CONTROL AND COORDINATION: FULL CHAPTER

1. Introduction to the Concept of Movement in Living Organisms:
• In the previous chapter, we explored the life processes related to the maintenance functions in living organisms.
• One common notion is that we associate movement with life; if something is moving, we tend to consider it alive.
2. Types of Movements in Living Organisms:
• Some movements in organisms are a result of growth, like in plants. For example, when a seed germinates and grows, we observe the seedling pushing through the soil.
• However, not all movements are linked to growth. Animals and certain plants exhibit movements that are independent of their growth. Examples include a cat running, children on swings, or buffaloes chewing cud.
3. The Association of Movement with Life:
• We tend to associate visible movements with life because we perceive them as responses to changes in the organism's environment.
• These movements are often seen as efforts by living organisms to adapt to changes in their surroundings for their benefit.
4. Movement as a Response to Environmental Changes:
• For instance, a running cat might be responding to the presence of a mouse.
• Living organisms use environmental changes to their advantage through movement. Plants grow towards sunlight, children seek pleasure in swinging, and buffaloes chew cud to aid digestion of tough food.
5. Controlled and Purposeful Movements:
• It's crucial to note that the movements in response to the environment are not random; they are carefully controlled.
• Different environmental changes trigger specific movements. For instance, we whisper when talking to friends in class rather than shouting, showing that the appropriate movement depends on the situation.
6. The Role of Recognition and Coordination:
• To achieve such controlled movements, living organisms must possess systems for recognizing various events in their environment.
• Recognition of environmental events is followed by the execution of the correct, coordinated movement in response.
7. Specialized Tissues for Control and Coordination:
• To facilitate this recognition and coordination, multicellular organisms employ specialized tissues.
• These specialized tissues play a vital role in providing control and coordination activities within the organism, aligning with the general principles of body organization in multicellular beings.

Role of Nervous System in Animals:

1. In animals, control and coordination are facilitated by nervous and muscular tissues.
2. These tissues play a vital role in responding to urgent and potentially dangerous situations, such as touching a hot object.

Detection of Environmental Information: 3. To detect changes in the environment, specialized nerve cells with receptor tips are employed.

4. These receptors are typically found in sense organs like the inner ear, nose, tongue, and others.
5. Different types of receptors, such as gustatory for taste and olfactory for smell, are responsible for detecting specific environmental cues.

Transmission of Information within Neurons: 6. Information acquired by these receptors triggers a chemical reaction that generates an electrical impulse at the dendritic tip of a nerve cell.

7. This electrical impulse then travels from the dendrite to the cell body and along the axon to its endpoint.
8. At the axon's endpoint, the electrical impulse initiates the release of certain chemicals.
9. These chemicals cross a synapse (a gap) and stimulate a similar electrical impulse in the dendrite of the next neuron.
10. This process represents the general scheme of how nervous impulses travel within the body.

Delivery of Impulses to Other Cells:

       11. A similar synapse allows the transmission of nervous impulses from neurons to other cells, such as muscle cells or glands.

Structure of Nervous Tissue:

      12. Nervous tissue is structured as an organized network of nerve cells, or neurons.

13. It is specialized for transmitting information via electrical impulses from one part of the body to another.

Impact of Blocked Nose on Taste:

       14. When your nose is blocked, there can be a difference in how sugar and food taste.

15. This variation occurs because the sense of taste is closely linked to the sense of smell.
16. The receptors responsible for detecting smell are located in the nasal passages.
17. When the nose is blocked, the ability to detect certain odor molecules is diminished, impacting the overall perception of flavor.
18. A similar situation may be experienced when you have a cold due to nasal congestion.

Reflex Actions in Response to Bright Light:

1. Common Understanding of Reflex Actions:
• Reflex actions are immediate responses to environmental stimuli that occur without conscious thought or control.
• Examples include quickly jumping out of the way of a bus, pulling one's hand away from a flame, or experiencing mouthwatering due to hunger.
2. Control and Coordination in Reflex Actions:
• Reflex actions involve responding to changes in the environment.
• Despite the lack of conscious thought or control, the body still exhibits purposeful actions in response to stimuli.
3. Response to a Dangerous Stimulus - Touching a Flame:
• Touching a flame is a dangerous situation for humans and animals alike.
4. Conscious Thinking vs. Reflexive Response:
• One way to respond to touching a flame would be to consciously think about the pain and the risk of getting burned before moving the hand away.
• However, thinking involves the transmission of nerve impulses, which can be a complex and time-consuming process.
5. Complex Nature of Thinking:
• Thinking is a complex activity that requires interactions among many nerve impulses from multiple neurons.
6. Thinking Tissue in the Brain:
• The thinking part of the brain, located in the forward end of the skull, receives signals from all parts of the body.
• It processes these signals before generating responses.
7. Need for Quick Response:
• In urgent situations like touching a hot object, relying solely on conscious thought may result in significant delay, potentially causing burns.
8. Role of Reflex Arcs:
• To address this issue, the body utilizes reflex arcs, which are efficient neural pathways for rapid responses to stimuli.
• Reflex arcs allow for a more direct connection between sensory input and motor output.
9. Location of Reflex Arc Connections:
• Reflex arc connections are typically made where sensory nerves first meet motor nerves.
• These connections are often formed within the spinal cord, where nerves from different parts of the body converge on their way to the brain.
10. The Efficiency of Reflex Arcs:
• Reflex arcs are evolutionarily advantageous because they provide swift responses, especially in situations where complex neural processing (thinking) is not necessary.
• Even in organisms with complex neural networks for thinking, reflex arcs remain efficient for quick reactions to immediate threats.
11. Sequence of Events in Reflex Actions:
• When a bright light is focused on your eyes, the following sequence of events occurs within a reflex arc:
• Sensory receptors in the eyes detect the intense light.
• Nerve impulses are generated and transmitted through sensory nerves.
• These impulses quickly reach the spinal cord, where a reflex arc is formed.
• In the spinal cord, a rapid response is generated without the need for conscious thought.
• Motor nerves carry the response signal to the muscles controlling the eye's reaction.
• The eye responds by contracting the iris or squinting, reducing the amount of light entering the eye and protecting it from potential harm.

Functions of the Human Brain and Spinal Cord:

1. Reflex Actions vs. Complex Functions:
• Reflex actions are not the only functions of the spinal cord. Humans possess complex thinking abilities.
• The spinal cord contains nerves that transmit information, while thinking involves more intricate mechanisms and neural connections, primarily located in the brain.
2. Central Nervous System (CNS):
• The central nervous system comprises the brain and spinal cord.
• It receives information from all parts of the body and integrates it.
3. Voluntary Actions and Muscle Control:
• Voluntary actions, like writing, talking, and moving objects, result from conscious decision-making.
• The brain sends messages to the muscles, facilitating voluntary actions.
• This communication between the central nervous system and muscles is the second way in which the nervous system functions.
4. Peripheral Nervous System (PNS):
• The peripheral nervous system includes cranial nerves arising from the brain and spinal nerves arising from the spinal cord.
• It facilitates communication between the central nervous system and other body parts.
5. Brain's Role in Thinking and Decision-Making:
• The brain enables thinking and taking actions based on that thinking.
• It consists of different regions responsible for various functions.
6. Three Major Parts of the Brain:
• The brain has three major regions: the fore-brain, mid-brain, and hind-brain.
7. Fore-Brain:
• The fore-brain is the primary thinking part of the brain.
• It contains regions specialized for receiving sensory impulses from various receptors.
• Separate areas within the fore-brain handle hearing, smell, sight, and other senses.
• Association areas in the fore-brain interpret sensory information by integrating it with data from other receptors and stored information.
• Decisions are made based on this interpretation and transmitted to motor areas that control voluntary muscle movement.
• Certain sensations, such as feeling full after eating, are associated with specific centers within the fore-brain.
8. Mid-Brain and Hind-Brain:
• The mid-brain and hind-brain control involuntary actions, which occur without conscious thought.
• These actions include heartbeat, digestion, and other functions.
• The medulla in the hind-brain governs various involuntary actions like blood pressure, salivation, and vomiting.
• The cerebellum, a part of the hind-brain, is responsible for precise voluntary actions, posture maintenance, and balance of the body.
9. Involuntary Muscle Movements:
• Between simple reflex actions and thought-out actions, there exists a category of muscle movements over which we have no conscious control.
• Examples include salivation, heartbeats, and digestion.
• The mid-brain and hind-brain regulate many of these involuntary actions.
10. Role of the Medulla:
• The medulla in the hind-brain is responsible for controlling various involuntary functions, ensuring their proper operation.
11. Cerebellum's Role:
• The cerebellum, located in the hind-brain, plays a crucial role in enabling precision in voluntary actions and maintaining body posture and balance.

Protection of Delicate Organs - Brain and Spinal Cord:

1. Brain Protection:
• The brain, a vital and delicate organ responsible for numerous bodily functions, requires careful protection.
• The body is designed with a specific safeguard: the brain is situated within a protective bony enclosure.
2. Bony Enclosure for the Brain:
• The brain is housed within a bony box, which provides a sturdy physical barrier.
• This bony box or cranial cavity shields the brain from external impacts and injuries.
3. Fluid-Filled Balloon Surrounding the Brain:
• Inside the protective cranial cavity, the brain is further safeguarded by a fluid-filled balloon-like structure.
• This cerebrospinal fluid-filled space provides additional shock absorption, preventing damage to the brain during sudden movements or impacts.
4. Spinal Cord Protection:
• Similar to the brain, the spinal cord, which is an extension of the central nervous system, requires protection.
• The vertebral column, commonly known as the backbone, serves as the protective structure for the spinal cord.
5. The Role of the Vertebral Column:
• Running your hand down the middle of your back, you can feel a hard and somewhat bumpy structure.
• This structure is the vertebral column, or backbone, consisting of a series of individual vertebrae.
6. Protection of the Spinal Cord:
• The vertebral column envelops and shields the spinal cord from external harm.
• It acts as a protective casing for the spinal cord, helping to prevent injury to this essential neural pathway.

How Nervous Tissue Causes Action:

1. Overview of Nervous Tissue Functions:
• Nervous tissue plays a crucial role in collecting information, transmitting it throughout the body, processing data, making decisions based on this information, and conveying decisions to muscles for action.
2. Role of Muscle Tissue in Action:
• When it comes to executing actions or movements, the final task is performed by muscle tissue.
3. Muscle Cell Movement:
• For muscle cells to move, they must change their shape, typically by shortening.
4. Mechanism of Muscle Cell Shape Change:
• Muscle cells achieve shape change through chemical processes within their cellular components.
5. Special Proteins in Muscle Cells:
• Muscle cells contain specific proteins that can alter both their shape and arrangement within the cell in response to electrical impulses from nerves.
6. Result of Protein Rearrangement:
• When these proteins rearrange in response to nerve impulses, the muscle cells assume a shorter form.
7. Different Types of Muscles:
• In previous discussions in Class IX, we learned about various types of muscles, including voluntary muscles and involuntary muscles.
8. Differences Between Voluntary and Involuntary Muscles:
• Voluntary muscles are under conscious control, meaning individuals can decide when to activate them, and they typically move in response to conscious commands.
• Involuntary muscles, on the other hand, function automatically without conscious effort or control.

 

 

Answer the questions.

1. What is the difference between a reflex action and walking?

2. What happens at the synapse between two neurons?

3. Which part of the brain maintains posture and equilibrium of the body?

4. How do we detect the smell of an agarbatti (incense stick)?

5. What is the role of the brain in reflex action?

 

1. Difference between a Reflex Action and Walking:
• Reflex Action:
• Reflex actions are involuntary and automatic responses to specific stimuli.
• They do not involve conscious thought and occur rapidly.
• Reflex actions are typically protective or defensive in nature, such as withdrawing a hand from a hot object.
• Walking:
• Walking is a voluntary action.
• It requires conscious control and coordination of muscles.
• Walking involves a series of voluntary muscle contractions and relaxation, coordinated by the brain, to move the body in a desired direction.
2. What Happens at the Synapse between Two Neurons:
• At the synapse between two neurons, the following events occur:
• When an electrical impulse (action potential) reaches the end of the axon of the presynaptic neuron, it triggers the release of chemical neurotransmitters.
• These neurotransmitters are released into the synaptic cleft, the tiny gap between the presynaptic neuron's axon terminal and the dendrite of the postsynaptic neuron.
• The neurotransmitters then bind to specific receptor sites on the membrane of the postsynaptic neuron.
• This binding leads to changes in the postsynaptic neuron's electrical charge, either depolarizing it (excitatory effect) or hyperpolarizing it (inhibitory effect).
• If the change in electrical charge is significant enough, it may generate an action potential in the postsynaptic neuron, continuing the transmission of the nerve impulse.
3. Part of the Brain that Maintains Posture and Equilibrium:
• The part of the brain responsible for maintaining posture and equilibrium (balance) of the body is the cerebellum, which is located in the hind-brain.
4. How We Detect the Smell of an Agarbatti (Incense Stick):
• When we detect the smell of an agarbatti or incense stick, it involves the olfactory system:
• Odor molecules from the incense stick are released into the air.
• These odor molecules enter our nasal passages during inhalation.
• Within the nasal passages, specialized olfactory receptors detect the presence of these molecules.
• These receptors send signals to the olfactory bulb in the brain.
• The brain processes these signals and interprets them as a particular smell, allowing us to perceive the aroma of the incense.
5. Role of the Brain in Reflex Action:
• The brain plays a role in reflex actions by:
• Receiving sensory information from the body, including signals from sensory receptors that detect stimuli.
• Processing this sensory information.
• Making decisions based on the sensory input, such as whether to initiate a reflex response or not.
• Sending signals to motor neurons and muscles to execute the reflex action.
• In some cases, the brain may also inhibit or modulate reflex responses based on higher cognitive functions, especially in situations where conscious thought and control are involved.

 

Coordination in Plants:

1. Absence of Nervous System and Muscles:
• Unlike animals, plants lack a nervous system and muscles for controlling and coordinating their activities.
2. Plant Responses to Stimuli:
• Plants are capable of responding to stimuli in their environment despite the absence of a nervous system.
• Their responses are a result of specialized mechanisms.
3. Example: 'Sensitive' or 'Touch-Me-Not' Plant (Mimosa family):
• When the leaves of a sensitive plant (chhui-mui) are touched, they exhibit rapid folding and drooping.
• This movement in the sensitive plant is quick and responsive to touch, and it does not involve growth.
4. Example: Seed Germination:
• During seed germination, the root grows downward into the soil, while the stem grows upward into the air.
• This directional movement of a seedling is a result of growth.
5. Two Types of Plant Movement:
• Plants display two distinct types of movement:
• Movement Dependent on Growth:
• Growth-related movement occurs when plant parts like roots and stems change their positions as they grow.
• Inhibited growth results in a lack of movement in these cases.
• Movement Independent of Growth:
• Some plant responses, such as the folding of sensitive plant leaves upon touch, are rapid and do not involve growth processes.
• These movements are immediate reactions to stimuli in the environment.

Immediate Plant Response to Stimuli (e.g., Touch):

1. Absence of Nervous and Muscle Tissues:
• Unlike animals, plants lack both nervous tissue and muscle tissue for sensing and responding to stimuli.
2. Detection of Touch:
• When a plant, like the sensitive plant, is touched, it needs to detect the touch without having specialized sensory organs.
3. Communication of Touch Information:
• Movement in response to touch occurs at a different location than the point of touch.
• To facilitate this movement, the plant must convey information about the touch event.
4. Absence of Specialized Information-Conducting Tissue:
• Unlike animals, plants do not possess specialized tissue for the conduction of information.
• Instead, they use electrical-chemical means to transmit information from one cell to another.
5. Role of Changing Cell Shape:
• In both animals and plants, some cells must change shape to enable movement.
• In plants, rather than specialized proteins like those in animal muscle cells, cell shape changes occur by altering the water content within the cells.
• This change in water content leads to swelling or shrinking of plant cells, resulting in changes in their shapes.
6. Immediate Response Mechanism in Plants:
• The immediate response to stimuli, such as touch, in plants involves:
• Detection of the stimulus by specialized cells.
• Transmission of information about the stimulus through electrical-chemical means, even in the absence of dedicated information-conducting tissue.
• Changing cell shapes through water content adjustments, which leads to rapid movement, as seen in the folding of sensitive plant leaves.

Plant Movements and Hormonal Coordination:

1. Variety in Plant Responses to Stimuli:
• Plants exhibit different responses to stimuli in their environment.
• These responses can be categorized into immediate movements and slow, directional growth movements.
2. Immediate Movements - Example: Sensitive Plant (Mimosa):
• In immediate responses, such as the folding of sensitive plant leaves upon touch, there is no growth involved.
• Touch detection and leaf movement are rapid but do not involve growth.
3. Directional Growth Movements:
• Some plant responses involve directional growth, where plant parts grow in a particular direction in response to external stimuli.
• These movements are relatively slow but contribute to the plant's ability to adapt to its environment.
4. Phototropic Movements:
• Environmental triggers like light or gravity influence the direction of plant growth.
• Phototropic movements can be either towards the stimulus (positive phototropism) or away from it (negative phototropism).
• Example: Shoots bending towards light (positive phototropism) while roots bending away from it (negative phototropism).
5. Geotropism - Response to Gravity:
• Roots typically exhibit positive geotropism (grow towards gravity), while shoots display negative geotropism (grow away from gravity).
• These growth responses help roots penetrate the soil and shoots grow upwards into the air.
6. Hydrotropism and Chemotropism:
• Hydrotropism refers to plant growth responses towards water.
• Chemotropism relates to growth influenced by chemicals.
• Examples and specific instances of these directional growth movements can be found in plant behavior.
7. Role of Plant Hormones:
• Hormones play a crucial role in coordinating plant growth, development, and responses to the environment.
• Different plant hormones regulate various aspects of plant physiology.
8. Auxin Hormone and Phototropic Growth:
• Auxin is a hormone synthesized at the shoot tip.
• When light comes from one side of the plant, auxin diffuses towards the shaded side.
• Higher auxin concentration on the shaded side stimulates cell elongation and growth on that side.
• This growth results in the plant appearing to bend towards the light source.
9. Other Plant Hormones:
• Gibberellins and auxins promote stem growth.
• Cytokinins encourage cell division, especially in fruits and seeds.
• Abscisic acid inhibits growth and can lead to effects like wilting of leaves.
10. Diversity in Plant Hormones:
• Plant hormones vary in their functions, promoting or inhibiting growth and responding to specific environmental cues.
11. Hormonal Coordination in Plants:
• Plant hormones are synthesized at one location and can diffuse to the areas where they are needed for specific actions.
• They help plants adapt to their surroundings by regulating growth, development, and responses to stimuli.

 

Answer the following questions

1. What are Plant Hormones?
• Plant hormones, also known as phytohormones, are chemical substances produced by plants in minuscule amounts that regulate various physiological processes within the plant. These hormones control growth, development, responses to stimuli, and coordination of plant activities.
2. Difference Between the Movement of Leaves of the Sensitive Plant and the Movement of a Shoot Towards Light:
• Movement of Leaves of the Sensitive Plant:
• The movement of leaves in the sensitive plant (like Mimosa) is an immediate response to touch or stimuli.
• It is rapid and does not involve growth; instead, it results from the rapid changes in the turgor pressure within cells, leading to leaf folding and drooping.
• Movement of Shoot Towards Light (Phototropic Movement):
• Shoots exhibit phototropic movement towards a light source.
• This movement is relatively slow compared to the immediate response of the sensitive plant.
• Phototropic movement involves growth towards the light source, where the plant's cells elongate on the shaded side, causing the shoot to bend towards the light.
3. Example of a Plant Hormone that Promotes Growth:
• Auxins are a class of plant hormones that promote the growth of plant tissues, especially in the context of cell elongation and expansion. They are responsible for phototropic and geotropic responses.
4. How Auxins Promote the Growth of a Tendril Around a Support:
• When a tendril of a plant like a pea plant comes in contact with a support, it detects the touch or support.
• Auxins, a plant hormone, accumulate on the side of the tendril away from the support.
• This uneven distribution of auxin leads to more rapid cell elongation on the side without support.
• As a result, the tendril bends and curls around the support structure, effectively allowing the plant to cling to it.
5. Experiment to Demonstrate Hydrotropism:
• Objective: To demonstrate hydrotropism, the directional growth response of plant roots towards a water source.
• Materials:
• Several small potted plants with well-established root systems
• Plastic containers
• Water
• Measuring tools
• Labels
• Light source
• Procedure:

1.                   Label the potted plants to keep track of their conditions.

2.                   Fill plastic containers with a uniform layer of soil.

3.                   Place one potted plant in each container and ensure that the roots are evenly buried in the soil.

4.                   Position the containers in an area with uniform light conditions.

5.                   Water the containers evenly so that the soil is moist but not saturated.

6.                   Observe and measure the initial direction of root growth (e.g., straight down).

7.                   Create a water source by placing a container filled with water at one side of the plants.

8.                   Ensure that the water source is at a distance from the plants, allowing the roots to respond to the moisture gradient.

9.                   Over several days, monitor the direction of root growth and record any changes.

10.               Compare the growth direction of roots towards the water source to demonstrate hydrotropism.

Questions for Experiment:

• What is the initial direction of root growth before introducing the water source?
• Do the roots exhibit a change in growth direction over time in response to the water source?
• Is there a noticeable difference in the growth pattern between plants exposed to the water source and those without it?

This experiment will illustrate how plant roots respond to moisture gradients and demonstrate hydrotropism, where roots grow in the direction of a water source.

Hormones in Animals and Their Functions:

1. Adrenaline in Response to Stress:
• Animals, including humans, use hormones like adrenaline to respond to stressful situations.
• When animals face danger, their bodies prepare for either fighting or fleeing.
• Adrenaline is secreted by the adrenal glands and released into the bloodstream.
• Adrenaline acts on target organs and tissues, including the heart, to facilitate immediate responses.
• Effects of adrenaline include increased heart rate, redirection of blood flow to muscles, and increased breathing rate.
2. Endocrine System:
• Adrenaline and other hormones are part of the endocrine system in animals.
• The endocrine system uses chemical signals (hormones) to coordinate various functions in the body.
3. Hormones vs. Plant Growth:
• Unlike plants that use hormones for directional growth responses, animal hormones serve different functions.
• Animals do not exhibit directional growth in response to hormones like plants.
4. Controlled Growth in Animals:
• Growth in animals is carefully regulated in specific regions of the body.
• Unlike plants that grow leaves in multiple locations, animals have controlled body designs even during growth.
5. Iodine and Thyroxin Hormone:
• Iodine is essential for the synthesis of thyroxin hormone, produced by the thyroid gland.
• Thyroxin regulates metabolism, including carbohydrate, protein, and fat metabolism.
• Iodine deficiency can lead to conditions like goitre, characterized by a swollen neck.
6. Growth Hormone and Dwarfism:
• The pituitary gland secretes growth hormone, which regulates growth and development.
• Growth hormone deficiency during childhood can result in dwarfism.
7. Puberty and Sex Hormones:
• During puberty, dramatic changes occur in appearance due to the secretion of sex hormones.
• Males produce testosterone, while females produce estrogen, leading to secondary sexual characteristics.
8. Insulin and Blood Sugar Regulation:
• Insulin is a hormone produced by the pancreas to regulate blood sugar levels.
• Insufficient insulin secretion can lead to diabetes, causing adverse effects on health.
• Feedback mechanisms regulate hormone secretion, ensuring the precise timing and quantity of hormones.
• For example, when blood sugar levels rise, the pancreas produces more insulin, and as levels fall, insulin secretion decreases.

 

1. How does chemical coordination take place in animals?
• Chemical coordination in animals occurs through the endocrine system, which involves the production and release of hormones.
• Hormones are chemical messengers secreted by various glands in the body.
• These hormones travel through the bloodstream and target specific organs or tissues, where they initiate specific responses or regulate physiological processes.
• The timing and amount of hormone secretion are regulated by feedback mechanisms to maintain homeostasis in the body.
2. Why is the use of iodised salt advisable?
• The use of iodised salt is advisable because iodine is essential for the production of thyroxin, a hormone produced by the thyroid gland.
• Thyroxin regulates various metabolic processes in the body, including carbohydrate, protein, and fat metabolism.
• Iodine deficiency can lead to thyroid-related disorders, such as goitre, characterized by a swollen neck.
• Iodised salt helps ensure an adequate intake of iodine, preventing these health issues.
3. How does our body respond when adrenaline is secreted into the blood?
• When adrenaline is secreted into the blood, the body undergoes various physiological responses to prepare for fight or flight in response to a stressful situation.
• These responses include:
• Increased heart rate: Adrenaline stimulates the heart to beat faster, providing more oxygen to muscles.
• Redistribution of blood flow: Blood is diverted from the digestive system and skin to skeletal muscles, enhancing physical readiness.
• Increased breathing rate: Adrenaline causes the diaphragm and rib muscles to contract, resulting in faster breathing.
• These combined effects make the body ready to respond quickly and effectively to a perceived threat.
4. Why are some patients of diabetes treated by giving injections of insulin?
• Some patients with diabetes are treated with insulin injections because their bodies do not produce or use insulin effectively.
• Insulin is a hormone produced by the pancreas that regulates blood sugar levels by facilitating the uptake of glucose into cells.
• In diabetes, either the pancreas does not produce enough insulin (Type 1 diabetes) or the body's cells do not respond properly to insulin (Type 2 diabetes).
• Insulin injections provide the necessary hormone to help cells absorb glucose, lowering blood sugar levels and preventing the harmful effects of high blood sugar, such as organ damage and complications.

 

1. Which of the following is a plant hormone?
• (d) Cytokinin.
2. The gap between two neurons is called a
• (b) Synapse.
3. The brain is responsible for
• (d) All of the above. (Thinking, regulating the heart beat, balancing the body)
4. What is the function of receptors in our body?
• Receptors in our body detect various stimuli or changes in the environment and convert them into electrical signals that can be interpreted by the nervous system. They play a crucial role in sensing external and internal changes and allow organisms to respond appropriately.
• When receptors do not work properly, it can lead to sensory deficiencies or incorrect responses to stimuli. For example, if the receptors for temperature sensation in the skin are damaged, a person may not be able to feel hot or cold objects, increasing the risk of burns or frostbite.
5. Draw the structure of a neuron and explain its function.
• I'm unable to draw diagrams, but I can describe the structure and function of a neuron.
• A neuron consists of:
• Cell body (soma): Contains the nucleus and other organelles.
• Dendrites: Branch-like extensions that receive incoming signals.
• Axon: A long, slender projection that conducts electrical impulses away from the cell body.
• Myelin sheath: A fatty insulating layer around the axon that speeds up signal transmission.
• Axon terminals: The ends of the axon that release neurotransmitters to transmit signals to other neurons or target cells.
• Neurons transmit electrical impulses (nerve impulses) from one part of the body to another. Dendrites receive signals, and if the signal is strong enough, it travels down the axon. At the axon terminals, neurotransmitters are released to transmit the signal to the next neuron or target cell.
6. How does phototropism occur in plants?
• Phototropism is the directional growth of plant parts in response to light.
• When light is detected by photoreceptors (like phototropins) in plant cells, it triggers the transport of the hormone auxin towards the shaded side of the plant.
• Higher auxin concentration on the shaded side stimulates cell elongation and growth, causing the plant to bend towards the light source.
7. Which signals will get disrupted in case of a spinal cord injury?
• In case of a spinal cord injury, the signals transmitted through the spinal cord would be disrupted. These signals include sensory information from the body to the brain and motor signals from the brain to muscles. As a result, there could be a loss of sensation, paralysis, or impaired muscle function below the level of the injury.
8. How does chemical coordination occur in plants?
• Chemical coordination in plants involves the use of plant hormones, also called phytohormones, to regulate growth, development, and responses to the environment.
• Plant hormones are synthesized at specific sites in the plant and are transported to target tissues or organs through the vascular system.
• These hormones, such as auxins, cytokinins, gibberellins, and abscisic acid, play roles in processes like phototropism, gravitropism, flowering, and stress responses.
9. What is the need for a system of control and coordination in an organism?
• A system of control and coordination is essential in organisms to:
• Respond to changes in the environment for survival.
• Regulate internal processes and maintain homeostasis.
• Coordinate various physiological functions and activities.
• Adapt to external and internal stimuli.
• Ensure efficient communication between cells, tissues, and organs.
10. How are involuntary actions and reflex actions different from each other?
• Involuntary actions are physiological responses or movements that occur without conscious control, such as heartbeat, digestion, and breathing.
• Reflex actions are rapid, involuntary responses to specific stimuli, typically involving a sensory receptor, sensory neuron, motor neuron, and an effector organ. Reflexes are protective and occur without conscious thought.
11. Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.
• Nervous System:
• Involves electrical impulses transmitted through neurons.
• Rapid communication and immediate responses.
• Localized effects and specific target cells.
• Short-duration responses.
• Endocrine (Hormonal) System:
• Involves chemical signals (hormones) released into the bloodstream.
• Slower communication and gradual responses.
• Widespread effects, affecting many cells or organs.
• Longer-duration responses.
• Both systems work together to regulate various physiological processes in animals.
12. What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs?
• Movement in a sensitive plant (like Mimosa pudica) is a rapid, reversible response to touch or mechanical stimuli. It involves the rapid folding and drooping of leaflets in response to touch, but this movement does not involve growth.
• Movement in our legs (muscle movement) is typically controlled and voluntary. It involves muscle contraction and skeletal movement, allowing us to walk, run, or perform various actions. This movement is conscious and controlled by the nervous system.