This figure is a map of a student’s skin surface used in a sensory investigation. A pair of blunt points was touched onto the skin at the same time. The stu...
Question 1 Report
This figure is a map of a student’s skin surface used in a sensory investigation. A pair of blunt points was touched onto the skin at the same time. The student reported whether they felt one point or two. The smallest separation at which two points could be felt was recorded. Receptors in the skin send impulses along sensory neurones to the brain. Areas with many receptors are expected to detect small differences in touch more accurately. The student washed their hands between tests and kept their eyes closed so that sight did not influence the response.
(a) Describe the difference in receptor cell density between the fingertip and forearm regions. [2]
(b) What is meant by a receptor? [2]
(c) Explain why the fingertip is likely to detect two points closer together than the forearm. [3]
(d) Give one reason why the student closed their eyes during the test. [1]
Answer Details
Skin receptors and two-point discrimination
- The fingertip has more receptor cells in a similar area than the forearm, so its receptors are closer together. [2]
- A receptor is a cell or structure that detects a stimulus and produces a nerve impulse. [2]
- The fingertip has more receptors, so each receptor serves a smaller area of skin. Two nearby points are therefore more likely to stimulate different receptors, allowing the brain to recognise them as two separate points. [3]
- The student closed their eyes to prevent visual information influencing the response. [1]
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