1. Cell Specialization

2. Unicellular organism – consists of only one cell –That one cell carries out all functions required to maintain the life of the organism

3. Multicellular organism – consists of more than one cell –Cells are specialized to perform certain functions (cell specialization/differentiation)

4. Examples of Cell Specialization 1. Neuron (nerve cell): –Sends info. from one part of the body to another –Very long and thin

5. Examples of Cell Specialization 2. Red blood cells: –Carry oxygen throughout body –Flattened disks so that they can easily flow through blood vessels Close-up: Blood cells in capillary

7. Examples of Cell Specialization 3. Sperm cell: –Fertilizes egg –Strong tail for quick swimming, distinct head for entering egg cell

8. * Cell differentiation is a result of different gene expression.

9. Cell Communication Cells communicate with one another by secreting and receiving chemicals

10. Cell Communication Chemicals released by one cell can influence the activity of another cell. –Ex: sensory cells to nerve cells to muscle cells

11. Cell Communication Hormones = communication chemicals that travel through the blood –Secreted by endocrine glands –Acts much slower than nerve impulses but effects last much longer –Only influence the action of target cells that have specific receptors –Two mechanisms:

12. Negative feedback –The end product stops the production of a hormone initially secreted

15. Positive feedback –The last step triggers more release of the hormone initially secreted Birth process triggered by low levels of progesterone ↓ Stimulates release of oxytocin ↓ Uterus contracts, stimulates more oxytocin release ↓ More contraction ↓ Baby is born!