CBSE Class 10 Science HOTs Control And Coordination Set 04

ASSERTION AND REASON QUESTIONS

Question. In the following Questions, the Assertion (A) and Reason (R) have been put forward. Read both 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.

Question. Assertion: Reflex arc works faster than thinking process of brain.
Reason: Reflex arc works in case of those animals who do not have thinking process.
(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.
Answer: (b) Both the Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.

Question. Assertion: Impulse travels from dendrite to cell body and then along the axon to its end.
Reason: Information acquired at the end of the dendrite tip of a nerve cell sets of an electric impulse.
(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.
Answer: (a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.

Question. Assertion: Brain is a delicate organ which is protected from injury
Reason: Only the bony box protects the brain from any shock.
(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.
Answer: (c) Assertion is true but the Reason is false.

Question. Assertion: Plants do have a nervous system for control and coordination
Reason: Plants use electro chemical means to convey information from cell to cell.
(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.
Answer: (d) The statement of the Assertion is false but the Reason is true.

Question. Assertion: On attaining puberty, breast size increases and reproductive organs develop in females.
Reason: Ovaries release hormone progesterone in female.
(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.
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) 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.
Answer: (a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.

Question. Assertion: A nerve impulse is an electrochemical event.
Reason: In a nerve impulse there are changes in the resting potential which spread down the nerve fiber. 
(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.
Answer: (a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.

CASE-BASED QUESTIONS

Spinal cord reflexes are simple behaviors produced by central nervous system (CNS) pathways that lie entirely within the spinal cord. The sensory afferent fibers that evoke these reflexes enter the spinal cord and activate spinal motor neurons directly or through a chain of one or more spinal interneurons. Although these pathways are entirely spinal, they are affected by descending pathways from the brain, either directly or through other spinal interneurons. Through these descending pathways, the brain exerts both short-term and long-term influence over spinal cord reflex function. In the short-term, the brain rapidly adjusts spinal reflexes to suit the needs of different tasks (e.g., standing vs. walking vs. running). In the long-term, it gradually shapes spinal reflexes during development, during skill acquisition later in life, and in response to CNS trauma and disease. The long-term changes that the brain induces in spinal cord reflexes involve activity-dependent plasticity in the spinal cord itself.

Question. Name the part of the brain which controls posture and balance of the body.
Answer: Cerebellum.

Question. What are the two components of the CNS in humans?
Answer: Brain and spinal cord.

Question. What is the function of adrenaline hormone? Or What is the significance of reflex action?
Answer: Adrenaline hormone prepares the body to face emergency situations by increasing heart rate, breathing rate and blood supply to muscles. Or Reflex action is significant because it provides an immediate response to a harmful stimulus, protecting the body from injury.

All living organisms have the ability to detect changes in external as well as internal environment and to respond and react appropriately to these changes. Such an ability of organisms is called irritability. The changes in the environment are called stimuli and the organs that detect them are response. The response to a stimulus may be carried out by the individual cell, tissue, organs or organ system. The movements shown in response to any stimulus are definite, highly controlled and coordinated. Various organs work in full cooperation and provide appropriate reaction for the stimulus and this is called coordination. Coordination in animals is brought about the nervous and endocrine systems i.e. nervous and chemical control. In plants, it is brought about only by chemicals (hormones). When we are frightened by a dog, we run away as fast as we can. Here fear of dog is the stimulus and running away is the response.

Question. What are the stimulus in (i) Geotropism and (ii) Chemotropism
Answer: (i) Gravity, (ii) Chemicals.

Question. What are the functions of hypothalamus?
Answer: Hypothalamus regulates various body functions like temperature, thirst, hunger, sleep, and controls the secretion of hormones from the pituitary gland.

Question. Why brain and spinal cord are considered as central nervous system? Or Where is glucagon secreted? What is its function?
Answer: Brain and spinal cord are considered the CNS because they receive information from all parts of the body and integrate it to coordinate responses. Or Glucagon is secreted by the pancreas. Its function is to increase the blood glucose level by stimulating the breakdown of glycogen in the liver.

When we eat food, our eyes, hands and mouth works in perfect coordination. The eyes focus on the food, the hands pick it up and take it to the mouth where it is chewed. All these actions are completed in a particular sequence. Similarly, internal functions of our body are carried out by the nervous system in a particular sequence.

Question. What is a reflex arc?
Answer: The pathway followed by nerve impulses in a reflex action is called a reflex arc.

Question. How is the spinal cord protected?
Answer: The spinal cord is protected by the vertebral column (backbone).

Question. How does an impulse travel in a nerve cell? Or Do plants also have nerve cells? How does coordination take place in plant cells?
Answer: An impulse travels in a nerve cell as an electrical signal from the dendrite to the cell body and then along the axon to its end. Or Plants do not have nerve cells. Coordination in plants occurs through chemical substances called phytohormones and by electrical-chemical signals between cells.

Pea plants need support to grow. It clings on any other support and grows. It is possible due to response of plant hormones to different stimuli. Normally, plants respond to such stimuli slowly. Plants respond to some stimuli by growing towards it or away from it.

Question. The ‘touch-me-not’ plant is an example of which tropism?
Answer: Nastic movement (Thigmonasty).

Question. Give one example of chemotropism.
Answer: Growth of a pollen tube towards the ovule.

Question. How does a pea plant cling to its support? Or Name four different types of tropisms shown by plants.
Answer: Pea plants have tendrils which are sensitive to touch. When they come in contact with a support, auxin diffuses to the side away from the support, causing faster growth on that side and making the tendril coil around the support. Or Phototropism, Geotropism, Hydrotropism, and Chemotropism.

Parkinson (PD) is a type of movement disorder that can affect the ability to perform common, daily activities. Although PD is associated with a wide range of symptoms, there are features of PD that most people with the condition will experience. These symptoms are typically divided into those that affect movement (motor symptoms) and those that do not (non-motor symptoms). The most common motor symptoms of PD are tremor (a form of rhythmic shaking), stiffness or rigidity of the muscles, and slowness of movement. A person with PD may also have trouble with posture, balance, coordination, and walking. Common non-motor symptoms of PD include sleep problems, constipation, anxiety, depression, and fatigue, among others. It is important to note that, although there are common symptoms of PD, they can vary greatly from person to person. Most people who develop the symptoms of PD do so sometime after the age of 50, but PD can affect younger persons as well. There are an estimated 1 million Americans living with PD and more than 10 million people worldwide.

Question. Name the hormone synthesised at the shoot tip of plants
Answer: Auxin.

Question. What is the significance of reflex action?
Answer: It allows the body to react quickly to stimuli to protect itself from danger or injury without the delay of conscious thinking.

Question. What are endocrine glands? Or Which hormone is released by hypothalamus gland? What is the function of this hormone?
Answer: Endocrine glands are ductless glands that secrete hormones directly into the bloodstream. Or Hypothalamus releases 'releasing hormones' which regulate the secretion of various hormones from the pituitary gland.

Plants do not move but they respond to their environment. It means their cells must be able to communicate with other cells. Hormones send messages between the cells. Plant hormones or phytohormones are also known as plant growth substances as they coordinate the activities of plants by controlling one or other aspect of the growth of the plant. The growth of the plant can be divided into three stages: cell division, cell enlargement and cell differentiation which occur in particular locations in a plant. The phytohormones also promote dormancy in seeds and buds, breaking of dormancy, stomata control, wilting and falling of leaves, fruit growth, ripening of fruits and delay in ageing of plants. The plant hormones are synthesised at places away from where they act and simply diffuse to the area of action.

Question. Name a plant hormone that inhibits growth.
Answer: Abscisic acid.

Question. Which hormone is synthesied when growing plants detect light? Where it is synthesied?
Answer: Auxin is synthesized at the shoot tips.

Question. Write two functions of cytokinins. Or Write two function of gibberellins.
Answer: (i) Promotes cell division and (ii) Delays ageing in plant parts. Or (i) Promotes growth of stem and (ii) Promotes seed germination.

Rohit saw an advertisement about iodised salt while watching TV. In the advertisement it was stated that one should take only iodised salt. He also remembered that the doctor has advised his elder sister to eat iodised salt when she had developed swollen neck. His teacher has also taught them about various animal hormones.

Question. Name the disease from which Rohit’s sister suffered. Why has the doctor advised her to eat iodised salt?
Answer: Goitre. Doctor advised iodised salt because iodine is essential for the synthesis of thyroxine hormone by the thyroid gland, which regulates metabolism and prevents goitre.

Question. Which hormone is known as emergency hormone? How it helps in coping during emergency? Or Name an endocrine gland that secretes a hormone called insulin. Why are some diabetes patients treated by giving insulin injections?
Answer: Adrenaline is known as the emergency hormone. it increases heart rate and breathing rate to supply more oxygen and energy to muscles. Or Pancreas secretes insulin. Diabetes patients are given insulin injections to lower their high blood glucose levels by helping the body cells absorb and use the glucose.

QUESTIONS

Question. What is the difference between a reflex action and walking?
Answer:
Reflex action:
(i) It is a spontaneous, involuntary response to a stimulus.
(ii) It is controlled by spinal cord.
(iii) This kind of response occur within the fraction of second.

Walking:
(i) It is a voluntary response to a stimulus.
(ii) It is controlled by brain.
(iii) This kind of response takes longer time.

Question. What happens at the synapse between two neurons?
Answer: Synapse is a gap present between two adjacent neurons. Here, the axon terminal of one neuron is in close proximity to the dendrite of the second neuron. When the information collected by the nerve endings of the dendrite tip of the nerve cells set up a chemical reaction that creates an electrical impulse. This impulse is sent to cell body and them along the axon it reaches the nerve ending of the axon. At the nerve ending, the electrical signals release chemicals. These chemicals cross the gap and again start a similar electrical impulse in another dendrite of another nerve cell. Thus, at the synapse, nerve impulse is transmitted from one neuron to other neuron.

Question. Which part of the brain maintains posture and equilibrium of the body?
Answer: Cerebellum which is a part of hindbrain maintains posture and equilibrium of the body.

Question. How do we detect the smell of an agarbatti (incense stick)?
Answer: In our nose, olfactory receptors are present. They detect the smell of incense stick and set off a chemical reaction. As a result, a nerve impulse is generated which is transmitted to sensory nerve. The sensory nerve relay the information in the form of nerve impulse to the brain via spinal cord. The olfactory lobe present in the forebrain interpret the message and we feel the smell.

Question. What is the role of the brain in reflex action?
Answer: Reflex action takes place in spinal cord. The information that a reflex action has provided goes on to reach the brain which stores the information and remembers it for future use.

Question. What are plant hormones?
Answer: A plant hormone is a chemical substance which is produced naturally in the plant and regulate growth and physiological processes to bring about control and coordination of various activities in plants.

Question. How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?
Answer:
Movement of leaves of sensitive plant:
(a) Movement of leaves of the sensitive plant is an example of nastic movements.
(b) Its stimulus is touch.
(c) It is not regarded as growth movement.

Movement of shoot towards light:
(a) Movement of shoot towards light is an example of tropic movement.
(b) Its stimulus is light.
(c) It is regarded as growth movement.

Question. Give an example of a plant hormone that promotes growth.
Answer: Auxin is a plant hormone that promotes growth.

Question. How do auxins promote the growth of a tendril around a support?
Answer: Tendrils are sensitive to touch or contact of other objects. When a tendril touches a support, the hormone auxin from the tip of the tendril diffuses towards the side of the tendril that is not in contact with the support. As a result, the side that is not in contact with the support grows faster than the side which is in contact with the support. This leads to the bending of tendril towards the support.

Question. How does chemical coordination take place in animals?
Answer: In animals, endocrine gland as a result of a stimulation releases a chemical substance called hormone directly into the blood. Blood carries the hormone to the target organ. In target organ, hormone transmit the information to bring about the effect.

Question. Why is the use of iodised salt advisable? 
Answer: Thyroid gland makes a hormone, thyroxine. Iodine is necessary for the thyroid gland to make this hormone. The thyroxine hormone regulates the metabolism of carbohydrates, fats and proteins in the body, so as to provide the best balance for growth. Deficiency of iodine in our diet results in a disorder called goitre in which thyroid gland becomes enlarged and thus, neck becomes swollen. Thus, use of iodised salt is advisable to prevent the goitre disease.

Question. How does our body respond when adrenaline is secreted into the blood?
Answer: Adrenal glands secrete hormone adrenaline which is called emergency hormone. This hormone is rapidly secreted in response to stress or during emergency situations. This hormone speeds up heart beat, rate of respiration and raises glucose level in the blood, so that we can get a lot of energy quickly to fight or flight from the emergency situation.

Question. Why are some patients of diabetes treated by giving injections of insulin?
Answer: Insulin plays an important role in sugar metabolism. Insulin lowers the blood sugar level. In some patients of diabetes, insulin secretion is reduced. Insulin injection is given to such patients to compensate for reduced insulin secretion.