Chapter 6 Control and Coordination Class 10 Question/Answers

1. What is the difference between a reflex action and walking?
   • Reflex Action (प्रतिवर्ती क्रिया): Reflex actions are automatic and rapid responses to stimuli, which do not involve conscious thought. For example, pulling your hand back when you touch something hot.
   • Walking (चलना): Walking is a voluntary action that involves coordination of the brain and muscles. It requires conscious control and planning.
2. What happens at the synapse between two neurons?
   • At the synapse (सिनैप्स), the junction between two neurons, electrical signals are converted into chemical signals to pass the information from one neuron to another. This process involves neurotransmitters.
3. Which part of the brain maintains posture and equilibrium of the body?
   • The cerebellum (अनुलंबिका) maintains posture and equilibrium of the body.
4. How do we detect the smell of an agarbatti (incense stick)?
   • The smell of an agarbatti (अगरबत्ती) is detected by olfactory receptors in the nose, which send signals to the brain.
5. What is the role of the brain in reflex action?
   • The brain does not play a direct role in reflex actions as these actions are managed by the spinal cord. However, the brain can modulate reflex responses.

Plant Hormones

1. What are plant hormones?
   • Plant hormones (पौधों के हार्मोन) are chemical substances that regulate the growth, development, and responses of plants to stimuli.
2. How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?
   • Movement in a sensitive plant (संवेदनशील पौधा) is called thigmonasty (स्पर्श संवेदना), which is a non-directional response to touch, while the movement of a shoot towards light (प्रकाश की ओर) is called phototropism (प्रकाशानुवर्तन), which is a directional growth response.
3. Give an example of a plant hormone that promotes growth.
   • Auxin (ऑक्सिन) is an example of a plant hormone that promotes growth.
4. How do auxins promote the growth of a tendril around a support?
   • Auxins (ऑक्सिन) promote growth by causing cells on the side of the tendril away from the support to elongate more, thus making the tendril curve towards the support.
5. Design an experiment to demonstrate hydrotropism.
   • To demonstrate hydrotropism (जलानुवर्तन), place seeds in a setup where one side of the soil is moistened while the other is kept dry. Observe the direction of root growth towards the moist side.

Chemical Coordination in Animals

1. How does chemical coordination take place in animals?
   • Chemical coordination in animals (रासायनिक समन्वय) is achieved through hormones secreted by endocrine glands, which regulate various physiological processes.
2. Why is the use of iodised salt advisable?
   • Iodised salt (आयोडीन युक्त नमक) is advisable because it prevents iodine deficiency, which can lead to thyroid gland problems.
3. How does our body respond when adrenaline is secreted into the blood?
   • When adrenaline (एड्रेनालिन) is secreted, it prepares the body for ‘fight or flight’ by increasing heart rate, blood pressure, and energy supply.
4. Why are some patients of diabetes treated by giving injections of insulin?
   • Diabetes patients (मधुमेह के मरीज) are given insulin (इंसुलिन) injections because their bodies do not produce enough insulin or cannot use it effectively, which is necessary to regulate blood sugar levels.

Exercises

1. Which of the following is a plant hormone?
   • (a) Insulin
   • (b) Thyroxin
   • (c) Oestrogen
   • (d) Cytokinin (साइटोकाइनिन).
2. The gap between two neurons is called a
   • (a) dendrite.
   • (b) synapse (सिनैप्स).
   • (c) axon.
   • (d) impulse.
3. The brain is responsible for
   • (a) thinking.
   • (b) regulating the heart beat.
   • (c) balancing the body.
   • (d) all of the above (उपरोक्त सभी).
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 (ग्राही) detect stimuli and send signals to the brain. If receptors do not work properly, it can lead to issues like numbness, inability to detect pain, or sensory impairments.
5. Draw the structure of a neuron and explain its function.
   • Neurons (न्यूरॉन) have a cell body, dendrites (डेंड्राइट्स), and an axon (ऐक्सॉन). They transmit electrical signals throughout the body.
6. How does phototropism occur in plants?
   • Phototropism (प्रकाशानुवर्तन) occurs when plants grow towards light due to the uneven distribution of auxins, causing cells on the darker side to elongate more.
7. Which signals will get disrupted in case of a spinal cord injury?
   • Spinal cord injury (रीढ़ की हड्डी की चोट) can disrupt motor and sensory signals between the brain and the rest of the body, leading to paralysis or loss of sensation.
8. How does chemical coordination occur in plants?
   • Chemical coordination in plants (पौधों में रासायनिक समन्वय) occurs through hormones that regulate growth and responses to stimuli.
9. What is the need for a system of control and coordination in an organism?
   • Control and coordination (नियंत्रण और समन्वय) are needed for efficient functioning of various physiological processes and responses to environmental changes.
10. How are involuntary actions and reflex actions different from each other?
    • Involuntary actions (अस्वेच्छिक क्रियाएँ) are automatic and controlled by the autonomic nervous system, like heartbeat. Reflex actions (प्रतिवर्ती क्रियाएँ) are rapid responses to stimuli, often mediated by the spinal cord.
11. Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.
    • Nervous mechanisms (तंत्रिका तंत्र) are fast and involve electrical impulses, while hormonal mechanisms (हार्मोनल तंत्र) are slower and involve chemical messengers.
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 (संवेदनशील पौधे में हरकत) is a rapid, non-directional response to touch (थिग्मोनैस्टी), while movement in our legs (पैरों में हरकत) is a voluntary action involving muscles and the nervous system.