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18 Cards in this Set
- Front
- Back
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What are action potentials transmitted from one cell to another?
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nerve to nerve = synapse
nerve to skeletal m. = neuromuscular junction nerve to gland/smooth m. = neuroeffector junction |
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How does an electrical synapse take place?
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Gap junctions (connexins) between neurons
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How does a chemical synapse take place?
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Action potential reaches terminal
Causes release of neurotransmitter Neurotransmitter binds to receptor |
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Describe what happens at a neuromuscular junction
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Calcium and sodium outside cell
Action potential arrives, positive inside cell Calcium drawn into cell through voltage-gated Ca channels Acetylcholine released from vesicles into synaptic cleft Acetylcholine will bind to ligand gated Na channels, influx of sodium into muscle cell (endplate potential) Action potential generated in muscle |
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Where does the endplate potential occur and what is it caused by?
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Postsynaptic membrane
Caused by acetylcholine Causes action potential in muscle cell |
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What terminates the action of ACh?
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ACh diffuses away from cleft
OR Enzyme acetylcholineterase breaks down ACh |
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What is Myasthenia gravis caused by?
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Muscle weakness caused by circulating antibodies blocking ACh
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Differences between neuromuscular junction and true synapse?
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NM chemical transmission, TS chemical or electrical
NM acetylcholine, TS many transmitters NM one to one synapse, TS many to one NM graded potential - e.p.p., TS excitatory/inhibitory p.s.p. NM excitatory, TS e or inhibitory NM fast transmission, TS fast or slow |
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What are the 2 types of ligand-gated ion channel?
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Directly-gated
Indirectly-gated - involves second messenger and channel |
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Give 3 examples of neurotransmitters that cause e.p.s.p.
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Glutamate
Noradrenaline Acetylcholine |
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Give 3 examples of neurotransmitters that cause i.p.s.p.
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Noradrenaline
GABA Glycine |
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In e.p.s.p, what type of polarization is there?
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Depolarization
Hyperpolarization in i.p.s.p. |
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What are 5 types of receptors?
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Chemo
Photo Noci Thermo Mechano |
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Where may sensory receptors be found?
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End of nerve fibres - direct
Separate sensory cell - indirect |
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How is a potential generated with mechanoreceptors?
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Membrane stretches, depolarization occurs and opens ion channel with cytoskeleton
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How is a potential generated with chemoreceptors?
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Chemical binds to receptor, second messenger binds to channel and opens it
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What happens when light hits a photoreceptor?
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Light hyperpolarises the cell, closes the Na channel, no Na enters cell
When dark, cGMP binds to channel, when light, cGMP broken into 5'AMP |
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What is adaptation when talking about receptors?
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Continous stimulus reduces sensitivity
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