Q1. [3] deep thorough-understanding
A student argues: 'Reflex arcs are a primitive leftover — animals with complex brains don't really need them anymore.' Using your understanding of how nervous impulses work, explain why this argument is flawed.
Generated by claude-sonnet-4-6 · 2026-06-26 01:01 · grounding rag
Model Answer
The student's argument is flawed for the following reasons:
- Speed of response: Thinking involves complex interactions of many neurons in the brain. If every response to a dangerous stimulus (like touching a hot object) required brain processing, it would take too long and cause harm. Reflex arcs, formed in the spinal cord itself, bypass the brain and allow an immediate response.
- Efficiency even in complex brains: Even after complex neuron networks evolved, reflex arcs continue to be more efficient for quick responses. The brain is simultaneously handling many functions, so offloading urgent responses to spinal reflex arcs reduces processing burden.
- Parallel processing: The information still travels to the brain, but the protective action occurs first. This makes reflex arcs a vital, not obsolete, feature of the nervous system.
Source: Chapter 6, Section 6.1.1 — What happens in Reflex Actions?
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Explanation
- The key examiner expectation is that you use the textbook reasoning: thinking is too slow for emergencies, and reflex arcs evolved precisely to handle rapid responses without waiting for brain processing.
- Mention that information does reach the brain, but the reflex action happens before — this shows you understand reflex arcs are complementary to, not replaced by, the brain.
- The direct quote from the passage — "even after complex neuron networks have come into existence, reflex arcs continue to be more efficient for quick responses" — is the strongest counter to the student's argument.
- Avoid writing a long essay; three clear points within the word limit is ideal for 3 marks.