The Nervous System (II) Rachel Cohen, Grace Huddleston, Artemis Metaxa, Elisa Rocha

★ Neuron ○specialized cell involved in transmitting messages from parts of the body to the brain ★ Chemical synapse ○Allow the neurons of the central nervous system to form interconnected neural circuits ★ Neurotransmitter ○The chemicals which allow the transmission of signals from one neuron to the next across synaptic clefts. (1) Basic Definitions

★ Provide the means through which the nervous system connects and controls the other systems of the body. ★ Synapses that transmit information via the secretion of chemical signs are neurotransmitters (1, 2) Chemical Synapse

★ Synapse is the site of communication between one neuron and another neuron ○neurotransmitters ★ Action potential at the presynaptic terminal opens channels and allow calcium ions to diffuse through channel proteins into the cell, stimulating the exocytosis of neurotransmitters (acetylcholine). (3) Chemical Synapse with Neurotransmitters

1: Action potential at the presynaptic terminal causes the opening of channels on the cell membrane. 2: These open channels allow for calcium ions to diffuse through channel proteins in the cell membrane. 3: These calcium ions simulate the exocytosis of vesicles filled with neurotransmitters (acetylcholine). 4: After the vesicles open at the cell membrane and the neurotransmitters exit the cell, they travel across the extracellular fluid of the synaptic cleft. 5: The neurotransmitters come in contact with receptors on the postsynaptic membrane (lipid gated sodium channels). 6: The presence of neurotransmitters stimulates the receptors causing them to open and allow for the entrance or exit of different ions depending on their concentrations. (3)

★ Specialized cells released at the end of a nerve fiber by the arrival of a nerve impulse ★ By diffusing across the synapse or junction, they cause the transfer of the impulse to another nerve fiber, a muscle fiber, or some other structure. ★ The electrical signals (nerve impulses) carried by neurons are passed on to other neurons at junctions called synapses ★ The signal may be directly transferred at electrical synapses or, if there is no physical link between adjacent neurons, the signal is carried across the gap by chemicals called neurotransmitters. ★ By using neurotransmitters, the nervous system can alter the way a message is passed on. (4) Neurotransmitters

★ Responsible for stimulation of muscles ○gastro-intestinal system ★ Found in Sensory neurons and autonomic nervous system ○and has a part in scheduling REM (dream) sleep. (4) Example: Acetylcholine

★ Serotonin is an inhibitory neurotransmitter ○involved in ones emotion and mood ○Too little serotonin has been shown to lead to depression, problems with anger control, obsessive-compulsive disorder, and suicide. ★ Plays a role in perception ○Hallucinogens such as LSD work by attaching to serotonin receptor sites and thereby blocking transmissions in perceptual pathways. (4) Example: Serotonin

★ Action potential enters terminal ○electrical signal ○opens calcium channels (Ca +2 ), facilitated diffusion ★ As calcium floods in, the vesicle becomes hypotonic compared to the surrounding solution ○calcium enters the vesicle, making the vesicle move towards the neuron membrane (6) Interaction: Electrical Energy

★ Exocytosis! ★ Chemicals (neurotransmitters) released ○ in the form of chemical energy ★ Bind to receptors of the other neuron ○ float until they find it ○ electrical signals could not float, so they must be changed to chemical signals (6) Interaction: Chemical Energy

(5)

S7guM1Gw0 (3) Recap Video

CREATIVE PROJECT! Need 14 volunteers

Step 1: Action Potential - Changes in electrical gradients of a cell membrane Step 2: Rush of calcium ions - Stimulus of the action potential causes a rush of calcium ions to enter the terminal Step 3: Vesicles - Vesicles contain neurotransmitters and begin to migrate towards the cell membrane (7) Step by Step

Step 4: Merge or “Kiss and Run” - The vesicles either merge with the cell membrane or open briefly at the membrane. Step 5: Synapse - Neurotransmitter chemicals float through the synaptic cleft Step 6: Receptors - Neurotransmitters bump into specific receptors of the other cell and bind with them (7) Step by Step

Step 7: Opening of Receptors - Receptors open to allow ions to flow in Step 8: Termination - An enzyme can break down the neurotransmitter chemical - Presynaptic neuron can have transporters, which suck the neurotransmitter up back into the synaptic button (7) Step by Step

1. Science Daily, ed. "Chemical Synapse." Science Daily. N.p., n.d. Web. 6 Nov National Center for Biotechnology Information. N.p., n.d. Web. 6 Nov Animation Chemical Synapse. Youtube. N.p., n.d. Web. 6 Nov Boeree, C. George, Dr. "Neurotransmitters." General Psychology. N.p., n.d. Web. 6 Nov < genpsyneurotransmitters.html>. 5. "Conversion of Signal: Electrical to Chemical." Access Excellence Reference Center. N.p., n.d. Web. 6 Nov < electrical_chemical_conversion.php>. 6. How Neurotransmission Works. The Brain: Understanding Neurobiology. National Institue of Health, n.d. Web. 6 Nov < lesson2_neurotransmission.htm>. 7. Brookshire, Bethany. "Back to Basics 1: Neurotransmission!" Neurotic Physiology. Scicurious, n.d. Web. 06 Nov Bibliography