Final answer:
Merkel's disks are slowly-adapting mechanoreceptors with small receptive fields that play a vital role in texture discrimination, particularly in the fingertips where they can sense fine details due to high sensory ending density. Their function is central to two-point discrimination tests used to measure touch acuity.
Step-by-step explanation:
The small Merkel disk receptive field is crucial for texture discrimination in the sense of touch. Merkel's disks are unencapsulated, slowly-adapting mechanoreceptors found in the skin that respond to touch. Their receptive fields are small, providing the ability to discern fine details and textures when objects come into contact with the skin, notably in areas with high sensory ending density, like the fingertips. This sensory attribute allows an individual to detect subtle differences in surfaces, such as the weave of a fabric or the smoothness of a stone. Merkel's disks work in concert with other types of mechanoreceptors, like Meissner's corpuscles, which also contribute to light touch discrimination but adapt rapidly compared to the slower adaptation of Merkel's disks.
Discrimination of fine touch is measured using two-point discrimination tests, which highlight the concentration of sensory endings and the size of receptive fields in the skin. The smaller the receptive field, as with Merkel's disks, the greater the ability to distinguish between two points that are close together. This is key in assessing touch acuity and can provide indications of the texture and detailed shape of objects.