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This property of the single nerve fibre is termed the all-or-none relationship. This relationship holds only for the unit of tissue; for nervous tissue the unit is the nerve cell, for skeletal muscle the unit is the individual muscle fiber and for the heart the unit is the entire auricles or the entire ventricles.
In that study, an increase in muscle fiber conduction velocity was observed when there was a higher level of voluntary muscle contraction, which agrees with the gradual recruitment of higher-force muscle types. [16] In Wistar rats, it was found that cell size is the crucial property in determining neuronal recruitment. [17]
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. [2] [3] When a motor neuron is activated, all of the muscle fibers innervated by the motor neuron are stimulated and contract. The activation of one motor neuron will result in a ...
The number of muscle fibers within each unit can vary within a particular muscle and even more from muscle to muscle: the muscles that act on the largest body masses have motor units that contain more muscle fibers, whereas smaller muscles contain fewer muscle fibers in each motor unit. [1]
The ECM has at least three functions: (1) to provide a framework binding muscle fibers together and ensure their proper alignment, (2) to transmit the forces, either from active muscle contraction or ones passively imposed on it, and (3) providing lubricated surfaces between muscle fibers and bundles enabling the muscle to change shape. [1]
A single motor neuron and the muscle fibers it innervates are called a motor unit. For example, the rectus femoris contains approximately 1 million muscle fibers, which are controlled by around 1000 motor neurons. Activity in the motor neuron causes contraction in all of the innervated muscle fibers so that they function as a unit.
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Unipennate muscles are those where the muscle fibers are oriented at one fiber angle to the force-generating axis and are all on the same side of a tendon. [1] The pennation angle in unipennate muscles has been measured at a variety of resting length and typically varies from 0° to 30°. [ 1 ]