Name: nerve signals that trigger muscle contraction
Uploaded: 2025-10-23T11:49:17.000Z
Duration: 1 min 15 s
Channel: JoVE

[Narrador]

Una contracción voluntaria
de músculo esquelético

empieza en el cerebro como
un esfuerzo consciente

del lóbulo frontal a la
corteza motora primaria,

antes de ser activado,
una neurona motora alfa

localizada en el asta
anterior de la espina dorsal.

La señal desciende al nervio

a la fibra de músculo
específica, tal como el bíceps

donde el potencial de acción

finaliza en la placa terminal motora,

donde la neurona motora
establece un contacto sináptico

con la fibra del músculo
y activa la liberación

del neurotransmisor acetilcolina,

que se difunde a través de la hendidura

sináptica y se enlaza a los receptores.

Como resultado, el sarcolema

se vuelve más permeable
a los iones de sodio

derivando en más potencial de acción

que se propaga a través
de su superficie externa

y hacia el interior de la fibra muscular

a través de tubos transverales o Túbulos-T

lo cual activa y libera
los iones de calcio

del retículo sarcoplasmático
hacia las miofibrillas.

Esta liberación de calcio
pone en marcha el traslado

de la actina-miosina y la observación

del acortamiento del
músculo y su contractura.

Webb, R. Clinton. "Contracción y relajación del músculo liso". Avances en Educación en Fisiología 27, no. 4 (1 de diciembre de 2003): 201–6. [<a href="https://doi.org/10.1152/advan.00025.2003" target="__blank">Fuente</a>]

Kuo, Ivana Y. y Barbara E. Ehrlich. "Señalización en la contracción muscular". Cold Spring Harbor Perspectives in Biology 7, no. 2 (febrero de 2015). [<a href="https://doi.org/10.1101/cshperspect.a006023" target="__blank">Fuente</a>]

contracción muscular

Muscle Contraction

En los músculos esqueléticos, la acetilcolina se libera mediante terminales nerviosas en la placa terminal motora, el punto de comunicación sináptica entre las neuronas motoras y las fibras musculares. La unión de la acetilcolina a sus receptores en el sarcolema permite la entrada de iones de sodio en la célula y desencadena un potencial de acción en la célula muscular. Así, las señales eléctricas del cerebro se transmiten al músculo. Posteriormente, la enzima acetilcolinesterasa descompone la acetilcolina para evitar una estimulación muscular excesiva.Las personas con el trastorno de miastenia gravis desarrollan anticuerpos contra el receptor de acetilcolina. Esto impide la transmisión de señales eléctricas entre la neurona motora y la fibra muscular y altera la contracción del músculo esquelético. La miastenia gravis se trata con medicamentos que inhiben la acetilcolinesterasa (lo que permite más oportunidades para que el neurotransmisor estimule los receptores restantes) o suprimen el sistema inmunológico (previniendo la formación de anticuerpos). <h4>Contracción del músculo liso</h4> A diferencia de los músculos esqueléticos, los músculos lisos presentes en las paredes de los órganos internos están inervados por el sistema nervioso autónomo y sufren contracciones involuntarias. La contracción está mediada por la interacción entre dos proteínas filamentosas,actina y miosina. La interacción de actina y miosina está estrechamente relacionada con la concentración de calcio intracelular. En respuesta a señales de neurotransmisores u hormonas o al estiramiento del músculo, el calcio extracelular ingresa a la célula a través de canales de calcio en el sarcolema o se libera intracelularmente desde el retículo sarcoplásmico. Dentro de la célula, el calcio se une a la proteína reguladora calmodulina. El complejo calcio-calmodulina luego activa la enzima quinasa de cadena ligera de miosina, que fosforila la miosina y le permite interactuar con la actina, provocando que el músculo se contraiga.

Contracción muscular

 

En los músculos esqueléticos, la acetilcolina es liberada por las terminales nerviosas en la placa terminal motora, el punto de comunicación sináptica ...

Education

Educación

JoVE Core

Biology

Biología

Human Biology

Biología Humana

Musculoskeletal System

Sistema musculoesquelético

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

nerve signals that trigger muscle contraction

Nerve signals trigger muscle contraction in both skeletal and smooth muscle, but the two muscle types use different control systems. In skeletal muscle, the signal begins at the motor end plate, which is the synapse between a motor neuron and a muscle fiber. In smooth muscle, contraction is controlled by the autonomic nervous system and happens without conscious control.

In skeletal muscle, motor nerve terminals release acetylcholine. This neurotransmitter binds to receptors on the sarcolemma, the muscle cell membrane, and lets sodium ions enter the cell. That change starts an action potential in the muscle cell and carries the electrical signal from the brain to the muscle. The enzyme acetylcholinesterase then breaks down acetylcholine so the muscle is not overstimulated.

Myasthenia gravis shows what happens when this signaling step is disrupted. In this disorder, antibodies form against the acetylcholine receptor. As a result, the signal between the motor neuron and the muscle fiber is blocked, and skeletal muscle contraction is weakened. Treatment may include drugs that inhibit acetylcholinesterase or medicines that suppress the immune system.

Smooth muscle in the walls of internal organs contracts in a different way. Its contraction depends on the interaction between actin and myosin, two filament proteins. This process is closely linked to calcium levels inside the cell, which can rise after neurotransmitter or hormone signals or when the muscle is stretched.

Calcium can enter smooth muscle from outside the cell through calcium channels on the sarcolemma, or it can be released from the sarcoplasmic reticulum inside the cell. Once inside, calcium binds to calmodulin, a regulatory protein. The calcium-calmodulin complex activates myosin light chain kinase, which phosphorylates myosin and lets it interact with actin, causing contraction.

Nerve Signals That Trigger Muscle Contraction

nerve-signals-that-trigger-muscle-contraction

what is the skeletal system?

Human Skeleton: Bones, Cells, and Disease

The human skeleton is a living framework made of 206 bones in adults. Bones connect with cartilage, tendons, and ligaments. This system gives the body support, protects organs, and helps with movement and locomotion. The skeleton has two main parts: the axial skeleton and the appendicular skeleton. The axial skeleton has 80 bones and includes the skull, the vertebral column, and the rib cage. The cranium, or upper skull, has eight bones that enclose the brain, while the lower part of the skull...

bone structure

Inside a Long Bone

Inside a long bone, osseous tissue is organized into two main types: cortical bone and cancellous bone. A femur is a clear example of this structure. The bone also includes outer coverings and inner spaces that support growth, repair, and blood cell production. Cortical bone, also called compact bone, forms the dense outer layer along the diaphysis, or shaft. It is covered by the periosteum, a membrane with connective tissue, capillaries, and nerves. Beneath the cortical layer is the medullary...

joints

Types of Joints in the Human Body

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skeletal muscle anatomy

Muscle Fibers, Tendons, and Contraction

Skeletal muscle moves the body by pulling on bones through tendons. Tendons are the connective tissue that attaches skeletal muscle to bones. When skeletal muscles contract, they create voluntary movement. Skeletal muscle is wrapped in layers of connective tissue. The outer layer is the epimysium, which helps protect the muscle. Beneath it, the perimysium surrounds and groups fasciculi, which are bundles of skeletal muscle cells called myocytes. These cells are also called skeletal muscle...

classification of skeletal muscle fibers

Skeletal Muscle Fiber Speed and Energy

Skeletal muscle fibers can be grouped by how fast they contract and how they make ATP, the energy cells use for movement. These differences also shape their physical features. Most human muscles contain all three fiber types, but in different amounts. Slow oxidative fibers, also called slow-twitch fibers, appear red because they have many capillaries and high levels of myoglobin, an oxygen-storing protein. They also contain more mitochondria, which make ATP through oxidative phosphorylation,...

muscle contraction

Nerve signals trigger muscle contraction in both skeletal and smooth muscle, but the two muscle types use different control systems. In skeletal muscle, the signal begins at the motor end plate, which is the synapse between a motor neuron and a muscle fiber. In smooth muscle, contraction is controlled by the autonomic nervous system and happens without conscious control. In skeletal muscle, motor nerve terminals release acetylcholine. This neurotransmitter binds to receptors on the sarcolemma,...

cross-bridge cycle

Calcium Control in Muscle Contraction

Calcium control in muscle contraction depends on ATP, motor neurons, and the sliding action of actin and myosin. As a muscle contracts, the thin and thick filaments overlap more, and the sarcomere, which is the contractile unit of the muscle, becomes shorter. This process uses energy from ATP and happens in a repeating cycle at the molecular level. Myosin drives the movement of actin through a cross-bridge cycle. When ATP attached to the myosin head is hydrolyzed to ADP, myosin shifts into a...

motor units

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...

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key terms and concepts

Learn how acetylcholine, calcium, and actin-myosin interactions drive skeletal and smooth muscle contraction, plus how myasthenia gravis disrupts signaling.

Nerve Signals That Trigger Muscle Contraction | JoVE K12

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Nerve Signals That Trigger Muscle Contraction

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