Travis pt 2

The muscular system is composed of various muscles and muscle groups that are used during running. However, in order to use these muscles, the nervous system plays a crucial role. Motor neurons in the central nervous system send impulses to the muscles used for running, causing muscle contraction. This process involves the release of calcium, which binds to troponin and moves tropomyosin, exposing binding sites. Myosin heads then attach to actin, forming cross bridges and pulling the actin filaments towards the center of the sarcomere. This shortens the sarcomere and results in muscle contraction. To begin with, I'll be introducing the muscular and the skeletal system. Now, for the muscular system, there are a lot of muscles and muscle groups that we use while we are running. Quadriceps, calves, hip flexors, all that stuff is needed when we are running. But at the same time, how are we supposed to use them when we can't even contract them? That's when the nervous system comes in. When we're ready to start running, motor neurons in the central nervous system carry out impulses to the effector organs, which, in this case, is the muscles used for running. These impulses reach the neuromuscular junction, which is the connection between the motor neuron and sarcolemma of a muscle fiber. Once these impulses arrive, the neuron depolarizes, thus beginning the muscle contraction. To begin, calcium rushes into the neuron, causing vesicles to release the neurotransmitter acetylcholine into the synaptic cleft. Acetylcholine binds to receptors on the sarcolemma of the muscle fiber, and then sodium diffuses into the cell while potassium diffuses. The inside of the cell becomes more positively charged, which is a process that we call the polarization of the threshold. Max potential is generated and travels over the entire surface of the cell and moves down into the T-tubules. The sarcoplasmic reticulum releases calcium into the cytoplasm. Calcium binds to troponin and moves tropomyosin, thus exposing binding sites. This is when myosin heads attach to binding sites on actin, forming cross bridges, and pull the actin filaments toward the center of the sarcomere. This is when the sarcomere shortens, and that is what we call muscle contraction.