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Unformatted text preview: Outline 4: I. Return to Neurotransmitters A. How they work in general: -Action potential reaching a bouton ("button") causes exocytosis - release of neurotransmitters. -This is often accomplished via the opening of voltage-gated Ca 2+ channels (permitting influx of Ca2+) -Neurotransmitters spill into the synaptic cleft and bind to receptors on the post-synaptic membrane. -These receptors are either ionotropic ("ion-channel linked receptors") or metabotropic ("G-protein-linked receptors") Ionotropic receptors cause immediate EPSPs or IPSPs by changing the shape of ion channels Metabotropic receptors can cause a slower onset of PSPs or other changes (e.g., changes in cellular metabolism, gene expression) 1 - Inhibitory neurotransmitters produce IPSPs - Excitatory neurotransmitters produce EPSPs II. Classes of Neurotransmitters: A. Amino Acids 1. Glutamate- the most prevalent excitatory neurotransmitter in the brain 2. GABA - the most common inhibitory neurotransmitter in the brain B. Monoamines 1. Catecholamines- synthesized from tyrosine Dopamine (DA) Norepinephrine (NE) (also known as noradrenaline) Epinephrine (E) (aka adrenaline) Which of these catecholamines is used is dependent upon the synthesizing enzymes in the neuron 2. Indolamines --Serotonin (5HT) - synthesized from tryptophan C. Acetylcholine - used by cholinergic neurons A, B and C are packaged in small vesicles D. Neuropeptides - packaged in large vesicles -tend to act via indirect receptors using 2nd messengers - e.g., endorphins (endogenous opiates) are neuropeptides E. Soluble Gases - nitric oxide and carbon monoxide -not packaged in vesicles -freely diffusible -at least some of their actions are via 2nd messengers III. DrugsAgonists Antagonists (more on drugs in a bit) 2 IV. Neurons are heterogeneous A. Different classes of neurons 1. Multipolar neurons - many dendrites and a single axon* The vast majority of neurons in the brain are multipolar (*or, rarely, they can be loosely classified as having no axon) 2. Bipolar neurons - a single dendrite on one end and an axon on the other Found in some sensory systems (e.g., retina and olfactory bulb) 3. Unipolar neurons (aka monopolar neurons)a single process leaving the soma which branches into 2, with dendrites on one end and axon terminals on the other. Neurons carrying touch information into the spinal cord are monopolar 3 B. Neurons vary in the nature of their communication 1. Length and myelination of axons 2. The neurotransmitters used for signaling 3. The type and configuration of synaptic inputs 4. The influence of non-chemical synapses "electrotonic coupling" 5. The influence of hormones V. Convergence and Divergence Convergence- the axons from many neurons can converge onto a single neuron Divergence - the axon from a single neuron can provide synaptic input onto many neurons 4 ...
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This note was uploaded on 04/20/2008 for the course PSY 308 taught by Professor Jones during the Spring '08 term at University of Texas.
- Spring '08