<P> Sympathetic nerves arise from near the middle of the spinal cord in the intermediolateral nucleus of the lateral grey column, beginning at the first thoracic vertebra of the vertebral column and are thought to extend to the second or third lumbar vertebra . Because its cells begin in the thoracic and lumbar regions of the spinal cord, the sympathetic nervous system is said to have a thoracolumbar outflow . Axons of these nerves leave the spinal cord through the anterior root . They pass near the spinal (sensory) ganglion, where they enter the anterior rami of the spinal nerves . However, unlike somatic innervation, they quickly separate out through white rami connectors (so called from the shiny white sheaths of myelin around each axon) that connect to either the paravertebral (which lie near the vertebral column) or prevertebral (which lie near the aortic bifurcation) ganglia extending alongside the spinal column . </P> <P> To reach target organs and glands, the axons must travel long distances in the body, and, to accomplish this, many axons relay their message to a second cell through synaptic transmission . The ends of the axons link across a space, the synapse, to the dendrites of the second cell . The first cell (the presynaptic cell) sends a neurotransmitter across the synaptic cleft where it activates the second cell (the postsynaptic cell). The message is then carried to the final destination . </P> <P> Presynaptic nerves' axons terminate in either the paravertebral ganglia or prevertebral ganglia . There are four different ways an axon can take before reaching its terminal . In all cases, the axon enters the paravertebral ganglion at the level of its originating spinal nerve . After this, it can then either synapse in this ganglion, ascend to a more superior or descend to a more inferior paravertebral ganglion and synapse there, or it can descend to a prevertebral ganglion and synapse there with the postsynaptic cell . </P> <P> The postsynaptic cell then goes on to innervate the targeted end effector (i.e. gland, smooth muscle, etc .). Because paravertebral and prevertebral ganglia are relatively close to the spinal cord, presynaptic neurons are generally much shorter than their postsynaptic counterparts, which must extend throughout the body to reach their destinations . </P>

Actions for which the sympathetic division of the ans is responsible include