Control and Coordination

Control and Coordination In the Chapter Control and coordination are the functions of the nervous system and hormones present in our bodies. The responses of the nervous system can be grouped as reflex action, voluntary action or involuntary action. The nervous system uses electrical impulses to send messages. The nervous system receives information from our sense organs and acts through our muscles. Chemical coordination is found in both plants and animals. Hormones produced in one part of an organism move to another part to get the desired effect. A feedback mechanism controls the action of the hormones. Intext Exercises Page No. 119 1. What is the difference between a reflex action and walking? Ans. Reflex action is a process by which we do something without thinking about it or without being in control of our reactions. It is done only by the spinal cord without the help of brain. While walking is a process which is done by thinking or it is performed by the brain unlike reflex action. 2. What happens at the synapse between two neurons? Ans. The electrical impulses set off the release of some chemicals at the synapse between two neurons. These chemicals cross the synapse and start a similar electrical impulse in a dendrite of the next neuron. 3. Which part of the brain maintains posture and equilibrium of the body? Ans. Posture and equilibrium of the body is maintained by midbrain. 4. How do we detect the smell of an agarbatti (incense stick)? Ans. The smell of an agarbatti is detected by the forebrain. There are separate areas of association where sensory impulses or information are interpreted by putting them together. These impulses of smell are detected by forebrain. 5. What is the role of the brain in reflex action? Ans. The nerves from all over the body meet in a bundle in the spinal cord. Reflex arcs are formed in the spinal cord itself although the information input also goes on to reach the brain. Page No. 122 1. What are plant hormones? Ans. The chemical substances released by various parts of plants to control the growth and various activities are called plant hormones. 2. 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 is neither towards nor always from stimulus like touch. While the movement of shoot is towards stimulus like light. The movement of leaves of sensitive plants is not directional while the movement of shoot is directional. 3. Give an example of a plant hormone that promotes growth. Ans. (i) Auxins help to increase the length of plants. (ii) Gibberellins help in the growth of stem. 4. How do auxins promote the growth of a tendril around a support? Ans. The tendrils are sensitive to touch. As these tendrils come in the contact with the support, the auxin diffuses towards the other side away from the support. So this part grows more rapidly than the other. This causes the tendril to circle around the support and thus climb upwards. Design an experiment to demonstrate hydrotropism. 5. Ans. Positive hydrotropism can be demonstrated with germinated seedlings which are allowed to grow on ground. The soil below the roots is separated by the polythene partition. The left side is kept moist but the right side is kept dry. The radicals at first grow in a downward direction due to the effect of gravity (positive geotropism) but after some time, the roots bend toward the moist soil (positive hydrotropism). This is evidently due to the closeness of the germinating roots of water. Page No. 125 1. How does chemical coordination take place in animals? Ans. Chemical coordination takes place in animals with the help of some chemical substances called hormones. Hormones are secreted by endrocrine glands. The timing and amount of hormone released are regulated by feedback mechanisms. 2. Why is the use of iodised salt advisable? Ans. The use of iodised salt is advisable because iodine is necessary for the thyroid gland to produce thryoxine hormone. Thyroxine regulates carbohydrates, protein and fat metabolism in the body so as to provide the best balance for growth. Iodine is essential for the synthesis of thyroxine. 3. How does our body respond when adrenaline is secreted into the blood? Ans. Adrenalin is secreted directly into the blood and is carried to different parts of the body. It acts on heart. As a result, the heart beats faster in order to supply more oxygen to our muscles. These muscles regulate various movements of the body. 4. Why are some patients of diabetes treated by giving injections of insulin? Ans. The patients of diabetes are treated by giving injections of insulin because insulin is hormone which is produced by the pancreas and helps in regulating blood sugar levels. If it is not secreted in proper amounts the sugar level in the blood rises causing many harmful effects. Exercise 1. Which of the following is a plant hormone? (a) Insulin (b) Thyroxin (c) Oestrogen (d) Cytokinin. Ans. (d) Cytokinin. 2. The gap between two neurons is called a (a) dendrite. (b) synapse. (b) photoperiodism (c) cytokinin (d) high rate of photosynthesis. Ans. (a) auxins 12. Which one of the following is not endocrine glands? (a) Pituitary (b) Thyroid (c) Adrenal (d) Salivary. Ans. (d) Salivary. 13. The secretions of endocrine glands are called as: (a) juices (b) solutions (c) hormones (d) excretions. Ans.(c) hormones 14. Which one of the following is not an endocrine gland? (a) Adrenal gland (b) Pituitary body (c) Prostate gland (d) Thyroid gland. Ans. (c) Prostate gland. 15. The hormone which stimulates milk production in mammal is known as: (a) glucagon (b) prolactin (c) progesterone (d) oestrogen. Ans. (b) prolactin 16. Which of the following substances is released in excess quantity during excitement? (a) Cortisone (c) Adrenaline (b) Serotonin Ans. (c) Adrenaline (d) Norepinephrine. 17. 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 detect smell. Ans. (a) Gustatory receptors detect taste while olfactory receptors detect smell. 18. In a neuron, conversion of electrical signal to a chemical signal occurs at (a) cell body (c) dendritic end (b) axonal end Ans. (b) axonal end (d) axon 19. Posture and balance of the body is controlled by (a) cerebrum (b) cerebellum (c) medulla (d) pons Ans. (b) cerebellum 20. Spinal cord originates from (a) cerebrum (b) medulla (c) pons (d) cerebellum Ans. (b) medulla 21. The movement of shoot toward light is (a) geotropism (b) hydrotropism (c) chemotropism (d) phototropism Ans. (d) phototropism 22. The main function of abscisic acid in plants is to (a) increase the length of cells (b) promote cell division (c) inhibit growth (d) promote growth of stem Ans. (c) inhibit growth 23. Which of the following is not associated with growth of plant? (a) Auxin (b) Gibberellins (c) Cytokinins (d) Abscisic acid Ans. (d) Abscisic acid 24. Iodine is necessary for the synthesis of which hormone? (a) Adrenaline (b) Thyroxin (c) Auxin (d) Insulin Ans. (b) Thyroxin 25. The shape of guard cells changes due to change in the (a) protein composition of cells (b) temperature of cells (c) amount of water in cells (d) position of nucleus in the cells Ans. (c) amount of water in cells 26. The growth of pollen tubes towards ovules is due to (a) hydrotropism (b) chemotropism (c) geotropism (d) phototropism Ans. (b) chemotropism 27. The movement of sunflower in accordance with the path of sun is due to (a) phototropism (b) geotropism (c) chemotropism (d) hydrotropism Ans. (a) phototropism 28. Which of the following statements about transmission of nerve impulse is incorrect? (a) Nerve impulse travels from dendritic end towards axonal end. (b) At the dendritic end electrical impulses bring about the release of some chemicals which generate an electrical impulse at the axonal end of another neuron. (c) The chemicals released from the axonal end of one neuron cross the synapse and generate a similar electrical impulse in a dendrite of another neuron. (d) A neuron transmit electrical impulses not only to another neuron but to muscle an gland cells. Ans. (b) At the dendritic end electrical impulses bring about the release of some chemicals which generate an electrical impulse at the axonal end of another neuron.. 29. 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 brain Ans. (c) medulla in hind brain 30. Which of the following is not an involuntary action? (a) Vomiting (b) Salivation (c) Heart beat (d) Chewing Ans. (d) Chewing 31. When a person is suffering from severe cold, he or she cannot (a) differentiate the taste of an apple from that of an ice cream. (b) differentiate the smell of a perfume from that of an agarbatti. (c) differentiate red light from green light (d) differentiate a hot object from a cold object Ans. (c) differentiate the smell of a perfume from that of an agarbatti. 32. Dwarfism results due to (a) Excess secretion of thyroxin (b) Less secretion of growth hormone (c) Less secretion of adrenaline (d) Excess secretion of growth hormone Ans. (b) Less secretion of growth hormone 33. A doctor advised a person to take an injection of insulin because (a) his blood pressure was low (b) his heart was beating slowly (c) he was suffering from goitre (d) his sugar level in blood was high Ans. (d) his sugar level in blood was high 34. The hormone which increases the fertility in males is called (a) oestrogen (b) testosterone (c) insulin (d) growth hormone Ans. (b) testosterone 35. Which of the following endocrine glands is unpaired? (a) Adrenal (b) Testes (c) Pituitary (d) Ovary Ans. (c) Pituitary 36. Junction between two neurons is called (a) cell junction (b) neuro muscular junction (c) neural joint (d) synapse Ans. (d) synapse (c) axon. (d) impulse. Ans. (b) synapse. 3. The brain is responsible for (a) thinking. (b) regulating the heart beat. (c) balancing the body. (d) all of the above. Ans. (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? Ans. The main function of receptors is to detect informations from the environment. These receptors are located in our sense organs. There are some situations where receptors do not work properly like mouth starts watering when we feel hungry touching a flame, knee-jerk, etc. In these situations, they take enough time if these are done by the brain. To solve these problems, the nerves move muscles in a simpler way. This is done by the spinal cord. 5. Draw the structure of a neuron and explain its function. Nucleus Dendrite Cell body Axon Nerve ending Ans. Function of neuron: The neuron is the structural and functional unit of the nervous system. It contains the following three parts: (i) Dendrites (ii) Cell body (iii) Axon. The impulses of information travel from dendrites to cell body, and then along the axon to its end. These impulses cross the synapse. At the end, the impulses travel from one neuron to the other up to the spinal cord or to the concerned part of body. 6. How does phototropism occur in plants? Ans. The directional or tropic movement towards the light or away from the light is called phototropism. The shoots respond by bending towards light, while roots respond by bending away from the light. 7. Which signals will get disrupted in case of a spinal cord injury? Ans. (i) All the signals and responses which pass from and to the brain through the spinal cord will get disturbed. (ii) Reflex actions will be disrupted. 8. How does chemical coordination occur in plants? Ans. In plants, 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. 9. What is the need for a system of control and coordination in an organism? Ans. A system of control and coordination in an organism is essential for the following: (i) to give response to external stimuli. (ii) for survival. (iii) for interaction between the environment and individual himself. 10. How are involuntary actions and reflex actions different from each other? Ans. Involuntary Action: (i) The action which we cannot do by thinking is called involuntary action. For example, beating of the heart. (ii) Involuntary actions are controlled by the brain. Reflex Action: (i) An action, i.e., a response which is immediate (spontaneous) and does not need processing by the brain is called a reflex action. For example, immediate removal of hand on touching a hot plate. (ii) Reflex actions are controlled by the spinal cord. 11. Compare and contrast nervous and hormonal mechanisms for control and coordination in animals. Ans. In human beings, the nervous system controls the various functions by small units called neurons. Neurons receive the information through sensory nerves and transfer them through motor nerves. Besides this, certain important functions like sugar level metabolism, growth and development, etc., are controlled by hormones secreted by various endocrine glands. Hence, it is true that nervous and hormonal systems together perform the function of control and coordination in human beings. 12. What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs? Ans. The movement in the sensitive plant is Haptonastic and non-directonal whereas movement in our legs is voluntary and they work according to our will. 1. Additional Questions (i) What is the function of dendrites? (ii) Mention the receptors for light and sound in animals. Ans. (i) Dendrites acquire the information. (ii) Receptors for light-Photoreceptors (Eyes) Receptors for sound-Phonoreceptors (Ears). 2. What is reflex action? Ans. Reflex action. It is sudden spontaneous, mechanical, involuntary response to astimulus by voluntary organs. 3. Give two examples of reflex action. Ans. (i) Closing of eyes in response to bright light. 4. (ii) Withdrawal of hand in case you touch a hot plate. Name three parts of neurons in complex reflex arc. Ans. A complex reflex arc is composed of afferent, connector and efferent neurons. 5. What is a neuron? Ans. Neuron is a structural and functional unit of nervous system. It is the largest cell of body. It has three components i.e. (i) cell body (ii) dendrites (iii) axon. 6. Name the largest cell present in human body. Ans. Neuron. 7. What are the three basic regions of the brain? Ans. Fore brain, Mid brain, Hind brain. 8. Which part of the brain controls the heart? Ans. Medulla oblongata. 9. Which part of the plant shows positive geotropism and why? Ans. The main roots of plants show positive geotropism due to differential growth caused by unequal distribution of auxins. 10. What are turgor movements? Ans. The turgor movements are based on the turgor pressure of the cells. These movements are caused by reversible changes in the cell size. Thus volume changes in the cells result in movements. 11. What is the effect of light on seedling? Ans. Light is essential for proper growth and in proper light they remain stout and green. Generally seedlings growing in dark become etiolated. 12. What is meant by term 'tropism'? Give examples. Ans. These are plant growth responses to different stimuli governed by auxins. Response to touch (thigmotropism), gravity (geotropism) and light (phototropism) are examples. 13. Define hydrotropism and chemotropism. Ans. Hydrotropism. It is the movement of plant organs in response to unilateral stimulus of water. Chemotropism. It is the response of plants towards chemicals. 14. Name the following: (i) Two types of glands present in our body. (ii) The types of glands that secrete hormones. (iii) The gland which functions both as exocrine and endocrine gland. (iv) The other name of hormones. (v) The gland which is called 'Master gland'. (vi) The two hormones secreted by posterior lobe of pituitary. Ans. (i) Exocrine glands and endocrine glands (ii) Endocrine glands or ductless glands (iii) Pancreas (iv) Chemical coordinators (messengers) (v) Pituitary gland (vi) Oxytocin and Vasopressin or ADH 15. Name the following: (i) The hormone of the pituitary gland which controls the activity of thyroid. (ii) The hormone of the pituitary gland which controls the activity of adrenal gland. (iii) The part of the pituitary gland which controls growth and development of gonads. (iv) The hormone that promotes the growth in our body. (v) The disease caused by the deficiency of growth hormone in children. (vi) The disease caused by the oversecretion of growth hormone in children. Ans. (i) Thyroid Stimulating Hormone (TSH) (ii) Adreno Corticotropic Hormone (ACTH) (iii) Anterior lobe (Adenohypophysis) (iv) Growth hormone. (v) Dwarfism (vi) Gigantism. 16. Name the following: (i) Anyone symptom of acromegaly. (ii) The hormone associated with lactation in mammals. (iii) The hormone which controls the water exchange in the renal tubules. (iv) The hormone secreted by thyroid gland. (vi) The diseases caused by the malfunctioning of thyroid gland. (v) The disease caused by the deficiency of iodine. Ans. (i) Thickness of bones