Nervous System and Plant Hormones Q&A

Nervous System and Plant Responses

Reflex Action Versus Walking

Question: Differentiate between reflex action and walking.

Answer: A reflex action is an involuntary action, which is a rapid and automatic response to stimuli. In contrast, walking is a voluntary action which requires our thinking and is under our control.

Synaptic Transmission

Question: What happens at the synapse between two neurons?

Answer: A synapse is the microscopic gap between two neurons. At the synapse, the electrical signals are converted into chemical messengers (neurotransmitters) that can easily cross over the gap and pass on to the next neuron, where they are again converted into electrical signals.

Brain Function

Posture and Equilibrium

Question: Which part of the brain maintains posture and equilibrium of the body?

• The Cerebellum.

Smell Detection

Question: How do we detect the smell of an agarbatti (incense stick)?

Answer: When the smell of the incense stick reaches our nose, the olfactory receptors present in our nose detect it and send this information to the forebrain in the form of electrical signals. The forebrain interprets this information as the smell of the incense stick, matching it with stored memories.

Brain's Role in Reflexes

Question: What is the role of the brain in reflex action?

Answer: The brain has no direct involvement in reflex action. These actions are mainly controlled by the Spinal Cord, as they do not require conscious thinking and must be very quick.

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Plant Hormones (Phytohormones)

Definition and Function

Question: What are plant hormones?

Answer: Plant hormones are fluids secreted within the plant, also known as phytohormones. Plant hormones regulate the growth and development of the plant. Examples of plant hormones include auxin and gibberellins.

Plant Movements

Question: How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?

Answer: The movements of the leaves of the sensitive plant are touch-sensitive and independent of growth. In contrast, the movement of the shoot towards light is growth-related and is known as phototropism.

Growth Promotion Example

Question: Give an example of a plant hormone that promotes growth.

• Auxin

Auxin and Tendril Growth

Question: How do auxins promote the growth of a tendril around a support?

Answer: When tendrils come into contact with any support, the part of the tendril in contact with the object does not grow as rapidly as the part of the tendril away from the object. This differential growth is caused by the action of the auxin hormone. Less auxin accumulates on the side of contact compared to the free side. As a result, auxin promotes faster growth on the free side, causing the tendrils to coil around the support.