What is the second way intensity is coded by the sensory system?

• A. Receptor potentials vary with stimulus intensity
• B. Absolute number of receptors stimulated
• C. External stimulus excites different receptor types producing a larger qualitative sensation
• D. Receptors adapt to sustained stimuli

Answer: (B)

Intensities are conveyed not only by how fast neurons fire, but also by how many receptors are activated. As stimulus strength increases, more receptors reach threshold and participate, so the absolute number of active receptors grows. This recruitment of additional receptors across a population provides a second, spatial form of coding that augments the signal sent to the brain, allowing stronger sensations without relying solely on higher firing rates. The other statements describe related ideas that don’t capture this recruitment mechanism: receptor potentials varying with intensity affect firing but aren’t the separate second coding method; changing receptor types would alter quality, not just intensity; and adaptation affects response over time, not immediate intensity coding.