1. Cell Communication

2. Multicellular Organisms
Signal transduction pathways coordinate the activities within individual cells that support the function of the organism as a whole

3. Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling

4. Another form of short distance signaling
Messages sent between neurons in Nervous system

5. Neurons (Nerves)
Specialized cells to transmit nerve impulses from one part of body to another
3 main parts
Dendrite (signal receiving end)
Cell body
Axon (signal sending end)

6. Many axons have a myelin sheath that acts as an electrical insulator.
Schwann cells, which form the myelin sheath, are separated by gaps of unsheathed axon over which the impulse travels as the signal propagates along the neuron

7. Synapses
junction between two neurons where messages are passed on by neurotransmitters

8. Resting neuron structure
Contain potassium (K+) ions inside neuron
Sodium (Na+) ions are outside plasma membrane and don’t normally pass inward

9. Polarized neuron Inactive (not sending an impulse)
Inside of neuron negatively charged to compared to outside

10. Stimulated neuron- Depolarization
Na+ gates in membrane open and Na+ rushes into cell causing inside to be more positive than outside of cell which activates neuron to transmit an action potential

11. Action potential
nerve impulse which causes the axon to release a neurotransmitter into synapse that binds to next neuron stimulating it

12. Cell Repolarization After action potential
K+ rushes out of cell causing the inside to become negative again
Must occur before neuron can send another nerve impulse

13. After repolarization Na+/K+ pump
Pumps K+ into cell and Na+ out to restore cell to make it polarized again

14. Transmission of information via neurotransmitters between neurons occur across synapses and result in responses
Responses can be stimulatory or inhibitory
Epinephrine
Acetylcholine
Norepinephrine
Dopamine
Serotonin
GABA

16. YOUTUBE Video

17. Long distance signaling in Humans
Requires cardiovascular system to transport hormones (chemical messages = ligands) to cells in other areas of body

18. Endocrine signals (hormones) are produced by endocrine cells that release signaling molecules, which are specific and can travel long distances through the blood to reach all parts of the body
Examples:
Insulin
Human growth hormone
Thyroid hormone
Testerone
Estrogen

19. Insulin