Control and Coordination

Welcome dear students! Today we are going to learn about Control and Coordination from Class 10 Science. In the previous chapter, we looked at life processes involved in the maintenance functions in living organisms. We often associate movement with life. Some movements result from growth, like a seedling pushing through soil over a few days. If growth stops, these movements stop. Other movements, like a cat running, children playing, or buffaloes chewing cud, are not caused by growth. We associate visible movements with life because they are responses to environmental changes. The cat runs because it sees a mouse. Plants grow toward sunshine. We move to protect ourselves from bright light or hot objects. This controlled movement depends on recognizing environmental events and responding correctly. Living organisms use systems for control and coordination, provided by specialized tissues in multicellular organisms. [CHECKPOINT] In animals, control and coordination are provided by nervous and muscular tissues. Touching a hot object is an urgent and dangerous situation. We detect it using specialized tips of nerve cells called receptors, usually located in our sense organs like the inner ear, nose, and tongue. Gustatory receptors detect taste, while olfactory receptors detect smell. Information acquired at the dendritic tip of a nerve cell sets off a chemical reaction that creates an electrical impulse. This impulse travels from the dendrite to the cell body, and then along the axon to its end. At the axon end, the electrical impulse triggers the release of chemicals. These chemicals cross the gap, or synapse, and start a similar electrical impulse in the dendrite of the next neuron. This is the general scheme of how nervous impulses travel. A similar synapse finally delivers impulses from neurons to muscle cells or glands. Nervous tissue is an organized network of neurons specialized for conducting information via electrical impulses. [CHECKPOINT] Let us look at the structure of a neuron. It has a nucleus inside the cell body, branching dendrites that acquire information, and a long axon that transmits the impulse to its nerve ending. At the neuromuscular junction, the axon ends near a muscle fibre, with capillaries and mitochondria visible. Now, please look at Figure six point one part a in your textbook and identify the parts of a neuron. First, identify where information is acquired. That is the dendritic tip. Second, identify through which part information travels as an electrical impulse. That is the axon. Third, identify where this impulse must be converted into a chemical signal for onward transmission. That is at the axon end, or nerve ending. Now, let us perform Activity six point one. Put some sugar in your mouth and note how it tastes. Now block your nose by pressing it between your thumb and index finger. Eat the sugar again. Notice if the taste changes. While eating lunch, block your nose the same way and see if you can fully appreciate the food taste. You will notice a difference. This happens because smell and taste are closely linked. When you have a cold, your blocked nose reduces your ability to taste food fully. We often use the word reflex for sudden actions, like jumping out of the way of a bus or pulling a hand from a flame. These are done without thinking or feeling in control. [CHECKPOINT] How is control achieved in reflex actions? Touching a flame is urgent. If we consciously think about the pain and decide to move, it takes time because thinking involves complex interactions of many nerve impulses from many neurons. The thinking tissue is the brain, which sits in the forward end of the skull. If we relied on the brain for every urgent response, we might get burnt. The body solves this with a reflex arc. Instead of going to the brain, nerves detecting heat connect directly to nerves moving muscles. This connection happens in the spinal cord, where nerves from the body meet in a bundle. Reflex arcs allow quick responses. The information also reaches the brain, but the action happens first. Figure six point two illustrates the reflex arc. Receptors in the skin detect heat or pain. A sensory neuron carries the message to the spinal cord. A relay neuron connects it to a motor neuron. The motor neuron sends a message to the effector muscle in the arm, causing it to contract and pull the hand away. [CHECKPOINT] Can you trace the sequence when bright light is focused on your eyes? The receptors detect light, send a signal via sensory neurons to the brain, which processes it and sends a motor signal to the muscles controlling the pupil, causing it to constrict. The spinal cord does more than reflexes. The brain is the main coordinating center. The brain and spinal cord form the central nervous system. They receive and integrate information. We also think about actions like writing, talking, or clapping. These are voluntary actions based on deciding what to do next. The brain sends messages to muscles via the peripheral nervous system, consisting of cranial nerves from the brain and spinal nerves from the spinal cord. The brain has three major parts: fore-brain, mid-brain, and hind-brain. The fore-brain is the main thinking part. It receives sensory impulses for hearing, smell, sight, and has association areas that interpret information by combining it with stored knowledge. [CHECKPOINT] Based on this, decisions are made and passed to motor areas controlling voluntary muscles. The fore-brain also has a hunger center that tells us when we have eaten enough. Figure six point three shows the human brain. It is protected by the cranium or skull. The fore-brain is the largest part. The mid-brain is below it. The hind-brain includes the pons, medulla, and cerebellum. The spinal cord extends downward. Some actions, like mouth watering at food or heartbeat, are involuntary. We cannot control them by thinking. These are controlled by the mid-brain and hind-brain. The medulla in the hind-brain controls blood pressure, salivation, and vomiting. The cerebellum, also in the hind-brain, controls precision of voluntary actions and maintains posture and balance, like walking in a straight line or riding a bicycle. A delicate organ like the brain needs careful protection. It sits inside a bony box, and inside that, it is contained in a fluid-filled balloon for shock absorption. [CHECKPOINT] The spinal cord is protected by the vertebral column or backbone, which you can feel down the middle of your back. Nervous tissue collects, sends, and processes information, then conveys decisions to muscles. Muscle tissue performs the final action. When a nerve impulse reaches a muscle, the muscle fibre moves by changing shape and shortening. Muscle cells have special proteins that change shape and arrangement in response to electrical impulses, giving the cell a shorter form. Voluntary muscles are under conscious control, while involuntary muscles are not. Let us answer the questions from this section. Question one: What is the difference between a reflex action and walking? Reflex action is an automatic, involuntary response to a stimulus that does not involve conscious thought and is controlled by the spinal cord. Walking is a voluntary action that involves conscious thought, planning, and coordination by the brain. Question two: What happens at the synapse between two neurons? [CHECKPOINT] At the synapse, the electrical impulse triggers the release of chemicals from the axon end. These chemicals cross the synaptic gap and trigger a similar electrical impulse in the dendrite of the next neuron. Question three: Which part of the brain maintains posture and equilibrium? The cerebellum in the hind-brain maintains posture and equilibrium. Question four: How do we detect the smell of an agarbatti? Olfactory receptors in the nose detect the chemical molecules from the incense. They generate an electrical impulse that travels to the olfactory region of the fore-brain, where it is interpreted as the smell of agarbatti. Question five: What is the role of the brain in reflex action? The brain is not directly involved in generating the reflex action, as it is processed in the spinal cord. However, the brain receives the information about the stimulus and the response, making us aware of it. Animals use a nervous system, but plants lack nervous tissue and muscles. So, how do they respond to stimuli? [CHECKPOINT] When we touch the leaves of the sensitive plant, they fold and droop quickly. When a seed germinates, roots grow down and stems grow up. Plants show two movement types: one independent of growth, and one dependent on growth. The sensitive plant moves without growth. Information about touch must be communicated from the touched point to the moving point. Plants use electrical-chemical means, but lack specialized conducting tissue. Cells change shape by changing their water content, causing swelling or shrinking. Plants like peas climb using tendrils. Tendrils are touch-sensitive. When they contact a support, the touching side grows slower than the free side, causing the tendril to coil around the support. Plants also respond slowly by growing directionally. Let us do Activity six point two. Fill a conical flask with water. Cover the neck with wire mesh. Place two or three freshly germinated bean seeds on the mesh. [CHECKPOINT] Take a cardboard box open on one side. Place the flask inside so the open side faces window light. After two or three days, shoots bend toward light, roots bend away. Turn the flask so shoots face away from light and roots toward light. Leave it for a few days. You will observe that old parts do not change direction, but new growth bends toward light for shoots and away for roots. This shows phototropism. Environmental triggers like light or gravity cause directional growth called tropism. Movements can be toward or away from the stimulus. Shoots show positive phototropism, bending toward light. Roots show negative phototropism, bending away. Roots grow downward due to gravity, showing positive geotropism. Shoots grow upward, showing negative geotropism. Hydrotropism is growth toward water. Chemotropism is growth toward chemicals, like pollen tubes growing toward ovules. [CHECKPOINT] Fast responses need fast transmission like electrical impulses, but impulses only reach connected cells and require reset time. Most organisms use chemical communication. Stimulated cells release compounds that diffuse and are detected by receptors on other cells. These are hormones. Plant hormones coordinate growth and responses. Auxin is synthesized at the shoot tip. When light comes from one side, auxin diffuses to the shady side, stimulating longer cell growth there, causing the plant to bend toward light. Gibberellins help stem growth. Cytokinins promote cell division, found in fruits and seeds. Abscisic acid inhibits growth and causes leaf wilting. Let us answer the plant questions. Question one: What are plant hormones? Plant hormones are chemical compounds synthesized in one part of the plant that diffuse to other parts to coordinate growth, development, and environmental responses. Question two: How is sensitive plant leaf movement different from shoot movement toward light? [CHECKPOINT] Sensitive plant movement is rapid, independent of growth, and caused by water loss in cells. Shoot movement toward light is slow, growth-dependent, and caused by uneven auxin distribution. Question three: Give an example of a plant hormone that promotes growth. Auxin, gibberellins, and cytokinins promote growth. Question four: How do auxins promote tendril growth around a support? When a tendril touches a support, auxin moves to the opposite side, causing faster growth on that side, making the tendril coil around the support. Question five: Design an experiment for hydrotropism. Take a porous pot filled with water. Place it in a tray of dry soil. Plant a seedling in the soil near the pot. After a few days, observe that the roots grow toward the porous pot, demonstrating positive hydrotropism. Animals use hormones for coordination too. In scary situations, squirrels prepare to fight or run. This requires energy and tissue integration. [CHECKPOINT] Electrical impulses alone are limited. Chemical signals like adrenaline, secreted by adrenal glands, reach all cells via blood. Adrenaline targets the heart, making it beat faster for more oxygen. Blood flow to digestive system and skin reduces, diverting to skeletal muscles. Breathing rate increases due to diaphragm and rib muscle contractions. This prepares the body for action. This is the endocrine system. Look at Figure six point seven. It shows endocrine glands in humans. In males, it shows hypothalamus, pineal gland, pituitary gland, parathyroid glands, thymus, thyroid gland, pancreas, adrenal glands, and testes. In females, it shows the same except ovaries instead of testes. Hypothalamus plays an important role in releasing many hormones. For example, when growth hormone levels are low, the hypothalamus releases growth hormone releasing factor, which stimulates the pituitary gland to release growth hormone. [CHECKPOINT] Iodised salt is important because iodine is needed for the thyroid gland to make thyroxin. Thyroxin regulates carbohydrate, protein, and fat metabolism for balanced growth. Iodine deficiency causes goitre, characterized by a swollen neck. Growth hormone from the pituitary regulates body growth. Deficiency in childhood causes dwarfism. Puberty changes are due to testosterone in males and oestrogen in females. Insulin from the pancreas regulates blood sugar. Deficiency causes diabetes, treated with insulin injections. Hormone secretion is regulated by feedback mechanisms. For example, high blood sugar triggers pancreas to release more insulin. As sugar falls, insulin secretion reduces. Let us complete Table six point one. Row one: Growth hormone, Pituitary gland, Stimulates growth in all organs. Row two: Thyroxin, Thyroid gland, Regulates metabolism for body growth. Row three: Insulin, Pancreas, Regulates blood sugar level. [CHECKPOINT] Row four: Testosterone, Testes, Development of male sex organs and puberty changes. Row five: Oestrogen, Ovaries, Development of female sex organs, regulates menstrual cycle. Row six: Adrenaline, Adrenal gland, Prepares body for fight or flight response. Row seven: Releasing hormones, Hypothalamus, Stimulates pituitary gland to release hormones. Let us answer the animal hormone questions. Question one: How does chemical coordination take place in animals? It occurs through hormones secreted by endocrine glands into the bloodstream, which carry them to target organs to regulate physiological processes. Question two: Why is iodised salt advisable? Iodine is essential for thyroxin synthesis, which regulates metabolism and growth. Deficiency causes goitre. Question three: How does the body respond to adrenaline? Heart beats faster, blood flow shifts to muscles, breathing rate increases, and blood flow to digestive system and skin decreases, preparing for action. [CHECKPOINT] Question four: Why are diabetes patients given insulin injections? Their pancreas does not secrete enough insulin to regulate blood sugar, so external insulin is needed to lower blood glucose levels. Let us review what we have learnt. Control and coordination are functions of the nervous system and hormones. Nervous responses are reflex, voluntary, or involuntary. The nervous system uses electrical impulses, gets information from sense organs, and acts through muscles. Chemical coordination occurs in plants and animals. Hormones move from one part to another for desired effects. A feedback mechanism regulates hormone action. Now let us solve the chapter exercises completely. Question one: Which is a plant hormone? Answer: Cytokinin. Question two: The gap between two neurons is called a? Answer: Synapse. Question three: The brain is responsible for? Answer: All of the above, including thinking, regulating heartbeat, and balancing the body. [CHECKPOINT] Question four: What is the function of receptors? Problems if they fail? Receptors detect environmental stimuli and convert them into nerve impulses. If they fail, we cannot detect stimuli like heat, light, or sound, leading to injuries, inability to navigate, or loss of taste and smell. Question five: Draw neuron structure and explain function. A neuron has a cell body with a nucleus, dendrites that receive signals, and an axon that transmits signals. At the axon end are nerve endings that release chemicals at synapses. Its function is to conduct electrical impulses for communication. Question six: How does phototropism occur? Light causes auxin to accumulate on the shaded side of the shoot. This stimulates faster cell elongation there, bending the shoot toward light. Question seven: Which signals are disrupted in spinal cord injury? Reflex actions and communication between the brain and body parts below the injury are disrupted, causing loss of voluntary movement and sensation. [CHECKPOINT] Question eight: How does chemical coordination occur in plants? Plant hormones like auxin, gibberellins, cytokinins, and abscisic acid are synthesized in one part and diffuse to target areas to regulate growth and responses. Question nine: Need for control and coordination? To detect environmental changes and respond appropriately for survival, maintain internal balance, and coordinate organ functions. Question ten: Difference between involuntary and reflex actions? Involuntary actions are controlled by the brain and occur continuously without conscious thought, like digestion. Reflex actions are sudden, automatic responses to specific stimuli, controlled by the spinal cord. Question eleven: Compare nervous and hormonal mechanisms. Nervous system uses electrical impulses, acts quickly, targets specific muscles or glands, and has short-term effects. Hormonal system uses chemicals in blood, acts slowly, targets multiple organs, and has long-term, widespread effects. [CHECKPOINT] Question twelve: Difference in movement between sensitive plant and legs? Sensitive plant movement is due to water loss in cells, independent of growth, and lacks specialized tissues. Leg movement is due to muscle contraction triggered by nerve impulses, dependent on specialized proteins, and controlled by the nervous system. We have covered every concept, activity, and question in this chapter. Remember that control and coordination are vital for all living organisms, whether through rapid nerve impulses or steady chemical hormones. Review the diagrams, memorize the hormone functions, and practice the exercise questions thoroughly for your exams. Thank you for listening! Keep revising and practicing. Goodbye! [CHAPTER_COMPLETE]