CBSE Class 10 Science Control and Coordination VBQs Set 02

Question. Which of the following is a plant hormone?
(a) Insulin
(b) Thyroxine
(c) Oestrogen
(d) Cytokinin
Answer: (d) Cytokinin is a plant hormone.

Question. The gap between two neurons is called a
(a) dendrite.
(b) synapse.
(c) axon.
(d) impulse.
Answer: (b) Synapse is known as the gap between two neurons.

Question. The brain is responsible for
(a) thinking.
(b) regulating the heart beat.
(c) balancing the body.
(d) All of the options
Answer: (d) The brain is responsible for thinking, regulating the heart beat and balancing the body as well.

Question. 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 collect informations about the changes in the environment. Receptors pass this information to central nervous system where message is interpreted and appropriate instructions are sent to effector which reveals response. These receptors are located in our sense organs. If receptors do not work properly, our body cannot convert environmental stimuli into impulses and hence, our body would not respond. For example, gustatory receptors are the receptors of taste located on the tongue. Now, if the gustatory receptors do not work properly, we will not be able to enjoy the taste of different types of food. Olfactory receptors are the receptors of smell located in the nasal cavity. If olfactory receptors present in our nose do not work properly, we will not be able to smell things.

Question. Which signals will get disrupted in case of a spinal cord injury?
Answer: All the signals and responses which pass from and to the brain through the spinal cord will get disturbed. Reflex actions will also get disrupted.

Question. How does chemical coordination occur in plants?
Answer: In plants, the stimulated cells release chemical compounds, which are called plant hormones. 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.

Question. What is the need for a system of control and coordination in an organism? 
Answer: The different organs of our body work in coordination when we perform any activity. For example, when we are taking food, our eyes help in locating the food, our nose detects the smell, our hand brings the food to our mouth, the teeth and jaw muscles chew the food and saliva starts the digestive process. So, control and coordination is essential in maintaining a state of stability and a steady state between the internal conditions of an organism and the external environment.

Question. How are involuntary actions and reflex actions different from each other?
Answer: Involuntary action is the set of muscle movement which does not require thinking. These actions are controlled by brain. Example of involuntary actions are beating of heart, breathing, etc. Involuntary actions are concerned with the functioning of the internal body parts.
Reflex action is defined as an unconscious, automatic and involuntary response of effectors, i.e. muscles and glands, to a stimulus, which is monitored through the spinal cord. Example of reflex action is the closing of eyes immediately when bright light is focussed to eyes. Reflex actions are connected with emergency.

Question. Compare and contrast nervous and hormonal mechanisms for control and coordination in animals. 
Answer:
Nervous mechanism:
(i) It is performed by nervous system which sent an electrical impulse along axons, and as a chemical across synapse and acts through effectors.
(ii) The information is transmitted instantaneously.
(iii) The effects are short-lived.

Hormonal mechanism:
(i) It is performed by chemical substances, called hormones, secreted by endocrine glands.
(ii) The information is transmitted slowly.
(iii) The effects are generally more prolonged.

Question. What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs?
Answer:
Movement in sensitive plant:
(a) The movement that takes place in a sensitive plant occurs in response to touch (stimulus).
(b) In this movement, the information is transmitted from cell to cell by electro-chemical signals as plants do not have any specialised tissue for conduction of impulses.
(c) The plant cells change shape by changing amount of water for this movement to take place.

Movement in our legs:
(a) Movement in our legs due to the voluntary actions.
(b) The signal or messages for these actions are passed to the brain and hence are consciously controlled.
(c) In animal muscle cells, some proteins are found which allow the movement to occur.

SELECT NCERT EXEMPLAR PROBLEMS

Question. Which of the following statements is correct about receptors?
(a) Gustatory receptors detect taste while olfactory receptors detect smell
(b) Both gustatory and olfactory receptors detect smell
(c) Auditory receptors detect smell and olfactory receptors detect taste
(d) Olfactory receptors detect taste and gustatory receptors smell
Answer: (a) Gustatory receptors detect taste while olfactory receptors detect smell

Question. Which of the following is not associated with growth of plant?
(a) Auxin
(b) Gibberellins
(c) Cytokinins
(d) Abscisic acid
Answer: (d) Abscisic acid

Question. Involuntary actions in the body are controlled by
(a) medulla in fore-brain
(b) medulla in mid-brain
(c) medulla in hind-brain
(d) medulla in spinal cord
Answer: (c) medulla in hind-brain

Question. Electrical impulse travels in a neuron from:
(a) Dendrite → Axon → Axonal end → Cell body
(b) Cell body → Dendrite → Axon → Axonal end
(c) Dendrite → Cell body → Axon → Axonal end
(d) Axonal end → Axon → Cell body → Dendrite
Answer: (c) Dendrite → Cell body → Axon → Axonal end

Question. Which of the following is not an involuntary action?
(a) Vomiting
(b) Salivation
(c) Heart beat
(d) Chewing
Answer: (d) Chewing

Question. Why is it advised to use iodised salt in our diet? 
Answer: Iodised salt contains iodine which is necessary for the thyroid gland to synthesise thyroxine hormone. Thyroxine regulates carbohydrate, protein and fat metabolism in the body to provide growth balance. Its deficiency causes goitre.

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

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

Question. What are the major parts of the brain? Mention the functions of different parts.
Answer: The major parts of the brain are:
(i) Fore-brain including cerebrum and olfactory lobes.
(ii) Mid-brain
(iii) Hind-brain including cerebellum, pons and medulla oblongata.
Functions of different parts are as follows:
(i) Fore-brain: There are specific regions in cerebrum for each kind of stimulus and response.
(a) Occipital lobe is the region for sight, i.e. visual reception.
(b) Temporal lobe is the region for hearing, i.e. auditory reception.
(c) Frontal lobe is the region for speech, facial muscular activities and higher mental activities.
(d) Parietal lobe is the region for taste, smell, touch and conscious association.
(e) Olfactory lobe receives sensation of smell.
(ii) Mid-brain: It controls reflex movements of the head, neck and trunk in response to visual and auditory stimuli.
(iii) Hind-brain:
(a) Cerebellum controls the coordination of body movements and posture.
(b) Pons take part in regulating respiration.
(c) Medulla oblongata is the regulating centre for swallowing, coughing, sneezing and vomiting.

Question. Name various plant hormones. Also give their physiological effects on plant growth and development.
Answer: The various plant hormones are auxin, gibberellin, cytokinin and abscisic acid. Their physiological effects on plant growth and development are as follows:
• Auxin – It is a growth hormone which helps in cell enlargement and cell differentiation. Auxin also promote fruit growth.
• Gibberellin – It also helps in the growth of the stem.
• Cytokinin – It promotes the cell division. It is present in high concentrations in the areas of rapid cell division such as fruits and seeds.
• Abscisic acid (ABA) – They are responsible for inhibiting or checking the growth. It also causes wilting of the leaves.

Question. Why is the flow of signals in a synapse from axonal end of one neuron to dendrite end of another neuron but not the reverse?
Answer: A chemical substance is released when the electrical signal reaches the axonal end of a neuron and this chemical diffuses to the dendrite end of another neuron, which generates electrical signal. Thus, at the axonal end, the electrical signals converted into chemical signals but at the dendrite end of neurons these chemicals are not present thus the reverse action is not possible.

Question. The hormone not secreted by ovary is
(a) Relaxin
(b) Progesterone
(c) Estrogen
(d) Testosterone

Answer: (d) Testosterone

Question. The nature of nerve impulse is
(a) Chemical
(b) Magnetic
(c) Electrochemical
(d) Electromagnetic

Answer: (c) Electrochemical

Question. Which of the following is the correct sequence regarding the flow of an impulse in a neuron?
(a) Dendrite \( \to \) Axon \( \to \) Cell Body
(b) Axon \( \to \) Dendrite \( \to \) Cell Body
(c) Axon \( \to \) Cell Body \( \to \) Dendrite
(d) Cell Body \( \to \) Axon \( \to \) Nerve Terminal

Answer: (d) Cell Body \( \to \) Axon \( \to \) Nerve Terminal

Question. The number of cranial nerves in mammals is
(a) 6
(b) 12
(c) 24
(d) 48

Answer: (b) 12

Question. In the following Questions, the Assertion and Reason have been put forward. Read the statements carefully and choose the correct alternative from the following: (a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion. (b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion. (c) Assertion is true but the Reason is false. (d) The statement of the Assertion is false but the Reason is true. Assertion: Plants respond to light, touch, gravitational force and other stimulus.
Reason: Plants use electrochemical means to convey information from cell to cell
(a) A
(b) B
(c) C
(d) D

Answer: (b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.

Question. Assertion: Insulin regulates blood sugar level
Reason: Insufficient secretion of insulin will cause diabetes
(a) A
(b) B
(c) C
(d) D

Answer: (a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.

Question. What causes shoots of plants to bend towards light?

Answer: The bending of shoots towards light is caused by the hormone auxin. When light comes from one side, auxin diffuses towards the shady side of the shoot tip. This higher concentration of auxin stimulates cells on the shady side to grow longer than those on the sunny side, causing the shoot to bend towards the light source.

Question. ‘There is a close coordination between nerves and hormones.’ Explain with an example.

Answer: Nerves and hormones work together to ensure a fast and sustained response. For example, in a 'fight or flight' situation, the nervous system quickly detects a threat and signals the adrenal glands. The glands then release the hormone adrenaline into the bloodstream, which acts on organs like the heart and lungs to prepare the body for action, maintaining the response initiated by the nerves.

Question. Name the major parts of the human brain. Which part of the brain maintains posture and equilibrium of the body?

Answer: The major parts of the human brain are the Forebrain (Cerebrum), Midbrain, and Hindbrain (Cerebellum, Pons, and Medulla). The cerebellum, part of the hindbrain, is responsible for maintaining posture and equilibrium of the body.

Question. (a) Draw the structure of a neuron and label its various parts. (b) How does nerve impulse travel from one neuron to another?

Answer: (a) [The diagram should include the cell body, nucleus, dendrites, axon, and nerve endings]. (b) A nerve impulse travels across a synapse. When an electrical signal reaches the axonal end of a neuron, it triggers the release of neurotransmitters (chemicals). These chemicals diffuse across the synaptic gap and bind to receptors on the dendrite of the next neuron, creating a new electrical impulse.

Question. (a) Define phototropism and geotropism. With a labelled diagram, describe an activity to show that light and gravity change the direction of plant parts. (b) Mention the role of each of the following plant hormones (i) Auxin (ii) Abscisic acid

Answer: (a) Phototropism is the growth of a plant part in response to light, while geotropism is growth in response to gravity. An activity involving a potted plant placed horizontally near a window can show the shoot bending up (negative geotropism/positive phototropism) and roots growing down (positive geotropism). (b) (i) Auxin: Promotes cell elongation and growth in shoots. (ii) Abscisic acid: Acts as a growth inhibitor, promoting seed dormancy and leaf wilting.

Reflex arcs have evolved in animals because the thinking process of the brain is not fast enough. In fact many animals have very little or none of the complex neuron network needed for thinking. So, it is quite likely that reflex arcs have evolved as efficient way of functioning in the absence of true thought processes. However, even after complex neuron networks have come into existing, reflex arcs continue to be more efficient for quick response.

Question. What is a reflex arc?

Answer: A reflex arc is the neural pathway that controls a reflex action. It typically consists of a sensory receptor, sensory neuron, an interneuron in the spinal cord, a motor neuron, and an effector (muscle or gland).

Question. State two advantages of reflex action.

Answer: (i) It allows for an immediate response to stimuli, which is essential for survival in emergency situations. (ii) It reduces the workload on the brain by handling routine or urgent responses through the spinal cord.

Question. What is involuntary action? Give an example. Or What will happen if reflex action is not available in human being?

Answer: An involuntary action is one that occurs without conscious thought, such as the heartbeat. Or If reflex action were unavailable, the body would react too slowly to harmful stimuli (like extreme heat), leading to severe tissue damage or injury as the brain would take too long to process the information.