Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
TYPES OF MUSCLE CONTRACTIONS Isometric contraction: when the ms. does not shorten during contraction while tension is increasing. Isotonic contraction: when the ms. shortens or lengthens while the tension on the ms. remains constant Isotonic (static) Contraction Isometric (Dynamic) Contraction Tension is constant Tension n the ms. Rises markedly Length is decreased or lengthened Length of the ms. is constant External work is done No work is done Mechanical efficiency = 25% Mechanicl efficiency = 0 Long duration Short duration less energy used/contraction More energy used/contraction Contraction occurs when the legs are Contraction occurs during standing moved in walking to maintain posture against gravity 1 Types of Isotonic (static) Contractions: Concentric: the muscle shortens, e.g. contraction of the biceps to produce elbow flexion. Eccentric: muscle lengthen or is stretched while contracting, e.g. lowering a load on the ground. Tension Variation 1. Passive tension: tension developed in the ms. length is increased while is not stimulated ( i.e. concentric contraction). 2. Total Tension: tension that a ms. develops when stimulated to contract isometrically.This tension also vary with the change of the initial length. 3. Active tension: is the difference between the total tension and the passive tension at any length( the amount of tension) actually generated by the contractile process. Tension increases with an increased length, but overstretch may lead to weakness of the muscle. Rupture of the muscle occur when it is stretched to about 3 times its equilibrium length of the relaxed muscle cut from its bony attachment. 2 Types of Skeletal Fibers : 1. Slow Oxidative or Type 1 Fibers: In postural ms. as can maintain contractions for long periods. Red fibers Produces ATP with high efficiency. Has a large number of mitochondria & mitochondrial enzymes. Has aerobic energy transfer. Is innervated by small motor neurons that activate small number of fibers 2. Fast Oxidative or Type II a Fibers: Are moderately resistant to fatigue. Have mytochondrias & considerable amount of myoglobin. Moderately red fibers. Moderately well developed capacity for aerobic & anaerobic energy transfer. Intermediate motor neuron, its activities are e.g; middle distance runnng, swimming,… 3. Fast Glycolitc or Type IIb Fibers: Rely on anaerobic glycolysis. Become fatigued easily. Few mitochondria. Little myoglobin → white fibers. Specialised in powerful, brief types of contractions. 3 – Large motor neurons that activate large number of fibers for heavy loads. – Mixed with other muscle fibers as in limb muscles, eye and finger muscles. 4