Reflex action

Correct answer: A. A quick response may occur through the spinal cord, but information later reaches the brain

A reflex arc is arranged for a rapid protective response. Receptors detect the stimulus, sensory neurons carry the impulse to the spinal cord, and motor neurons quickly activate the effector before conscious processing is complete. However, the sensory information is also relayed to the brain, allowing the person to become aware of pain or contact afterwards. Therefore option A corrects the misconception; the other statements deny essential parts of the reflex arc.

Correct answer: A. Stimulus to receptor to sensory nerve to spinal cord to motor nerve to effector to response

The reflex arc follows a fixed functional sequence. A stimulus is detected by a receptor, and a sensory neuron carries the impulse to the spinal cord for rapid processing. A motor neuron then carries the outgoing impulse to an effector, such as a muscle or gland, which produces the response. Option A includes every essential stage in the correct order. The other sequences mix unrelated organs or reverse the pathway.

Correct answer: A. Sensory nerve

In a reflex arc, the receptor detects the stimulus and the sensory nerve carries the impulse from the skin towards the spinal cord. Since the receptors are already active but the message fails before reaching the spinal cord, the sensory nerve is the most likely damaged part. A motor nerve carries commands away from the spinal cord, the muscle performs the response, and the thyroid is unrelated here.

Correct answer: B. The spinal cord gives a rapid response and the brain receives information later

A reflex action is organised for speed and protection. Sensory information enters the spinal cord, which rapidly sends a motor command to withdraw the hand before conscious interpretation is completed. The same event is then communicated to the brain, where pain is consciously recognised. Thus option B is correct. The message does reach the brain; muscles do not interpret pain, and hormones are not responsible for this immediate pathway.

Correct answer: A. Long-term growth and changes during adolescence.

Nervous control uses fast electrical impulses and is well suited to immediate, short-lived actions such as withdrawing from heat or blinking. Endocrine control uses hormones released into the blood; it generally begins more slowly, but its effects can be widespread and persist longer. Growth and the physical changes of adolescence require sustained regulation over time, so option A is the best answer. The other options are rapid protective responses better served by nerves.

Correct answer: A. क्योंकि मांसपेशी को सिकुड़ने के लिए तंत्रिका संदेश चाहिए

The governing concept is the role of an effector in a response pathway. A muscle is an effector that contracts only after receiving an appropriate motor nerve impulse from the nervous system. Thus, even a structurally normal muscle will not act when the response message is absent, making option A correct. It does not work independently, produce light, or require insulin simply to be visible.