Test: Control & Coordination - 1 - UPSC MCQ

Plant hormones are typically transported through specialized tissues like the xylem and phloem within the plant, aiding in long-distance communication. In contrast, animal hormones are primarily transported through the bloodstream or other bodily fluids, enabling them to reach target tissues and organs throughout the organism for various physiological responses.

• Plants do not have any nervous system but yet if we touch a sensitive plant such as Mimosa pudica, the leaves of the plant close down. This is due to nastic movement.
• The response of the plant parts in response to an external stimulus in which the direction of response is not determined by the direction of the stimulus is known as a nastic movement.
• As plants do not have any nervous system they use chemical means for communication.
• The chemical means involve plant hormones which help them to coordinate and communicate.

• Receptors: These are specialized structures that detect stimuli and convert them into electrical signals.


• Sensory neuron: The electrical signals generated by receptors are transmitted to the central nervous system (CNS) via sensory neurons.


• Spinal cord: In the spinal cord, the sensory signals are processed and a response is generated.


• Motor neuron: The response signal is then transmitted from the CNS to the effector organ (muscle or gland) via motor neurons.


• Muscle: The effector organ (muscle) receives the signal and produces a response, such as contracting in the case of a muscle reflex.

Therefore, the correct sequence of the components of a reflex arc is: Receptors → Sensory neuron → Spinal cord → Motor neuron → Muscle.

Thyroxin is secreted by thyroid gland. Testes secrete male hormone testosterone.