운동 단위와 근전도의 관계
운동 단위:
단일 운동 뉴런과 그에 연결된 신경 섬유는 여러 개의 근육 섬유를 자극한다. 다수의 단일 신경 섬유를 통하여 하나의 운동 뉴런에 의해 자극받은 근육 섬유를 운동 단위라고 부른다. 운동 단위에 있는 근육 섬유의 수는 다양하며 예를 들어 고양이 다리 근육에서는 단위 당 약 120에서 165개의 근육 섬유가 있다.
근전도검사:
운동 단위 활동은 검사를 진행할 근육에 동축 전극을 삽입하여 측정한다. 그다음 전극을 근전계에 연결하고 근육 운동을 하면 활동 전위가 기록되는데, 이를 근전도라고 한다.
비어있는 바늘에 절연된 내부 와이어를 삽입하여 동축 전극을 만들고 바늘 끝의 바로 근처에 있는 근육의 작은 부피에서 발생하는 변화를 기록한다. 따라서 전극 근처의 활성 섬유에서 가장 높은 전기적 활동이 관찰된다. 때로는 근육 깊이 들어가는 동축 전극 대신 표면 전극을 사용한다. 표면 전극을 사용하여 기록할 때는 두 개의 전극을 적당한 거리를 두고 검사할 근육 위에 놓는다.
근육이 정지해 있을 때는 어떤 활동 전위도 기록되지 않지만, 근육이 활성화되기 시작하면 전극 근처에 있는 운동 뉴런의 비동기적 방전으로부터 활동 전위가 발생한다. 최소한의 자발적 활동을 하는 동안, 단지 몇 개의 운동 단위만 발생하고, 자발적 활동이 증가하면서 더 많은 운동 단위가 활성화된다. 이것을 운동 단위의 동원이라고 한다.
근육 활동의 등급화는 활성화된 운동 단위의 수에 대한 척도이다. 말초 신경 연구는 말초 신경 부상을 포함한 운동 단위 장애와 근긴장증과 중증근육무력증을 포함한 신경 근육 장애의 진단에 있어 임상적으로 중요한 의미가 있다.
Motor unit’s relation with electromyogram (EMG)
Motor unit:
A single motoneuron and it’s axons supply not only just a muscle fiber, but also several muscle fibers. The muscle fiber that is supplied by one motor neuron through its single axon along with branches are called a Motor Unit. A variety of muscle fibers are present. It is observed in cat leg muscles that approximately 120¬, 165 fibers are present in one motor unit.
EMG
A motor unit activity is measured through a coaxial electrode in to the muscle that is tobe studied. Next they are connected to electromyography (EMG). A recording is obtained during muscular activity. This recording is called an electromyogram (EMG).
A hollow needle can be made in to a coaxial electrode introducing an insulated inner wire with in it. Possible changes are recorded from small volume of the muscles in immediate neighbourhood of the tip of the needle. Thus, it is has been observed that most of the electrical activity is from the active fibers near the electrodes. Sometimes, surface electrodes is used instead of deep muscle coaxial electrode. In this recording method, two surface electrodes are placed over the muscle to be studied at a reasonable distance.
When the muscle is at rest, no action potential is recorded; however, as soon as the muscle becomes active, potentials are recorded. The potential recorded during activity is as a result of the asynchronous discharge of motoneurons in the vicinity of the electrodes. During minimal voluntary activity, only a few number of motor units discharges, and as voluntary effort increases the more number of units is activated. This is called as recruitment of motor units
Gradation of muscular activity is a part of the function of a number of motor units activated. Electrographic studies have clinically importance in the diagnosis of motor unit disorders including peripheral nerve injuries, neuromuscular disorders such as myotonia and myasthenia gravis, so on and so forth.
Motorunit’s relation with electromyogram (EMG)
Motorunit:
A single motor neuronmotoneuronand it’s axonaxons innervate1supply not onlyjust a muscle fiber, but also several muscle fibers. The mMusclefibersthatis supplied innervated by one motor neuron throughits single axon along with branches are called a MmotorUunit.ThenumberA variety of musclefibers ina motor unit variesare present2 .It is has been observedin cat leg muscles that approximately 120–, 165fibers are present in one motor unit.
EMG
A motor unit
activity is measured through inserting3 a coaxial electrode in tothe muscle that is to be studied. Next, theelectrode isthey areconnected to an electromyographelectromyography(EMG)4. A recording is obtained during muscular activity. Thisrecording is called an electromyogram (EMG).
A hypodermic hollow5needle can be made in to a coaxial electrode by introducing aninsulated inner wire with in into it. Possiblechanges are recorded from small volume of the muscles in immediate neighbourhoodof the tip of the needle. Thus, it is has been observed that most of theelectrical activity is from the active fibers near the electrodes. Sometimes,surface electrodes is used instead of deep muscle coaxial electrode. In thisrecording method, two surface electrodes are placed over the muscle to bestudied at a reasonable distance.
When themuscle is at rest, no action potential is recorded; however, as soon as themuscle becomes active, action 6potentials are recorded. Thepotential recorded during activity is as a result of the asynchronous dischargeof motoneurons in the vicinity of the electrodes. During minimal voluntaryactivity, only a few number of motor units aredischargeddischarges, and as voluntary effort activity increases,the morenumberof units areis activated.This is called recruitment of motor units.7
Gradation ofmuscular activity is a function of thea part of thefunction of a number of motor units activated. Electromyographic8Electrographic studies have clinicallyimportance in diagnosis of motor unit disorders including peripheral nerveinjuries, neuromuscular disorders such as myotonia and myasthenia gravis, so onand so forth.
Motor unit’s and their relationwith electromyograms (EMG)1
Motor unit :
A single motor neuronmotoneuronand its it’s2axonaxonsinnervate3supply not onlyjust a muscle fiber, but also several muscle fibers; these fibers constitute The mMuscle fibersthatis supplied innervated by one motor neuron throughits single axon along with branches are called MmotorUunit.The numberA variety of musclefibers ina motor unit variesare present4 .It The motor unit of cat legmuscles is has been observedin that hasapproximately 120–, 165 fibers are present in one motor unit5.
Electromyography: EMG
A Mmotor unit activity is recorded by measured throughinserting6a coaxial electrode in to the muscle of interest that isto bestudied. Next, the electrode isthey areconnected to an electromyographelectromyography(EMG)7. A and a recording isobtained during of muscularactivity. knownas an electromyogram is obtained. Thisrecording is called an electromyogram (EMG).8
A hypodermic hollow9 needlecan be made in to converted into a coaxial electrode by introducingan insulated inner wire with in into it. Possible Cchangesare recorded from the small volume of themuscles are recorded in the immediate vicinityneighbourhood of the tip of the needle tip.Thus, it is has been observed that most the highest ofthe electrical activity is observedfrom inthe active fibers near the electrodes. Sometimes, surface electrodes are is10used instead of deep muscle coaxial electrodes.In this recording method, two surfaceelectrodes are placed at a reasonable distance onthe skin overlying over themuscle to be studied at a reasonable distance.
When themuscle is at rest, no action potential is recorded;11 however, as soon as themuscle becomes active, action potentials results fromare recorded. The potential recorded duringactivity is as a result of the asynchronous discharge of motor neurons12motoneuronsin the vicinity of the electrodes. During minimal voluntary activity, only afew numberof motor units are dischargeddischarges,and as voluntary effort activity increases,the morenumberof units areis activated.This is called motor unit recruitment of motor units.13
The Ggradation of muscular activity is a functionof thea part of the function of anumber of activated motor units activated. Electromyographic Electrographic14studies are clinically importanthave clinically importance in the diagnosis of motor unit disorders, including peripheral nerve injuries, and neuromuscular disorders, such asincluding myotonia and myasthenia gravis, so on and so forth15.
Motor units and their relation with electromyograms
Motor unit:
A single motor neuron and its axon innervate several muscle fibers; these fibers constitute a motor unit. The number of muscle fibers in a motor unit varies. The motor unit of cat leg muscles has approximately 120–165 fibers.
Electromyography:
Motor unit activity is recorded by inserting a coaxial electrode into the muscle of interest. Next, the electrode is connected to an electromyograph and a recording of muscular activity, known as an electromyogram, is obtained.
A hypodermic needle can be converted into a coaxial electrode by introducing an insulated inner wire into it. Changes from the small volume of muscles are recorded in the immediate vicinity of the needle tip. Thus, the highest electrical activity is observed in the active fibers near the electrodes. Sometimes, surface electrodes are used instead of deep muscle coaxial electrodes. In this method, two surface electrodes are placed at a reasonable distance on the skin overlying the muscle to be studied.
When the muscle is at rest, no action potential is recorded; however, as soon as the muscle becomes active, action potential results from the asynchronous discharge of motor neurons in the vicinity of the electrodes. During minimal voluntary activity, only a few motor units are discharged, and as voluntary activity increases, more units are activated. This is called motor unit recruitment.
The gradation of muscular activity is a function of the number of activated motor units. Electromyographic studies are clinically important in the diagnosis of motor unit disorders, including peripheral nerve injuries, and neuromuscular disorders, including myotonia and myasthenia gravis.
