Can someone answer this

Diffusion.

Explanation:

Diffusion is the net movement of anything from a region of higher concentration to a region of lower concentration.

When the moves in, the moves out.

when a reversible reaction is occurring in both directions at the same rate; the products and reactants do not change in concentration. a chemical reaction where the compound is broken into its constituent parts.

after receiving a stimus, the sensory receptors send(s) signals to the appropriate area of the body.  

the must be sensory neurons.  

hope its .