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9-Autonomic Nervous System Figs BW

the preganglionic neuron have its soma cell body in

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Unformatted text preview: NS consist of 2 neurons in a row, one synapsing on another. -the preganglionic neuron have its soma (cell body) in the CNS and it sends axon out to periphery. in the periphery there's a collection of postganglionic cell bodies cluster together in a autonomic ganglion. this autonomic ganglion send an axon (postganglionic axon) that goes out to periphery and contacts target tissue. -both pre and post ganglionc axons are unmyelinated. they are small in diameter and conduct slowly. -therefore, these neurons are known as pre and post in terms of flow of info to the right. one neuron is upstream, the other is downstream of that ganglion. -the postg neuron, when they enter the tissue, branch extensively within the tissue. these branches are from a single axon, so they branch through target organ. and there's no nerve terminal in terms of bulb at end of axon, but there are swellings all along the axons (see arrows). in these presynaptic varicosity (swelling) of the postganglionic neurons are vesicles of mitochondria, active zones, voltage-gated ion channels basically all the machinery necessary to cause neurotransmitter release. there can be large number of varicosity (thousands) per axon (see bottom right pic). -now there's no synapse in terms of a very close gap between pre and postsynaptic membrane. but rather have postsynaptic receptors (see bottom left pic). the synaptic cleft (distance between transmitter release site in membrane of varicosity and...
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