Sunday, July 21, 2024

Control and Coordination

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NCERT Solutions for Class 10 Science Chapter 10

This chapter dives into the amazing world of how our bodies and plants maintain control and coordinate their functions. Here’s a quick breakdown of the key concepts:

In Animals:

  • Nervous System: The control center, sending messages through neurons (nerve cells) to various body parts. It can be categorized into:
    • Central Nervous System (CNS): Brain and spinal cord, responsible for processing information and sending commands.
    • Peripheral Nervous System (PNS): Network of nerves that carries messages between the CNS and muscles/glands (sensory and motor neurons).
  • Reflex Actions: Quick, involuntary responses to stimuli, not requiring conscious thought (e.g., knee jerk reflex).
  • Hormones: Chemical messengers produced by glands that travel through blood to target organs, influencing various processes (e.g., growth, development, metabolism).

In Plants:

  • Limited Nervous System: Plants lack a complex nervous system like animals.
  • Chemical Coordination: Hormones and other chemicals play a key role in communication and regulating growth, development, and responses to stimuli (e.g., light, touch).
  • Tropisms: Growth movements in response to external stimuli (e.g., phototropism – growth towards light).

Overall:

  • Both animals and plants have mechanisms to control and coordinate their internal functions and responses to the environment.
  • Animals use a combination of nervous and hormonal systems, while plants rely primarily on chemical coordination.

Additional points to remember:

  • The chapter also covers the structure and function of nephrons (kidney filtering units) and their role in maintaining water and electrolyte balance.
  • Importance of maintaining homeostasis (stable internal environment) for optimal functioning.

Questions (Page 105)

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

Ans : 

FeatureReflex ActionWalking
ControlInvoluntary (no conscious thought)Voluntary (requires conscious decision)
SpeedRapid (almost instant)Slower and adjustable
SpecificitySpecific stimulus-response (e.g., blink reflex)More variable (can change speed, direction)
Neural ControlSpinal cord reflex arcBrain and spinal cord coordination

2. What happens at the synapse between two neurons?

Ans : 

  1. Electrical signal arrives at the presynaptic neuron.
  2. Chemical messengers (neurotransmitters) jump across the gap.
  3. They bind to receptors on the postsynaptic neuron.
  4. This can either:
    • Excite the neuron (more likely to fire a signal).
    • Inhibit the neuron (less likely to fire a signal).
  5. Used neurotransmitters are cleaned up.

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

Ans : The part of the brain that maintains posture and equilibrium of the body is the cerebellum.

The cerebellum is located at the back of the brain, just above the brainstem. It’s like a coordination center, working with other parts of the nervous system to:

  • Receive sensory information about your body’s position and movement (from muscles, joints, inner ear).
  • Analyze this information and compare it to desired movements.
  • Send signals to adjust muscle activity to maintain balance and posture.
  • Help with coordination of complex movements like walking, running, and jumping.

So, the cerebellum acts like a fine-tuning knob, ensuring your body stays upright and moves smoothly.

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

Ans : Our sense of smell plays a vital role in our daily lives, allowing us to appreciate pleasant aromas like the burning of an agarbatti (incense stick).

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

Ans : Reflexes are fast, automatic actions (like knee jerk) and traditionally thought not to involve the brain. Here’s the update:

  • Brain Involvement? Maybe: While the spinal cord handles the main reflex arc, the brain might:
    • Fine-tune reflex strength (e.g., stronger pull away from a burning hot object).
    • Learn and adjust reflexes based on experience (e.g., less blinking after repeated touches).
    • Help coordinate complex reflexes (e.g., swallowing).

Brain and spinal cord work together for both quick reflexes and the ability to adapt them!

Questions (Page 108)

1. What are plant hormones ?

Ans : Plants can’t move around like animals, but they still need to control their growth, development, and response to their environment. That’s where plant hormones, also known as phytohormones, come in! These are chemical messengers produced within the plant that act in very low concentrations but have a big impact on various processes.

2. How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light ?

Ans : 

FeatureSensitive Plant (Thigmotropism)Shoot Towards Light (Phototropism)
Type of MovementRapid leaf folding and droopingSlower bending growth
Cause of MovementTouch or physical contactLight stimulus
MechanismDisruption of turgor pressureUnequal auxin distribution
SpeedVery fast (seconds)Slower (hours/days)
ReversibilityRecovers original positionMaintains bent position

3. Give an example of a plant hormone that promotes growth.

Ans : Auxin is a prime example of a plant hormone that promotes growth in various ways.

4. How do auxins promote the growth of a tendril around a support ?

Ans : Tendrils wrap around supports thanks to a clever auxin trick.

  1. Auxin (growth hormone) builds up on the side away from the touch.
  2. This side grows slower.
  3. The opposite side, with less auxin, grows faster.
  4. This unequal growth causes the tendril to bend and coil around the support for a secure grip.

5. Design an experiment to demonstrate hydrotropism.

Ans : This experiment aims to demonstrate how plant roots grow towards a source of water, a phenomenon known as hydrotropism.

Materials:

  • Two identical containers (e.g., beakers or jars)
  • Two lids or covers for the containers (optional)
  • Potting soil or seed starting mix
  • Seeds of a fast-germinating plant (e.g., beans, peas)
  • Water
  • Cotton balls (optional)
  • Ruler (optional)

Procedure:

  1. Prepare the Containers:
    • Fill one container (Container A) with moist potting soil, leaving about 1 inch of space at the top.
    • Fill the other container (Container B) with half moist potting soil and half dry potting soil (unwatered) or create a separation with a piece of cardboard or plastic in the middle. You can also use cotton balls soaked in water on one side of Container B (optional).
    • If using lids, poke small holes for ventilation (optional).
  2. Planting the Seeds:
    • Plant 2-3 seeds at an equal depth in the center of the moist soil in each container.
  3. Watering (Optional):
    • Lightly water Container A again to ensure the soil is moist throughout. Avoid overwatering.
  4. Placement:
    • Place both containers in a well-lit location with similar light conditions (e.g., a sunny windowsill).
  5. Observation:
    • Observe the containers daily for at least a week (or until root growth is evident).
    • You can gently brush away some soil to see the direction of root growth (optional).
    • Measure root length if desired (optional).

Expected Results:

  • The roots in Container A (with consistently moist soil) should grow straight down searching for water.
  • The roots in Container B (with one side dry or containing a water source) should show a preference for the moist side or cotton balls with water, exhibiting a bend towards the water source.

Conclusion:

By observing the root growth patterns in both containers, you can see how roots are sensitive to moisture and tend to grow in the direction of a water source. This demonstrates the phenomenon of hydrotropism in plants.

Questions (Page 111)

1. How does chemical coordination take place in animals ?

Ans : In animals, chemical coordination is achieved through a well-orchestrated interplay between two key systems:

  1. Endocrine System: This network of glands produces chemical messengers called hormones that travel through the bloodstream to reach target organs throughout the body. Hormones influence various processes like growth, development, metabolism, reproduction, and response to stress.
  2. Nervous System: This intricate network of neurons transmits electrical signals rapidly to specific organs or muscles. While the nervous system provides a fast, point-to-point communication, it doesn’t reach all cells directly.

2. Why is the use of iodised salt advisable ?

Ans : Iodized salt is regular salt with a tiny boost of iodine, a mineral our body needs for growth, development, and proper function. Lack of iodine can cause serious health problems, especially in children.

3. How does our body respond when adrenaline is secreted into the blood ?

Ans : Adrenaline, also known as epinephrine, is a hormone produced by the adrenal glands that plays a critical role in the “fight-or-flight” response. When adrenaline surges into your bloodstream, your body undergoes a series of dramatic changes to prepare you for immediate action in a perceived threat or danger.

4. Why are some patients of diabetes treated by giving injections of insulin ?

Ans : There are two main reasons why some diabetics need insulin injections:

  1. Type 1 Diabetes: In this type, the body’s immune system mistakenly attacks and destroys the insulin-producing cells in the pancreas. This means the body can’t produce any insulin on its own. Without insulin, sugar (glucose) can’t properly enter cells for energy, leading to high blood sugar levels (hyperglycemia). Insulin injections replace the missing insulin and help regulate blood sugar.
  2. Type 2 Diabetes: In this more common type, the body may still produce insulin, but it either doesn’t make enough or the cells become resistant to its effects. This can also lead to high blood sugar. While lifestyle changes and medications may be enough to manage Type 2 diabetes initially, some patients eventually require insulin injections if their body can’t keep blood sugar under control on its own.

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

(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 : (b) 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 : Receptors are specialized cells located throughout our body that detect changes in the environment, both internal and external. They act as sensory gatekeepers, constantly gathering information and sending it to the brain for processing.

Problems with Faulty Receptors:

  • Reduced or no sensation: If a receptor is damaged or malfunctioning, it can’t detect stimuli properly. This can lead to:
    • Vision problems: Difficulty seeing in dim light, blurry vision, or complete blindness (depending on the severity).
    • Hearing loss: Reduced ability to hear sounds or complete deafness.
    • Loss of taste or smell: Inability to taste or smell food or difficulty distinguishing flavors and aromas.
    • Loss of touch: Inability to feel pain, heat, or cold, potentially leading to injuries.
    • Problems with balance and coordination: Difficulty walking or maintaining balance due to faulty signals from inner ear receptors.
  • Phantom sensations: Sometimes, a malfunctioning receptor can send false signals to the brain, creating sensations that aren’t actually present (e.g., phantom limb pain).

5. Draw the structure of a neuron and explain its function.

Ans : A neuron, also known as a nerve cell, is the basic unit of the nervous system. It’s responsible for transmitting information throughout the body. Here’s a breakdown of its structure and function:

Structure:

  • Cell Body (Soma): The central part of the neuron containing the nucleus and other organelles, responsible for maintaining the cell’s life functions.
  • Dendrites: Branching, tree-like structures that receive signals from other neurons and transmit them towards the cell body.
  • Axon: A single, long fiber that carries electrical signals away from the cell body towards other neurons or muscles.
  • Myelin Sheath (optional): A fatty insulating layer surrounding the axon in some neurons, which speeds up the transmission of electrical signals.
  • Synapse: The junction between the axon of one neuron and the dendrite of another neuron or a muscle cell. This is where the signal is transmitted from one cell to another.

Function:

Neurons communicate through electrical signals called action potentials. Here’s the basic process:

  1. Receiving Information: Sensory neurons receive stimuli from the environment (light, sound, touch, etc.) through their dendrites.
  2. Generating a Signal: If the stimulus is strong enough, an electrical signal (action potential) is generated in the cell body.
  3. Sending the Signal: The action potential travels down the axon, aided by the myelin sheath in some cases.
  4. Transmission at the Synapse: At the synapse, the electrical signal triggers the release of chemical messengers called neurotransmitters.
  5. Receiving Neuron or Muscle: Neurotransmitters bind to receptors on the dendrite of another neuron or a muscle cell.
  6. Action or Response: Depending on the neurotransmitter and receptor interaction, the receiving neuron may generate its own action potential, or a muscle cell may contract.

6. How does phototropism occur in plants ?

Ans : Plants bend towards light in a phenomenon called phototropism. Here’s the exciting science behind it:

  1. Light Detection: The tips of shoots (stems) and roots contain special plant hormones called auxins. These auxins are sensitive to light.
  2. Unequal Auxin Distribution: When light hits a plant from one side, auxin gets unevenly distributed within the shoot tip.
  3. Auxin’s Influence on Growth: Auxin generally promotes cell elongation. However, in phototropism, auxin plays a bit of a sneaky trick.
  4. Shaded Side Grows Faster: Light exposure reduces the amount of active auxin on the side of the shoot facing the light. This allows the cells on the shaded side, with more active auxin, to elongate faster.
  5. The Plant Bends: As the shaded side grows longer and pushes outwards, the entire shoot bends towards the light source. This differential growth steers the plant in the direction of sunlight.
  6. Continuous Process: Phototropism is a continuous process. As the plant bends, the auxin distribution keeps adjusting, ensuring the plant continues to grow towards the light source.

7. Which signals will get disrupted in case of a spinal cord injury ?

Ans : In the unfortunate event of a spinal cord injury, both the signals traveling down the spinal cord from the brain to control muscles and the signals traveling up the spinal cord to the brain from the body are disrupted. This disruption can lead to varying degrees of paralysis and sensory loss depending on the severity and location of the injury.

8. How does chemical coordination occur in plants ?

Ans : Plants, unlike animals with a nervous system, rely on chemical messengers to coordinate their growth, development, and response to the environment. This fascinating process is called chemical coordination.

9. What is the need for a system of control and coordination in an organism ?

Ans : Organisms need control and coordination for two main reasons:

  1. Maintain Internal Balance (Homeostasis): Control systems keep vital aspects like temperature and blood sugar stable, ensuring the organism functions properly.
  2. Respond Effectively: The ability to sense and react to the environment (like a predator) is crucial for survival. Control systems trigger responses like fight-or-flight for appropriate action.

10. How are involuntary actions and reflex actions different from each other ?

Ans : 

FeatureInvoluntary ActionsReflex Actions
OriginBrain (brainstem)Spinal Cord
SpeedSlow or fastVery rapid
ExamplesHeartbeat, breathingKnee jerk, hot object withdrawal
Conscious ControlLimited or noNo

11. Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.

Ans : 

FeatureNervous SystemEndocrine System
CommunicationElectrical signalsChemical messengers (hormones)
SpeedFast (milliseconds)Slow (seconds to minutes)
SpecificityTargetedWidespread effects
Duration of EffectShort-termLong-term

12. What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs ?

Ans : 

FeatureSensitive PlantOur Legs
MechanismTurgor pressure changes in cellsMuscle contraction and relaxation
StimulusExternal touch or stimuli (not voluntary)Voluntary control by nervous system
SpeedSlow, passive responseWide range: slow, controlled to fast (sprinting)
Movement ControlLimited in direction and rangeWide range of complex movements
Specialized TissueNoneSkeletal and muscular systems
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