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

моторная единица относится к одному моторному нейрону, расположенному в спинном мозге, и популяции мышечных волокон, которые он иннервирует. В то время как все скелетные мышечные волокна иннервируется только одним моторным нейроном, аксоны от каждого моторного нейрона могут разветвляться на несколько окончаний, формируя нервно-мышечные соединения по всей мышце. В результате, стимуляция одной моторной единицы приводит к слабому сокращению всей мышцы.В зависимости от необходимого уровня контроля, количество волокон на единицу может варьироваться от всего нескольких волокон в мышцах, которым требуется точное перемещение, на несколько сотен в менее точных мышцах, рассчитанных на поднятие веса.

Стифани, Николас. "Моторные нейроны и генерация разнообразия спинальных моторных нейронов." Frontiers in Cellular Neuroscience 8 (9 октября 2014 г.). [<a href="https://doi.org/10.3389/fncel.2014.00293" target="__blank">Источник</a>]

Двигательные единицы

Motor Units

Двигательная единица состоит из двух основных компонентов: одиночного эфферентного двигательного нейрона (то есть нейрона, который передает импульсы от центральной нервной системы) и всех мышечных волокон, которые он иннервирует. Моторный нейрон может иннервировать несколько мышечных волокон, которые являются отдельными клетками, но только один мотонейрон иннервирует одно мышечное волокно. 

 Нижние двигательные нейроны - это эфферентные нейроны, которые контролируют скелетные мышцы, наиболее распространенный тип мышц в организме. Тела клеток нижних мотонейронов расположены в спинном мозге или стволе головного мозга. Те, что находятся в стволе мозга, передают нервные сигналы через черепные нервы и в первую очередь контролируют мышцы головы и шеи. Нижние двигательные нейроны, исходящие из спинного мозга, посылают сигналы по спинномозговому нерву и в основном контролируют мышцы конечностей и туловища. 

 Нижний мотонейрон запускает потенциал действия, который одновременно сокращает все клетки скелетных мышц, которые иннервирует нейрон. Таким образом, двигательные единицы - это функциональные единицы скелетных мышц. 

 Размер двигательной единицы или количество мышечных волокон, которые иннервирует нижний двигательный нейрон, зависит от размера мышцы, а также скорости и точности движения. Мышцы глаз и пальцев, требующие быстрого и точного управления, обычно контролируются небольшими двигательными единицами. В этих единицах мотонейроны соединяются с небольшим количеством мышечных волокон. Напротив, двигательные единицы для движений конечностей и туловища обычно большие и состоят из множества мышечных волокон.

Моторная единица состоит из двух основных компонентов: одного эфферентного моторного нейрона (т.е. нейрона, который несет импульсы от центральной нервной системы).

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JoVE Core

Biology

Биология

Human Biology

Биология человека

Musculoskeletal System

Опорно-двигательная система

KEY TERMS AND CONCEPTS

ОСНОВНЫЕ ТЕРМИНЫ И ПОНЯТИЯ

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

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

Joints are the places where adjacent bones connect. They are also called articulations or articular surfaces. Joints help the body move and stay stable. Joints can be classified by structure or by function. Structural classification depends on the material that forms the joint and whether there is a space between the bones. By structure, joints are fibrous, cartilaginous, or synovial. Fibrous joints are connected by fibrous tissue and have no cavity between the bones. Because of this, they do...

bone remodeling

How Hormones Control Bone Turnover

Bone turnover is a continuous process in which old bone is broken down and new bone is built. Osteoclasts carry out bone resorption, and osteoblasts carry out bone formation. In adults, this balanced cycle helps maintain bone mass and calcium homeostasis. Mechanical stress can also stimulate turnover as part of normal maintenance and repair. Parathyroid hormone, or PTH, helps control blood calcium levels by increasing bone resorption when calcium is low. It is released from the parathyroid...

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 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,...

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

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...

the spinal cord

Spinal Cord Structure and Dermatomes

The spinal cord is the main nerve pathway of the central nervous system. It carries sensory signals from the body to the brain and motor signals from the brain to the body. It begins at the foramen magnum, the opening at the base of the skull, and extends to the level of the first or second lumbar vertebra. In cross-section, the spinal cord is cylindrical and contains both gray matter and white matter. The central canal lies in the middle and is a remnant of the lumen of the primitive neural...

nociception

Pain Signaling and Inflammation

Pain signaling begins when the body detects a harmful stimulus. Sharp objects, open flames, and corrosive chemicals can trigger this response. Sensory receptors called nociceptors, which sit on nerve endings, detect these noxious stimuli and use ion channels to turn them into electrical signals. Those electrical signals travel through sensory neurons to the brain, where they are experienced as pain. This warning system helps an organism avoid damage and stay safe. Pain is therefore an...

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.

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How Motor Units Control Muscle Movement

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