1. Homeostasis and cells
Section 7.4

2. 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

3. 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

4. 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

5. 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