Final answer:
The Fitzpatrick skin type most likely to tan and least likely to burn is Type 4, characterized by its higher melanin content that offers greater protection against UV radiation. When the epidermis is burned, free nerve endings are most likely to be affected and responsible for pain detection.
Step-by-step explanation:
The Fitzpatrick skin type that is most likely to tan and least likely to burn is Type 4.
In the Fitzpatrick skin typing system, Type 4 skin has a higher melanin content compared to Types 2 and 3, which provides more protection against ultraviolet radiation, leading to more efficient tanning and reduced risk of burning. This skin type typically refers to Mediterranean, Asian, or Hispanic backgrounds and rarely burns but tans with ease. On the other hand, Type 5 skin has an even greater melanin content and might be even more resistant to sunburn, but within the options provided, Type 4 is the correct answer.
Concerning the receptors in the skin, if you were to burn your epidermis, the most affected receptor type would be free nerve endings. Free nerve endings are distributed throughout the epidermis and are responsible for detecting pain, temperature, and touch. These are the sensory receptors that would trigger the pain sensation commonly associated with a burn.