Autonomic nervous system origin

The locus cemleus is important for the regulation of attentional states and autonomic nervous system activity. It has also been implicated in the autonomic and stress-like effects of opiate withdrawal. A noradrenergic pathway originating from the locus cemleus which descends into the spinal cord is part of the descending inhibitory control system, which has an inhibitory effect on nociceptive transmission in the dorsal horn. 

The concept of chemical neurotransmission originated in the 1920s with the classic experiments of Otto Loewi (which were themselves inspired by a dream), who demonstrated that by transferring the ventricular fluid of a stimulated frog heart onto an unstimulated frog heart he could reproduce the effects of a (parasympathetic) nerve stimulus on the unstimulated heart (Loewi Navratil, 1926). Subsequently, it was found that acetylcholine was the neurotransmitter released from these parasympathetic nerve fibers. As well as playing a critical role in synaptic transmission in the autonomic nervous system and at vertebrate neuromuscular junctions (Dale, 1935), acetylcholine plays a central role in the control of wakefulness and REM sleep. Some have even gone as far as to call acetylcholine a neurotransmitter correlate of consciousness (Perry et al., 1999). 

Muscarinic receptors are responsible for postganglionic parasympathetic neurotransmission and thus for control of a wide range of smooth muscle, cardiac muscle and secretory responses. Some responses originating in the sympathetic division of the autonomic nervous system, such as sweating and piloerection, also are mediated through muscarinic receptors. 

The biology of the monoamines is described in detail elsewhere. In simple terms, they facilitate transmission in neural pathways that originate in nuclei of the brainstem and have descending projections to the autonomic nervous system and widespread ascending projections to sites in the limbic system and cortex. These pathways modulate many aspects of behavioural function as well as anxiety responses. Of the three monoamines, the role of serotonin in anxiety is best understood, but the picture is complex as increased serotonergic activity may be anxiogenic or anxiolytic depending on the site of action (Bell and Nutt 1998). 

Neurologic pathways in the sympathetic nervous system originate from the thoracic (T1 to T12) and the upper lumbar segments (LI and L2) of the spinal cord. Neurologic pathways in the parasympathetic nervous system originate from cranial nerves III, VII, IX, and X, from the brainstem, and the sacral segments S2, S3, and S4 from the spinal cord. This is why the parasympathetic nervous system is also known as the craniosacral division of the autonomic nervous system. 

Kawashima T. The autonomic nervous system of the human heart with special reference to its origin, course, and peripheral distribution. Anat Embryol (Berl) 2005 209 425-38. 

Parasympathetic (PANS) The part of the autonomic nervous system that originates in the cranial nerves and the sacral part of the spinal cord... 

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