1. The Nervous System Feeling nervous? By: Conor Chinitz, Kelvin Chen, Nathan Bolton, Jack Clifford

2. What is the Nervous System? The Nervous System - a network of specialized cells responsible for organizing and transmitting electrochemical signals throughout the body (2). Composed of excitable cells called neurons (nerve cells) Neurons "fire" electrical signals to send messages " I thought I fired you! Why are you still working? " " Because I'm a neuron. "

3. "No matter how inherently lazy you feel, you are never really doing nothing... " —Kelvin

4. Neuron Structure Source: mhhe.com

5. The Axon Axons are output zones where messages are sent to other cells 1.Trigger Zone - junction between cell body and axon (2) 2.Nodes of Ranvier and Myelin Sheaths - conduction and insulation zones along axon, respectively (2) 3.Axon Terminal - end of axon (2)

6. Summary of Major Structures StructureFunction SomaCell body; contains nucleus; processes signals Dendrites Receives electrical signals from neighboring neurons and directs to soma (input) AxonsTransmits signals to neighboring neurons (output) Myelin SheathBead-like lipid structures that wrap around axons to facilitate signalling Axon: "Let's connect. " Dendrite: "On Facebook? " Axon: "No! With each other! " Sources: 2,3

7. Neurons at Rest In order for neurons to fire, they store electrical energy in the form of Na + and K + ions (2,3) Neurons at rest maintain a constant charge (voltage difference) o Resting Potential - the inherent voltage difference across the plasma membrane of an axon at rest (-70 millivolts) (2,3) Voltage difference caused by imbalance of Na + and K + ions across axon membrane (2,3)

8. Ion Distribution in Neurons At "rest," ions are still constantly entering and leaving the membrane through transport proteins(2) Facilitated ion transport happens actively and passively: 1.Passive transport: Na + and K + seep through channel proteins 2.Active transport: sodium-potassium pumps use ATP to move ions against concentration gradient (2 K + enter: 3 Na + exit) (2) Resting potential is a misnomer as the cell is not at rest but constantly working to maintain this ratio (2)

9. Ion distribution at rest Source: www.wikieducator.org

10. Action Potential When the neuron is at rest, it has a negative charge (2) Action Potential occurs when stimulus overcomes the threshold (>-70mV) (2) o at action potential, there is a reversal of Na + and K + ions in membrane (2) o sudden ion influx results in a reversal of charge (membrane becomes positive in respect to extracellular fluid) (2) Neuron 1: "Girl, what happened to you?" Neuron 2: "Your stimulus carried me over my threshold!"

11. Ion Behavior during Action Potential Stimulus overcomes threshold of excitation is reached and initiates action potential (stimulus > -70 mV) Ion permeability changes: 1.Voltage-gated Na + channel open, allowing Na + to rush in 2.axon interior is now positively charged in respect to extracellular fluid (polarity reversal) 3.Voltage-gated K + channel open, allowing K + to rush out 4.axon interior is now back to being negatively charged in respect to extracellular fluid Sodium-Potassium pump then restores resting-potential distribution of Na + to K + Source: 2

12. Source: library.thinkquest.org

13. Source: https://www.youtube.com/watch?v=U0NpTdge3aw&feature= player_embedded Still Confused?

14. Myelin Sheath Insulates electrical signal traveling along the axon o Prevents electrical signal from dispersing (2) Enhances rate of action potential propagation (2)

15. source: www.biology-forums.com

16. Thank you! We hope this presentation excited your neurons.

17. Bibliography 1 ) Abedon, Stephen T. "Transport Across Membranes." Home. Ohio State University, 28 Mar. 1998. Web. 24 Oct. 2011.. 2) Starr, Cecie, and Ralph Taggart. Biology: The Unity and Diversity of Life. 5 th ed. Belmont, Calif.: Wadsworth Pub. Co., 1989. Print. 3) Campbell, Neil, and Heyden Robin. Biology: Exploring Life. Florida: Pearson Education, Inc., 2009. Print.

18. Further Exploration Interactive Program for Action Potential: o http://outreach.mcb.harvard.edu/animations/actionpotential.sw f Applications of Neurons: o http://www.wired.com/wiredscience/2009/04/lasercontrolledhu mans/ o http://www.ted.com/talks/lang/eng/ed_boyden.html