In this theory, the muscles contract when actin filaments slide over myosin filaments resulting in a shortening of the length of the sarcomeres, and hence, a shortening of the muscle fibers. Muscles are believed to contract through a process called the Sliding Filament Theory. The point where the muscle is attached to a bone that remains in a fixed position is called the origin. The point where the muscle is attached to a bone that moves is called the insertion. When a muscle contracts, only one of these bones will move. The muscle is connected to two bones in order to allow movement to occur through a joint. The ends of the muscle connect to bone through a tendon. When groups of myofibrils are bound together by connective tissue, they make up muscle fibers. When groups of actin and myosin filaments are bound together by connective tissue they make the myofibrils. The actin and myosin filaments lie on top of one another it is this arrangement of the filaments that gives muscle its striated or striped appearance. Myosin filaments are thick and dark when compared with actin filaments, which are much thinner and lighter in appearance. The actin and myosin filaments form the contractile part of the muscle, which is called the sarcomere. Myofibrils are made up of two types of protein: Actin myofilaments, and myosin myofilaments. Muscle fibers also contain glycogen granules as a stored energy source, and myofibrils, which are threadlike structures running the length of the muscle fiber. Muscle fibers also contain many mitochondria, which are energy powerhouses that are responsible for the aerobic production of energy molecules, or ATP molecules. The epimysium covers the whole surface of the muscle. A muscle is made up of many muscle fasciculi, which are surrounded by a thick collagenous layer of connective tissue called the epimysium. A group of muscle fibers surrounded by the perimysium is called a muscle fasciculus. The group of muscle fibers and the endomysium are surrounded by more connective tissue called the perimysium. A group of muscle fibers are encased within more connective tissue called the endomysium. This is called muscle fiber recruitment.Įach muscle fiber is surrounded by connective tissue called an external lamina. Only a small number of muscle fibers will contract to bend one of our limbs, but if we wish to lift a heavy weight then many more muscles fibers will be recruited to perform the action. The nerve and the fibers it controls are called a motor unit. Each nerve will control a certain number of muscle fibers. This signals the muscle fibers to contract. When we choose to contract a muscle fiber-for instance we contract our bicep to bend our arm upwards-a signal is sent from our brain via the spinal cord to the muscle. Each muscle fiber is an individual muscle cell and may be anywhere from 1 mm to 4 cm in length. They are under conscious control, which means that we can consciously choose to contract a muscle and can regulate how strong the contraction actually is. Skeletal muscles are attached to the skeleton and are responsible for the movement of our limbs, torso, and head. Responsible for many tasks, including movement of food along intestines, enlargement and contraction of blood vessels, size of pupils, and many other contractions. Responsible for the contraction of the heart. Muscular Strength and Endurance Types of Muscle However, achieving the best muscular performance requires the assistance of a trained professional.įor more information on muscular fitness and endurance, please click on the link below: This chapter explores many ways to resistance train. Resistance training is the method of developing muscular strength and muscular endurance, which in turns improves wellness. Muscular strength is the amount of force that a muscle can produce one time at a maximal effort, and muscular endurance is the ability to repeat a movement over an extended period of time. The largest portion of energy expenditure in the body happens in muscles while helping us perform daily activities with ease and improving our wellness. Muscles are used for movement in the body. Without muscle cells, we would be unable to stand, walk, talk, or perform everyday tasks. There are over 600 muscles in the human body they are responsible for every movement we make, from pumping blood through the heart and moving food through the digestive system, to blinking and chewing. Muscles are powered by muscle cells, which contract individually within a muscle to generate force. Muscles are highly specialized to contract forcefully. Assess your muscular strength and endurance.Describe an effective resistance exercise program.Describe muscular structure and function.
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