At any moment, each of these specialized brain neurons might be receiving multiple messages from multiple sources, but is only selectively responding to certain information about the timing or frequency of the impulses it is receiving. Related Stories.
Methods for measuring sympathetic nervous system activity. Heart rate variability (HRV), the beat-to-beat variation in heart rate, is an indirect method of measuring autonomic nervous system activity, with contributions from both the sympathetic and parasympathetic nervous systems.ine electrodes are used to record 'bursts' of activity from multiple or single afferent and efferent nerve axons in the skin and muscle. The common peroneal nerve is typically chosen for this method (because it is easily accessible) and measures the efferent postganglionic muscle sympathetic nerve activity (MSNA).
Also, (from UW Health site )The purpose of the nerve block is to find out if your sympathetic nerves are causing your pain. A stellate ganglion block is a test to diagnose and treat sympathetic dependent pain in your hand, arm or shoulder. The pain may come from the nerves in your neck near the spine. These nerves control sweating, heart rate, blood vessels, pupil dilatation, movement of food through the intestines, and many other body functions. Sometimes these nerves do not work right and cause pain. It can be on either side of your body.