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10 Cards in this Set
- Front
- Back
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What are the two types of synapses and how do they differ?
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1. Electrical synapse
- Fast (between gap junctions) - Bidirectional - Occurs between neurones of CNS (glia-glia or glia-neurone) 2. Chemical synapse - Unidirectional - Pre synaptic terminal sends neurotransmitters to post syn receptors |
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Describe the process how chemical synapses transmit signals.
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1. AP invades nerve terminal.
2. Depolarisation triggers voltage-dependent Ca channels to open. 3. Ca influx to presynaptic terminal. 4. Ca triggers neurotransmitter release by exocytosis. 5. Neurotransmitter diffuse across synaptic cleft to bind to recs on post synaptic membrane. 6. Effect on post synapse. 7. Rapid termination of signal by reuptake of neurotransmitters or enzymatic breakdown. |
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What are the two types of neurotransmitter receptors and how do they differ?
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1. Metabotropic receptors
- Slow but long lived - G-protein coupled - When neurotransmitter binds causes a conformational change to rec and activates G-protein to either indirectly close/open ion channels or stim or inh enzymes 2. Ionotropic receptors - Fast but short lived - Ligand-gated - When neurotransmitter binds directly opens/closes ion channels. |
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What are the four groups of major neurotransmitters and give examples of each?
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1. Amino acids
- Glutamate (excitatory CNS) - GABA (inhibitor CNS) - Glycine (CNS) 2. Monoamines - Noradrenaline (autonomic symp) - Serotonin (found in prozac) - Dopamine (CNS/PNS control voluntary movement; valid in Parkinsons) 3. Neuroactive peptides - Tachykinins (Substance P, neurokinin A) - Opioids (Enkephalins) 4. Ach (at neuromuscular junctions of skeletal muscles) |
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Describe the electrical effect of ionotropic receptor activation.
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1. Neurotransmitters such as glutamate and Ach diffuse across synaptic cleft and bind to the iono. receptors on ion channels.
2. Ion channels open to allow Na+ to enter. 3. Na+ influx causes a bit of depolarisation. It is only a small excitatory post synaptic potential (EPSP) as it won't last long because there are many mechanisms to pump Na+ back out again. |
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Describe the electrical effect of ionotropic receptor inhibition.
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1. Neurotransmitters such as GABA and Glycine diffuse across synaptic cleft to bind to the iono. receptors on ion channels.
2. Ion channels open to allow Cl- to enter. 3. Cl- influx causes a bit of hyperpolarisation. It is only a small inhibitory post synaptic potential (IPSP) because mechanisms pump Cl- out. |
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Explain spatial summation.
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Spatial summation is the summing of post synaptic potentials and is generated by multiple, separate synapses.
One excitatory synapse is insufficient to cause AP because below threshold. Multiple synapses will cause enough voltage to open Na channels to reach threshold. |
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What happens when an excitatory synapse and inhibitory synapse act on one neurone?
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Spatial summation will cause them to cancel each other out so no electrical activity happens.
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Explain temporal summation.
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Temporal summation is the summing of postsynaptic potentials generated at the same synapse and they occur in rapid succession (high frequency).
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Draw AP graphs for temporal and spatial summation.
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