Chapter 6: Control and coordination

Multiple Choose Question And Answer :

1. Which of the following is a plant hormone?

(a) Insulin

(b) Thyroxin

(c) Oestrogen

(d) Cytokinin.

Answer: (d) Cytokinin

[ Cytokinins are a class of plant hormones that promote cell division, growth, and development in plants.]

2. The gap between two neurons is called a

(a) dendrite.

(b) synapse.

(c) axon.

(d) impulse.

Answer: (b) synapse

[ The small gap between two neurons where nerve impulses pass is called a Synapse.]

3. The brain is responsible for

(a) thinking.

(b) regulating the heart beat.

(c) balancing the body.

(d) all of the above.

Answer: (d) all of the above

[ The brain controls multiple vital functions such as:  (a) thinking and decision-making

(b) regulating the heartbeat (through the nervous system)

(c) maintaining body balance (via the cerebellum)

So, all the given options are functions of the brain. ]

Short Question and Answer :

3. Which part of the brain maintains posture and equilibrium of the body? [1M]

Answer: The cerebellum maintains posture and equilibrium of the body.

1. What are plant hormones ? [1M]

Answer: Plant hormones are chemical substances produced in plants that control and regulate growth, development and responses to stimuli. They are made in small amounts and transported to different parts of the plant. Plant hormones help in processes like cell division, growth of roots and shoots, flowering, fruit formation and response to light and gravity.

3. Give an example of a plant hormone that promotes growth. [1M]

Answer:  An example of a plant hormone that promotes growth is auxin. It helps in the elongation of cells, especially in stems and shoots, allowing the plant to grow.

Q.  What happens in Reflex Actions? [2M]

Answer: In reflex action, the body gives a quick and automatic response to a stimulus without thinking. When we touch something hot or sharp, receptors in the skin send a message through sensory nerves to the spinal cord. The spinal cord immediately sends a response through motor nerves to the muscles. The muscles then act, like pulling the hand away. The brain is informed after the action is done. Reflex actions are very fast and help protect the body from injury.

Q. How are these Tissues protected?  [2M]

Answer: The brain and spinal cord are protected by strong structures. The brain is protected by the skull (cranium), while the spinal cord is protected by the vertebral column. Both are covered by three protective membranes called meninges. In addition, cerebrospinal fluid surrounds them and acts as a shock absorber. These protections prevent injury and help the nervous tissues function safely.

Q. How does the Nervous Tissue cause Action? [2M]

Answer: Nervous tissue causes action by transmitting electrical signals called nerve impulses. When a stimulus is received, receptors generate an impulse that travels through neurons to the brain or spinal cord. The nervous system processes this information and sends impulses through motor neurons to muscles or glands. As a result, muscles contract or glands release substances, producing a response or action in the body.

1. What is the difference between a reflex action and walking?  [2M]

Answer: The difference between a reflex action and walking are :

2. What happens at the synapse between two neurons?  [2M]

Answer: At the synapse, the nerve impulse cannot jump directly from one neuron to another. When an impulse reaches the end of the first neuron, it releases chemical substances called neurotransmitters. These chemicals cross the small gap (synaptic cleft) and stimulate the next neuron. This starts a new electrical impulse in the second neuron, allowing the message to continue.

4. How do we detect the smell of an agarbatti (incense stick)? [2M]

Answer: We detect the smell of an agarbatti when its aroma spreads in the air. The smell particles enter our nose and dissolve in the mucus lining. They stimulate the olfactory receptors present in the nose. These receptors send nerve impulses to the brain, and the brain recognises the smell of the agarbatti.

5. What is the role of the brain in reflex action? [2M]

Answer: The brain does not control reflex action directly. Reflex actions are controlled by the spinal cord to give a quick response. However, the brain receives the information after the reflex action is completed. It helps us understand what happened and can control future actions if needed.

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

Answer:  The movement of the leaves of a sensitive plant is a rapid, automatic response to touch, called a nastic movement. It does not depend on the direction of the stimulus. In contrast, the movement of a shoot towards light is a slow, directional growth movement called phototropism, where the plant grows towards the light source. While leaf movement is quick and temporary, shoot movement is gradual and permanent.

4. How do auxins promote the growth of a tendril around a support?  [2M]

Answer: Auxins promote the growth of a tendril around a support by causing cells on the side away from the support to grow faster than the side touching the support. This unequal growth makes the tendril bend and curl around the support, helping the plant climb and secure itself.

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? [3M]

Answer: Receptors in our body detect changes in the environment, called stimuli, like touch, light, sound, taste, or temperature, and send signals to the brain or spinal cord. If receptors do not work properly, the body cannot sense these changes correctly. For example, if touch receptors fail, one might not feel pain from injuries; if taste or smell receptors are damaged, food may lose its flavour; and if light receptors in the eyes are affected, vision problems can occur. This can lead to accidents or health issues.

Long Question and Answer :

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