Superior cervical ganglion
Cell biology

The superior cervical ganglion contains some 1 million nerve cell bodies. There are a number of neuron types in the SCG ranging from low threshold to high threshold neurons. The neurons with a low threshold have a faster action potential firing rate, while the high threshold neurons have a slow firing rate. Another distinction between SCG neuron types is made via immunostaining. Immunostaining allows the classification of SCG neurons as either positive or negative for neuropeptide Y (NPY), which is found in a subgroup of high-threshold neurons. Low threshold, NPY-negative neurons are secretomotor neurons, innervating salivary glands. High threshold, NPY-negative neurons are vasomotor neurons, innervating blood vessels. High threshold, NPY-positive neurons are vasoconstrictor neurons, which innervate the iris and pineal gland.
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