Name: how motor units control muscle movement
Uploaded: 2025-10-23T11:49:15.000Z
Duration: 46 s
Channel: JoVE

Una unidad motriz se refiere
a una neurona motriz,

localizada en la médula espinal,

y la cantidad de fibras
musculares que ésta inerva.

Mientras que cada fibra muscular
del esqueleto es inervada

únicamente por una neurona motriz,

los axones de cada neurona motriz

pueden ramificarse en
diversas terminaciones,

formando uniones neuromusculares
en todo el músculo.

Como resultado, la estimulación
de una sola unidad motriz

ocasiona una contracción
débil del músculo entero.

Dependiendo del nivel de
control que se necesite,

el número de fibras por
unidad puede variar.

Desde pocas en músculos que
requieren un movimiento preciso,

hasta cientos en músculos
con una carga mayor de peso.

Stifani, Nicolás. "Las neuronas motoras y la generación de diversidad de neuronas motoras espinales". Frontiers in Cellular Neuroscience 8 (9 de octubre de 2014). [<a href="https://doi.org/10.3389/fncel.2014.00293" target="__blank">Fuente</a>]

unidades motoras

Motor Units

Una unidad motora está formada por dos componentes principales: una única neurona motora eferente (es decir, una neurona que transporta impulsos desde el sistema nervioso central) y todas las fibras musculares que inerva. La neurona motora puede inervar múltiples fibras musculares, que son células individuales, pero solo una neurona motora inerva una sola fibra muscular. Las neuronas motoras inferiores son neuronas eferentes que controlan el músculo esquelético, el tipo de músculo más abundante del cuerpo. Los cuerpos celulares de las neuronas motoras inferiores se encuentran en la médula espinal o el tronco del encéfalo. Los que se encuentran en el tronco del encéfalo transmiten señales nerviosas a través del nervio craneal y controlan principalmente los músculos de la cabeza y el cuello. Las neuronas motoras inferiores que se originan en la médula espinal envían señales a lo largo del nervio espinal y controlan principalmente los músculos de las extremidades y el tronco. Una neurona motora inferior dispara un potencial de acción que, a la vez, contrae todas las células del músculo esquelético que inerva la neurona. Por tanto, las unidades motoras son unidades funcionales del músculo esquelético. El tamaño de una unidad motora, o la cantidad de fibras musculares que inerva la neurona motora inferior, varía según el tamaño del músculo y la velocidad y precisión que requiere el movimiento. Los músculos de los ojos y los dedos, que requieren un control rápido y preciso, generalmente están controlados por pequeñas unidades motoras. En estas unidades, las neuronas motoras se conectan a una pequeña cantidad de fibras musculares. Por el contrario, las unidades motoras para los movimientos de las extremidades y el tronco son generalmente grandes y están formadas por muchas fibras musculares.

Unidades motoras

Una unidad motora consta de dos componentes principales: una sola neurona motora eferente (es decir, una neurona que transporta impulsos fuera del sistema nervioso central) ...

Education

Educación

JoVE Core

Biology

Biología

Human Biology

Biología Humana

Musculoskeletal System

Sistema musculoesquelético

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

how motor units control muscle movement

Motor units control skeletal muscle movement. A motor unit includes one efferent motor neuron, which carries signals away from the central nervous system, and all of the muscle fibers it innervates. A single motor neuron can connect with multiple muscle fibers, but each muscle fiber is innervated by only one motor neuron.

Lower motor neurons are the efferent neurons that control skeletal muscle, the most abundant type of muscle in the body. Their cell bodies are found in the spinal cord or brain stem. Neurons in the brain stem send signals through cranial nerves and mainly control muscles in the head and neck.

Lower motor neurons in the spinal cord send signals through spinal nerves. These neurons mainly control muscles in the limbs and body trunk. When a lower motor neuron fires an action potential, all of the skeletal muscle cells it innervates contract at the same time.

Motor units are the functional units of skeletal muscle. Their size depends on the size of the muscle and on how fast and precise the movement must be. Muscles in the eyes and fingers usually have small motor units for rapid, precise control, while motor units for limb and trunk movement are generally large and contain many muscle fibers.

How Motor Units Control Muscle Movement

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motor units

Motor units control skeletal muscle movement. A motor unit includes one efferent motor neuron, which carries signals away from the central nervous system, and all of the muscle fibers it innervates. A single motor neuron can connect with multiple muscle fibers, but each muscle fiber is innervated by only one motor neuron. Lower motor neurons are the efferent neurons that control skeletal muscle, the most abundant type of muscle in the body. Their cell bodies are found in the spinal cord or...

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key terms and concepts

Learn how motor units link one motor neuron to many muscle fibers, and why small or large motor units help control precise or powerful movements.

How Motor Units Control Muscle Movement | JoVE K12

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How Motor Units Control Muscle Movement

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