Lateral grey column

The lateral grey column (lateral column, lateral cornu, lateral horn of spinal cord, intermediolateral column) is one of the three grey columns of the spinal cord (which give the shape of a butterfly); the others being the anterior and posterior grey columns. The lateral grey column is primarily involved with activity in the sympathetic division of the autonomic motor system. It projects to the side as a triangular field in the thoracic and upper lumbar regions (specifically T1 L2) of the postero lateral part of the anterior grey column.

The nervous system is the system of neurons, or nerve cells that relay electrical signals through the brain and body. A nerve cell receives signals from other nerve cells through tree branch like extensions called dendrites and passes signals through a long extension called an axon (or nerve fiber). Synapses are places where one cell's axon passes information to another cell's dendrite by sending chemicals called neurotransmitters across a small gap called a synaptic cleft. Synapses occur in various locations, including ganglia (singular: ganglion), which are masses of nerve cell bodies. Preganglionic nerve cells in the sympathetic nervous system (all of which come from the lateral grey column), use the neurotransmitter acetylcholine, while postganglionic sympathetic nerve cells use norepinephrine.

The nervous system is divided into the central nervous system (brain and spinal cord) and the peripheral nervous system (everything else). The peripheral nervous system is divided into the somatic nervous system (voluntary processes) and the autonomic nervous system (involuntary processes). The autonomic nervous system is divided into the parasympathetic nervous system (normal functioning) and the sympathetic nervous system (emergency functioning). The lateral grey column mediates the functions of the sympathetic nervous system.

The spinal cord is divided into 31 segments, located between the vertebrae. Each segment is defined by a posterior root entering it and an anterior root exiting it. Each of these roots is the end of a spinal nerve connecting the spinal cord to the body. The vertebral column is divided into four groups of vertebrae: (from top to bottom) cervical, thoracic, lumbar, and sacral.

The lateral grey column is present at 17 levels of the spinal cord, specifically through levels T1 L2 (sympathetic outflow) as well as through levels S2 S4 (parasympathetic outflow). Both these segments are located within the first thoracic vertebra to the first or second lumbar vertebra as the spinal cord ends here and the nerves form the cauda equina. The lateral grey column is composed of sympathetic preganglionic visceral motor neurons which are part of the autonomic nervous system. The cells of the intermediolateral cell column are fusiform or star shaped, and of a medium size. The intermediolateral cell column exists at vertebral levels T1 L2 and mediates the entire sympathetic innervation of the body. Blood vessels contract (vasoconstriction), which reduces bleeding and conserves body heat (the exception is blood vessels fueling large muscles that would be used in running or fighting). The pupils dilate, improving vision. Perspiration increases in certain areas of the body (the purpose of this is not yet fully understood, but there is some evidence that the odor produced by this sweat serves as a signal to other individuals).

The lateral grey column plays an important role in the sympathetic division of the visceral (autonomic) motor system. Neuron cell bodies in the lateral column send their axons to synapse on sympathetic ganglia that innervate autonomic and pelvic organs; in fact, all preganglionic neurons in the sympathetic nervous system originate in the lateral grey column. The lumbar splanchnic nerves from the upper two lumbar segments synapse in the abdomen on the inferior mesenteric ganglia, associated with the inferior mesenteric artery.

Horner's syndrome is characterized by small pupils, sunken eyes, partially drooping eyelid, and dryness of the skin on the face. It is caused by problems in autonomic pathways such as damage to the lateral grey column. A study estimated the number of nerve cells in the lateral grey columns of 21 people with progressive autonomic failure in comparison with a control group. This same study found that an average of 75 percent of the lateral column cells were lost in people with progressive autonomic failure. Multiple system atrophy (MSA) is an adult onset disorder that is a sporadic and progressive. MSA is characterized by a combination of ataxia, parkinsonism, and autonomic dysfunction. A study did a comparison with the lateral grey column nerve cell count between 15 cases of patients with MSA and a control group. All cases of MSA had lost over 50 percent of their lateral horn cells which shows the involvement of the intermediolateral columns in MSA. Lichtheim's disease (also known as subacute combined degeneration) is the result of a vitamin B12 deficiency and is associated with pernicious anemia. The disease is characterized by the degeneration of both the lateral and posterior columns, which results in symptoms such as a spastic ataxic gait and paranoia. Patients may also feel tingling or weakness in their limbs and torso.