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!