The NCERT Solutions for Class 10 Science Chapter 7 focuses on Control and Coordination. It begins with an introduction to the nervous system in animals and humans and the concept of reflex actions. The chapter also explores the Human Brain with a labelled diagram and explains how it functions and causes action. Coordination in Plants is also covered, touching upon responsiveness to stimulus and growth-related movements. You will also learn about Hormones and their functions.
The topics in Chapter 7 include:
Home Revise can help you comprehend the Nervous System and Human Brain effectively. You can learn how to draw and label the various diagrams easily.
Chapter 7 Control and Coordination Exersice
Q.1 What is the difference between a reflex action and walking?
Ans: A reflex action is an automatic spontaneous response to a stimulus. It does not involve any thinking. For example, when the bright light is focused on our eyes, we immediately close it. Walking, on the other hand, is a voluntary action. It is acquired through learning. A voluntary action is under our conscious control.
Q.2 What happens at the synapse between two neurons?
Ans: Synapse is a small gap that occurs between the last portion of axon of one neuron and the dendrite of the other neuron. It acts as the passage for the transfer of the impulse in one direction only. The transfer of impulses occurs as the chemicals are produced in only one side of the neuron i.e., the axon's side. From axon, the impulses travel across the synapse to the dendrite of the other neuron.
Q.3 Which part of the brain maintains posture and equilibrium of the body?
Ans: Cerebellum, a part of hindbrain is responsible for maintaining posture and equilibrium of the body.
Q.4 How do we detect the smell of an agarbatti (incense stick)?
Our brain is divided into three main parts- forebrain, midbrain and hindbrain. Forebrain is the thinking part of our brain. It has separate areas that are specialized for hearing, smelling, sight, taste, touch, etc. The forebrain also has regions that collect information or impulses from the various receptors. When the smell of an incense stick reaches us, the olfactory receptors located in our forebrain detects it. Then, the forebrain interprets it by putting it together with the information received from other receptors and also with the information already stored in the brain.
Q.5 What is the role of the brain in reflex action?
Ans: Reflex action is a sudden response to a stimulus and do not involve any thinking. In a reflex action, the stimulus is detected by the sensory nerves that carry the impulse to the spinal cord where it is interpreted and the response is send back by the motor neuron. The pathway followed by the reflex action is called reflex arc. Reflex arc is formed in the spinal cord. The brain is only aware of the signal and the response that has taken place. However, the brain has no role to play in the creation of the response.
Q.6 What are plant hormones?
Ans: Plant hormones or phytohormones are naturally-occurring organic substances synthesized in minute quantities in the plant body and help in regulating plant growth and other physiological processes. The five major types of phytohormones are auxins, gibberellins, cytokinins, abscisic acid, and ethylene.
Q.7 How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?
Ans: The movement of leaves of the sensitive plant, Mimosa pudica or "touch me not"; occurs in response to touch or contact. Here, touch or contact acts as stimuli. This movement is independent of growth. The movement of shoot towards light is known as phototropism. This type of movement is directional and is growth dependent.
Q.8 Give an example of a plant hormone that promotes growth.
Ans: Auxin is an example of growth-promoting plant hormone.
Q.9 How do auxins promote the growth of a tendril around a support?
Ans: Auxin is synthesized at the tip of shoot. It helps the cell to grow longer. When a tendril comes in contact with a support, auxin stimulates faster growth of the cells on the opposite side, so that the tendril forms a coil around the support. This is how auxins promote the growth of a tendril around a support.
Q.10 Design an experiment to demonstrate hydrotropism.
Ans: Aim of the experiment: To demonstrate hydrotropism.
Method: Place germinating seeds in a moist saw dust or cotton contained in a sieve or mesh wire.
Observation: At first radicles appear and they grow downwards towards the gravity. After sometime the radicles again bend back and move towards the sieve containing saw dust or cotton.
Conclusion: Roots show both hydrotropic as well as geotropic response. Hydrotropic response is stronger than geotropic response.
Q.11 How does chemical coordination take place in animals?
Ans: Chemical coordination in animals take place with the help of hormones. Hormones are the chemical messengers that regulate the physiological processes in living organisms. Hormones are secreted by endocrine glands. Hence, we can say that the chemical coordination in animals take place through the endocrine system.
Q.12 Why is the use of iodised salt advisable?
Ans: Iodised salt is advised for the normal functioning of the thyroid gland. Iodine stimulates the thyroid gland to produce thyroxin hormone. It also regulates carbohydrate, fat, and protein metabolism in our body. Deficiency of this hormone results in the enlargement of the thyroid gland. This is called goiter, which is characterized by a swollen neck.
Q.13 How does our body respond when adrenaline is secreted into the blood?
Ans: Adrenaline is a hormone secreted by the adrenal glands. It is also known as emergency hormone. It is produced in response to joy, anger, fear or any kinds of stress. When secreted in large amounts, it speeds up the heartbeat and increases the blood supply to skeletal muscles, increases the breathing rate and blood pressure. All these responses enable the body to deal with any stress or emergency.
Q.14 Why are some patients of diabetes treated by giving injections of insulin?
Ans: Diabetes is a disease in which the level of sugar in the blood rises. Insulin is the hormone secreted by the pancreas that helps in regulating the blood sugar level. So, diabetic patients are treated by giving injections of insulin.
Q.15 Which of the following is a plant hormone?
(a) Insulin
(b) Thyroxin
(c) Oestrogen
(d) Cytokinin
Ans: (d) Cytokinin is a plant hormone.
Q.16 The gap between two neurons is called a
(a) dendrite.
(b) synapse.
(c) axon.
(d) impulse.
Ans: (b) The gap between two neurons is called a synapse.
Q.17 The brain is responsible for
(a) thinking.
(b) regulating the heart beat.
(c) balancing the body.
(d) all of the above.
Ans: (d) The brain is responsible for thinking, regulating the heart beat and balancing the body.
Q.18 What is the function of receptors in our body? Think of situations where receptors do not work properly. What problems are likely to arise?
(a) thinking.
(b) regulating the heart beat.
(c) balancing the body.
(d) all of the above.
Ans: Receptors are sensory structures (organs/tissues or cells) present all over the body. The receptors are either grouped, such as, in case of eye or ear, or scattered, like, in case of skin. All the information from the environment is detected by the receptors.
Functions of receptors:
(i) They sense the external stimuli.
(ii) They pass on the information in the form of electrical impulse to brain by nerve cells.
(iii) The brain then sends the response in the form of electrical impulse to the effector organ for the response.
If the receptors do not work properly then the information from the environment will not be detected and the body will not respond accordingly.
Q.19 Draw the structure of a neuron and explain its function.
Ans: Neuron or nerve cells are the functional units of the nervous system. The three main parts of a neuron are axon, dendrite, and cell body.
Functions of the three parts of a neuron:
Axon: It conducts messages away from the cell body.
Dendrite: It receives information from axon of another neuron and conducts the messages towards the cell body.
Cell body: It contains nucleus and cytoplasm. It is mainly concerned with the maintenance and growth.
Q.20 How does phototropism occur in plants?
Ans: The growth movement in plants in response to light stimulus is known as phototropism. The shoots show positive phototropism and the roots show negative phototropism. This means that the shoots bend towards the source of light whereas the roots bend away from the light source.
Q.21 Which signals will get disrupted in case of a spinal cord injury?
The reflex arc connections between the input and output nerves meet in a bundle in the spinal cord. In fact, nerves from all over the body meet in a bundle in the spinal cord on their way to the brain. In case of any injury to the spinal cord, the signals coming from the nerves as well as the signals coming to the receptors will be disrupted.
Q.22 How does chemical coordination occur in plants?
Ans: Chemical coordination in plants occurs with the help of hormones. Plant hormones or phytohormones are naturally-occurring organic substances synthesized in minute quantities in the plant body and help in regulating plant growth and other physiological processes. The five major types of phytohormones are auxins, gibberellins, cytokinins, abscisic acid, and ethylene.
Q.23 What is the need for a system of control and coordination in an organism?
A multicellular organism has diverse structure and functions. The maintenance of the body functions in response to changes in the body by working together of various integrated body systems is known as coordination. All the movements that occur in response to stimuli are carefully coordinated and controlled. In animals, the control and coordination movements are provided by nervous and endocrine system.
These two systems controls and coordinates by:
(i) The release of chemical messengers called the hormones from the endocrine system.
(ii) By the conduction of nerve impulse from the nervous system.
Q.24 How are involuntary actions and reflex actions different from each other?
Ans:
Involuntary actions:
i. Involuntary actions cannot be consciously controlled.
ii. These actions are however directly under the control of the brain.
Reflex actions:
i. Reflex actions are sudden, unconscious automatic response to some change in an environment.
ii. These are controlled by spinal cord.
Q.25 Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.
Ans:
Nervous system mechanism:
i. The information is conveyed in the form of nerve impulse.
ii. The nerve impulses are conducted through nerve fibres.
iii. The flow of information is rapid and the response is quick.
iv. Its effects are short lived.
Hormonal system mechanism:
i. The information is conveyed in the form of chemical messengers.
ii. The information is transmitted or transported through blood.
iii. The information travels slowly and the response is slow.
iv. It has prolonged effects.
Q.26 What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs?
Ans:
Movement in sensitive plants
i. Movement that takes place in a sensitive plant such as Mimosa pudica occurs in response to touch (stimulus)is an example of involuntary action.
ii. For 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.
iii. For this movement to occur, the plant cells change shape by changing the amount of water in them.
Movement in our legs:
i. Movement in our legs is an example of voluntary action.
ii. The signal or messages for these actions are passed to the brain and hence are consciously controlled.
iii. In animal muscle cells, some proteins are found which allow the movement to occur.