Supraspinal vasomotor neurons send projections to the intermediolateral cell column, which is composed of sympathetic preganglionic neurons (SPN) through the T1-L2 segments. The supraspinal neurons act on the SPN and its tonic firing, modulating its action on the peripheral sympathetic chain ganglia and the<unk> renal medulla. The sympathetic ganglia act directly on the blood vessels they innervate throughout the body, controlling vessel diameter and resistance, while the<unk> renal medulla indirectly controls the same action through the release of epinephrine and norepinephrine. The descending<unk>  pathways, which are responsible for the supraspinal communication with the SPN, are interrupted resulting in decreased sympathetic outflow below the level of the injury. In this circumstance, the SPN is controlled only by spinal influences. The first couple of weeks after a spinal injury, the decreased sympathetic outflow causes reduced blood pressure and sympathetic reflex. Eventually, synaptic reorganization and plasticity of SPN develops into an overly sensitive state, which results in abnormal reflex activation of SPN due to afferent stimuli, such as bowel or bladder distension. Reflex activation results in systemic vasoconstriction below the spinal cord disruption. The peripheral arterial vasoconstriction and hypertension activates the baroreceptors, resulting in a parasympathetic surge originating in the central nervous system, which inhibits the sympathetic outflow; however, the parasympathetic signal is unable to transmit below the level of the spinal cord lesion. This results in vasodilation, flushing, pupillary constriction and nasal stuffiness above the spinal lesion, while there's piloerection, pale and cool skin below the lesion due to the prevailing sympathetic outflow. The reason this issue is much more prominent for lesions at or above the T6 level is because the Splanchnic nerves emerge from the T5 level and below. Loss of brain's control over T6 and below causes splanchnic arteries to reflexively vasoconstrict and since the Splanchnic arteries are the body's largest reservoir for circulating blood, their vasocontriction dramatically affects the blood pressure of the body.
Autonomic dysreflexia
Neuroglycopenia
Monoplegia
Neuromyotonia
Hyperreflexia
Paresis
Synesthesia
Myotonia