in response to the environment are carefully controlled. This means living things need systems for control and coordination. In complex organisms, special tissues do this job.

In animals, the nervous system and muscles provide control and coordination. When we touch a hot object, special nerve cell tips, called receptors, detect this. These receptors are in our sense organs like the skin, eyes, and tongue. The information from a receptor starts an electrical signal, or impulse, in a nerve cell. This impulse travels along the nerve cell, from its receiving end (dendrite) to its body, and then along a long part called the axon. At the end of the axon, chemicals are released. These chemicals cross a tiny gap, called a synapse, to the next nerve cell, starting a new electrical signal. This is how messages travel. Sometimes, these messages go to muscles, making them act, or to glands.

Sometimes, we react very quickly without thinking, like pulling our hand away from a flame. This is a reflex action. Thinking is a complex process involving many nerve cells in the brain. The brain is protected inside the skull and is connected to nerves from all over the body. If we had to think about every quick action, we might get hurt. So, the body has reflex arcs. These are simpler, faster pathways where nerves detecting a signal (like heat) are directly connected to nerves that move muscles, often in the spinal cord. The spinal cord is a bundle of nerves protected by the backbone. Information also goes to the brain, but the reflex action happens first.

The brain is the main control center. It has different parts. The fore-brain is the main thinking part. It receives information from senses like sight and hearing and helps us make decisions. The mid-brain and hind-brain control many actions we don’t think about, like breathing and heartbeat. A part of the hind-brain called the cerebellum helps with balance and precise movements like walking or picking up a pencil. The brain is protected by the skull and a fluid that acts like a cushion.

Plants also respond to their surroundings, even though they don’t have a nervous system or muscles. When you touch a touch-me-not plant, its leaves fold quickly. This is not due to growth. The plant uses electrical and chemical signals to send information from cell to cell, and cells change shape by taking in or losing water. Plants also show movements related to growth. For instance, a plant shoot grows towards light, and roots grow downwards due to gravity. These are called tropic movements. Plant hormones control these growth movements. Auxin is a hormone made at the shoot tip that helps cells grow longer. If light comes from one side, auxin moves to the shady side, making those cells grow more, so the shoot bends towards the light. Other plant hormones include gibberellins for stem growth, cytokinins for cell division, and abscisic acid which can stop growth.

Animals also use chemical signals called hormones for control and coordination. When an animal is in a scary situation, a hormone called adrenaline is released from the adrenal glands. Adrenaline travels through the blood to different parts of the body. It makes the heart beat faster, sending more oxygen to muscles, and increases breathing rate. This prepares the body to either fight or run away. Hormones also control growth in animals. For example, growth hormone from the pituitary gland controls how tall we grow. Thyroxin from the thyroid gland (which needs iodine to work) controls how the body uses food for energy and growth. Insulin from the pancreas controls blood sugar levels. The release of hormones is often controlled by a feedback mechanism. For instance, if blood sugar rises, the pancreas releases more insulin. When blood sugar falls, insulin release is reduced. This keeps body functions balanced.

Textbook solutions

Intext Questions and Answers I

1. What is the difference between a reflex action and walking?

Answer: A reflex action is a sudden action in response to something in the environment, where we do something without thinking about it, or without feeling in control of our reactions. Reflex arcs are formed in the spinal cord itself and are efficient for quick responses. Walking, on the other hand, is a voluntary action which is based on deciding what to do next.

Activities like walking are possible due to a part of the hind-brain called the cerebellum, which is responsible for precision of voluntary actions and maintaining the posture and balance of the body. Therefore, a reflex action is an involuntary, rapid response primarily controlled by the spinal cord, whereas walking is a voluntary, controlled action coordinated by the brain that involves conscious thought and decision.

2. What happens at the synapse between two neurons?

Answer: At the synapse between two neurons, when an electrical impulse reaches the end of the axon of one neuron, it sets off the release of some chemicals. These chemicals cross the gap, or synapse, and start a similar electrical impulse in a dendrite of the next neuron. This is where the electrical impulse must be converted into a chemical signal for onward transmission.

3. Which part of the brain maintains posture and equilibrium of the body?

Answer: A part of the hind-brain called the cerebellum is responsible for precision of voluntary actions and maintaining the posture and balance of the body.

4. How do we detect the smell of an agarbatti (incense stick)?

Answer: We detect the smell of an agarbatti (incense stick) when olfactory receptors detect the smell. These receptors are located in our sense organs, specifically in the nose.

5. What is the role of the brain in reflex action?

Answer: In a reflex action, reflex arcs are formed in the spinal cord itself; however, the information input also goes on to reach the brain. Thus, the brain is informed of the event.

Intext Questions and Answers II

1. What are plant hormones?

Answer: Different plant hormones help to coordinate growth, development and responses to the environment. They are synthesised at places away from where they act and simply diffuse to the area of action.

2. How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?

Answer: The movement of leaves of the sensitive plant is different from the movement of a shoot towards light in several ways.

In the movement of leaves of the sensitive plant, there is no growth involved in this movement. The plant must actually move its leaves in response to touch. For this movement, information that a touch has occurred must be communicated. The plants also use electrical-chemical means to convey this information from cell to cell, and plant cells change shape by changing the amount of water in them, resulting in swelling or shrinking, and therefore in changing shapes. Furthermore, the movement of the sensitive plant in response to touch is very quick.

On the other hand, the movement of a shoot towards light is caused by growth. It is a directional movement where plants respond to stimuli slowly by growing in a particular direction. This movement involves a hormone called auxin, synthesised at the shoot tip, [which] helps the cells to grow longer. When light is coming from one side of the plant, auxin diffuses towards the shady side of the shoot. This concentration of auxin stimulates the cells to grow longer on the side of the shoot which is away from light. Thus, the plant appears to bend towards light. This growth-related movement of plants will be even slower.

3. Give an example of a plant hormone that promotes growth.

Answer: An example of a plant hormone that promotes growth is auxin, which is a hormone synthesised at the shoot tip, and helps the cells to grow longer.

4. How do auxins promote the growth of a tendril around a support?

Answer: Auxins are produced at the shoot tip and stimulate cell growth. When a tendril comes into contact with a support, auxins stimulate faster growth of cells on the opposite side of the tendril, causing it to coil around the support. This results in the tendril resembling a watch spring.

5. Design an experiment to demonstrate hydrotropism.

Answer: To demonstrate hydrotropism, you can try the following experiment:

• Obtain two small beakers and label them as A and B.
• Fill beaker A with water.
• Create a cylindrical-shaped filter paper bridge and place it between beaker A and beaker B.
• Attach a few germinating seeds to the middle of the filter paper bridge.
• Cover the entire set-up with a transparent plastic container to retain moisture.

Observation: The roots of the germinating seeds should grow towards beaker A, demonstrating the phenomenon of hydrotropism.

Intext Questions and Answers III

1. How does chemical coordination take place in animals?

Answer: Chemical, or hormonal, means of information transmission are used in animals for coordination. If a chemical signal, or hormone, is sent, it reaches all cells of the body and provides wide-ranging changes. This is done in many animals, including human beings, using hormones, such as adrenaline, which are secreted from glands like the adrenal glands. Hormones are secreted directly into the blood and carried to different parts of the body. The target organs or the specific tissues on which a hormone acts respond to it. For instance, adrenaline causes the heart to beat faster, increases oxygen supply to muscles, reduces blood flow to the digestive system and skin by contracting muscles around small arteries in these organs, diverts blood to skeletal muscles, and increases the breathing rate due to contractions of the diaphragm and rib muscles. These responses enable the animal body to deal with situations. Such animal hormones are part of the endocrine system, which constitutes a second way of control and coordination in the animal body.

Instead of generating an electrical impulse, stimulated cells can release a chemical compound. This compound diffuses all around the original cell. If other cells around have the means to detect this compound using special molecules on their surfaces, then they would be able to recognise information, and even transmit it. This process, though slower than electrical impulses, can potentially reach all cells of the body, regardless of nervous connections, and can be done steadily and persistently. These compounds, or hormones, are used by multicellular organisms for control and coordination.

2. Why is the use of iodised salt advisable?

Answer: The use of iodised salt is advisable because iodine is necessary for the thyroid gland to make thyroxin hormone. Thyroxin regulates carbohydrate, protein and fat metabolism in the body so as to provide the best balance for growth. Iodine is essential for the synthesis of thyroxin. In case iodine is deficient in our diet, there is a possibility that we might suffer from goitre.

3. How does our body respond when adrenaline is secreted into the blood?

Answer: When adrenaline is secreted directly into the blood and carried to different parts of the body, the target organs or the specific tissues on which it acts respond. For example, the heart beats faster, resulting in a supply of more oxygen to our muscles. The blood to the digestive system and skin is reduced due to the contraction of muscles around small arteries in these organs. This diverts the blood to our skeletal muscles. The breathing rate also increases because of the contractions of the diaphragm and the rib muscles. All these responses together enable the animal body to be ready to deal with the situation.

4. Why are some patients of diabetes treated by giving injections of insulin?

Answer: Some patients of diabetes are treated by giving injections of insulin because insulin is a hormone produced by the pancreas that helps in regulating blood sugar levels. If insulin is not secreted in proper amounts, the sugar level in the blood rises, causing many harmful effects. Therefore, as a treatment, they might be taking injections of insulin.

Exercise Questions and Answers

1. Which of the following is a plant hormone?

(a) Insulin
(b) Thyroxin
(c) Oestrogen
(d) Cytokinin.

Answer: (d) Cytokinin.

2. The gap between two neurons is called a

(a) dendrite.
(b) synapse.
(c) axon.
(d) impulse.

Answer: (b) synapse.

3. The brain is responsible for

(a) thinking.
(b) regulating the heart beat.
(c) balancing the body.
(d) all of the above.

Answer: (d) all of the above.

4. What is the function of receptors in our body? Think of situations where receptors do not work properly. What problems are likely to arise?

Answer: The function of receptors in our body is to detect all information from our environment. These receptors are usually located in our sense organs, such as the inner ear, the nose, the tongue, and so on. For example, gustatory receptors will detect taste while olfactory receptors will detect smell. Receptors also detect changes like a bright light focussed on our eyes or when we touch a hot object, enabling us to respond to protect ourselves.

If receptors do not work properly, problems are likely to arise. For instance, if the olfactory receptors that detect smell are not working, as can happen when one has a cold or if the nose is blocked, one might not be able to fully appreciate the taste of food. If receptors that detect heat do not work, a person might not detect touching a hot object and therefore might not be able to respond quickly to prevent getting burnt.

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

Answer: A neuron is specialised for conducting information via electrical impulses from one part of the body to another. Information is acquired at the end of the dendritic tip of a nerve cell. This sets off a chemical reaction that creates an electrical impulse. This impulse travels from the dendrite to the cell body, and then along the axon to its end. At the end of the axon, the electrical impulse sets off the release of some chemicals. These chemicals cross the gap, or synapse, and start a similar electrical impulse in a dendrite of the next neuron.
The parts of a neuron are:

(i) Information is acquired at the dendritic tip.
(ii) Information travels as an electrical impulse through the dendrite, cell body, and along the axon.
(iii) At the axon end, this impulse must be converted into a chemical signal for onward transmission to the next neuron.

6. How does phototropism occur in plants?

Answer: Phototropism in plants occurs when growing plants detect light. A hormone called auxin, synthesised at the shoot tip, helps the cells to grow longer. When light is coming from one side of the plant, auxin diffuses towards the shady side of the shoot. This concentration of auxin stimulates the cells on the side of the shoot which is away from light to grow longer. Thus, the plant appears to bend towards light. Shoots respond by bending towards light while roots respond by bending away from it.

7. Which signals will get disrupted in case of a spinal cord injury?

Answer: In case of a spinal cord injury, several signals will get disrupted. Nerves from all over the body meet in a bundle in the spinal cord on their way to the brain; therefore, the transmission of signals from various parts of the body to the brain would be affected. Similarly, signals from the brain that instruct muscles to move must also pass through the spinal cord, so these would also be disrupted. Reflex arcs are formed in the spinal cord itself, so these reflex actions would also be affected or lost. The communication between the central nervous system and other parts of the body, facilitated by spinal nerves arising from the spinal cord, would be impaired.

8. How does chemical coordination occur in plants?

Answer: Chemical coordination in plants occurs through plant hormones. Instead of generating an electrical impulse, stimulated cells in plants can release a chemical compound, or hormone. This compound diffuses all around the original cell. If other cells around have the means to detect this compound using special molecules on their surfaces, then they would be able to recognise information, and even transmit it. This process is slower than electrical impulses but can potentially reach all cells of the body and can be done steadily and persistently. Different plant hormones help to coordinate growth, development, and responses to the environment. They are synthesised at places away from where they act and simply diffuse to the area of action.

9. What is the need for a system of control and coordination in an organism?

Answer: There is a need for a system of control and coordination in an organism because all movement in response to the environment must be carefully controlled. Each kind of a change in the environment evokes an appropriate movement in response. Such controlled movement must be connected to the recognition of various events in the environment, followed by only the correct movement in response. In other words, living organisms must use systems providing control and coordination to ensure that responses to stimuli are appropriate and beneficial. In multicellular organisms, specialised tissues are used to provide these control and coordination activities, in keeping with the general principles of body organisation.

10. How are involuntary actions and reflex actions different from each other?

Answer: Involuntary actions and reflex actions are different in several ways, although both occur without conscious thought. Reflex actions are very sudden actions in response to something in the environment, where we do something without thinking about it or without feeling in control of our reactions, such as pulling a hand back from a flame. The process of detecting the signal and responding with an output action is completed quickly through a connection called a reflex arc, often formed in the spinal cord, because the thinking process of the brain is not fast enough for such immediate responses.

Involuntary actions, on the other hand, are a set of muscle movements over which we do not have any thinking control, such as our mouth watering when we see food we like, our hearts beating, breathing, or digestion. We cannot control these actions easily by thinking about them. Many of these involuntary actions, including blood pressure, salivation, and vomiting, are controlled by the mid-brain and hind-brain (specifically the medulla).

So, while both are non-conscious, reflex actions are typically rapid, often protective responses to immediate stimuli via reflex arcs, whereas involuntary actions include a broader range of ongoing, automatic bodily functions regulated by specific parts of the brain.

11. Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.

Answer: Both nervous and hormonal mechanisms are essential for control and coordination in animals, but they differ significantly.

Nervous Mechanism:

• Transmission: Uses electrical impulses transmitted along nerve fibres.
• Speed: Very fast. Electrical impulses are an excellent means for rapid responses.
• Reach: Localised. Electrical impulses will reach only those cells that are connected by nervous tissue, not each and every cell in the animal body.
• Duration of Effect: Usually short-lived. Once an electrical impulse is generated and transmitted, the cell takes time to reset before transmitting another, so cells cannot continually transmit impulses.
• Pathways: Information travels through an organised network of nerve cells or neurons.

Hormonal Mechanism:

• Transmission: Uses chemical messengers called hormones, which are secreted by endocrine glands directly into the blood and transported throughout the body.
• Speed: Slower than nervous transmission, as hormones diffuse and are transported via blood.
• Reach: Widespread. Hormones can potentially reach all cells of the body, regardless of nervous connections.
• Duration of Effect: Can be long-lasting. Hormonal actions can be done steadily and persistently, providing wide-ranging changes.
• Pathways: Hormones travel through the bloodstream to target organs or specific tissues.

Comparison (Similarity): Both systems provide control and coordination, enabling the organism to respond to stimuli and regulate bodily functions.

Contrast (Differences): The nervous system provides rapid, short-term, localised control, ideal for quick responses to environmental changes. The hormonal system provides slower, more sustained, widespread control, often regulating growth, development, metabolism, and longer-term physiological processes. The nervous system uses electrical signals via neurons, while the hormonal system uses chemical signals (hormones) via the bloodstream.

12. What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs?

Answer: The manner in which movement takes place in a sensitive plant (like the chhui-mui) and the movement in our legs differs significantly:

Movement in a Sensitive Plant:

• Tissues Involved: There is no nervous tissue, nor any muscle tissue involved.
• Mechanism of Cell Movement: Plant cells change shape by changing the amount of water in them, resulting in swelling or shrinking, and therefore in changing shapes. This movement, like the folding of leaves upon touch, does not involve growth.
• Information Conduction: Plants use electrical-chemical means to convey information that a touch has occurred from cell to cell, but there is no specialised tissue for the conduction of information as in animals.
• Nature of Response: It is a rapid response to a stimulus like touch.

Movement in Our Legs:

• Tissues Involved: Control and coordination are provided by nervous and muscular tissues. Motor areas in the brain control the movement of voluntary muscles, like leg muscles.
• Mechanism of Cell Movement: When a nerve impulse reaches the muscle, the muscle fibre must move. Muscle cells move by changing their shape so that they shorten. Muscle cells have special proteins that change both their shape and their arrangement in the cell in response to nervous electrical impulses, giving the muscle cells a shorter form.
• Information Conduction: Information is transmitted as electrical impulses via an organised network of nerve cells (neurons) from the brain to the leg muscles.
• Nature of Response: Leg movement is typically a voluntary action, controlled by the thinking part of the brain, although reflex movements of legs also occur.

Extras

Additional MCQs (Knowledge Based)

1. Which of the following movements in plants is primarily a result of growth?

A. Folding of Mimosa leaves
B. A seedling pushing soil aside
C. Chewing cud by buffaloes
D. A cat running

Answer: B. A seedling pushing soil aside

2. Information from the environment is detected by specialised tips of some nerve cells. These tips are often located in our ________.

A. Muscles
B. Bones
C. Sense organs
D. Blood vessels

Answer: C. Sense organs

3. At the end of an axon, an electrical impulse triggers the release of chemicals. These chemicals cross the ________ to transmit the signal to the next neuron.

A. Cell body
B. Dendrite
C. Synapse
D. Myelin sheath

Answer: C. Synapse

4. Gustatory receptors : Taste :: Olfactory receptors : ________.

A. Sight
B. Smell
C. Touch
D. Sound

Answer: B. Smell

5. Which of the following best describes a reflex arc?

A. A complex thought process in the brain
B. The pathway for voluntary muscle movement
C. A quick, automatic response pathway, often via the spinal cord
D. The storage of memories in the fore-brain

Answer: C. A quick, automatic response pathway, often via the spinal cord

6. The main coordinating centre of the body, where information is processed and integrated, is the ________.

A. Spinal cord
B. Heart
C. Brain
D. Kidneys

Answer: C. Brain

7. Identify the part of the human brain primarily responsible for precision of voluntary actions and maintaining posture and balance.

A. Cerebrum
B. Medulla
C. Cerebellum
D. Hypothalamus

Answer: C. Cerebellum

8. Which of these actions is primarily controlled by the medulla in the hind-brain?

A. Riding a bicycle
B. Solving a puzzle
C. Blood pressure regulation
D. Picking up a pencil

Answer: C. Blood pressure regulation

9. The brain is protected by a bony box and a fluid-filled balloon. What is the primary function of the fluid-filled balloon?

A. To provide nutrition
B. To provide shock absorption
C. To transmit electrical signals
D. To produce hormones

Answer: B. To provide shock absorption

10. How do muscle cells primarily cause movement at the cellular level?

A. By increasing their overall size
B. By changing their shape and shortening
C. By releasing chemical energy as heat
D. By rapidly dividing and multiplying

Answer: B. By changing their shape and shortening

11. The rapid folding of leaves in a chhui-mui (touch-me-not) plant upon being touched is an example of:

A. Movement due to growth
B. Movement independent of growth
C. Phototropism
D. Geotropism

Answer: B. Movement independent of growth

12. In the touch-me-not plant, how do cells change shape to cause movement?

A. By altering protein structure
B. By changing the amount of water in them
C. By rapid cell division
D. By releasing hormones

Answer: B. By changing the amount of water in them

13. The directional growth of a plant shoot towards light is known as:

A. Geotropism
B. Hydrotropism
C. Phototropism
D. Chemotropism

Answer: C. Phototropism

14. Which plant hormone, synthesised at the shoot tip, helps cells to grow longer and is involved in phototropism?

A. Gibberellin
B. Cytokinin
C. Auxin
D. Abscisic acid

Answer: C. Auxin

15. Identify the plant hormone that primarily promotes cell division, often found in higher concentrations in fruits and seeds.

A. Auxin
B. Gibberellin
C. Abscisic acid
D. Cytokinin

Answer: D. Cytokinin

16. Which of the following is an effect of abscisic acid in plants?

A. Promotes stem growth
B. Promotes cell division
C. Inhibits growth and causes wilting
D. Bends shoot towards light

Answer: C. Inhibits growth and causes wilting

17. In a scary situation, which hormone is secreted by the adrenal glands to prepare the body for “fight or flight”?

A. Insulin
B. Thyroxin
C. Adrenaline
D. Growth hormone

Answer: C. Adrenaline

18. Which of the following is NOT a typical response caused by adrenaline secretion?

A. Increased heart rate
B. Increased blood flow to digestive system
C. Increased oxygen supply to muscles
D. Increased breathing rate

Answer: B. Increased blood flow to digestive system

19. Iodine is essential for the synthesis of which hormone by the thyroid gland?

A. Insulin
B. Thyroxin
C. Adrenaline
D. Oestrogen

Answer: B. Thyroxin

20. A deficiency of which hormone in childhood can lead to dwarfism?

A. Thyroxin
B. Insulin
C. Growth hormone
D. Testosterone

Answer: C. Growth hormone

21. Which gland produces insulin, a hormone that helps in regulating blood sugar levels?

A. Pituitary gland
B. Thyroid gland
C. Adrenal gland
D. Pancreas

Answer: D. Pancreas

22. The timing and amount of hormone released are often regulated by:

A. Conscious thought
B. Feedback mechanisms
C. The nervous system only
D. External temperature

Answer: B. Feedback mechanisms

23. Consider the following parts of the nervous system: P. Brain, Q. Spinal Cord, R. Cranial Nerves, S. Spinal Nerves. Which of these constitute the Central Nervous System (CNS)?

A. P and R
B. P and Q
C. R and S
D. Q and S

Answer: B. P and Q

24. Which of the following is a primary function of the fore-brain?

A. Regulating heartbeat
B. Maintaining balance
C. Main thinking part
D. Controlling reflex actions

Answer: C. Main thinking part

25. The growth of pollen tubes towards ovules in plants is an example of:

A. Phototropism
B. Geotropism
C. Chemotropism
D. Hydrotropism

Answer: C. Chemotropism

26. Which of these is a characteristic of chemical communication (hormones) compared to electrical impulses?

A. Faster transmission
B. Reaches only specific connected cells
C. Can reach all cells of the body
D. Shorter duration of effect

Answer: C. Can reach all cells of the body

27. Testosterone in males and oestrogen in females are primarily responsible for:

A. Regulating blood sugar
B. Changes associated with puberty
C. Controlling metabolic rate
D. Promoting overall body growth

Answer: B. Changes associated with puberty

28. A person experiences a swollen neck, a symptom of goitre. This condition is often associated with a deficiency of:

A. Calcium
B. Iron
C. Iodine
D. Vitamin C

Answer: C. Iodine

29. Which of the following is an example of an involuntary action NOT typically controlled by the medulla?

A. Salivation
B. Vomiting
C. Walking in a straight line
D. Blood pressure regulation

Answer: C. Walking in a straight line

30. The peripheral nervous system consists of:

A. Brain and spinal cord
B. Nerves arising from brain and spinal cord
C. Only sensory neurons
D. Only motor neurons

Answer: B. Nerves arising from brain and spinal cord

31. What is the primary role of receptors in an organism?

A. To execute responses
B. To transmit signals rapidly
C. To detect changes in the environment
D. To store information

Answer: C. To detect changes in the environment

32. If a person touches a hot object, the immediate withdrawal of the hand is typically a:

A. Voluntary action
B. Conditioned response
C. Reflex action
D. Hormonal response

Answer: C. Reflex action

33. Which part of a neuron primarily receives information?

A. Axon
B. Synapse
C. Dendrite
D. Nucleus

Answer: C. Dendrite

34. The upward growth of shoots and downward growth of roots are examples of response to:

A. Light
B. Water
C. Chemicals
D. Gravity

Answer: D. Gravity

35. Which of the following plant hormones inhibits growth?

A. Auxin
B. Gibberellin
C. Cytokinin
D. Abscisic acid

Answer: D. Abscisic acid

36. The endocrine system uses chemical signals called ________ for control and coordination.

A. Neurotransmitters
B. Impulses
C. Hormones
D. Enzymes

Answer: C. Hormones

37. Given below are descriptions of plant responses. Select the one that is a tropic movement.

Person	Description
W	Leaves of Mimosa fold on touch
X	A root grows towards a water source
Y	A flower opens in the morning
Z	A seed germinates

A. W
B. X
C. Y
D. Z

Answer: B. X

38. The vertebral column protects the ________.

A. Brain
B. Heart
C. Lungs
D. Spinal cord

Answer: D. Spinal cord

39. Which of the following is NOT a major region of the human brain?

A. Fore-brain
B. Mid-brain
C. Hind-brain
D. Cranial-brain

Answer: D. Cranial-brain

40. The sensation of feeling full after eating is associated with a centre in the:

A. Hind-brain
B. Mid-brain
C. Fore-brain
D. Spinal cord

Answer: C. Fore-brain

Additional MCQs (Competency Based)

1. A person accidentally touches a very hot pan. What is the most likely immediate sequence of events in their nervous system leading to pulling their hand away?

(a) Sensory neuron -> Brain -> Motor neuron -> Muscle contraction
(b) Sensory neuron -> Spinal cord -> Motor neuron -> Muscle contraction
(c) Brain -> Sensory neuron -> Spinal cord -> Muscle contraction
(d) Motor neuron -> Spinal cord -> Sensory neuron -> Muscle contraction

Answer: (b) Sensory neuron -> Spinal cord -> Motor neuron -> Muscle contraction

2. A gardener observes that a potted plant kept near a window with light coming predominantly from one side is bending towards that window. Which plant hormone is primarily responsible for this observation, and how does it cause the bending?

(a) Gibberellin, by promoting uniform cell elongation on all sides of the stem.
(b) Auxin, by accumulating on the shaded side of the stem, promoting cell elongation there.
(c) Cytokinin, by stimulating cell division primarily on the side of the stem facing the light.
(d) Abscisic acid, by inhibiting growth on the side of the stem facing the light.

Answer: (b) Auxin, by accumulating on the shaded side of the stem, promoting cell elongation there.

3. “The fore-brain is the main thinking part of the brain. It has regions which receive sensory impulses from various receptors. Separate areas of the fore-brain are specialised for hearing, smell, sight and so on. There are separate areas of association where this sensory information is interpreted by putting it together with information from other receptors as well as with information that is already stored in the brain.”

Based on this information, if a person sees a familiar face and recognizes it, which part of the brain is primarily involved in integrating the visual information with stored memories for recognition?

(a) Medulla in the hind-brain
(b) Cerebellum in the hind-brain
(c) Association areas in the fore-brain
(d) Mid-brain

Answer: (c) Association areas in the fore-brain

4. Assertion (A): Reflex arcs have evolved in animals because the thinking process of the brain is often not fast enough to deal with urgent situations effectively.
Reason (R): Reflex arcs typically involve a direct connection between sensory input and motor output, often processed at the level of the spinal cord, which bypasses complex brain processing for a quicker response.

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.

Answer: (a) Both A and R are true and R is the correct explanation of A.

5. Assertion (A): Plants exhibit various movements, such as shoots bending towards light and roots growing downwards in response to gravity.
Reason (R): These plant movements are facilitated by a complex nervous system and specialized muscle tissues, similar to those found in animals.

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.

Answer: (c) A is true, but R is false.

6. Match the hormone in Column A with its primary function in Column B, then select the correct code:

Column A (Hormone)	Column B (Function)
(i) Insulin	Regulates general metabolism and is essential for balanced body growth
(ii) Adrenaline	Prepares the body for emergency ‘fight or flight’ situations
(iii) Thyroxin	Regulates blood sugar levels by facilitating glucose uptake by cells
(iv) Growth Hormone	Stimulates overall growth and development of the body

Codes:

(a) (i)-3, (ii)-2, (iii)-1, (iv)-4
(b) (i)-4, (ii)-1, (iii)-2, (iv)-3
(c) (i)-3, (ii)-1, (iii)-4, (iv)-2
(d) (i)-2, (ii)-3, (iii)-1, (iv)-4

Answer: (a) (i)-3, (ii)-2, (iii)-1, (iv)-4

7. Arrange the following events in the correct order of a nerve impulse transmission across a typical chemical synapse:

(i) Release of neurotransmitter chemicals into the synaptic cleft
(ii) An electrical impulse arrives at the axon terminal of the pre-synaptic neuron
(iii) Neurotransmitter chemicals bind to specific receptors on the dendrite of the post-synaptic neuron
(iv) Generation of a new electrical impulse or appropriate response in the post-synaptic neuron

(a) (i) -> (ii) -> (iii) -> (iv)
(b) (ii) -> (i) -> (iii) -> (iv)
(c) (ii) -> (iii) -> (i) -> (iv)
(d) (iv) -> (iii) -> (ii) -> (i)

Answer: (b) (ii) -> (i) -> (iii) -> (iv)

8. Consider the following hypothetical data on hormone levels and physiological states:

State 1: After a carbohydrate-rich meal; Blood Glucose Level – 180 mg/dL (High); Insulin Level – Significantly Elevated
State 2: During a sudden encounter with a perceived threat; Adrenaline Level – Markedly Elevated; Heart Rate – Increased
State 3: An individual with a consistently low basal metabolic rate and feeling lethargic; Thyroxin Level – Consistently Low
State 4: During a period of rapid increase in height and muscle mass in an adolescent; Growth Hormone Level – Elevated

Which of these states correctly pairs a physiological condition or event with its associated hormone level, reflecting a plausible regulatory response or condition?

(a) State 1 only
(b) State 1 and State 2 only
(c) State 1, State 2, and State 4 only
(d) All states (1, 2, 3, and 4)

Answer: (d) All states (1, 2, 3, and 4)

Additional Questions and Answers

1. Which tissues provide control and coordination in animals?

Answer: In animals, control and coordination are provided by nervous and muscular tissues.

2. What is a neuron?

Answer: Nervous tissue is made up of an organised network of nerve cells or neurons, and is specialised for conducting information via electrical impulses from one part of the body to another.

3. What term describes the junction between two neurons?

Answer: The gap, or synapse, is the junction between two neurons where chemicals cross to start a similar electrical impulse in a dendrite of the next neuron.

4. What is a reflex arc?

Answer: A reflex arc is a connection where nerves that detect a signal, such as heat, are connected to nerves that move muscles in a simpler way, allowing the process of detecting the input and responding to it by an output action to be completed quickly.

5. Which part of the central nervous system forms reflex arcs?

Answer: Reflex arcs are formed in the spinal cord itself, although the information input also goes on to reach the brain.

6. What are the three major regions of the human brain?

Answer: The brain has three major parts or regions, namely the fore-brain, mid-brain and hind-brain.

7. What are plant hormones?

Answer: Plant hormones are compounds used by multicellular organisms that help to coordinate growth, development and responses to the environment. They are synthesised at places away from where they act and simply diffuse to the area of action.

8. What is Immediate Response to Stimulus?

Answer: Immediate response to stimulus, such as in the sensitive plant, is a type of movement where the plant moves its leaves in response to touch without any growth involved. Information that a touch has occurred is communicated using electrical-chemical means from cell to cell, and some cells change shape by changing the amount of water in them, resulting in swelling or shrinking, and therefore in changing shapes, to cause the movement.

9. What is Movement Due to Growth?

Answer: Movement due to growth is when plants respond to stimuli slowly by growing in a particular direction. Because this growth is directional, it appears as if the plant is moving. An example is how tendrils of some plants, which are sensitive to touch, circle around an object and cling to it because the part of the tendril in contact with the object does not grow as rapidly as the part away from the object.

10. What is phototropism?

Answer: Phototropism is a directional, or tropic, movement where, in response to light, shoots respond by bending towards light while roots respond by bending away from it.

11. What is geotropism?

Answer: Geotropism is the upward and downward growth of shoots and roots, respectively, in response to the pull of earth or gravity.

12. What are gibberellins?

Answer: Gibberellins are plant hormones which, like auxins, help in the growth of the stem.

13. What are cytokinins?

Answer: Cytokinins are plant hormones that promote cell division, and are present in greater concentration in areas of rapid cell division, such as in fruits and seeds.

14. Which hormone inhibits growth in plants and causes wilting?

Answer: Abscisic acid is an example of a hormone which inhibits growth in plants; its effects include wilting of leaves.

15. What is the endocrine system?

Answer: The endocrine system, which uses animal hormones, constitutes a second way of control and coordination in the body.

16. Which gland secretes adrenaline?

Answer: Adrenaline is secreted from the adrenal glands.

17. Which hormone regulates metabolism for body growth?

Answer: Thyroxin regulates carbohydrate, protein and fat metabolism in the body so as to provide the best balance for growth.

18. What is the primary function of insulin?

Answer: Insulin is a hormone which is produced by the pancreas and helps in regulating blood sugar levels.

19. What is the role of thyroxin?

Answer: Thyroxin regulates carbohydrate, protein and fat metabolism in the body so as to provide the best balance for growth. Iodine is essential for the synthesis of thyroxin.

20. Which hormone regulates growth and development in the human body?

Answer: Growth hormone, secreted by the pituitary, regulates growth and development of the body.

21. Explain how electrical impulses are transmitted in the nervous system.

Answer: Information, acquired at the end of the dendritic tip of a nerve cell, sets off a chemical reaction that creates an electrical impulse. This impulse travels from the dendrite to the cell body, and then along the axon to its end. At the end of the axon, the electrical impulse sets off the release of some chemicals. These chemicals cross the gap, or synapse, and start a similar electrical impulse in a dendrite of the next neuron. This is a general scheme of how nervous impulses travel in the body. A similar synapse finally allows delivery of such impulses from neurons to other cells, such as muscles cells or gland. Nervous tissue is made up of an organised network of nerve cells or neurons, and is specialised for conducting information via electrical impulses from one part of the body to another.

22. Describe how reflex actions occur via a reflex arc.

Answer: In a reflex action, if the nerves that detect a stimulus, such as heat, were to be connected to the nerves that move muscles in a simpler way, the process of detecting the signal or the input and responding to it by an output action might be completed quickly. Such a connection is commonly called a reflex arc. Reflex arc connections between the input nerve and the output nerve are best made at the point where they first meet each other. Nerves from all over the body meet in a bundle in the spinal cord on their way to the brain. Reflex arcs are formed in this spinal cord itself, although the information input also goes on to reach the brain. The reflex arc typically involves receptors (e.g., in skin) detecting a stimulus, a sensory neuron transmitting the signal to the spinal cord, a relay neuron in the spinal cord, a motor neuron carrying the signal from the spinal cord, and an effector (e.g., muscle in arm) producing the response.

23. Discuss the protective structures of the brain and spinal cord.

Answer: A delicate organ like the brain, which is so important for a variety of activities, needs to be carefully protected. For this, the body is designed so that the brain sits inside a bony box. Inside the box, the brain is contained in a fluid-filled balloon which provides further shock absorption. The spinal cord is protected by the vertebral column or backbone, which is a hard, bumpy structure felt when running a hand down the middle of the back.

24. Explain how muscle cells change shape to cause movement.

Answer: The simplest notion of movement at the cellular level is that muscle cells will move by changing their shape so that they shorten. Muscle cells change their shape due to the chemistry of cellular components. Muscle cells have special proteins that change both their shape and their arrangement in the cell in response to nervous electrical impulses. When this happens, new arrangements of these proteins give the muscle cells a shorter form.

25. Describe the mechanism of phototropism in plant shoots.

Answer: When growing plants detect light, a hormone called auxin, synthesised at the shoot tip, helps the cells to grow longer. When light is coming from one side of the plant, auxin diffuses towards the shady side of the shoot. This concentration of auxin stimulates the cells to grow longer on the side of the shoot which is away from light. Thus, the plant appears to bend towards light.

26. Compare the functions of auxins and abscisic acid in plant growth.

Answer: Auxins are plant hormones that help in promoting growth; for example, auxin synthesised at the shoot tip helps the cells to grow longer. Abscisic acid is an example of a hormone which inhibits growth. Its effects include wilting of leaves.

27. Explain how adrenaline prepares the body for emergency situations.

Answer: In many animals, including human beings, a hormone called adrenaline is secreted from the adrenal glands to prepare for fighting or running away. Adrenaline is secreted directly into the blood and carried to different parts of the body. The target organs or the specific tissues on which it acts include the heart. All these responses together enable the animal body to be ready to deal with the situation:

(i) The heart beats faster, resulting in supply of more oxygen to our muscles.
(ii) The blood to the digestive system and skin is reduced due to contraction of muscles around small arteries in these organs. This diverts the blood to our skeletal muscles.
(iii) The breathing rate also increases because of the contractions of the diaphragm and the rib muscles.

28. Discuss the role of feedback mechanisms in regulating hormone levels.

Answer: It is important that hormones should be secreted in precise quantities, and a mechanism is needed through which this is done. The timing and amount of hormone released are regulated by feedback mechanisms. For example, if the sugar levels in blood rise, they are detected by the cells of the pancreas which respond by producing more insulin. As the blood sugar level falls, insulin secretion is reduced. A feedback mechanism regulates the action of the hormones.

29. Compare electrical coordination in animals with chemical coordination in plants.

Answer: Electrical coordination in animals involves electrical impulses transmitted through nervous tissue. This is an excellent means for rapid communication, but it has limitations.

(i) Firstly, electrical impulses will reach only those cells that are connected by nervous tissue, not each and every cell in the animal body.
(ii) Secondly, once an electrical impulse is generated in a cell and transmitted, the cell will take some time to reset its mechanisms before it can generate and transmit a new impulse, meaning cells cannot continually create and transmit electrical impulses.

Chemical coordination in plants involves plant hormones. These hormones are synthesised at places away from where they act and simply diffuse to the area of action. This chemical communication is slower than electrical impulses but can potentially reach all cells of the body, regardless of nervous connections (which plants lack in the specialised sense of animals), and it can be done steadily and persistently. Plant hormones help to coordinate growth, development, and responses to the environment. While plants also use electrical-chemical means to convey information from cell to cell, they lack specialised tissue for the rapid conduction of information seen in animal nervous systems.

30. Describe the roles of the fore-brain, mid-brain and hind-brain in coordinating body functions.

Answer: The brain has three major parts or regions: the fore-brain, mid-brain, and hind-brain, each responsible for integrating different inputs and outputs.

(i) Fore-brain: The fore-brain is the main thinking part of the brain. It has regions which receive sensory impulses from various receptors. Separate areas of the fore-brain are specialised for hearing, smell, sight, and so on.
(ii) Mid-brain and Hind-brain: Many involuntary actions are controlled by the mid-brain and hind-brain. All involuntary actions including blood pressure, salivation, and vomiting are controlled by the medulla in the hind-brain.
(iii) Cerebellum (in the Hind-brain): The hind-brain also includes the cerebellum, which is responsible for the precision of voluntary actions and maintaining the posture and balance of the body. Activities like walking in a straight line, riding a bicycle, and picking up a pencil are possible due to the cerebellum.