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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] For instance, thigh muscles can have a thousand fibers ...
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 muscles of the posterior compartment of the thigh are the: [2] [3] biceps femoris muscle, which consists of a short head and a long head. semitendinosus muscle; semimembranosus muscle; These muscles (or their tendons) apart from the short head of the biceps femoris, are commonly known as the hamstrings.
The medial compartment of thigh is one of the fascial compartments of the thigh and contains the hip adductor muscles and the gracilis muscle. The obturator nerve is the primary nerve supplying this compartment. The obturator artery is the blood supply to the medial thigh. The muscles in the compartment are: gracilis; adductor longus; adductor ...
The fascia lata is the strong and deep fascia of the thigh that surrounds the thigh muscles and forms the outer limits of the compartments. Internally the muscle compartments are divided by the lateral and medial intermuscular septa. The three groups of muscles contained in the compartments have their own nerve supply: [1]
The semimembranosus muscle (/ ˌ s ɛ m i ˌ m ɛ m b r ə ˈ n oʊ s ə s /) is the most medial of the three hamstring muscles in the thigh. It is so named because it has a flat tendon of origin. It lies posteromedially in the thigh, deep to the semitendinosus muscle. It extends the hip joint and flexes the knee joint.
The sartorius acts as a flexor on both the hip and knee, but, due to its oblique course, also contributes to medial rotation of the leg as one of the pes anserinus muscles (with the knee flexed), and to lateral rotation of the hip joint. [23] There are four posterior thigh muscles.
Motor unit plasticity is defined as the ability of motoneurons and their respective effector muscles to physically and functionally change as a result of activity, age, and other factors. Motor unit plasticity has implications for improved athletic performance and resistance to immobility as a result of age.