| A | B |
|---|
| neuron | a nerve cell is also called a |
| hormone | a chemical released by endrocrine glands is called a |
| gland | a ____ is an organ that produces a chemical |
| impulse | a message in a nerve cell is a ___ |
| alvoeli | oxygen enters the blood in tiny sacs called ___ |
| enzyme | an ___ is a chemical that breaks down food |
| antibody | a chemical that destroys a specific kind of pathogen is a |
| pathogen | an organism that causes disease is called a |
| endocrine gland | a tissue or organ that releases a chemical into the bloodstream is a |
