Lateral horn of the spinal cord

The lateral horn of the spinal cord, also known as the intermediolateral nucleus, is a component of the spinal cord that plays a crucial role in the autonomic nervous system. It is primarily involved in the sympathetic nervous system and is located in the thoracic and upper lumbar segments of the spinal cord.

Anatomy

The lateral horn is a small, pointed projection of gray matter found in the thoracic (T1 to T12) and upper lumbar (L1 to L2 or L3) regions of the spinal cord. It is situated between the dorsal horn and the ventral horn and is most prominent in the thoracic segments.

Location

The lateral horn is located in the intermediate zone of the spinal cord, specifically in the lateral part of the intermediate gray matter. It is visible in cross-sections of the spinal cord as a lateral protrusion of the gray matter.

Structure

The lateral horn contains the cell bodies of preganglionic sympathetic neurons. These neurons are part of the autonomic nervous system and are responsible for transmitting signals from the central nervous system to the sympathetic ganglia.

Function

The primary function of the lateral horn is to serve as a relay center for the sympathetic nervous system. The preganglionic neurons located in the lateral horn send their axons out through the ventral root of the spinal nerve to synapse with postganglionic neurons in the sympathetic ganglia.

Sympathetic Nervous System

The sympathetic nervous system is responsible for the "fight or flight" response, which prepares the body for stressful or emergency situations. It increases heart rate, dilates airways, and inhibits digestion, among other effects.

Preganglionic Neurons

The preganglionic neurons in the lateral horn release the neurotransmitter acetylcholine at their synapses with postganglionic neurons. These postganglionic neurons then release norepinephrine at their target organs.

Clinical Significance

Damage to the lateral horn can disrupt the function of the sympathetic nervous system, leading to a variety of clinical symptoms. Conditions such as Horner's syndrome can result from lesions affecting the sympathetic pathways.

Horner's Syndrome

Horner's syndrome is characterized by ptosis, miosis, and anhidrosis, and can occur due to disruption of the sympathetic pathways that originate in the lateral horn.

Spinal Cord Injuries

Injuries to the thoracic or upper lumbar regions of the spinal cord can affect the lateral horn and impair autonomic functions, leading to issues with blood pressure regulation, thermoregulation, and other autonomic processes.

Development

The lateral horn develops from the neural tube during embryogenesis. It differentiates from the intermediate zone of the developing spinal cord and becomes populated with preganglionic sympathetic neurons.

See Also

• Spinal cord
• Sympathetic nervous system
• Autonomic nervous system
• Gray matter

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