Homeostasis

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Homeostasis

• Biology
• 10/27/10

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Homeostasis

• What does it mean?
• homeo
• The same
• Keeping internal physical and chemical conditions
  relatively constant despite changes in their
  internal and external environment.

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Unicellular Organisms

• How do they maintain homeostasis?
• Grow
• Respond to environment
• Transform energy
• reproduce

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Unicellular Organisms

• Can be prokaryotes or eukaryotes
• More in numbers than multicellular organisms
• Examples
• Bacteria
• Algae
• Fungi

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Unicellular Organisms

• To maintain homeostasis
• Needs to find sources of energy for food
• Keep concentrations of water and minerals within
  certain levels
• Respond quickly to changes in the environment

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Multicellular Organisms

• How do they maintain homeostasis?
• Cells become specialized for particular tasks and
  communicate with one another
• They must work together!

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Multicellular Organisms

• Cell Specialization
• To move
• React to environment
• Produce substances the organism needs

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Multicellular Organisms

• Specialized animal cells
• Trachea epithelium, epidermis(stratified squamous
  epithelium)
• Specialized plant cells
• Xylem, phloem

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Levels of Organization

• Specialized cells--gt organized into
• Tissues--gt organized into
• Organs--gt organized into
• Organ Systems digestive, respiratory,
  reproductive, urinary, excretory, etc

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Cellular Communication

• Communicate with chemical signals
• Chemical signals
• speed up or slow down activity of cells
• Can cause cell to change what it is doing
• Hormones

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Cellular Communication

• Cellular junctions
• Cells form connections to neighboring cells
• Why?
• Can hold cells strongly together
• Can allow small particles carrying chemical
  messages to pass from one cell to another

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Cellular Communication

• Receptors
• What are they? Where are they located?
• Site where signaling molecule can bind
• Located on cell membrane or cytoplasm inside the
  cell.

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Cellular Communication

• Cellular Junction examples
• Cardiac muscle, uterus muscle (gap junction)
• Muscle contraction
• Human Lungs