If a radioactive substance starts at 100 grams and decays to 12.5 grams in 21.6 hours, what is the substance's half-life? a. 3 hours b. 7.2 hours c. 14.4 hours d. 21.6 hours

An organ system consists of a group of organs that performs specific functions necessary for the survival of an organism. humans have eleven different organ systems: integumentary, skeletal, muscular, nervous, endocrine, circulatory, lymphatic, respiratory, digestive, urinary, and reproductive. discuss the function of neurons, the brain and the spinal cord within the human nervous system while explaining the interrelationship of each organ.