what are the muscle fibers under the control of a single motor axon
A motor unit
Motor unit A motor unit is made up of a motor neuron and the skeletal muscle fibers innervated by that motor neuron's axonal terminals. Groups of motor units often work together to coordinate the contractions of a single muscle; all of the motor units within a muscle are considered a motor pool. The concept was proposed by Charles Scott Sherrington. All muscle fibres in a motor unit are of the same fibre type. When a motor unit is activated, all of its fibres contract. In vertebrates, the force of a muscle contraction is controlled by the number of activated motor
Motor unit
neuron and the muscle fibers it innervates is a motor unit. A motor neuron pool contains the cell bodies of all the alpha motor neurons involved in contracting a single muscle. Alpha motor neurons (α-MNs) innervating the head and neck are found in the brainstem; the remaining α-MNs innervate the rest of the body and are found in the spinal cord. There are more α-MNs in the spinal cord than in the brainstem, as the number of α-MNs is directly proportional to the amount of fine motor control in that muscle. For example, the muscles of a single finger have
Alpha motor neuron
Motor unit recruitment Motor unit recruitment refers to the activation of additional motor units to accomplish an increase in contractile strength in a muscle. A motor unit consists of one motor neuron and all of the muscle fibers it stimulates. All muscles consist of a number of motor units and the fibers belonging to a motor unit are dispersed and intermingle amongst fibers of other units. The muscle fibers belonging to one motor unit can be spread throughout part, or most of the entire muscle, depending on the number of fibers and size of the muscle. When a motor neuron
Motor unit recruitment
Motor unit A motor unit is made up of a motor neuron and the skeletal muscle fibers innervated by that motor neuron's axonal terminals. Groups of motor units often work together to coordinate the contractions of a single muscle; all of the motor units within a muscle are considered a motor pool. The concept was proposed by Charles Scott Sherrington. All muscle fibres in a motor unit are of the same fibre type. When a motor unit is activated, all of its fibres contract. In vertebrates, the force of a muscle contraction is controlled by the number of activated motor
Motor unit
Extrafusal muscle fiber Extrafusal muscle fibers are the skeletal standard muscle fibers that are innervated by alpha motor neurons and generate tension by contracting, thereby allowing for skeletal movement. They make up the large mass of skeletal muscle tissue and are attached to bone by fibrous tissue extensions (tendons). Each alpha motor neuron and the extrafusal muscle fibers innervated by it make up a motor unit. The connection between the alpha motor neuron and the extrafusal muscle fiber is a neuromuscular junction, where the neuron's signal, the action potential, is transduced to the muscle fiber by the neurotransmitter acetylcholine. Extrafusal
Extrafusal muscle fiber
not identical even when performing the same motion repeatedly; natural variation in position, velocity, and acceleration of the limb occur even during seemingly identical movements. Another difficulty in motor control is unifying the different ways to study movements. Three distinct areas in studying motor control have emerged: limb mechanics, neurophysiology, and motor behavior. Studies of limb mechanics focus on the peripheral motor system as a filter which converts patterns of muscle activation into purposeful movement. In this paradigm, the building block is a motor unit (a neuron and all the muscle fibers it innervates) and complex models are built to
Degrees of freedom problem
can help in distinguishing a myopathy from a neuropathy. Motor units are generally categorized based upon the similarities between several factors: The typing of motor units has thus gone through many stages and reached a point where it is recognized that muscle fibers contain varying mixtures of several mysosin types that can not easily be classified into specific groups of fibers. The three (or four) classical fiber types represent peaks in the distribution of muscle fiber properties, each determined by the overall biochemistry of the fibers. Motor unit A motor unit is made up of a motor neuron and the
Motor unit
determine levels of fatigue. The lower conduction velocities enable the slower motor neurons to remain active. A motor unit is defined as one motor neuron and all of the muscle fibers it innervates. When a motor unit fires, the impulse (called an action potential) is carried down the motor neuron to the muscle. The area where the nerve contacts the muscle is called the neuromuscular junction, or the motor end plate. After the action potential is transmitted across the neuromuscular junction, an action potential is elicited in all of the innervated muscle fibers of that particular motor unit. The sum
Electromyography
tea road to lhasa]", "Zheng He: Tracing the Epic Voyages of China’s Greatest Explorer", "Japan: The Soul of a Nation", "Marco Polo, A Photographer’s Journey", and many others. He has won numerous awards from the National Press Photographers Association and the Asian American Journalists Association. He is also a frequent lecturer and conducts workshops across Asia and the United States. Michael Yamashita Michael Yamashita is an American photographer who was born in 1949 in San Francisco, California, but grew up in Montclair, New Jersey. In 1971 he graduated from Wesleyan University with a degree in Asian studies and later went
Michael Yamashita
by Charles Aznavour on October 3, 1996. Not only does the venue host entertainment events, it is one of the few zéniths that serves as a sporting arena. The venue is the home arena of the Orléans Loiret Basket. The arena has hosted concerts by Grégoire, Julien Clerc, Patrick Fiori, and Joan Baez. It is the eighth incarnation of the "Le Zénith" franchise. The Zénith de Toulouse is an indoor arena located in Toulouse. The venue was designed by André and Serge Gresy, who have also done the Palais Nikaia, Zénith d'Auvergne and the Grande Halle d'Auvergne. The arena began
Le Zénith
HMS Suffolk (1680) HMS "Suffolk" was a 70-gun third-rate ship of the line of the Royal Navy, built by contract of 20 February 1678 by Sir Henry Johnson at his Blackwall Yard and launched in May 1680. "Suffolk" was commanded by Captain Wolfran Cornwall at the Battle of Beachy Head in 1690, and by Captain Christopher Billopp at the Battle of Barfleur in 1692. She was rebuilt by Johnson at Blackwall in 1699, and took part in the Battle of Vélez-Málaga in 1704. She was rebuilt for a second time at Chatham Dockyard, from where she was relaunched on 13
HMS Suffolk (1680)
later include Tibet into his Yuan dynasty, and the region remained administratively separate from the conquered provinces of Song dynasty China. According to the Tibetan traditional view, the khan and the lama established "priest-patron" relations. This meant administrative management and military assistance from the khan and assistance from the lama in spiritual issues. Tibet was conquered by the Mongols before the Mongol invasion of South China. After the conquest of the Song dynasty, Kublai Khan consolidated Tibet into the new Yuan dynasty, but Tibet was ruled under the Bureau of Buddhist and Tibetan Affairs (Xuanzheng Yuan), separate from the Chinese
Mongol invasions of Tibet
failures. In Norway, the Germans did retain the twelve divisions, indicating the Germans assessed a higher threat there. Besides being implausible, Cockade also failed because the Allies did not work hard enough to make the deception look real. The Royal Navy would not risk its battleships and Eaker did not want to divert resources from the strategic bombing offensive. Cockade did have one success: the Germans believed the story that the Allies had 51 divisions in the British Isles, when there were only 17 divisions. This became important in deception operations in 1944. Cockade was best summarized by Sir Arthur
Operation Cockade
neurons within the muscle spindle detect the degree of stretch and send a signal to the CNS. The CNS activates alpha motor neurons in the spinal cord, which cause extrafusal muscle fibers to contract and thereby resist further stretching. This process is also called the stretch reflex. The interface between a motor neuron and muscle fiber is a specialized synapse called the neuromuscular junction. Upon adequate stimulation, the motor neuron releases a flood of acetylcholine (Ach) neurotransmitters from the axon terminals from synaptic vesicles bind with the plasma membrane. The acetylcholine molecules bind to postsynaptic receptors found within the motor
Motor neuron
Camillo Golgi. The body of the organ is made up of strands of collagen that are connected at one end to the muscle fibers and at the other merge into the tendon proper. Each tendon organ is innervated by a single afferent type Ib sensory nerve fiber (Aɑ fiber) that branches and terminates as spiral endings around the collagen strands. The Ib afferent axon is a large diameter, myelinated axon. Each neurotendinous spindle is enclosed in a capsule which contains a number of enlarged tendon fasciculi (intrafusal fasciculi). One or more nerve fibres perforate the side of the capsule and
Golgi tendon organ
by training. The old trained men have succinate dehydrogenase activities within their type IIa muscle fibers similar to those in young men and twofold higher than in old normal fit men. Neural changes like reduced motor unit discharge rates, increased variability of motor unit discharge activity, altered recruitment and derecruitment behavior mediate modifications in muscle control. On the other hand, physiological deleterious factors including motor unit loss, increased motor unit innervation ratios also affect muscle force. Through strength training, old adults can significantly improve their force control. The rapid adaptation suggests modifications in motor unit activation, increased excitability of motoneuron
Aging movement control
because end-plate reinnervation is just starting. However, after that time period, end-organ contact plays a role in influencing the reinnervation ability of the axon. When the end of the pathway is a muscle contact area, there is a significant difference in the number of motor neurons reinnervating. These are trophic factors that are discussed in detail in above sections. These factors can influence where an axon grows towards, mostly from chemotaxis effects that the different proteins have on the growing axon's directionality. The trophic factors differ between motor and sensory pathways, which is a major influential factor in preferential motor
Preferential motor reinnervation
nerve as noted above is a mixed nerve consisting of both sensory and motor nerve fibers. The sensory fibers' origin include the pharynx, middle ear, posterior one-third of the tongue (including taste buds); and the carotid body and sinus. These fibers terminate at the medulla oblongata. The motor fibers' origin is the medulla oblongata, and they terminate at the parotid salivary gland, the glands of the posterior tongue, and the stylopharyngeus muscle (which dilates the pharynx during swallowing). The branchial motor component of CN IX provides voluntary control of the stylopharyngeus muscle, which elevates the pharynx during swallowing and speech.
Glossopharyngeal nerve
A motor unit
Title: Motor unit. Content: Motor unit A motor unit is made up of a motor neuron and the skeletal muscle fibers innervated by that motor neuron's axonal terminals. Groups of motor units often work together to coordinate the contractions of a single muscle; all of the motor units within a muscle are considered a motor pool. The concept was proposed by Charles Scott Sherrington. All muscle fibres in a motor unit are of the same fibre type. When a motor unit is activated, all of its fibres contract. In vertebrates, the force of a muscle contraction is controlled by the number of activated motor
Muscle fibers
Motor unit.
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