One of the first concepts that students of neuroscience are exposed to is the overall organization of the nervous system and the two principle divisions of it: the Peripheral Nervous System (PNS) and the Central Nervous System (CNS). In sensory systems, this fundamental division plays a particularly prominent role in the information processing stream that integrates and processes information from the external environment to the CNS. To better understand the differences between the roles that the PNS and CNS play in information processing, we developed a relatively simple in-class laboratory exercise. The experimental methods used to determine several aspects of a subject's discriminative capacity (threshold detection, amplitude discrimination, duration discrimination) are described. These methods were used either under control conditions or after the students altered their skin sensitivity (i.e., the PNS) by cold water immersion. At the conclusion of the lab exercise, students will thoroughly understand the principle of the PNS vs. CNS, as well as a fundamental understanding of quantitative sensory testing. This fundamental understanding of sensory testing provides a foundation for students to pursue or investigate other aspects of sensory information processing in either independent studies or subsequent lab exercises.