Class 10 Science Control And Coordination Notes


A plant hormone is a chemical substance which is produced naturally in the plant and regulate growth and physiological processes o bring about control and coordination of various activities in plants.

The plant hormones regulate many functions in plants.

  • growth of root, stem and leaves (cell division, cell elongation and cell differentiation)
  • growth of fruits
  • opening and closing of stomata
  • germination of seeds
  • flowering of plant etc.

There are four major types of plant hormones which are involved in the control and coordination in plants:

  1. Auxins
  2. Gibberellins
  3. Cytokinins
  4. Abscisic acid (ABA)
Promote cell enlargement and cell differentiation.
Promote fruit growth. (responsible for phototropic and geotropic responses in plants).
Promote cell enlargement and cell differentiation in the presence of auxins.
Promote fruit growth.
Help in breaking dormancy of seeds and buds.
Promote cell division.
Promote fruit growth.
Help in breaking dormancy of seeds and buds.
Delay the ageing in leaves.
Promote opening of stomata.
Abscisic acid (ABA, growth inhibitor)
Promote the dormancy of seeds and buds.
Promote closing of stomata.
Promote the wilting and falling of leaves.


It is a structure which secretes a specific substances in body.
  • Exocrine glands
  • Endocrine glands
Exocrine glands
Endocrine glands
A gland which secretes its product into a duct or tube is called exocrine gland.
A gland which does not have a duct & secretes its product directly into blood stream is called endocrine gland.
Eg. Salivary gland secretes saliva into a duct called salivary duct.
Eg. Pituitary gland, thyroid gland.

Endocrine system:


Hormones are the chemical messengers that regulate the biological processes in living organisms.


  • They are produced by ductless glands i.e. their secretion is directly releases into the blood.
  • They are released in traces i.e. in a very little quantity.
  • They act on specific tissues or organs called target organs.
  • They are organic compounds.
  • They are generally slow in action.
  • They act away from the site of production.  
Name of the gland
Hormone secreted
Deficiency or excess
Present in brain
Produces ‘releasing hormones’ and ‘inhibitory hormones’
Regulate the secretion of hormones from pituitary gland
Pituitary gland (master gland)
Present just below the brain
Secretes several enzymes for ex. Growth hormone (HGH)
Controls the development of bones and muscles.
Deficiency of growth hormone in childhood leads to dwarfism and excess leads to gigantism (giantness)
Thyroid gland
Attached to wind pipe
Thyroxine (contains iodine)
Control the rate of metabolism of fats, proteins and carbohydrates.
Deficiency of thyroxine causes goiter.
Four parathyroid glands embedded in thyroid gland.
Regulate calcium and phosphate level in blood.
Lower part of neck and upper part of chest
Thymus hormone
Plays a role in development of immune system in the body.
Note: it is larger in young children but shrink after puberty
Pancreas (both exocrine and endocrine)
Just below the stomach
Insulin and glucagon
Control blood sugar level.
Insulin: lowers blood sugar level.
Glucagon: higher blood sugar level.
Deficiency of insulin causes diabetes.
Adrenal (both exocrine and endocrine)
Located on the top of two kidney
Adrenaline hormone
Regulate heart beat, breathing rate, blood pressure and carbohydrate metabolism.
Note: it is also known as gland of emergency.
Testes (present only in males)
Outside the abdominal cavity within the scrotum
Male sex hormone i.e. testosterone
Control development of male sex organ and male sex features such as deeper voice, beard etc.
Also makes the male gamete sperms.
Present only in females
Female sex hormones i.e. oestrogen and progesterone
Oestrogen: control the development of female sex organ and female sex features such as feminine voice, soft skin, mammary glands etc.
Progesterone: maintaining the pregnancy.
Control the uterus changing during menstrual cycle.
Ovaries make the female gamete called ova or egg.



  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 reactions. It is done by only 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 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 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 the 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.
  6. What are plant hormones? Ans:    The chemical substances released by various part of plants to control growth and various activities are called plant hormones.
  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 is neither towards nor away from stimulus like touch. While 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.
  8. 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.
  9. 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.
  10. 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 endocrine glands. The timing and amount of hormones released are regulated by feedback mechanisms.
  11. Why is the use of iodised salt advisable? Ans:    The use of iodised salt is advisable because iodine is necessary for the thyroid gland o produce thyroxine 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.
  12. How does our body respond when adrenaline secreted into the blood? Ans:    Adrenaline 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.
  13. Why are some patients of diabetes treated by infections of insulin? Ans:    The patients of diabetes are treated by giving injections of insulin. Insulin is a 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.
  14. 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 in formations from the environment. These receptors are located in our sense organs. There are some situations which receptors do not work properly, like mouth starts water when we feel hungry, touching a flame, knee – jerk, etc.
                            In these situations, they take enough time if these done by brain. To solve these problems, the nerves made muscles in a simpler way. This is done by the spinal cord.
  15.  Explain the structure and function of neurone? Ans:    The neuron is the structure and functional unit of the nervous system. It contain 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.                        
  16. 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.
  17. Which signals will get disrupted in case of a spinal cord injury? Ans:    (i) All the signals are responses which pass from and to the brain through the spinal cord will get disturbed.
                (ii) Reflex actions will be disrupted.
  18. 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 synthesized at placed away from where they act and simply diffuse to the area of action.
  19. What is the need for a system of control and coordination in an organism? Ans:    Every little change in the environment evokes an appropriate movement in response. For example, if we want to talk to our friends in class, we whisper rather than shouting loudly. Thus, the movement to be made depends on the event that is triggering it. Therefore, such controlled movement must be connected to the recognition of various events in the environment, followed by only the correct movement in response. In other words, living organisms must use systems providing control and coordination. In multicellular organisms, specialized tissues are used to provide control and coordination activities.
  20. How are involuntary actions and reflex actions different from each other? Ans:    Involuntary Action: (i) The action which we cannot do by thinking; 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 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.
  21. Compare and contrast nervous system 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.
  22.  What is the difference between the manner in which movement in the sensitive plant and movement in our legs takes place? Ans:    Movement in sensitive plant: Movement in the sensitive plant leaves takes place in response to touch (shock) stimulus. When terminal pulvini is touched, the stimulus is conducted to its base and the pulvini droop down. This happens due to change (decrease) in osmotic pressure causing shrinkage, when the stimulus time is over, osmotic pressure increases and the cells swell, causing to the pulvini become normal. This is an example of growth independent movement.
                            Thus, movement happens at a point different from the point of touch (stimulus). So, the information that a touch has occurred is communicated through electrical – chemical means from cell to cell, but not through specialized tissues. Plant cells change in shape by changing the amount of water in them, resulting in swelling or shrinking, during movement.
                Movement in our legs: Our legs are provided with nerves which are connected to muscles. To lift the leg, he brain passes information to nerves.
                            The information travels as an electrical impulse. On reaching the leg muscles, the impulse is converted into a chemical signal and the muscles contract to lift the leg. Movement of legs takes place due to muscle contraction and relaxation, which is under the control of our nervous system.
                            In the nervous system, electrical impulses are generated for quick transmission of information. But there are limitations:
                (i) Impulses will reach only those cells that are connected by the nervous tissue.
                (ii) Once an electrical impulse is generated in a cell and transmitted, the cell takes some time to generate another impulse. That is, cells cannot continuously create and transmit electrical impulses.
                            Hormones are chemical messengers that diffuse to all cells of the body. The body cells using special molecules on their surfaces, recognize information and even transmit it. Hormones are synthesized at places away from where they act.
                            Hormones can reach all cells of the body (through blood in animals) regardless of nervous connections, and it can be done steadily and persistently.
  23. Name the system in animals which help in the process of control and coordination. Ans:    (i) Nervous system
                (ii) Hormonal (Endocrine) system
  24. Name the largest cell in the human body. Ans:    Nerve cell or neuron.
  25. Have the old parts of the shoot and root changed direction? Ans:    The old parts of roots and shoots of plant change their directions slightly (very less), while new parts move more.
  26. What are the main divisions of nervous system? Ans:    The nervous system is broadly divisible into two parts:
                (i) Central nervous system,                 (ii) Peripheral nervous system
  27. Give four examples of simple human reflexes. Ans:    (i) Knee – jerk reflex in which the leg is involuntarily extended forward as a result of a sharp tap below the knee – as in a relaxed (freely hanging) leg.
    (ii) Closing of the eyelids when an object suddenly approaches the eye or when a strong beam of light is flashed cross.
    (iii) Withdrawal of the hand on pricking a pin or a horn.
    (iv) Movement of the diaphragm.      
  28. Design an experiment to demonstrate hydrotropism. Ans:    Positive hydrotropism can be demonstrated with terminated seedlings, which are allowed to grow on ground. The soil below the roots is separated by a polythene partition. The left side is kept moist but the right side is kept ry.

                        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 to water.

  1. Write two differences between the response of the plants and response of the animals to stimuli? Ans.    There are no specialised tissue in plants to conduct the information.
    Presence of specialised protein in animal muscle cells allow it to change shape whereas plant cells change shape by changing the amount of water in them.
  2. State how concentration of auxins stimulates the cells to grow longer on the side of the shoot which is away from light? Ans.    When growing plant detect light, a hormone called auxins is synthesized at the shoot tip, which helps the cells to grow longer.
    When the light is coming from one aide of the plant, auxins diffuses towards the shady side of the shoot.
    The concentration of auxins stimulates the cells to grow longer on the side of the shoot which is away from light.
    In this way, the plant appears to bend towards light.
  3. How does our body maintain blood sugar level? Ans.    Normally, blood glucose level increases after eating a meal.
    When blood sugar level rises, cells in pancreas releases insulin, causing the body to absorb glucose from the blood and lowering the blood sugar level to normal.
    When blood sugar level drops oo low, the level of insulin declines and other cells in pancreas release glucagon, which causes the liver to convert stored glycogen back into glucose and release into the blood.
  4. How does feedback mechanism regulate the hormone secretion? Ans.    The feedback mechanism regulates the timing and amount of hormone to be secreted, e.g., if a person has more sugar in his blood, it is detected by the cells of the pancreas. As a result, more insulin will be secreted to control the sugar level. In the reverse situation, the secretion of insulin will be depleted.
  5. Explain how the human body responds when adrenaline is secreted into the blood? Ans.    When an organism confronts any scary situation, adrenaline is secreted from the adrenal gland and sent directly into blood which is then circulated to various parts of the body, resulting into the following:
    The heart starts beating faster. As a result, more amount of oxygen is supplied to the muscles.
    The blood supply to the digestive system and the skin is reduced due to contraction of muscles around small arteries. This diverts the blood to the skeletal muscles.
    The breathing rate also increases from because of the contractions of the diaphragm and rib muscles.

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Practice Question

Question 1 Which among the following is not a base?
B) $NH_4OH$
C) $C_2H_5OH$
Question 2 What is the minimum resistance which can be made using five resistors each of 1/2 Ohm?
A) 1/10 Ohm
B) 1/25 ohm
C) 10 ohm
D) 2 ohm
Question 3 Which of the following statement is incorrect? ?
A) For every hormone there is a gene
B) For production of every enzyme there is a gene
C) For every molecule of fat there is a gene
D) For every protein there is a gene

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