CBSE Class 10 Science Control and Coordination VBQs Set 03

Animals-Nervous System

Question. Sensory nerve of a reflex arc carries information from the receptor cells to the
(a) spinal cord
(b) brain
(c) muscles of the effector organ
(d) bones of the receptor organ
Answer: (a) spinal cord

Question. The part in which gustatory receptors are present in our body is
(a) inner ear
(b) skin
(c) tongue
(d) inner lining of nose.
Answer: (c) tongue

Question. Assertion (A) : The brain allows us to think and take actions based on that thinking.
Reason (R) : The hind brain is the main thinking part of the brain which has regions which receive sensory impulses from various receptors.
(a) Both (A) and (R) are true and (R) is the correct explanation of the assertion (A).
(b) Both (A) and (R) are true, but (R) is not the correct explanation of the assertion (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.

SA I 

Question. Name the part of brain which is responsible for the following actions :
(i) Maintaining posture and balance
(ii) Beating of heart
(iii) Thinking
(iv) Blood pressure
Answer: (i) Cerebellum (part of hindbrain) is responsible for maintaining posture and balance. (ii) Medulla oblongata (part of hindbrain) controls the beating of the heart. (iii) Cerebrum (part of forebrain) is the main thinking part of the brain. (iv) Medulla oblongata controls blood pressure.

Question. (a) How is the brain and spinal cord protected in human beings?
(b) State one main function of (i) Medulla and (ii) Cerebellum.
Answer: (a) The brain is protected by a bony box called the cranium and is further cushioned by cerebro-spinal fluid contained within three membranes called meninges. The spinal cord is protected by the vertebral column (backbone).
(b) (i) Medulla controls involuntary actions like breathing and blood pressure. (ii) Cerebellum maintains posture and balance during activities like walking or cycling.

Question. What is a nerve impulse? State the direction followed by a nerve impulse while travelling in the body of an organism.
Answer: A nerve impulse is an electrical signal that travels along a neuron to transmit information. The direction followed is:
Dendrite
\( \implies \) Cell body
\( \implies \) Axon
\( \implies \) Nerve ending
\( \implies \) Synapse (to the next neuron).

Question. (a) Name one gustatory receptor and one olfactory receptor in human beings.
(b) Write ‘a’ and ‘b’ in the given flow chart of neuron through which information travels as an electrical impulse.
Dendrite \( \to \) ‘a’ \( \to \) ‘b’ \( \to \) End point of Neuron
Answer: (a) Gustatory receptor: Tongue (senses taste). Olfactory receptor: Nose (senses smell).
(b) 'a' represents the Cell body (Cyton) and 'b' represents the Axon.

Question. Write the main functions of the following :
(a) sensory neuron
(b) cranium
(c) vertebral column
(d) motor neuron.
Answer: (a) Sensory neuron: Transmits impulses from receptors/sense organs to the Central Nervous System. (b) Cranium: Protects the brain from external injuries. (c) Vertebral column: Protects the spinal cord and provides structural support. (d) Motor neuron: Transmits impulses from the Central Nervous System to effectors like muscles or glands.

SA II 

Question. Why does the flow of signals in a synapse from axonal end of one neuron to dendritic end of another neuron take place but not in the reverse direction? Explain.
Answer: At the axonal end, neurotransmitters are released into the synapse when an electrical impulse arrives. These chemicals diffuse across the gap and bind to specific receptors present only on the dendritic end of the next neuron, triggering a new electrical impulse. Since receptors are absent on the axonal end and neurotransmitters are not released from dendrites, the signal cannot travel in reverse.

Question. List in tabular form three distinguishing features between cerebrum and cerebellum.
Answer:

Question. "Reflex arcs continue to be more efficient for quick responses”. Justify this statement giving reason.
Answer: Reflex arcs involve only the spinal cord and bypass the brain's complex thinking process. This significantly reduces the time between the detection of a stimulus and the response, making it more efficient for survival in dangerous or urgent situations where a quick response is critical.

Question. (a) Define reflex arc.
(b) Trace the sequence of events which occur in our body when a bright light is focussed on your eyes.
Answer: (a) A reflex arc is the neural pathway that controls a reflex action. (b) Bright light (Stimulus)
\( \implies \) Photoreceptors in Retina (Receptor)
\( \implies \) Sensory neuron
\( \implies \) Brain/Spinal cord
\( \implies \) Motor neuron
\( \implies \) Iris muscles (Effector)
\( \implies \) Pupil size decreases (Response).

Question. Mention three major regions of brain. Write one function of each.
Answer: 1. Forebrain: Main thinking part, controls voluntary actions and stores information. 2. Midbrain: Controls reflex movements of the head, neck, and trunk. 3. Hindbrain: Controls involuntary actions like blood pressure (medulla) and maintains posture and balance (cerebellum).

LA 

Question. What constitutes the central and peripheral nervous systems? How are the components of central nervous system protected? Which signals will get disrupted in case of a spinal cord injury?
Answer: The Central Nervous System (CNS) consists of the brain and spinal cord. The Peripheral Nervous System (PNS) consists of cranial nerves (from the brain) and spinal nerves (from the spinal cord). The brain is protected by the cranium and meninges with cerebro-spinal fluid, and the spinal cord is protected by the vertebral column. In case of a spinal cord injury, reflex actions and the transmission of sensory and motor signals between the brain and parts of the body below the site of injury will be disrupted.

Coordination in Plants

Question. In plants the role of cytokinin is
(a) Promote cell division
(b) Wilting of leaves
(c) Promote the opening of stomatal pore
(d) Help in the growth of stem.
Answer: (a) Promote cell division

Question. Assertion (A) : Plant hormones are chemicals produced in plants which help to coordinate growth, development and response to stimulus and environment.
Reason (R) : Abscisic acid is a plant hormone that promotes cell division.
(a) Both (A) and (R) are true and (R) is the correct explanation of the assertion (A).
(b) Both (A) and (R) are true, but (R) is not the correct explanation of the assertion (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.

VSA 

Question. State one example of chemotropism.
Answer: The growth of a pollen tube towards the ovule in a flower is an example of positive chemotropism.

SA I 

Question. Where are auxins synthesised in a plant? Which organ of the plant shows :
(i) Positive phototropism
(ii) Negative geotropism
(iii) Positive hydrotropism
Answer: Auxins are synthesised at the tips of shoots and roots. (i) Stem/Shoot shows positive phototropism. (ii) Stem/Shoot shows negative geotropism. (iii) Root shows positive hydrotropism.

Question. Name a plant hormone responsible for bending of a shoot of a plant when it is exposed to unidirectional light. How does it promote phototropism?
Answer: Auxin is responsible. When unidirectional light falls on a shoot, auxin diffuses towards the shady side of the shoot. The high concentration of auxin on the shady side stimulates cells to grow longer, causing the shoot to bend towards the light.

Question. How do auxins promote the growth of a tendril around a support ?
Answer: When a tendril comes in contact with a support, auxin diffuses to the part of the tendril not in contact with the support. This causes that part to grow faster than the part in contact, making the tendril circle and wind around the support.

Question. State the two types of movements seen in plants. Give one example of each type.
Answer: 1. Tropic movements (growth-dependent): Example, phototropism (stem bending towards light). 2. Nastic movements (growth-independent): Example, folding of leaves in 'touch-me-not' (Mimosa pudica).

SA II 

Question. State the function of each of the following plant hormones :
(a) Gibberellins
(b) Auxins
(c) Abscisic acid
Answer: (a) Gibberellins promote stem elongation and seed germination. (b) Auxins promote cell elongation and phototropism. (c) Abscisic acid inhibits growth and causes wilting of leaves and closing of stomata.

Question. What are plant hormones? Name the plant hormones responsible for the following :
(i) Growth of stem
(ii) Promotion of cell division
(iii) Inhibition of growth
(iv) Elongation of cells
Answer: Plant hormones (phytohormones) are chemical substances produced naturally in plants that coordinate growth and physiological processes. (i) Gibberellins. (ii) Cytokinins. (iii) Abscisic acid. (iv) Auxins.

Question. Define phototropism. Name the plant hormone which is responsible for phototropism.
Answer: Phototropism is the growth movement of a plant part in response to a light stimulus. Auxin is the hormone responsible for this movement.

LA 

Question. (a) What are phytohormones? List four types of phytohormones. Where are these hormones synthesised?
(b) What happens when a growing plant detects light? Explain in brief.
Answer: (a) Phytohormones are chemical messengers in plants. Four types: Auxins, Gibberellins, Cytokinins, and Abscisic acid. They are synthesised in various parts like shoot tips, root tips, seeds, and developing leaves. (b) When a plant detects light, auxins migrate to the shaded side, causing those cells to elongate faster. This results in the bending of the stem toward the light source (phototropism).

Question. List the sequences of events that occur when a plant is exposed to unidirectional light, leading to bending of a growing shoot. Also name the hormone synthesised and the type of movement that takes place.
Answer: 1. Unidirectional light stimulus is detected at the shoot tip. 2. Auxin hormone is synthesised. 3. Auxin diffuses toward the shady side of the shoot. 4. Cells on the shady side elongate more than those on the sunny side. 5. The shoot bends toward the light. The movement is positive phototropism.

Hormones in Animals

VSA 

Thyroid gland is a bilobed structure situated in our neck region. It secretes a hormone called thyroxine. Iodine is necessary for the thyroid gland to make thyroxine. Thyroxine regulates carbohydrates, protein and fat metabolism in the body. It promotes growth of body tissues also. When there is an excess of thyroxine in the body, a person suffers from hyperthyroidism and if this gland is underactive it results in hypothyroidism. Hyperthyroidism is diagnosed by blood tests that measure the levels of thyroxine and Thyroid Stimulating Hormone (TSH). Hypothyroidism is caused due to the deficiency of iodine in our diet resulting in a disease called goitre. Iodised salt can be included in our diet to control it.

Question. (i) Where is thyroid gland situated? (ii) State the function of thyroxine in human body. (iii) What is hyperthyroidism? (iv) How can we control hypothyroidism?
Answer: (i) Neck region. (ii) Regulates carbohydrates, protein, and fat metabolism. (iii) Condition caused by excess thyroxine. (iv) By including iodised salt in the diet.

Question are based on table given below:
Study the table in which the levels of Thyroid Stimulating Hormone (TSH) in women are given and answer the questions that follow on the basis of understanding of the following paragraph and the related studied concepts : Women are at greater risk for developing abnormal TSH levels during menstruation, while giving birth and after going through menopause. Around 5% of women in the United States have some kind of thyroid problem compared to 3% of men.

Question. (i) A 35 years old woman has TSH level 6.03 mU/L. What change should she bring in her diet to control this level? (ii) When do women face a greater risk of abnormal TSH level? (iii) State the consequence of low TSH level. (iv) Name the mineral that is responsible for synthesis of hormone secreted by thyroid gland.
Answer: (i) The level is high; she should use iodised salt and consult a doctor. (ii) During menstruation, childbirth, and menopause. (iii) It indicates hyperthyroidism. (iv) Iodine.
Thyroid Stimulating Hormone (TSH) stimulates thyroid gland to produce thyroxine. Study the table given below. It is important to monitor TSH levels during pregnancy. High TSH levels and hypothyroidism can especially affect chances of miscarriage. Therefore, proper medication in consultation with a doctor is required to regulate/control the proper functioning of the thyroid gland.

Question. (i) Give the full form of TSH. (ii) State the main function of TSH. (iii) Why do TSH levels in pregnant women need to be monitored? (iv) A pregnant woman has TSH level of 8.95 mU/L. What care is needed for her?
Answer: (i) Thyroid Stimulating Hormone. (ii) To stimulate the thyroid gland to produce thyroxine. (iii) To prevent risk of miscarriage and ensure proper development. (iv) She needs immediate medical consultation and likely hormonal medication.

SA II 

Question. A squirrel is in a scary situation. Its body has to prepare for either fighting or running away. State the immediate changes that take place in its body so that the squirrel is able to either fight or run.
Answer: Adrenaline is secreted directly into the blood. The heart beats faster to supply more oxygen to muscles. Blood flow to the digestive system and skin is reduced, and diverted to skeletal muscles. Breathing rate increases. These changes prepare the squirrel for action.

Question. Why is chemical communication better than electrical impulses as a means of communication between cells in a multicellular organisms?
Answer: Electrical impulses can only reach cells connected by nervous tissue and require time to reset after each impulse. Chemical communication (hormones) can reach all cells of the body via the blood, can provide long-lasting effects, and coordinate various physiological processes across different organs simultaneously.

Question. A cheetah, on seeing a prey moves towards him at a very high speed. What causes the movement of his muscles? How does the chemistry of cellular components of muscles change during this event?
Answer: Motor nerve impulses trigger the movement. Muscle cells contain specialized proteins that change their shape and arrangement in response to electrical signals. This leads to the shortening (contraction) of muscle fibres. This shape change is driven by biochemical reactions involving ATP and calcium ions.

Question. Name the hormones secreted by the following endocrine glands and specify one function of each: (a) Thyroid (b) Pituitary (c) Pancreas.
Answer: (a) Thyroid: Thyroxine; regulates metabolism. (b) Pituitary: Growth hormone; regulates growth and development. (c) Pancreas: Insulin; regulates blood sugar levels.

Question. (a) How does chemical coordination take place in animals? (b) It is advised to use iodised salt. Give reason.
Answer: (a) It takes place through hormones secreted by endocrine glands directly into the blood. (b) Iodine is essential for the synthesis of thyroxine by the thyroid gland. Its deficiency can lead to goitre.

Question. (a) An old man is advised by his doctor to take less sugar in his diet. Name the disease from which the man is suffering. Mention the hormone due to imbalance of which he is suffering from this disease. Which endocrine gland secretes this hormone? (b) Name the endocrine gland which secretes growth hormone. What will be the effect of the following on a person (i) deficiency of growth hormone (ii) excess secretion of growth hormone?
Answer: (a) Disease: Diabetes. Hormone: Insulin. Gland: Pancreas. (b) Gland: Pituitary. (i) Deficiency causes dwarfness. (ii) Excess causes gigantism.

Question. Name the hormone required for the following. Also mention the name of endocrine gland from which that hormone is secreted: (a) Lowering of blood glucose. (b) Development of moustache and beard in human males. (c) Metabolism of carbohydrates, fats and proteins.
Answer: (a) Insulin; Pancreas. (b) Testosterone; Testes. (c) Thyroxine; Thyroid.

Question. (a) Complete the following table: (i) Thyroxine, (ii) Growth Hormone, (iii) Insulin. (b) List three characteristics of animal hormones.
Answer: (a) (i) Function: Regulates metabolism. (ii) Gland: Pituitary. (iii) Function: Lowers blood sugar. (b) 1. Secreted in small quantities. 2. Poured directly into the blood. 3. Act on specific target organs.

LA 

Question. (a) Name the hormone secreted by (i) Pituitary, and (ii) Thyroid stating one main function of each. Name the disorder a person is likely to suffer from due to the deficiency of the above mentioned hormones. (b) How is the timing and amount of hormone released regulated ? Explain with an example.
Answer: (a) (i) Growth hormone; function: growth; deficiency: dwarfism. (ii) Thyroxine; function: metabolism; deficiency: goitre. (b) Regulated by a feedback mechanism. Example: When blood sugar rises, pancreatic cells secrete insulin. As sugar levels fall, insulin secretion is reduced.

Question. (a) Name one organ each where growth hormone is synthesised in man and plant. (b) List the sequence of events that occur when a plant is exposed to unidirectional light, leading to bending of a growing shoot. Also name the hormone and the type of movement.
Answer: (a) Man: Pituitary gland. Plant: Shoot tip. (b) Light detected at tip
\( \implies \) Auxin synthesised
\( \implies \) Auxin migrates to shady side
\( \implies \) Shady side cells elongate faster
\( \implies \) Shoot bends towards light. Hormone: Auxin. Movement: Positive phototropism.