Nervous System

1. Nervous System Group 2 Eric Pinsker-Smith, Ian Kinney, George Hatzipetrou

3. Chemical Synapses • Are specialized junctions where neurons signal to each other and non-neuronal cells • Connect neurons to form circuits within the nervous system • Allow nervous system to interact with other systems of the body http://upload.wikimedia.org/wikipedia/commons/3/30/Chemical_synapse_schema_cropped.jpg (4. Starr, Taggart Textbook)

4. Neurotransmitters • Are molecules that transmit signals to cells through synapses • Two examples are histamine, which is part of the immune system and triggers inflammatory responses all throughout the body, and acetylcholine, which triggers action potentials in muscles, glands, spinal cord, and brain (4. Starr, Taggart Textbook). http://upload.wikimedia.org/wikipedia/commons/2/26/Acetylcholine.png http://en.wikipedia.org/wiki/File:Histamine3d.png

5. How Electrical Signals Transform into Chemical signals and why they do this • Neurons always have a negative charge. (-70 millivolts) evenly distributed throughout the neuron. The charge is carried by sodium ions • When a neuron is pressed or pulled, the cells movement redistributes the ions, making it charged. • If a sufficient charge is reached, it will trigger a release of sodium ions. This energy release is powerful, lasts for 1 milli second and sends a strong electric current down the axon. • Source: Principles of Neural Science

6. How Electrical Signals Transform into Chemical signals and why they do this • This electronic signal reaches the neurotransmitters stored in the end of the axon. • The electricity excites them and starts their exocytosis, in which they leave the neuron, trigger receptors in the adjacent neuron, then diffuse back into the neuron in which it started. psychology.about.com/od/biopsychology/f/neuron01.htm

7. Why is this conversion necesary? • This is important because electricity can't cross the synaptic cleft, only chemicals can. • This allows for the transportation of signals between neurons. http://en.wikipedia.org/wiki/Principles_of_Neural_Science http://images.google.com/imgres?q=chemical+synapses&num=10&hl=en&biw=1202&bih=591&tbm=is=55

8. How neurotransmitters cross the neural membrane and how that signal is then received by an adjacent neuron • Synapses serve as the means to allow neurons to pass signals to another cell. • When a cell has a voltage disturbance, (one side more positively charged than the other) this is known as an action potential, in which an electrical current is released. An action potential is the local voltage change across the cell wall as a nerve impulse is transmitted. Each neuron has a different charge. Gated channels for calcium ions span the presynaptic cell's membrane, and they open once action potential occurs. http://img.tfd.com/mk/S/X2604-S-70.png

9. Cont... • Neurons carry a negative charge, and thus are filled with sodium ions. The calcium ions on the outside hold a positive charge, and they therefore diffuse into the neuron. • This intake of calcium stimulates a release of sodium ions in the form of an electric current. • This current excites the neurotransmitters which are in vesicles, and they undergo exocytosis and leave the neuron. • The neurotransmitters then diffuse into the postsynaptic cell, where they stimulate receptors.

10. Bibliography • Bullock, T.H., Bennett, M.V.L., Johnston, D., Josephson, R., Marder, E., Fields R.D. 2005. The Neuron Doctrine, Redux, Science, V.310, p. 791–793. • Kandel E.R., Schwartz, J.H., Jessell, T.M. 2000. Principles of Neural Science, 4th ed., McGraw-Hill, New York. • Peters, A., Palay, S.L., Webster, H, D., 1991 The Fine Structure of the Nervous System, 3rd ed., Oxford, New York • Starr, Cecie, and Ralph Taggart. Biology: The Unity and Diversity of Life. Ninth ed. Pacific Grove: Brooks/Cole, 2001. Print. • "What Is a Neuron." Psycology.net. N.p., n.d. Web. 3 Nov. 2012. <psychology.about.com/od/biopsychology/f/neuron01.htm>.