Final answer:
Thresholds in a Coulter counter allow for differentiating cells from debris and accurately counting them by detecting resistance changes as cells pass through an aperture.
Step-by-step explanation:
Thresholds in a Coulter counter are parameters set to detect cells passing through an aperture by measuring changes in electrical resistance. These thresholds help in differentiating between various cell types, debris, or noise in the sample. As cells are drawn through the aperture in the Coulter counter, they cause a momentary change in resistance, which is detected and counted by an electronic sensor, allowing for accurate cell counting.