The primary muscles involved in dorsiflextion of the …show more content…
They originate on the lateral surface of the fibula. The fibularis longus inserts on the base of the first metatarsal and medial cuneiform, the fibularis brevis inserts at the base of the fifth metatarsal. Posterior muscles are divided into superficial and deep muscles, the superficial muscles which plantarflex the ankle have different origins, but all merge into the calcaneal tendon which inserts into the back of the calcaneous. The gastrocnemius muscle has two heads, the medial head originates from the medial condyle and the lateral head originates from the lateral condyle of the femur. The plantaris muscle originates at the supercondylar line of the femur and the soleus muscle originates on the shaft of the tibia and fibula. There are also the deep muscles that plantarflex the ankle and flex the toes. The flexor digitorum longus muscle plantarflexes the ankle and flexes the lateral four toes, it originates on the posterior surface of the tibia and inserts into the bases of the distal phalanges of the lateral four toes. The flexor hallicus longus plantarflexes the ankle and flexes the big toe, it originates on the distal two-thirds of the posterior surface of the shaft of the fibula and inserts into the base of the distal phalanx of the big toe. The tibialis posterior plantarflexes the ankle and inverts the foot, it originates on the posterior surfaces of the shafts …show more content…
The thick and thin filaments are two types of protein filaments that together form cylindrical structures called myofibrils which extend along the muscle. Thick filaments are formed from a group of proteins called myosin. Thin filaments are formed from three proteins called actin, troponin and tropomyosin. Muscle tissue is described in terms of units called sacromeres. These units are defined as overlapping groups of the thick and thin filaments. The length of a sacromere and the zones within each sacromere (H zone, I band and A band) are determined by the position of how the thick and thin filaments are relative to each other. During muscle contraction the myosin heads on the thick filament attach to the thin filaments and pull it to the centre (M line) of each sacromere. The appearance of this action is the transition from relaxed to fully contracted muscle. As the thin filaments slide over the thick filaments the H zones and I bands become narrower until they disappear when the muscle is in a fully contracted state. During muscle relaxation the myosin heads on the thick filaments detach from their hold on the thin filaments which allows them to slide back to their relaxed position and the H zones and I bands reappear. This process happens as a result of instructions sent to activate and deactivate these tissues via the nervous