Homeostasis and cells Section 7.4

How do individual cells maintain homeostasis? Unicellular organisms can grow, respond to the environment, transform energy and reproduce Bacteria are highly adaptable Many processes are the same as in multicellular organisms

How can cells work together to maintain homeostasis? Cells in multicellular organisms are interdependent They can each become specialized for specific tasks, and communicate with one another to maintain homeostasis Some can move Some can react to the environment Some produce substances the organism needs

Levels of organization Cells are organized into tissues Groups of tissues are called organs Each muscle in your body is an individual organ Muscle Tissue Nerve tissue Connective tissue Each tissue performs an essential task Organs complete specialized tasks Organs come together to form organ systems Division of labor allows organisms to maintain homeostasis

Cellular communication Cells can communicate through chemical signals passed from one cell to another Signals can speed up or slow down the activities of cells that receive them Can cause a cell to change what it is doing Certain cells form cellular junctions Some hold cells together Others small ”messengers” to pass through A cell must have a receptor to respond to a signal Can be on the cell membrane or in the cytoplasm Example – electrical signal that causes heart to start contracting is the pacemaker Ions carry the signal from pacemaker over millions of heart cells, causing them to contract simultaneously Other junctions hold the heart cell together, so the heart does not rip