What is the Anterior Horn of the Spinal Cord?

Responsibility for Movement

The anterior horn as depicted in Henry Gray's Human Anatomy.

The anterior horn of the spinal cord (also called the anterior cornu, anterior grey column or ventral horn) is the front column of grey matter in the spinal cord. It is one of the three grey columns. 

The anterior horn of the spinal cord contains motor neurons that affect the skeletal muscles while the posterior grey column receives information regarding touch and sensation. The anterior horn is the column where the cell bodies of alpha motor neurons are located.

The anterior horn of the spinal cord, directed forward, is wide and rounded or quadrangular in shape. Its posterior section is called the base, and its anterior section is called the head. It is separated from the surface of the medulla spinalis by a layer of white substance which is traversed by the bundles of the anterior nerve roots. In the thoracic region, the postero-lateral part of the anterior column projects laterally as a triangular field, which is named the lateral grey column.

More About Motor Neurons

The anterior horn of the spinal cord is made up of three different types of neurons: large alpha motor neurons, medium gamma motor neurons and small neurons thought to be interneurons. These neurons differ in both their morphology and in their patterns of connectivity. They are organized in the same manner as the muscles they innervate.

The anterior horn of the spinal cord is frequently mentioned in conversations about motor neuron diseases such as polio or amyotrophic lateral sclerosis (ALS).

When the spinal cord develops, the posterior part becomes responsible for managing most aspects of sensation, and the anterior is more responsible for movement.

When you move, the cells of your cerebral cortex send a message to cells in the spinal cord. These cells then relay the message out to the peripheral nervous system and muscles.

The nerve cells that are responsible for relaying messages between the brain and the peripheral nervous system are called motor neurons.

The nerves that send messages between the cerebral cortex and the spine are called upper motor neurons, and those that relay messages from the spine to the muscles are called lower motor neurons. These neurons communicate by synapses in the anterior horn of the spinal cord.

Motor Neuron Diseases

Diseases that selectively attack these neurons are called motor neuron diseases. As the name suggests, motor neuron diseases reduce someone's ability to move. The best-known example is amyotrophic lateral sclerosis, but other examples include polio, primary lateral sclerosis, and Kennedy's disease.

Neurologists use their physical exam to determine where the disease is in the body. If the problem is with the upper motor neurons alone, then certain exam findings like rigidity and spasticity may develop, whereas if just the lower motor neurons are involved, other exam findings like atrophy and fasiculations are present.

In some forms of motor neuron disease, such as ALS, both upper and lower motor neuron signs are present.

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