E X E R C I S E S CHAPTER 6 Control and Coordination SCIENCE NCERT TEXTBOOK (CBSE) CLASS 10:

 E X E R C I S E S  

CHAPTER  6  Control and  Coordination


1. Which of the following is a plant hormone?

Answer: (c) Cytokinin

Cytokinin is a plant hormone that promotes cell division and growth in plants.

2. The gap between two neurons is called a:

Answer: (d) Synapse

The synapse is the gap between two neurons where neurotransmitters are released to transmit signals.

3. The brain is responsible for:

Answer: (d) All of the above

The brain is responsible for thinking, regulating heartbeats, and balancing the body.

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?

Receptors in our body detect stimuli (like light, sound, touch, or chemicals) and send signals to the brain for interpretation. If receptors do not work properly, it can lead to various issues, such as:

  • Vision problems (if photoreceptors in the eyes do not function properly).
  • Hearing loss (if auditory receptors are impaired).
  • Loss of touch or feeling (if skin receptors are damaged).
  • Impaired sense of smell or taste (if chemoreceptors are malfunctioning).

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

Structure of a Neuron:

  • Cell Body (Soma): Contains the nucleus and other organelles.
  • Dendrites: Branch-like extensions that receive signals from other neurons.
  • Axon: Long, thin projection that carries electrical impulses away from the cell body.
  • Axon Terminal: The end of the axon that releases neurotransmitters to communicate with other neurons or muscles.
  • Myelin Sheath: Fatty layer that insulates the axon and speeds up impulse transmission.

Function: Neurons transmit electrical signals throughout the body, allowing for communication between the brain, spinal cord, and other parts of the body.

6. How does phototropism occur in plants?

Phototropism is the growth of plants toward or away from light. It occurs when cells in the plant's stem or roots respond to light by elongating on one side. This is due to the hormone auxin, which accumulates on the shaded side of the plant, causing the cells there to grow longer and the plant to bend toward the light.

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

Spinal cord injuries can disrupt signals between the brain and the body, leading to:

  • Loss of voluntary motor control (e.g., movement of arms and legs).
  • Loss of sensory perception (e.g., touch, pain).
  • Disruption of autonomic functions (e.g., heart rate, digestion).
  • Paralysis or loss of feeling below the injury site.

8. How does chemical coordination occur in plants?

In plants, chemical coordination is primarily governed by plant hormones like auxins, cytokinins, gibberellins, ethylene, and abscisic acid. These hormones regulate growth, development, and responses to environmental stimuli. For example, auxins regulate phototropism and gravitropism, while ethylene controls fruit ripening.

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

Control and coordination are essential to ensure that all parts of an organism function harmoniously. It helps to:

  • Maintain homeostasis (internal balance).
  • Respond to external stimuli (e.g., light, temperature, danger).
  • Regulate physiological processes (e.g., heartbeat, breathing).
  • Enable movement, growth, and development.

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

  • Involuntary Actions: These are actions that occur without conscious control, but they involve the brain. For example, breathing, heartbeat, digestion.
  • Reflex Actions: These are rapid, automatic responses to stimuli that do not involve the brain directly. They occur through the spinal cord, such as pulling your hand away from a hot object.

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

  • Nervous System:

    • Fast response (milliseconds).
    • Short duration.
    • Uses electrical impulses to transmit signals.
    • Involves neurons and the brain/spinal cord.
    • Controls quick actions like reflexes and muscle movements.

  • Hormonal System:

    • Slower response (seconds to minutes).
    • Longer duration.
    • Uses chemical signals (hormones) released into the bloodstream.
    • Involves glands like the thyroid, pancreas, and adrenal glands.
    • Regulates growth, metabolism, and long-term changes like puberty.

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

  • Sensitive Plant (Mimosa pudica): The movement in sensitive plants is due to turgor pressure changes in cells, causing rapid bending of leaves when touched. This is a response to external stimuli and is an example of nastic movement (non-directional).
  • Leg Movement: In humans, leg movement involves muscle contractions controlled by the nervous system. It is a voluntary movement that allows us to walk, run, etc., and is directed by nervous coordination.

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