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Lecture 4

Week 4 - Neurotransmitters

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PSY 324
Ayesha Khan

Week 4 NeurotransmittersOctober0111702 PMNeurotransmitters and NeuromodulatorsThere are many different kinds of neurotransmittersIn the brain most synaptic communication is accomplished by two neurotransmitters one with excitatory effects glutamine and one with inhibitory effects GABAAnother inhibitory neurotransmitter is found in the spinal cord and lower brain stem glycine All other neurotransmitters have modulating effects rather than informationtransmitting effects That is the release of neurotransmitter other than glutamate or GABA tends to activate or inhibit entire circuits of neurons that are involved in particular brain functionsExample acetylcholine activates the cerebral cortex which stimulates learning but the information that is learned and remembered is transmitted by neurons that secrete glutamate and GABAAcetylcholinePrimary neurotransmitter secreted by efferent axons of the central nervous systemAll muscular movement is accomplished by the release of acetylcholine and ACh is also found in the ganglia of the autonomic nervous system and at the target organs of the parasympathetic branch of the ANS Also play a role inREM sleepLearning especially higher learningControl electrical rhythms of the hippocampus which includes memory formationThese synapses are said to be acetylcholinergicThe axons and terminal buttons of the acetylcholinergic neurons are distributed widely throughout the brain The effects of Ach in the brain are generally facilitoryComposed of two components choline made by the breakdown of lipids and acetate aka acetic acid Acetate is transferred from a molecule of acetyl CoA ACh is produced in the presence of the enzyme choline acetyltransferase ChATTwo drugs botulinum toxin and the venom of the black widow spider affect the releaseof acetylcholineBotulinum toxin prevents the release of AChBlack widow spider venomhas the opposite effect it stimulates the release of AChRemember how acetylcholine esterase AChE breaks down ACh after being released by the terminal button There are several drugs that disable AChEFor example breaking down AChE in people with myasthenia gravis would help them regain their strength In this disease the body attacks its own ACh receptors which leaves patients very weak By breaking down AChE the person is able to use what ACh they have to move their musclesThere are two types of AChreceptors ionotropic and metabotropic The ionotropic receptor is stimulated by nicotine nicotinic receptorBecause muscle fibres must be able to contract rapidly they contain the rapid ionotropic nicotinic receptorsThe metabotropic receptor is stimulated by muscarine a drug found in the poison mushroom muscarinic receptorsBecause muscarinic receptors are metabotropic in nature and thus control ion channels through the production of second messengers their actions are slower and more prolonged than those of nicotinic receptorsThe CNS contains all kinds of receptors but muscarinic predominateJust as two different drugs stimulate the two classes of acetylcholine receptors two different drugs block themAtropine blocks muscarinic receptors This blocks the effect of acetylcholine relaxing musclesCurare blocks nicotinic receptors Because of this curare causes paralysisThe MonoaminesDopamine norepinephrine epinephrine and serotonin are four chemicals that belong to aBiological Psychology Page 1
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