Nervous System: Neurotransmitters and Neural Synapses By Idan Waksman, Rey Duran and Kyle Johnston Chemical Synapse and Neurotransmitters -When action potentials (electrical impulses) reach the presynaptic neuron output zone, the axon, they may trigger the neuron to release one or more neurotransmitter, which goes through the chemical synapse and then into the postsynaptic neuron called the dendrite. (2) ELECTRICAL AND CHEMICAL SIGNALS - The synaptic cleft, a divide between two neurons only a few nanometers wide, is a barrier for the electrical signal carried by one neuron to the other. Think of an electrical circuit; the synaptic cleft would be considered a “short” (1). - The electrical signal traveling down the presynaptic neuron cannot cross the fluid-filled synaptic cleft. Chemical neurotransmitters, however, can (1). Chemical Synapse and Neurotransmitters (cont.) -The calcium ions then flow inside the cell and down the gradient, which causes the release of neurotransmitters into the synaptic cleft. (2) -Neurotransmitters are chemicals that transmit signals from a neuron to a target cell across the synapse. -They become released into and diffuse across the synaptic cleft, through exocytosis. (3) Chemical synapse animation Histamine and Dopamine; 2 examples of specific neurotransmitters -Histamine is an organic nitrogen compound involved in local immune responses. It also regulates physiological function in the gut and acts as a neurotransmitter. It is located in the stomach lining. (5) -Dopamine is a neurotransmitter in the brain that affects a variety of different behaviors. The major areas it affects include movement, cognition, and motivation. Crossing the Neural Membrane -When the neurotransmitters arrive at the input zone of an adjacent neuron, they attach to the proteins and send a message for the proteins to open. (4) Here is a Fun Video! How does this happen? - At the presynaptic ending, the action potential causes the vesicles containing neurotransmitters to bind to the membrane. They fuse and release the neurotransmitters into the synaptic cleft in exocytosis (3). - Ions carry the electrical charge through the neuron. In chemical neurotransmission, a specific neurotransmitter binds to the receptor site on the postsynaptic neuron, causing the ion channel to open and allowing the ions to cross the membrane(1). Animation REFERENCES 1. Stufflebeam, Robert. "Neurons, Synapses, Action Potentials, and Neurotransmission."The Mind Project. Illinois State University, 2008. Web. 02 Nov. 2012. <http://www.mind.ilstu.edu/curriculum/neurons_intro/neurons_intro.php>. 2. "How Neurotransmission Works." The Brain: Understanding Neurobiology. National Institute of Health, 2010. Web. 3 Nov. 2012. <http://science.education.nih.gov/supplements/nih2/addiction/activities/lesson2_neuro transmission.htm>. 3. Chudler, Eric C. "The Synapse." Neuroscience for Kids. University of Washington, 2012. Web. 05 Nov. 2012. <http://faculty.washington.edu/chudler/synapse.html>. 4. Starr, Cecie, and Ralph Taggart. Biology: The Unity and Diversity of Life. 9th ed. N.p.: Thomson Learning, 2001. Print. 5. "Histamine." ScienceDaily. ScienceDaily LLC, n.d. Web. 05 Nov. 2012. <http://www.sciencedaily.com/articles/h/histamine.htm>.