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5.1.3 Synapses (Transmission across synapse: (summation: (combined effect…
5.1.3 Synapses
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Role of synapses:
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ensure action potentials are transmitted in the correct direction; only presynaptic bulb has ACh vesicles
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Structure:
acetylcholinesterase:
enzyme found in the synaptic cleft; hydrolyses the ACh into ethanoic acid and choline to stop the transmission of signals so synapse does not continue to produce action potentials in the post synaptic membrane
if ACh is left in synaptic cleft then it will continue to open the sodium ion channels in post synaptic membrane and cause action potentials
ethanoic acid and choline are recycled and re-enter the synaptic bulb by diffusion and are recombined to ACh using ATP from respiration
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post-synaptic membrane:
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channels consist of five polypeptide molecules; two have special receptor site complementary to the neurotransmitter
if neurotransmitter is present in the synaptic cleft it binds to the two receptor sites causing the sodium ion channel to open
pre-synaptic bulb:
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many mitochondria for active processes needing ATP; large smooth ER to package neurotransmitter into vesicles; lots of vesicles containing ACh, voltage gated calcium ion channels on plasma membrane
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