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Muscles differ in the number of motor units that they contain, and how many muscle fibres are within each unit (innervation ratio). In a general sense, muscles that require specificity of movement, such as muscles in charge of eye movement, have fewer fibres per unit, while those that are meant for less specific tasks, such as the calf muscles ...
General depiction of a motor unit, consisting of a motor neuron innervating a group of muscle fibers. Motor unit recruitment is the activation of additional motor units to accomplish an increase in contractile strength in a muscle. [1] A motor unit consists of one motor neuron and all of the muscle fibers it stimulates.
Henneman’s size principle describes relationships between properties of motor neurons and the muscle fibers they innervate and thus control, which together are called motor units. Motor neurons with large cell bodies tend to innervate fast-twitch, high-force, less fatigue-resistant muscle fibers, whereas motor neurons with small cell bodies ...
In vertebrates, the force of a muscle contraction is controlled by the number of activated motor units. 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 ...
While individual muscle units' contract as a unit, the entire muscle can contract on a predetermined basis due to the structure of the motor unit. Motor unit coordination, balance, and control frequently come under the direction of the cerebellum of the brain. This allows for complex muscular coordination with little conscious effort, such as ...
Within a motor unit, all the muscle fibers are of the same type (e.g. type I (slow twitch) or Type II fibers (fast twitch)), and motor units of multiple types make up a given muscle. Motor units of a given muscle are collectively referred to as a motor pool. The force produced in a given muscle thus depends on: 1) How many motor neurons are ...
The motor unit: a single motor neuron and the muscle fibers that it innervates. A motor pool consists of all of the motor neurons that innervate a single muscle. Distinct skeletal muscles are controlled by groups of individual motor units. Such motor units are made up of a single motor neuron and the muscle
1 frontalis: head, occipitofrontalis, forehead (left/right) skin of eyebrow and glabella: epicranial aponeurosis: ophthalmic artery: facial nerve [CNVII], temporal branch: wrinkles eyebrow: procerus, corrugator supercilii, and orbicularis oculi muscles [1] 2 1 orbicularis oculi, orbital part head, forehead/eyelid (left/right) frontal bone ...