In experiments conducted on the squid’s giant axon, which of the following statements is TRUE?

• A. The giant axon is unique to mammals and not found in invertebrates.
• B. The experiments demonstrated that action potentials are generated by the movement of glucose across the membrane.
• C. The squid’s giant axon is primarily involved in photosynthesis.
• D. The giant axon was used because its large size makes it easier to insert electrodes and record electrical activity.

Answer: (D)

Verified step by step guidance

1. Step 1: Begin by identifying the key concept in the problem, which is the squid’s giant axon. The giant axon is a well-known structure in invertebrates, specifically squids, and is not unique to mammals. This eliminates the first option as incorrect.
2. Step 2: Understand the function of the giant axon. It is involved in transmitting nerve impulses, not in photosynthesis. Photosynthesis is a process related to plants and some bacteria, not animal axons. This eliminates the third option.
3. Step 3: Recall the mechanism of action potentials. Action potentials are generated by the movement of ions (such as sodium and potassium) across the membrane, not glucose. This eliminates the second option.
4. Step 4: Consider why the squid’s giant axon is used in experiments. Its large size makes it easier to insert electrodes and record electrical activity, which is crucial for studying nerve impulses and action potentials.
5. Step 5: Conclude that the correct answer is: 'The giant axon was used because its large size makes it easier to insert electrodes and record electrical activity.' This statement aligns with the purpose of using the squid’s giant axon in neurophysiological research.