How does an impulse travel from receptor cells to effector. cells

      Receptors detect changes in the environment, and then start an electrical signal along the neurons. These move towards the central nervous system. The receptors are groups of specialized cells. They are able to detect the changes in environment and they are also able to stimulate electrical impulses in response.

Explanation:

I had this on a test and I got it right. Have a nice day!

in 1859, charles darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. he defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".