Somatic - Sympathetic

• There are two major targets of the sympathetic system: visceral and somatic. The visceral sympathetic components extend rostral to the head from three cervical chain ganglia. All of the organs receive sympathetic-postganglionic motor inputs from the chain ganglia or from collateral ganglia where postganglionic sympathetic neurons are located. Somatic sympathetic projections are to the entire head/body vassculature, sweat glands and hair follicle muscles.

• Remarkably, all of the sympathetic system arises from the lateral horn of the spinal cord. This sensory-motor region of the cord is further limited to segments formed by nerves emerging between thoracic 1 to lumbar 2. The motor targets of these preganglionic neurons are the sympathetic ganglia that lie along the vertebral column (paravertebral). Other axons pass through these ganglia to more distal collateral ganglia.

• These second level ganglion neurons (postganglionic) project to lacrimal glands, the pupil dilatory muscle, salivary glands, thoracic and abdominal organs (e.g the heart, lungs etc). In addition, there are projections over the entire body to sweat glands (sudiferous glands), piloerectile muscles of the hair follicles and smooth muscle of blood vessels. Blood flow is controlled for various body regions and viscera by contraction or passive blood pressure dilatation.

• Visceral organ sensory inputs to the CNS (except parasympathetic) enter through these 14 segments of the cord. These are reflex connections of the viscera as well as for temp regulation (blood flow, sweating and piloerection).