| A | B |
|---|
| Cell | The basic unit of structure and function in living things. |
| Cell Membrane | The outside boundary of a cell; controls which substances can enter or leave the cell. |
| Nucleus | The control center of a cell that directs the cell’s activities; contains the chemical instructions that direct all the cell’s activities and determine the cell’s characteristics. |
| Cytoplasm | The region of a cell located inside the cell membrane or between the cell membrane and nucleus; contains a gel-like material and cell organelles. |
| Tissue | A group of similar cells that perform a specific function in an organism. |
| Muscle tissue | A body tissue that contracts or shortens, making body parts move. |
| Nerve Tissue | A body tissue that carries messages back and forth between the brain and every other part of the body. |
| Connective Tissue | A body tissue that provides support for the body and connects all of its parts. |
| Epithelial Tissue | A body tissue that covers the surfaces of the body, inside and out. |
| Organ | A structure in the body that is composed of different kinds of tissue. |
| Organ System | A group of organs that work together to perform a major function in the body. |
| Homeostasis | The process by which an organism’s internal environment is kept stable in spite of changes in the external environment. |
| Stress | The reaction of a person’s body and mind to threatening, challenging, or disturbing events. |
