(a) Write three main functions of the nervous system.

(b) In the absence of muscle cells, how do plant cells show movement?

(a) Three Main Functions of the Nervous System:

1. Information Acquisition (Sensation): It detects changes in the environment (stimuli) through specialized receptors located in our sense organs (e.g., gustatory receptors for taste, olfactory receptors for smell).
2. Information Processing and Integration: It conducts the acquired information via electrical impulses to the central nervous system (brain and spinal cord), where the information is integrated, interpreted, and decisions are made.
3. Response Generation (Motor Action): It conveys the processed decisions from the central nervous system to the effector organs, such as muscles or glands, to trigger an appropriate response (e.g., muscle contraction or gland secretion).

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(b) How Plant Cells Show Movement in the Absence of Muscle Cells:

Plants do not have specialized muscle tissues or proteins, yet they show movement through two distinct mechanisms:

1. By Changing Water Content (Turgor Changes - Growth-independent):

• For immediate responses (like the folding of leaves in the sensitive plant Mimosa pudica), plant cells change their shape by changing the amount of water in them.
• This results in the swelling or shrinking of cells, which alters their shape and causes the leaves to fold or droop.

1. By Directional Growth (Tropic Movements - Growth-dependent):

• Plants respond to environmental stimuli (like light, gravity, water, or touch) slowly by growing in a particular direction.
• For example, in tendrils, the part in contact with a support does not grow as rapidly as the part away from the support. This differential growth causes the tendril to circle and cling to the support.
• Similarly, shoots bend towards light (phototropism) and roots grow downwards towards gravity (geotropism) due to unequal growth rates in different parts of the plant tissue.