The Muscular System

Topics: Muscle contraction, Myosin, Muscle Pages: 3 (1044 words) Published: March 11, 2013
Q9.Explain how the muscle produces movement and different types of contraction.(M3) Sliding filament theory.
Each muscle fibre is made up of smaller fibres called myofibrils. These contain even smaller structures called actin which is a thin, contractile protein filament, containing 'active' or 'binding' sites and myosin filaments which are a thick, contractile protein filament, with Myosin Heads. These filaments slide in and out between each other to form a muscle contractions, this is why it is known as the sliding filament theory. Firstly I am going to explain how the filaments slide. In a relaxed muscle the cross bridges are detached from the actin filaments. When you muscle contracts they attach themselves and provide a contractile force. The thick filaments are made up of myosin molecules, each of the molecules contain a long rod-shaped tail; a shorter rod-shaped neck and 2 globular heads which will form the cross bridges. In the muscle there are 2 flexible hinge like regions. The hinge between the neck and tail allow the cross bridges to attach and detach them-selves from the actin filament. The hinge next to the globular head allows the head to tilt; this tilt is the power stroke. The myosin molecules on one side of the bare zone are placed in one direction and the others on the opposite side in the opposite direction. As the heads always tilt towards their tails they always propel the actin filaments on each side of the H zone in the proper direction. The actin molecules are also found in the chains which are placed on each side of the Z line. Now I will explain the sliding filament theory of a contracting muscle. A nervous impulse arrives at the neuromuscular junction, which causes a release of a chemical called Acetylcholine. Due to the Acetylcholine being present it causes the depolarisation of the motor end plate which travels throughout the muscle by the transverse tubules also known as T tubules, causing...
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