1. sensory receptors detect changes of internal or external stimulus 2. integrating center respond to stimulus to maintain homeostasis 3. effectors sends signals to proper areas of the body regarding the stimulus

The structure of a dna molecule is best described as a. one long strand of nucleic acids b. two strands of dna nucleotides joined by hydrogen bonds c. two strands of amino acids joined by hydrogen bonds d. one long strand of amino acids