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Introduction to Neurotransmission

This article provides an overview of neurotransmission, including the function and characteristics of neurons, the process of synaptic transmission, and the role of neurotransmitters in signal transmission. It also explores the differences between axons and dendrites and explains the concept of action potential.

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Introduction to Neurotransmission

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  1. An Introduction to Neurotransmission William Wisden Dept of Clinical Neurobiology INF 364 William.Wisden@urz.uni-heidelberg.de

  2. http://www.indstate.edu/thcme/mwking/home.html http://www.indstate.edu/thcme/mwking/nerves.html http://faculty.washington.edu/chudler/neurok.html http://faculty.washington.edu/chudler/chnt1.html Explore the Brain and Spinal Cord The Neuron Fundamental Neuroscience - second edition Squire, Bloom, McConnell, Roberts, Spitzer, Zigmond Academic Press, 2003

  3. A neuron

  4. The action potential

  5. Hodgkin & Huxley, 1939

  6. Rate of action potential firing is information

  7. The dendrite

  8. Differences between axons and dendrites Axons Dendrites Take information away from the cell body Bring information to the cell body Smooth Surface Rough Surface (dendritic spines) Generally only 1 axon per cell Usually many dendrites per cell No ribosomes Have ribosomes Can have myelin No myelin insulation Branch further from the cell body Branch near the cell body

  9. Dendrites constitute a kind of neural microchip for complex computations

  10. Rate of action potential firing is information Frequency code of impulses within the axons Place/topological code depending on which axons are active

  11. Chemical synapse Axon-dendrite Axo-axonic Axon-soma

  12. Passing information between neurons Gap junctions -electrical transmission fast both directions Chemical transmission slower - unidirectional integrative amplifies and regenerates the signal

  13. The synapse

  14. OUT IN Calcium entry is excitatory Calcium is a second messenger which binds to target proteins e.g. Calmodulin

  15. Electrical Trigger for Neurotransmission Action potential Ca2+ Axon Terminal Neurotransmitter Mobilization and Release Diffusion of Neurotransmitters Across the Synaptic Cleft Spine Dendrite

  16. Action potential Depolarization Ca2+

  17. Electrical properties

  18. How is the action potential generated? http://faculty.washington.edu/chudler/ap.html

  19. OUT EXCITATORY + IN INHIBITORY - INHIBITORY -

  20. Look at the animation! http://faculty.washington.edu/chudler/ap.html

  21. Neurotransmitters

  22. Excitatory Excitatory Inhibitory

  23. Simple transmitters: g-aminobutyric acid (GABA) glutamic acid (glutamate) acetylcholine (Ach)

  24. OUT Cl- Na+ Na+ Glu GABA ACh Cl- Na+ Na+ GABAA receptor Glutamate/AMPA receptor Inhibition Excitation Acetylcholine receptor IN

  25. Neurons and glial cells

  26. The process of chemical neurotransmission can be divided into five steps 1. Synthesis of the neurotransmitter in the presynaptic neuron 2. Storage of the neurotransmitter and/or its precursor in the presynaptic nerve terminal 3. Release of the neurotransmitter into the synaptic cleft 4. Binding and recognition of the neurotransmitter by target receptors 5. Termination of the action of the released transmitter

  27. Life cycle of a neurotransmitter

  28. An excitatory (glutamatergic) synapse

  29. A synapse using g-aminobutyric acid (GABA)

  30. A synapse that uses acetylcholine (ACh)

  31. Simple circuits

  32. Feed-forward inhibition

  33. Negative feedback Feedback inhibition

  34. Neocortex Interneuron - uses GABA Pyramidal neuron - uses glutamate

  35. Ionotropic and metabotropic receptors Fast Ion flow in/out milliseconds Slow Second messenger cascades seconds

  36. Ionotropic Metabotropic

  37. OUT Cl- Na+ Glu GABA Cl- Na+ GABAA receptor Glutamate/AMPA receptor Inhibition Excitation IN

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