Wednesday, March 2, 2011

Chapter Nine The Muscular System (Blog 7)

Chapter nine focuses on the muscular system of the body and its components. The muscular system provides seven major functions within the body. The first function of the muscular system is to provide the body with movement including walking, running, chewing and manipulating objects with the hands. The second function of the muscular system is the maintenance of body posture which keeps us standing or sitting in an erect position at all times. The third function of the muscular system is respiration in which the muscles of the thorax carry out the movements necessary for breathing. The fourth function of the muscular system is the production of body heat which helps keep the temperature of our bodies regulated at 37Celcius under normal conditions. The fifth function of the muscular system is the process of commuincation in which the skeletal muscles are an essential component of this functionin that they allow us the speak, write, type and control our facial muscles. The sixth function of the muscular system is the constriction of organs and vessels within the body. The constriction of our organs and vessels constric our smooth muscles that allows our organs and vessels to constrict in order to help food propel through the digestive tract and remove waste materials from the body such as urine from the urinary bladder and to regulate the flow of blood through the vessels.

There are three types of skeletal muscle contained within the body. Smooth muscle helps transport substances throughout the body and is found in the walls of hollow organs. Skeletal muscle helps aid in voluntary movement of the body and is located within the skeletal muscle of bone ends. Cardiac muscle helps blood circulate throughout the body and is located within the wall of the heart. Both skeletal and cardiac muscle are striated and smooth muscle is nonstriated. 

Skeletal muscle contains numerous structures such as nerves and blood vessels, skeletal muscle fibers, actin and myosin filaments, and sarcomeres. Actin is a thin myofilament contained within the muscle that form sacromeres which are joined at each end to form the myofibrils. Myosin is the thick myofilament that also forms the sacromere together with the actin myofilament. The sacromere is the basic structural and functional unit of skeletal muscle.

The most difficult component of the muscular system for me to understand was the sliding filament model and how it related to the response and contraction of the muscle fibers. I was having difficulty grasping the understanding that each band (A, I and H Band) within the sliding filament model changed its direction and length as each muscle within the body contracted. In reference to actin and myosin, during each muscle contraction neither one changed in length but instead the two would slide past one another within the model. Based on my initial understanding of what I origiinally thought was the correct function of the sliding filament model, my perception was that because actin was a thin myofilament it decreased in length as the muscle contracted and myosin being the thick filament it increased in length as the muscle contracted. After an indepth class lecture on the sliding filament model I was finally able to understand that both actin and myosin are essential important components of the sliding filament model and that without the action of the two components muscle contraction would be an absent process within the body.

The questions that I developed from the studying of chapter nine were:

(1) What would occur within the body pertianing to the  function of the muscles without the use of the sliding filament model?

(2)If either of the respiration components were absent from the energy sources of the body, how would it negatively effect the muscular system as a whole?

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