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UNC-Chapel Hill BIOC 108 - 4.1

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4.1 – NeurotransmittersNeurons: nerve cells Dendrites: receive signals from other neurons Cell body: (soma) transmits signal to axon Axon: carries signal towards axon terminal  Covered in a myelin sheath for protection  Depolarization occurs here, causing electrical wave  Axon terminal: connects with dendrites of another neuron, - Causes chemical neurotransmission, where neurotransmitter is released at synpase (communication between cells) Synaptic Transmission: between axon terminal of one neurotransmitter and dendrite of another neurotransmitter» Synaptic vesicles are in the presynaptic neurotransmitter (axonterminal)  Small membrane bound organelles  Contain neurotransmitters waiting for a signal» Action Potential: - Flow of Na+ across membrane = depolarization - Influx of calcium ions - Causes synaptic vesicles to fuse with membrane and release neurotransmitters, which will bind to a receptor in the post-synaptic neuron (dendrites)- Causes influx of cations (+) = EPSP = excitatory postsynaptic potential - Neurotransmitter is then released from receptor and inactivatedo Degraded by enzymes in synaptic clefto Reuptake and repacking in vesicles for reuse Neurotransmitters: chemical messengers that all nerve cells use to talk toone another  Synthesized in pre-synaptic axon terminal  Stored in synaptic vesicles Released by action potentials/calcium influx Crosses synaptic clef to post-synaptic neuron (EPSP)  Mechanism for shutting of Examples = glutamate, GABA, acetylcholine, biogenic amines (dopamine, serotonin, norepinephrine, epinephrine)Regulation of Neurotransmitters: - Synthesis: which neurotransmitters are being made and how much - Packaging: how neurotransmitters are being packed into the vesicles- Synaptic fusion & release- Receptor binding & downstream effects: - Breakdown: oxidizing the neurotransmitters- Reuptake- Autoregulation: neurotransmitters bind to presynaptic cell receptorsGlutamate & Gaba = both present throughout the brain! » Glutamate: primary excitatory neurotransmitter- Very important for learning and memory- Most abundant neurotransmitter in the brain» GABA: primary inhibitory neurotransmitter- Synthesized from glutamate, but has opposite efectAcetylcholine: only neurotransmitter at neuromuscular junctions Has a role in arousal, attention, memory, motivation  Alzheimer: decreased levels of acetylcholine  Myasthenia gravis: attacks acetylcholine post synaptic receptors leading to reduced signaling and muscle weakness  Botulism: inhibits the release of acetylcholine Biogenic Amines: function depends on where they are located in the brain Dopamineo Movement o Cognition – procedural learning, memory, cellular learningo Normal mood – pleasure, laughter, etc.o Motivation – reward, reinforcement Norepinephrine o Attention, reward, anxiety, stress response, fight or flight Epinephrine o Adrenaline, fight or flight response Serotonino Emotion, mood, anxiety, depression, OC, sleep & wakefulnesso Made from tryptophan Synthesis of Catecholamines (dopamine and norepinephrine) from Tyrosine:» Intermediate = DOPA Parkinson’s Disease: - Due to a loss of dopamine producing neurons - Symptoms: tremors and rigid muscles - Treatments: no cure, DA agonist, preventing DA breakdown Depression: o Co-morbid with many other psychiatric disorders o Not all symptoms must be present in everyone o Treatments: medications that block serotonin and norepinephrine reuptake  Increased 5HT and NE o Monoamine Theory of Depression: decreased levels of monoamine neurotransmitters helps treating depression Alcohol and Drug Addiction: o Health problems, disability, failure to meet major responsibilities o Addictive because they release dopamine concentrations at synapseDA = presynaptic dopaminergic terminal  DAT5HT = presynaptic serotonergic terminal  HttNE = presynaptic noradrenergic terminal 

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