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E4 Neurotransmitters And Synapses


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For the IB Biology course: Option E: Neurobiology and Behaviour. Includes TOK discussion on drugs laws and the use of science in policy.

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  • Contact Top Class IB Tutors for any assignment help: Email: Website: IB theory of knowledge (TOK) essay help tutors example sample Online Assignment Help/Tuition all over the world (100% guarantees for top class grades): Mail us or call us for any query: Email: Website: Ph: +91 9911918255 and +91 9918492994 The theory of knowledge (TOK) requirement is central to the educational philosophy of the Diploma Programme. It is a stated aim of TOK that students should become aware of the interpretative nature of knowledge, including personal ideological biases, regardless of whether, ultimately, these biases are retained, revised or rejected. In that sense ToK is the glue that binds the different academic components of the IB Diploma together. IB Tutor provides assignment writing help in all the IB subjects. 1 IB maths mathematics studies IA tutor help HL SL exploration extended essay example sample 2. IB physics IA labs extended essay help tutors example sample 3. IB chemistry IA labs extended essay help tutors example sample 4. IB Biology IA labs extended essay help tutors example sample 5. IB written task WT 1 & 2 help tutors example sample 6. IB Written Assignment WA 1 & 2 online help tutors example sample 7. IB English Extended Essay EE online help tutors example sample 8. IB English IOP IOC online help tutors example sample 9. IB theory of knowledge (TOK) essay help tutors example sample, TOK Presentation help guidance 10. IB economics IA commentary extended essay help tutors example sample eco 11. IB business management bm IA extended essay help tutors sample example 12. IB ITGS (information technology in a global society) project extended essay help tutors example sample 13. IB history geography IA extended essay help tutors example sample 14. IB Environmental systems & society ESS Lab Report IA Extended Essay EE Help Tutor Sample Example Online
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E4 Neurotransmitters And Synapses

  1. 1. Assessment Statements Obj. State that some neurotransmitters excite postsynaptic transmission and others E4.1 1 inhibit postsynaptic transmission. Explain how decision-making in the CNS can result from the interaction between the E4.2 3 activities excitatory and inhibitory presynapatic neurons at synapses. Explain how psychoactive drugs affect the brain and personality by either increasing E4.3 3 or decreasing postsynaptic transmission. List three examples of excitatory and three examples of inhibitory psychoactive drugs. E4.4 • Excitatory: nicotine, cocaine, amphetamines 1 • Inhibitory: benzodiazepines, alcohol, tetrahydrocannabinol (THC) Explain the effects of cocaine and THC in terms of their action at synapses in the E4.5 3 brain. Discuss the causes of addiction, including genetic predisposition, social factors and E4.6 3 dopamine secretion. Be sure you have a solid understanding of action potentials and synapses as you work through this subtopic.Command terms: Assessment statements from: Online IB Biology Subject Guide
  2. 2. Communication via SynapsesSynapses are a fundamental part of neuralpathways as they regulate decision-makingin terms of exciting or inhibiting the post-synaptic neurons.Review:• Action potentials (AP) reach terminal bud of the pre-synaptic neuron.• Neurotransmitters (NT), chemical messengers, diffuse across the synapse to bind with receptors on the post- Work through this tutorial: synaptic membrane.Neurotransmitters are:• Excitatory, which means they excite the post-synaptic neuron (contributing to depolarisation and propagation of the AP.OR:• Inhibitory, hyperpolarising the post- synaptic neuron and preventing AP.
  3. 3. Neurotransmitters can be excitatory or inhibitory Neurotransmitters (NT) are proteins • diffuse across the synaptic cleft • bind with a receptor on the post-synaptic neuron. Whether or not the post-synaptic neuron propagates the action potential depends on: • Which NT diffuses across • Which receptors they bind to • Which ions flow in/out of the post-synaptic neuron • Whether or not depolarisation reaches threshold Excitatory NTs cause depolarisation • e.g. ACh, dopamine 0mv • NT binds, Na+ channels open, Na+ rushes in depolarisation • Membrane potential depolarises, AP propagated threshold Inhibitory NTs cause hyperpolarisation resting • e.g. GABA, dopamine (on different pathways)-70mv • NT binds to receptor hyperpolarisation • K+ channels open, K+ rushes out • OR Cl- channels open, Cl- rushes in • Membrane potential become more negative • Action potential is prevented from propagating time
  4. 4. is a useful example of an inhibitory neurotransmitter.
  5. 5. Decision-making in the Central Nervous System (CNS) The axons of many pre-synaptic neurons feed into the dendrites of one post-synaptic neurons via synapses. axon The ‘decision’ whether or not to propagate the action potential along the axon of the synapse post-synaptic neuron takes place in a region of the cell body called the axon hillock. This is achieved through summation of the incoming impulses. If the total axon hillock impulse reaches threshold, the post-synaptic neuron depolarises and the action potential is propagated. If the sum does not reach threshold, the AP is not propagated. There are two main methods of summation: temporal and spatial.Diagram adapted from:
  6. 6. Decision-making in the Central Nervous System (CNS) Test out temporal and spatial summation: Temporal summation • Action potentials arrive in rapid succession • Depolarisation in the axon hillock is summative • If it reaches threshold before repolarisation, the AP is propagated. Spatial summation • Action potentials arrive simultaneously from multiple sources • Some neurotransmitters are excitatory (increasing depolarisation) • Other NTs are inhibitory (hyperpolarising). • Summation in the axon hillock is summative. • If it reaches threshold the AP is propagated.Diagram adapted from:
  7. 7. How do psychoactive drugs affect the brain? Before thinking about how drugs affect the synapses, be sure you understand how they work and are reset. • Some NTs have a normal excitatory function • Other NTs have a normal inhibitory function In general, psychoactive drugs can: 1. Increase or decrease the release of NTs (e.g. THC – cannabis) 2. Breakdown re-uptake proteins which are responsible for returned used components of NTs to the pre-synaptic neuron (ready to use again) 3. Block re-uptake proteins (e.g.cocaine) 4. Mimic or block NTs, binding to the receptors on post-synaptic membranes 5. Inhibit production of new NTsWork through the excellent animations and explanations from
  8. 8. Excitatory drugs increase Examples: • Nicotine, amphetamines, cocainepost-synaptic transmission What is the effect of cocaine? Normal: • Dopamine acts as excitatory NT • Dopamine is re-uptaken by pumps on the pre- synaptic membrane. With Cocaine: • Cocaine blocks re-uptake pumps • Dopamine remains in synaptic cleft • More dopamine continues to be released • Summative increase in post-synaptic transmission Effects on mood: • Dopamine is involved in reward pathways, enhancing feelings of pleasure • Longer-lasting feelings as dopamine is not re- uptaken Effects on behaviour: • feelings of euphoria • increased energy and alertness • highly addictive • association with depression as body reduces production of own dopamine over time
  9. 9. Inhibitory drugs decrease Examples: • Alcohol, benzodiazapines, THCpost-synaptic transmission What is the effect of tetrahydrocannibol (THC)? Normal: • Dopamine release is moderated (inhibited) by GABA With THC: • THC mimics cannabinoids and inhibits GABA release by binding to cannabinoid receptors • GABA cannot inhibit dopamine release • More dopamine is released Effects on mood: • Dopamine is involved in reward pathways, enhancing feelings of pleasure • Not as extreme release of dopamine as with cocaine, but still higher than normal Effects on behaviour: • intoxication • hunger • memory impairment • potential dependency
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  11. 11. A scale of harm for drugs Which dots represent: • tobacco? • alcohol? • heroin? • cocaine? • THC/ cannabis? • ecstasy? Drag the red dot to point you think represents alcohol. How can drugs cause physical harm? How can drug use lead to addiction (dependency)? What factors contribute to development of addiction?ActivePrompt link: or
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  13. 13. @IBiologyStephen Please consider a donation to charity via Biology4Good. Click here for more information about Biology4Good charity donations. This is a Creative Commons presentation. It may be linked and embedded but not sold or re-hosted.