Communications in the Nervous System

1. Communications in the Nervous System Blueprint was general idea Now the details

2. Objectives- THE STUDENT WILL: • Analyze Parts of the Neuron • create an illustration of a Neuron • Summarize the importance of nerves for the PERIFRIAL NERVOUS SYSTEM • Explain how neurons communicate

3. Nervous system components • Neurons (nerve cells) make up part of N.S • Neurons brain’s communication specialist • 100 billion or more in brain • Held in place by Glia (GLEE-uh) • Glial cells- Greek for glue • 90% of brain is Glia cells

4. Glia cells cont. • Neurons with nutrients • Insulate them • Provide protections from toxins • Remove debris when neurons die • Give go ahead to tell neurons to start talking

5. Diagram of Neuron

6. Glia=Glue

7. Structure of the Neuron • 3 main parts: Dendrites, Cell body, Axon • Dendrites- Greek for Little tree; antennas with communication with nerve cells • Cell body- shaped like a pyramid or sphere, decides if neuron FIRES OR NOT, biochemical machinery • Axon- Greek for axel, transmits messages away from the cell body to other neurons, muscles and glands. Can split and divide into branches= axon terminals

8. chapter 4 Structure of a neuron Dendrites Receive information from other neurons and transmit toward the cell body Cell body Keeps the neuron alive and determines whether it will fire Axon Extending fiber that conducts impulses away from the cell body and transmits to other cells.

9. Another neuron

10. More Neuron Structure • Myelin sheath- Cover for the axons, fatty • Constrictions in the M.S. called nodes • Divide into segments so look like sausage • M.S. also keep signals from adjacent cells out

11. Myelin sheath • Also CAN SPEED UP Conduction of Neural impulses • OR like in multiple sclerosis, loss of Myelin causes erratic nerve signals, leading to loss of sensation, weakening, paralysis, lack of communication, vision weak

12. Myelin Sheath

13. Peripheral Nervous System OB #3 • Fibers of individual neurons (axons, dendrites) • Collect and bundle together called Nerves • Like lines in a telephone cable • Human body has 43 pairs of Peripheral nerves

14. Nerves Cont. • Left/right side of body • Most enter or leave spinal cord • However; 12 pairs in the head, Cranial nerves, connect to the brain. • SO Senses : Smell, taste

17. Stem Cell Controversy • 1990 Mammals can produce CNS cells after infancy • Human brain and body organs have such cells • Called stem cells • In animal studies, Can reproduce if exercise, die if stress or nicotine • Controversy; Scientist use aborted fetuses and test tube embryos

18. chapter 4 Neurons in the news Neural regeneration The ability of neurons to grow back after injury or damage Stem cells Immature cells that renew themselves and have the potential to develop into mature cells

19. How Neurons Communicate • Separated by synaptic cleft, neurons don’t touch • Axon terminal and one neuron almost touch • Synaptic cleft + axon terminal+ covering membrane= synapse

20. chapter 4 How neurons communicate Axon terminals release neurotransmitter. Neurotransmitter enters synapse. Neurotransmitter binds to receptors that it fits.

21. Synapse

22. This is how NEURONS TALK • Action potential- When a nerve cell is stimulated, creates electrical voltage. • Like fuse on firecracker • Neurotransmitter- neural impulse reaches axon terminal, must reach across synaptic cleft, synaptic vessels, reach axon terminal= release a few thousand neurotransmitters • Excitatory (good) inhibitory (neg)

23. chapter 4 Action potential A brief change in electrical voltage that occurs between the inside and outside of an axon when a neuron is stimulated.

24. chapter 4 Neurotransmitter Chemical released by a transmitting neuron at the synapse and capable of affecting the activity of a receiving neuron

25. Neurotransmitter crossing a synapse

26. Summary • Parts of Neuron • How do they communicate?