Science (086) — AI-generated practice question

When a nail pierces the foot, the sensory nerve impulse travels to the spinal cord, where a reflex arc is completed. The motor nerve immediately signals the foot muscles to withdraw — all without involving the brain. Simultaneously, the pain signal continues travelling up to the brain (fore-brain), which takes slightly longer due to the greater distance and complex neural processing involved. Hence, pain is felt a moment after withdrawal.

Why this delay is useful: If the body waited for the brain to consciously process pain before responding, valuable time would be lost, risking greater injury. The reflex arc allows an immediate protective response, making it a faster and more efficient survival mechanism.

Source: Chapter 6, Section 6.1.1 – Reflex Actions

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• Examiners expect two distinct parts: (1) the biological reason for the delay (reflex arc in spinal cord vs. signal reaching the brain), and (2) the usefulness of this delay/reflex system.
• Key terms to use: reflex arc, spinal cord, brain, sensory/motor nerve — these fetch marks.
• Don't confuse "delay is useful" with the delay itself being beneficial; it's the reflex acting before conscious perception that is useful.
• Avoid writing an essay — keep it tight and structured as above for full 3-mark credit.