Hypotonia : decreased or lost muscle tone. These muscles are Flaccid. These muscles are loose and appear flattened rather than rounded. Disorders of the nervous system, disruptions in the balance of Na, Ca++, or Mg may result in flaccid paralysis. This is a loss of muscle tone, decreased tendon reflexes, atrophy (wasting) and degeneration of muscles. Flaccid : When motor neurons serving a skeletal muscle are damaged or cut this results in a state of limpness or loss of use.
Hypertonia : increased muscle tone.
Spasticity is characterized by increased muscle tone, increased tendon reflexes, and pathological reflexes. As mentioned above, disorders of the nervous system and imbalances may result in Spastic Paralysis (partial paralysis in which the muscle exhibits some rigidity.
Types of Skeletal Muscle Contraction
Muscle contractions are classified as either Isotonic or Isometric
Isotonic Contractions : the tension (force of contraction) developed by themuscle remains almost constant while the muscle changes length. This form of contraction is used for body movements and for moving objects. There are 2 types of Isotonic contractions: Concentric Isotonic Contraction : If the tension generated is great enough to overcome the resistance of the object to be moved, the muscle shortens and pulls on another structure, such as a tendon, to produce movement and to reduce the angle at the joint (ex: picking a book up off of a table). Eccentric Isotonic Contraction : when the length of a muscle increases during a contraction (ex: placing the book back on the table). For reasons not understood, repeated eccentric isotonic contractions (ex: walking downhill) produce more muscle damage and more delayed-onset muscle soreness than do concentric isotonic contractions. Isometric Contractions : the tension generated is not enough to exceed the resistance of the object to be moved, and the muscle does not change length (ex: holding a book steady using an outstretched arm). These contractions are important for maintaining posture and supporting objects in a fixed position. Isometric contractions also stabilize joints as others are moved, thus most activities include both isotonic and isometric contractions.
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