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Motor Units

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A motor unit consists of two main components: a single efferent motor neuron (i.e., a neuron that carries impulses away from the central nervous system) and all of the muscle fibers it innervates. The motor neuron may innervate multiple muscle fibers, which are single cells, but only one motor neuron innervates a single muscle fiber.

Motor Units

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Updated: May 16, 2026

ALS - Motor Neuron Disease: Mechanism and Development of New Therapies

ALS - Motor Neuron Disease: Mechanism and Development of New Therapies

Published on: July 29, 2007

Spinal cord: motor neuron diseases.

Kourosh Rezania¹, Raymond P Roos

¹Department of Neurology, University of Chicago Medical Center, Chicago, IL 60637, USA. krezania@neurology.bsd.uchicago.edu

Neurologic Clinics

|November 29, 2012

Summary

This summary is machine-generated.

This article reviews spinal cord motor neuron diseases, focusing on amyotrophic lateral sclerosis (ALS). While genes for familial ALS are known, the exact cause of this complex disease remains unclear.

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Area of Science:

Neurology
Neuroscience
Genetics

Background:

Spinal cord motor neuron diseases impact lower motor neurons in the ventral horn.
Amyotrophic lateral sclerosis (ALS) is the most prevalent spinal cord motor neuron disease, affecting both upper and lower motor neurons.
Other motor neuron diseases exclusively impact lower motor neurons.

Purpose of the Study:

To provide an overview of spinal cord motor neuron diseases.
To highlight amyotrophic lateral sclerosis (ALS) as the most common form.
To discuss the current understanding of motor neuron disease pathogenesis.

Main Methods:

Literature review of spinal cord motor neuron diseases.
Focus on clinical and genetic aspects of amyotrophic lateral sclerosis (ALS).
Discussion of lower motor neuron-only diseases.

Main Results:

Amyotrophic lateral sclerosis (ALS) affects both upper and lower motor neurons.
Other motor neuron diseases are characterized by isolated lower motor neuron involvement.
Genetic factors for familial ALS have been identified.

Conclusions:

The pathogenesis of amyotrophic lateral sclerosis (ALS) remains largely unknown despite genetic discoveries.
Further research is needed to elucidate the complex mechanisms underlying motor neuron degeneration.